Ketamine differentially restores diverse alterations of neuroligins in brain regions in a rat model of neuropathic pain-induced depression.

PubMed

Pan, Wei; Zhang, Guang-Fen; Li, Hui-Hui; Ji, Mu-Huo; Zhou, Zhi-Qiang; Li, Kuan-Yu; Yang, Jian-Jun

2018-07-04

Depression is present in a large proportion of patients suffering from chronic pain, and yet the underlying mechanisms remain to be elucidated. Neuroligins (NLs), as a family of cell-adhesion proteins, are involved in synaptic formation and have been linked to various neuropsychiatric disorders. Here, we studied the alterations in NL1 and NL2 in the medial prefrontal cortex (mPFC), the anterior cingulate cortex (ACC), and the hippocampus in a rat model of neuropathic pain-induced depression, and whether ketamine, a rapid and robust antidepressant, could restore these abnormalities. In the present study, we found that spared nerve injury induced significant mechanical allodynia and subsequent depressive-like symptoms, along with decreased NL1 and increased NL2 in the mPFC, decreased NL1 in the ACC, and decreased NL2 in the hippocampus. In addition, brain-derived neurotrophic factor (BDNF) was reduced in these brain regions. It is noteworthy that ketamine (10 mg/kg) relieved neuropathic pain-induced depressive behaviors and restored alterations of BDNF and NLs in the mPFC and the hippocampus at 24 h and 72 h after the administration of ketamine, but only restored BDNF in the ACC. In conclusion, NLs showed diverse changes in different brain regions in the rat model of neuropathic pain-induced depression, which could be reversed differentially by the administration of ketamine.

Antinociceptive Effect of Intrathecal Injection of Genetically Engineered Human Bone Marrow Stem Cells Expressing the Human Proenkephalin Gene in a Rat Model of Bone Cancer Pain.

PubMed

Sun, Yi; Tian, Yuke; Li, Haifeng; Zhang, Dengwen; Sun, Qiang

2017-01-01

Background . This study aimed to investigate the use of human bone marrow mesenchymal stem cells (hBMSCs) genetically engineered with the human proenkephalin (hPPE) gene to treat bone cancer pain (BCP) in a rat model. Methods . Primary cultured hBMSCs were passaged and modified with hPPE, and the cell suspensions (6 × 10 6 ) were then intrathecally injected into a rat model of BCP. Paw mechanical withdrawal threshold (PMWT) was measured before and after BCP. The effects of hPPE gene transfer on hBMSC bioactivity were analyzed in vitro and in vivo. Results . No changes were observed in the surface phenotypes and differentiation of hBMSCs after gene transfer. The hPPE-hBMSC group showed improved PMWT values on the ipsilateral side of rats with BCP from day 12 postoperatively, and the analgesic effect was reversed by naloxone. The levels of proinflammatory cytokines such as IL-1 β and IL-6 were ameliorated, and leucine-enkephalin (L-EK) secretion was augmented, in the hPPE-engineered hBMSC group. Conclusion . The intrathecal administration of BMSCs modified with the hPPE gene can effectively relieve pain caused by bone cancer in rats and might be a potentially therapeutic tool for cancer-related pain in humans.

Standard analgesics reverse burrowing deficits in a rat CCI model of neuropathic pain, but not in models of type 1 and type 2 diabetes-induced neuropathic pain.

PubMed

Rutten, Kris; Gould, Stacey A; Bryden, Luke; Doods, Henri; Christoph, Thomas; Pekcec, Anton

2018-09-17

Burrowing is a rodent behavior validated as a robust and reproducible outcome measure to infer the global effect of pain in several inflammatory pain models. However, less is known about the effect of analgesics on burrowing in neuropathic pain models and no studies have determined burrowing performance in models of diabetes-associated neuropathic pain. To compare the sensitivity of the burrowing assay in different neuropathic pain models: mononeuropathic pain and diabetic polyneuropathy. Burrowing performance was determined by the amount of substrate left in a hollow tube by rats with chronic constriction injury (CCI). In addition, burrowing performance, locomotion and pain development was assessed in the Zucker diabetic fatty (ZDF) rat model, resembling type-2 diabetes. Efficacy of clinically-active reference drugs (opioids, gabapentin and/or pregabalin) were investigated in these models. Burrowing behavior was additionally assessed in a second model, induced by streptozotocin (STZ) treatment, resembling type-1 diabetes. In the CCI model, moderate but consistent burrowing deficits were observed that persisted over a period of ≥20 days. Systemic administration of morphine, pregabalin and gabapentin reversed this deficit. In contrast, none of the reference drugs improved marked burrowing deficits detected in ZDF rats, and pregabalin did not reverse severe burrowing deficits observed in STZ rats. Burrowing performance cannot necessarily be used as pain-related readout across pain models and largely depends on the model used, at least in models of neuropathy. Specifically, analgesic drug effects might be masked by general diabetes-associated alteration of the animals' well-being, resulting in false negative outcomes. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Minocycline Effects on IL-6 Concentration in Macrophage and Microglial Cells in a Rat Model of Neuropathic Pain.

PubMed

Moini-Zanjani, Taraneh; Ostad, Seyed-Nasser; Labibi, Farzaneh; Ameli, Haleh; Mosaffa, Nariman; Sabetkasaei, Masoumeh

2016-11-01

Evidence indicates that neuropathic pain pathogenesis is not confined to changes in the activity of neuronal systems but involves interactions between neurons, inflammatory immune and immune-like glial cells. Substances released from immune cells during inflammation play an important role in development and maintenance of neuropathic pain. It has been found that minocycline suppresses the development of neuropathic pain. Here, we evaluated the analgesic effect of minocycline in a chronic constriction injury (CCI) model of neuropathic pain in rat and assessed IL-6 concentration from cultured macrophage and microglia cells. Male Wistar rat (n=6, 150-200 g) were divided into three different groups: 1) CCI+vehicle, 2) sham+vehicle, and 3) CCI+drug. Minocycline (10, 20, and 40 mg/kg) was injected one hour before surgery and continued daily to day 14 post ligation. Von Frey filaments and acetone, as pain behavioral tests, were used for mechanical allodynia and cold allodynia, respectively. Experiments were performed on day 0 (before surgery) and days 1, 3, 5, 7, 10, and 14 post -injury. At day 14, rats were killed and monocyte-derived macrophage from right ventricle and microglia from lumbar part of the spinal cord were isolated and cultured in RPMI and Leibovitz's media, respectively. IL-6 concentration was evaluated in cell culture supernatant after 24 h. Minocycline (10, 20, and 40 mg/kg) attenuated pain behavior, and a decrease in IL-6 concentration was observed in immune cells compared to CCI vehicle-treated animals. Minocycline reduced pain behavior and decreased IL-6 concentration in macrophage and microglial cells.

Opiate self-administration as a measure of chronic nociceptive pain in arthritic rats.

PubMed

Colpaert, F C; Tarayre, J P; Alliaga, M; Bruins Slot, L A; Attal, N; Koek, W

2001-03-01

The study examined the validity of oral fentanyl self-administration (FSA) as a measure of the chronic nociceptive pain that develops in rats with adjuvant arthritis independently of acute noxious challenges. Arthritic rats self-administered more of a 0.008 mg/ml fentanyl solution (up to 3.4 g/rat per day) than non-arthritic controls (0.5 g/rat per day) and did so with a biphasic time course that reached peak during weeks 3 and 4 after inoculation with Mycobacterium butyricum. The time course paralleled both the disease process and the chronic pain. Continuous infusion of dexamethasone during weeks 3 and 4 via subcutaneous osmotic pumps at 0.0025-0.04 mg/rat per day disrupted the arthritic disease and decreased FSA to a level (i.e. by 65%) similar to that observed in non-arthritic rats. Continuous naloxone (2.5 mg/rat per day) decreased FSA (by 55%) in arthritic but not in non-arthritic animals. Continuous, subcutaneous infusion of fentanyl also decreased arthritic FSA in a manner that varied with dose at 0.04-0.16 mg/rat per day doses, but leveled off at 47% of controls with 0.31 mg/rat per day. The effects of continuous fentanyl on arthritic FSA occurred only with those doses and dose-dependent dynamics with which fentanyl also induced dependence in non-arthritic rats. The findings indicate that pain, rather than the rewarding or dependence-inducing action of fentanyl mediates FSA in arthritic rats. Paralleling patient-controlled analgesic drug intake, FSA offers a specific measure allowing the dynamic effects of neurobiological agents to be studied in this unique animal model of persistent nociceptive pain.

Inhibition of AAK1 Kinase as a Novel Therapeutic Approach to Treat Neuropathic Pain

PubMed Central

Kostich, Walter; Hamman, Brian D.; Li, Yu-Wen; Naidu, Sreenivasulu; Dandapani, Kumaran; Feng, Jianlin; Easton, Amy; Bourin, Clotilde; Baker, Kevin; Allen, Jason; Savelieva, Katerina; Louis, Justin V.; Dokania, Manoj; Elavazhagan, Saravanan; Vattikundala, Pradeep; Sharma, Vivek; Das, Manish Lal; Shankar, Ganesh; Kumar, Anoop; Holenarsipur, Vinay K.; Gulianello, Michael; Molski, Ted; Brown, Jeffrey M.; Lewis, Martin; Huang, Yanling; Lu, Yifeng; Pieschl, Rick; O’Malley, Kevin; Lippy, Jonathan; Nouraldeen, Amr; Lanthorn, Thomas H.; Ye, Guilan; Wilson, Alan; Balakrishnan, Anand; Denton, Rex; Grace, James E.; Lentz, Kimberley A.; Santone, Kenneth S.; Bi, Yingzhi; Main, Alan; Swaffield, Jon; Carson, Ken; Mandlekar, Sandhya; Vikramadithyan, Reeba K.; Nara, Susheel J.; Dzierba, Carolyn; Bronson, Joanne; Macor, John E.; Zaczek, Robert; Westphal, Ryan; Kiss, Laszlo; Bristow, Linda; Conway, Charles M.

2016-01-01

To identify novel targets for neuropathic pain, 3097 mouse knockout lines were tested in acute and persistent pain behavior assays. One of the lines from this screen, which contained a null allele of the adapter protein-2 associated kinase 1 (AAK1) gene, had a normal response in acute pain assays (hot plate, phase I formalin), but a markedly reduced response to persistent pain in phase II formalin. AAK1 knockout mice also failed to develop tactile allodynia following the Chung procedure of spinal nerve ligation (SNL). Based on these findings, potent, small-molecule inhibitors of AAK1 were identified. Studies in mice showed that one such inhibitor, LP-935509, caused a reduced pain response in phase II formalin and reversed fully established pain behavior following the SNL procedure. Further studies showed that the inhibitor also reduced evoked pain responses in the rat chronic constriction injury (CCI) model and the rat streptozotocin model of diabetic peripheral neuropathy. Using a nonbrain-penetrant AAK1 inhibitor and local administration of an AAK1 inhibitor, the relevant pool of AAK1 for antineuropathic action was found to be in the spinal cord. Consistent with these results, AAK1 inhibitors dose-dependently reduced the increased spontaneous neural activity in the spinal cord caused by CCI and blocked the development of windup induced by repeated electrical stimulation of the paw. The mechanism of AAK1 antinociception was further investigated with inhibitors of α2 adrenergic and opioid receptors. These studies showed that α2 adrenergic receptor inhibitors, but not opioid receptor inhibitors, not only prevented AAK1 inhibitor antineuropathic action in behavioral assays, but also blocked the AAK1 inhibitor–induced reduction in spinal neural activity in the rat CCI model. Hence, AAK1 inhibitors are a novel therapeutic approach to neuropathic pain with activity in animal models that is mechanistically linked (behaviorally and electrophysiologically) to α2 adrenergic signaling, a pathway known to be antinociceptive in humans. PMID:27411717

The Effect of Gabapentin and Tramadol in Cancer Pain Induced by Glioma Cell in Rat Femur.

PubMed

Corona-Ramos, Janette Nallely; Déciga-Campos, Myrna; Romero-Piña, Mario; Medina, Luis A; Martínez-Racine, Issac; Jaramillo-Morales, Osmar A; García-López, Patricia; López-Muñoz, Francisco Javier

2017-08-01

Preclinical Research The presence of pain as part of the cancer process is variable. Glioblastoma multiform (GBM) can produce bone metastasis, a condition that involves other pathological phenotypes including neuropathic and inflammatory pain. Tramadol and gabapentin are drugs used in the treatment of neuropathic pain. However, there are no studies evaluating their analgesic effects in bone metastasis. We produced a pain model induced by the inoculation of glioma cells (10 5 ) into the rat femur, by perforating the intercodiloid fossa. Painful behavior was evaluated by measuring mechanical allodynia using the Von Frey test while thermal hyperalgesia was assessed in the plantar test. Histopathological features were evaluated and antinociceptive responses were compared using tramadol and gabapentin. The inoculation of cells inside the right femur produced nociceptive behaviors. Tramadol and gabapentin produced an anti-allodynic effect in this condition, but tramadol did not produce an anti-hyperalgesic response. The development of this model will allow us to perform tests to elucidate the pathology of bone metastasis, cancer pain, and in particular the pain produced by glioma. Drug Dev Res 78 : 173-183, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Inducible nitric oxide synthase inhibition by 1400W limits pain hypersensitivity in a neuropathic pain rat model.

PubMed

Staunton, C A; Barrett-Jolley, R; Djouhri, L; Thippeswamy, T

2018-04-01

What is the central question of this study? Can modulation of inducible NO synthase reduce pain behaviour and pro-inflammatory cytokine signalling in a rat model of neuropathic pain? What is the main finding and its importance? Nitric oxide synthase-based therapies could be effective for the treatment of peripheral neuropathic pain. Peripheral neuropathic pain (PNP), resulting from injury to or dysfunction of a peripheral nerve, is a major health problem that affects 7-8% of the population. It is inadequately controlled by current drugs and is characterized by pain hypersensitivity, which is believed to be attributable to sensitization of peripheral and CNS neurons by various inflammatory mediators. Here we examined, in a rat model of PNP: (i) whether reducing levels of nitric oxide (NO) with 1400W, a highly selective inhibitor of inducible NO synthase (iNOS), would prevent or attenuate pain hypersensitivity; and (ii) the effects of 1400W on plasma concentrations of several cytokines that are secreted after iNOS upregulation during chronic pain states. The L5 spinal nerve axotomy (SNA) model of PNP was used, and 1400W (20 mg kg -1 ) was administered i.p. at 8 h intervals for 3 days starting at 18 h post-SNA. Changes in plasma concentrations of 12 cytokines in SNA rats treated with 1400W were examined using multiplex enzyme-linked immunosorbent assay. The SNA rats developed behavioural signs of mechanical and heat hypersensitivity. Compared with the vehicle/control, 1400W significantly: (i) limited development of mechanical hypersensitivity at 66 h post-SNA and of heat hypersensitivity at 42 h and at several time points tested thereafter; and (ii) increased the plasma concentrations of interleukin (IL)-1α, IL-1β and IL-10 in the SNA rats. The findings suggest that 1400W might exert its analgesic effects by reducing iNOS and altering the balance between the pro-inflammatory (IL-1β and IL-1α) and anti-inflammatory (IL-10) cytokines and that therapies targeting NO or its enzymes might be effective for the treatment of PNP. © 2018 The Authors. Experimental Physiology © 2018 The Physiological Society.

Coenzyme Q10 ameliorates pain and cartilage degradation in a rat model of osteoarthritis by regulating nitric oxide and inflammatory cytokines.

PubMed

Lee, Jennifer; Hong, Yeon Sik; Jeong, Jeong Hee; Yang, Eun Ji; Jhun, Joo Yeon; Park, Mi Kyoung; Jung, Young Ok; Min, Jun Ki; Kim, Ho Youn; Park, Sung Hwan; Cho, Mi-La

2013-01-01

To investigate the effect of CoenzymeQ10 (CoQ10) on pain severity and cartilage degeneration in an experimental model of rat osteoarthritis (OA). OA was induced in rats by intra-articular injection of monosodium iodoacetate (MIA) to the knee. Oral administration of CoQ10 was initiated on day 4 after MIA injection. Pain severity was assessed by measuring secondary tactile allodynia using the von Frey assessment test. The degree of cartilage degradation was determined by measuring cartilage thickness and the amount of proteoglycan. The mankin scoring system was also used. Expressions of matrix metalloproteinase-13 (MMP-13), interleukin-1β (IL-1β), IL-6, IL-15, inducible nitric oxide synthase (iNOS), nitrotyrosine and receptor for advanced glycation end products (RAGE) were analyzed using immunohistochemistry. Treatment with CoQ10 demonstrated an antinociceptive effect in the OA animal model. The reduction in secondary tactile allodynia was shown by an increased pain withdrawal latency and pain withdrawal threshold. CoQ10 also attenuated cartilage degeneration in the osteoarthritic joints. MMP-13, IL-1β, IL-6, IL-15, iNOS, nitrotyrosine and RAGE expressions were upregulated in OA joints and significantly reduced with CoQ10 treatment. CoQ10 exerts a therapeutic effect on OA via pain suppression and cartilage degeneration by inhibiting inflammatory mediators, which play a vital role in OA pathogenesis.

Face-to-face comparison of the predictive validity of two models of neuropathic pain in the rat: analgesic activity of pregabalin, tramadol and duloxetine.

PubMed

Le Cudennec, Camille; Castagné, Vincent

2014-07-15

We compared the preclinical analgesic activity of three marketed drugs with different pharmacological properties, pregabalin, tramadol and duloxetine, described as effective against neuropathic pain in the clinic. These drugs were tested against evoked pain in two different neuropathic models in the rat, the Bennett (CCI) and the Chung (SNL) models. The selected endpoints were tactile allodynia, tactile hyperalgesia, heat hyperalgesia and cold allodynia. Although all three drugs displayed analgesic activity, the effects observed varied according to the behavioral evaluation. Pregabalin showed clear analgesic effects against cold allodynia and tactile hyperalgesia in both the CCI and Chung models. Tramadol was active against all four endpoints in the Chung model with similar effects in the CCI model, apart from tactile allodynia. Duloxetine inhibited tactile allodynia and heat hyperalgesia in both neuropathic pain models. It also displayed efficacy against tactile hyperalgesia in the CCI model and against cold allodynia in the Chung model. These data confirm that the CCI and the Chung models of neuropathic pain do not detect the activity of analgesics with the same sensitivity. Furthermore, the mode of stimulation (tactile or thermal) and the type of endpoint (allodynia or hyperalgesia) can further influence the observed efficacy of gold standards as well as novel compounds developed for treating neuropathic pain symptoms. Copyright © 2014. Published by Elsevier B.V.

Bone mesenchymal stem cells attenuate radicular pain by inhibiting microglial activation in a rat noncompressive disk herniation model.

PubMed

Huang, Xiaodong; Wang, Weiheng; Liu, Xilin; Xi, Yanhai; Yu, Jiangming; Yang, Xiangqun; Ye, Xiaojian

2018-06-01

Spinal disk herniation can induce radicular pain through chemical irritation caused by proinflammatory and immune responses. Bone marrow mesenchymal stem cells (BMSCs) are a unique type of adult stem cell with the functions of suppressing inflammation and modulating immune responses. This study was undertaken to observe the effect of intrathecal BMSCs on the treatment of mechanical allodynia and the suppression of microglial activation in a rat noncompressive disk herniation model. The model was induced by the application of nucleus pulposus (NP) to the L5 dorsal root ganglion (DRG). The study found that the use of NP in the DRG can induce abnormal mechanical pain, increase the contents of the proinflammatory factors TNF-α and IL-1β, decrease the content of the anti-inflammatory cytokine TGF-β1 and activate microglia in the spinal dorsal horns (L5) (P < 0.05). BMSC administration could increase the mechanical withdrawal thresholds dramatically, decrease the contents of IL-1β and TNF-α, increase the content of TGF-β1 significantly (P < 0.05) and inhibit microglial activation in the bilateral spinal dorsal horn. Our results indicate that BMSC administration can reduce mechanical allodynia and downregulate the expression of proinflammatory cytokines by inhibiting microglial activation in the spinal dorsal horn in a rat noncompressive disk herniation model.

Mu-Opioid (MOP) receptor mediated G-protein signaling is impaired in specific brain regions in a rat model of schizophrenia.

PubMed

Szűcs, Edina; Büki, Alexandra; Kékesi, Gabriella; Horváth, Gyöngyi; Benyhe, Sándor

2016-04-21

Schizophrenia is a complex mental health disorder. Clinical reports suggest that many patients with schizophrenia are less sensitive to pain than other individuals. Animal models do not interpret schizophrenia completely, but they can model a number of symptoms of the disease, including decreased pain sensitivities and increased pain thresholds of various modalities. Opioid receptors and endogenous opioid peptides have a substantial role in analgesia. In this biochemical study we investigated changes in the signaling properties of the mu-opioid (MOP) receptor in different brain regions, which are involved in the pain transmission, i.e., thalamus, olfactory bulb, prefrontal cortex and hippocampus. Our goal was to compare the transmembrane signaling mediated by MOP receptors in control rats and in a recently developed rat model of schizophrenia. Regulatory G-protein activation via MOP receptors were measured in [(35)S]GTPγS binding assays in the presence of a highly selective MOP receptor peptide agonist, DAMGO. It was found that the MOP receptor mediated activation of G-proteins was substantially lower in membranes prepared from the 'schizophrenic' model rats than in control animals. The potency of DAMGO to activate MOP receptor was also decreased in all brain regions studied. Taken together in our rat model of schizophrenia, MOP receptor mediated G-proteins have a reduced stimulatory activity compared to membrane preparations taken from control animals. The observed distinct changes of opioid receptor functions in different areas of the brain do not explain the augmented nociceptive threshold described in these animals. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Establishment of a rat model of chronic Prostatitis/Chronic Pelvic Pain Syndrome (CP/CPPS) induced by immunization with a novel peptide T2.

PubMed

Ihsan, Awais Ullah; Khan, Farhan Ullah; Nawaz, Waqas; Khan, Muhammad Zahid; Yang, Mengqi; Zhou, Xiaohui

2017-07-01

The exact etiological mechanism of Chronic Prostatitis/chronic pelvic pain syndrome (CP/CPPS) is still unclear however autoimmunity is the most valid theory. We developed a rat model of Chronic Prostatitis/chronic pelvic pain syndrome by using a novel peptide (T2) isolated from TRPM8. This model might be beneficial in elucidating mechanisms involved in the pathogenesis of Chronic Prostatitis/Chronic Pelvic Pain Syndrome (CP/CPPS). 40 male Sprague-Dawley rats with an average weight of 180-220g were equally distributed into five groups. The normal control group was injected with normal saline (.9% NACL), the CFA group with CFA, AL(OH)3 group was given AL(OH)3 injection, T2 group using a novel peptide T2 and T2+AL(OH)3+CFA group was injected with T2+AL(OH)3+CFA. Dosing to all rat groups were injected subcutaneously. Hematoxylin and eosin staining and Immunohistochemistry were used to investigate inflammatory cell infiltration and IL-1β in the prostate tissue respectively. ELISA technique was used to measure the serum level of CRP and TNF-α. T-test was used to analyze the results. Maximum infiltration of inflammatory cells and the highest level of IL-1β in the prostate tissue was observed in T2+AL(OH)3+CFA group as revealed by histopathology and Immunohistochemistry, respectively. Furthermore, T2+AL(OH)3+CFA group attained the peak value of serum TNF-α and CRP as determined by ELISA technique. Our results demonstrated that T2 in combination with AL(OH)3 and CFA induced severe Prostatitis in rats. We believe that our present model will be highly beneficial for investigation of the pathophysiology of Chronic Prostatitis/Chronic Pelvic Pain Syndrome. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Use of dynamic weight bearing as a novel end-point for the assessment of abdominal pain in the LPS-induced peritonitis model in the rat.

PubMed

Gruen, Michael; Laux-Biehlmann, Alexis; Zollner, Thomas M; Nagel, Jens

2014-07-30

Chronic pelvic pain (CPP) is defined as long-lasting and severe pelvic pain persisting over six months in cyclic or non-cyclic chronic manner. Various pathologic conditions like endometriosis, abdominal infections, intra-peritoneal adhesions or infection, underlie CPP which is often the leading symptom of the associated diseases. Pharmacological approaches addressing CPP are hampered by the absence of a straight-forward, objective, and reliable method for the assessment of CPP in rodents. In the presented study, the dynamic weight bearing system (DWB) was employed for the first time for the evaluation of pelvic pain in a rat model of LPS-induced peritonitis. Rats were pretreated with the COX-2 inhibitor rofecoxib and PGE2 levels were evaluated in peritoneal lavage. DWB analysis revealed that rats treated with LPS showed a relief posture by a significantly increased weight distribution to the front when compared to vehicle-treated animals. This effect was prevented by rofecoxib treatment indicating the sensitivity of the model for pelvic pain related to peritonitis. Analysis of the PGE2 levels in the peritoneal fluid indicated a correlation with the relief posture intensity. In contrast to others weight bearing approaches, the use of DWB allows evaluation of spontaneous posture changes as a consequence of pelvic pain. Taken together, we were able to show, that DWB combined with LPS-induced peritonitis may deliver a new reliable animal model addressing pelvic pain with high construct validity (peritoneal inflammation), and face validity (pain related relief posture). Copyright © 2014 Elsevier B.V. All rights reserved.

Electroconvulsive stimulation (ECS) increases the expression of neuropeptide Y (NPY) in rat brains in a model of neuropathic pain: a quantitative real-time polymerase chain reaction (RT-PCR) study.

PubMed

Okabe, Tadashi; Sato, Chiyo; Matsumoto, Keisuke; Ozawa, Hitoshi; Sakamoto, Atsuhiro

2009-11-01

Electroconvulsive shock therapy (ECT) has been widely used as an effective and established treatment for refractory depression and schizophrenia. Some reports have shown that ECT is also effective for treating refractory neuropathic pain. In a rat model of neuropathic pain produced by chronic constrictive injury (CCI) of the sciatic nerve, thermal hyperalgesia, and mechanical allodynia were observed from day 2 after surgery. An electroconvulsive shock (ECS) was administered to rodents once daily for 6 days on days 7-12 after CCI operation using a pulse generator. Thermal and mechanical stimulation tests were performed to assess pain thresholds. Real-time polymerase chain reaction was used to measure the gene expression levels for 5HT(1A)R, 5HT(2A)R, neuropeptide Y (NPY), and GABAA(alpha1)R in the brain. After ECS, the latency to withdrawal from thermal stimulation was significantly increased; however, pain withdrawal thresholds in response to mechanical stimulation were not significantly changed. Expression ratios of NPY were significantly greater after ECS. Symptoms of neuropathic pain improved and expression of NPY in the brain was increased in CCI model rats after ECS, suggesting that changes in the expression of NPY in the brain may be related to the mechanism of action of ECT in treating neuropathic pain.

Modulation of enteric neurons by interleukin-6 and corticotropin-releasing factor contributes to visceral hypersensitivity and altered colonic motility in a rat model of irritable bowel syndrome

PubMed Central

Buckley, Maria M; O'Halloran, Ken D; Rae, Mark G; Dinan, Timothy G; O'Malley, Dervla

2014-01-01

Abstract The search for effective therapeutic strategies for irritable bowel syndrome (IBS) is hampered by an incomplete understanding of its underlying pathophysiology. Stress and altered plasma cytokine profiles indicative of immune activation are characteristic of the disorder. The neuromodulatory effects of interleukin-6 (IL-6) and corticotropin-releasing factor receptor (CRFR) 1 in visceral pain and stress-induced defecation in the Wistar Kyoto (WKY) rat model of IBS were investigated. Sprague Dawley and WKY rats were administered anti-IL-6 receptor antibodies (xIL-6R, 0.5 mg kg−1 i.p) with or without the CRFR1 antagonist antalarmin (10 mg kg−1 i.p). Post-intervention, the pain threshold to colorectal distension and stress-induced faecal output were compared and changes in colonic mucosal protein expression were investigated. The neuro-stimulatory effects of IBS plasma on the myenteric plexus is mediated by IL-6, IL-8 and CRF. The stimulatory effects of these soluble factors on myenteric neuron excitability and colonic contractility were additive. Moreover, inhibition of IL-6 and CRF1 receptors in vivo in the WKY IBS rat model normalized stress-induced defecation (P < 0.01) and visceral pain sensitivity (P < 0.001) with associated changes in protein expression of the tight junction proteins occludin and claudin 2, the visceral pain-associated T-type calcium channel CaV3.2 and intracellular signalling molecules STAT3, SOCS3 and ERK1/2. These studies demonstrate the additive effects of immune and stress factors on myenteric neuronal excitability. Moreover, combined targeting of peripheral IL-6 and CRF1 receptors is effective in alleviating IBS-like symptoms in the WKY rat. Thus, crosstalk between stress and immune factors during IBS flares may underlie symptom exacerbation. PMID:25260633

Genome-Wide Transcriptional Profiling of Skin and Dorsal Root Ganglia after Ultraviolet-B-Induced Inflammation

PubMed Central

Paterson, Kathryn J.; Sisignano, Marco; Schmid, Ramona; Rust, Werner; Hildebrandt, Tobias; Geisslinger, Gerd; Orengo, Christine; Bennett, David L.; McMahon, Stephen B.

2014-01-01

Ultraviolet-B (UVB)-induced inflammation produces a dose-dependent mechanical and thermal hyperalgesia in both humans and rats, most likely via inflammatory mediators acting at the site of injury. Previous work has shown that the gene expression of cytokines and chemokines is positively correlated between species and that these factors can contribute to UVB-induced pain. In order to investigate other potential pain mediators in this model we used RNA-seq to perform genome-wide transcriptional profiling in both human and rat skin at the peak of hyperalgesia. In addition we have also measured transcriptional changes in the L4 and L5 DRG of the rat model. Our data show that UVB irradiation produces a large number of transcriptional changes in the skin: 2186 and 3888 genes are significantly dysregulated in human and rat skin, respectively. The most highly up-regulated genes in human skin feature those encoding cytokines (IL6 and IL24), chemokines (CCL3, CCL20, CXCL1, CXCL2, CXCL3 and CXCL5), the prostanoid synthesising enzyme COX-2 and members of the keratin gene family. Overall there was a strong positive and significant correlation in gene expression between the human and rat (R = 0.8022). In contrast to the skin, only 39 genes were significantly dysregulated in the rat L4 and L5 DRGs, the majority of which had small fold change values. Amongst the most up-regulated genes in DRG were REG3B, CCL2 and VGF. Overall, our data shows that numerous genes were up-regulated in UVB irradiated skin at the peak of hyperalgesia in both human and rats. Many of the top up-regulated genes were cytokines and chemokines, highlighting again their potential as pain mediators. However many other genes were also up-regulated and might play a role in UVB-induced hyperalgesia. In addition, the strong gene expression correlation between species re-emphasises the value of the UVB model as translational tool to study inflammatory pain. PMID:24732968

Expression profiling of genes modulated by minocycline in a rat model of neuropathic pain

PubMed Central

2014-01-01

Background The molecular mechanisms underlying neuropathic pain are constantly being studied to create new opportunities to prevent or alleviate neuropathic pain. The aim of our study was to determine the gene expression changes induced by sciatic nerve chronic constriction injury (CCI) that are modulated by minocycline, which can effectively diminish neuropathic pain in animal studies. The genes associated with minocycline efficacy in neuropathic pain should provide insight into the etiology of neuropathic pain and identify novel therapeutic targets. Results We screened the ipsilateral dorsal part of the lumbar spinal cord of the rat CCI model for differentially expressed genes. Out of 22,500 studied transcripts, the abundance levels of 93 transcripts were altered following sciatic nerve ligation. Percentage analysis revealed that 54 transcripts were not affected by the repeated administration of minocycline (30 mg/kg, i.p.), but the levels of 39 transcripts were modulated following minocycline treatment. We then selected two gene expression patterns, B1 and B2. The first transcription pattern, B1, consisted of 10 mRNA transcripts that increased in abundance after injury, and minocycline treatment reversed or inhibited the effect of the injury; the B2 transcription pattern consisted of 7 mRNA transcripts whose abundance decreased following sciatic nerve ligation, and minocycline treatment reversed the effect of the injury. Based on the literature, we selected seven genes for further analysis: Cd40, Clec7a, Apobec3b, Slc7a7, and Fam22f from pattern B1 and Rwdd3 and Gimap5 from pattern B2. Additionally, these genes were analyzed using quantitative PCR to determine the transcriptional changes strongly related to the development of neuropathic pain; the ipsilateral DRGs (L4-L6) were also collected and analyzed in these rats using qPCR. Conclusion In this work, we confirmed gene expression alterations previously identified by microarray analysis in the spinal cord and analyzed the expression of selected genes in the DRG. Moreover, we reviewed the literature to illustrate the relevance of these findings for neuropathic pain development and therapy. Further studies are needed to elucidate the roles of the individual genes in neuropathic pain and to determine the therapeutic role of minocycline in the rat neuropathic pain model. PMID:25038616

Human psychophysics and rodent spinal neurones exhibit peripheral and central mechanisms of inflammatory pain in the UVB and UVB heat rekindling models.

PubMed

O'Neill, Jessica; Sikandar, Shafaq; McMahon, Stephen B; Dickenson, Anthony H

2015-09-01

Translational research is key to bridging the gaps between preclinical findings and the patients, and a translational model of inflammatory pain will ideally induce both peripheral and central sensitisation, more effectively mimicking clinical pathophysiology in some chronic inflammatory conditions. We conducted a parallel investigation of two models of inflammatory pain, using ultraviolet B (UVB) irradiation alone and UVB irradiation with heat rekindling. We used rodent electrophysiology and human quantitative sensory testing to characterise nociceptive processing in the peripheral and central nervous systems in both models. In both species, UVB irradiation produces peripheral sensitisation measured as augmented evoked activity of rat dorsal horn neurones and increased perceptual responses of human subjects to mechanical and thermal stimuli. In both species, UVB with heat rekindling produces central sensitisation. UVB irradiation alone and UVB with heat rekindling are translational models of inflammation that produce peripheral and central sensitisation, respectively. The predictive value of laboratory models for human pain processing is crucial for improving translational research. The discrepancy between peripheral and central mechanisms of pain is an important consideration for drug targets, and here we describe two models of inflammatory pain that involve ultraviolet B (UVB) irradiation, which can employ peripheral and central sensitisation to produce mechanical and thermal hyperalgesia in rats and humans. We use electrophysiology in rats to measure the mechanically- and thermally-evoked activity of rat spinal neurones and quantitative sensory testing to assess human psychophysical responses to mechanical and thermal stimulation in a model of UVB irradiation and in a model of UVB irradiation with heat rekindling. Our results demonstrate peripheral sensitisation in both species driven by UVB irradiation, with a clear mechanical and thermal hypersensitivity of rat dorsal horn neurones and enhanced perceptual responses of human subjects to both mechanical and thermal stimulation. Additional heat rekindling produces markers of central sensitisation in both species, including enhanced receptive field sizes. Importantly, we also showed a correlation in the evoked activity of rat spinal neurones to human thermal pain thresholds. The parallel results in rats and humans validate the translational use of both models and the potential for such models for preclinical assessment of prospective analgesics in inflammatory pain states. © 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society.

Benefits of Preventive Administration of Chlorella sp. on Visceral Pain and Cystitis Induced by a Single Administration of Cyclophosphamide in Female Wistar Rat.

PubMed

Hidalgo-Lucas, Sophie; Rozan, Pascale; Guérin-Deremaux, Laetitia; Baert, Blandine; Violle, Nicolas; Saniez-Degrave, Marie-Hélène; Bisson, Jean-François

2016-05-01

Chlorella sp. is a green microalgae containing nutrients, vitamins, minerals, and chlorophyll. In some communities, Chlorella sp. is a traditional medicinal plant used for the management of inflammation-related diseases. In a rat model, ROQUETTE Chlorella sp. (RCs) benefits were investigated on visceral pain and associated inflammatory parameters related to cystitis both induced by cyclophosphamide (CYP). RCs was orally administered every day from day 1-16 (250 and 500 mg/kg body weight). Six hours after an intraperitoneal injection of 200 mg/kg body weight of CYP, body temperature, general behavior, food intake, and body weight were recorded. Twenty-four hours after CYP injection, rats were tested in two behavioral tests, an open field and the aversive light stimulus avoidance conditioning test, to evaluate the influence of pain on general activity and learning ability of rats. After euthanasia, bladders were weighed, their thickness was scored, and the urinary hemoglobin was measured. RCs orally administered at the two dosages significantly reduced visceral pain and associated inflammatory parameters related to cystitis both induced by CYP injection, and improved rat behavior. To conclude, RCs demonstrated beneficial effects against visceral pain and cystitis.

Central sensitization and neuropathic features of ongoing pain in a rat model of advanced osteoarthritis

PubMed Central

Havelin, Joshua; Imbert, Ian; Cormier, Jennifer; Allen, Joshua; Porreca, Frank; King, Tamara

2015-01-01

Osteoarthritis (OA) pain is most commonly characterized by movement-triggered joint pain. However, in advanced disease, OA pain becomes persistent, ongoing and resistant to treatment with NSAIDs. The mechanisms underlying ongoing pain in advanced OA are poorly understood. We recently showed that intra-articular (i.a.) injection of monosodium iodoacetate (MIA) into the rat knee joint produces concentration-dependent outcomes. Thus, a low dose of i.a. MIA produces NSAID-sensitive weight asymmetry without evidence of ongoing pain while a high i.a. MIA dose produces weight asymmetry and NSAID-resistant ongoing pain. In the present studies, palpation of the ipsilateral hindlimb of rats treated 14 days previously with high, but not low, doses of i.a. MIA produced FOS expression in the spinal dorsal horn. Inactivation of descending pain facilitatory pathways by microinjection of lidocaine within the rostral ventromedial medulla (RVM) induced conditioned place preference (CPP) selectively in rats treated with the high dose of MIA. CPP to intra-articular lidocaine was blocked by pretreatment with duloxetine (30 mg/kg, i.p. at −30 min). These observations are consistent with the likelihood of a neuropathic component of OA that elicits ongoing, NSAID resistant pain and central sensitization that is mediated, in part, by descending modulatory mechanisms. This model provides a basis for exploration of underlying mechanisms promoting neuropathic components of OA pain and for the identification of mechanisms that may guide drug discovery for treatment of advanced OA pain without the need for joint replacement. PMID:26694132

The use of motion analysis to measure pain-related behaviour in a rat model of degenerative tendon injuries.

PubMed

Fu, Sai-Chuen; Chan, Kai-Ming; Chan, Lai-Shan; Fong, Daniel Tik-Pui; Lui, Po-Yee Pauline

2009-05-15

Chronic tendinopathy is characterized with longstanding activity-related pain with degenerative tendon injuries. An objective tool to measure painful responses in animal models is essential for the development of effective treatment for tendinopathy. Gait analysis has been developed to monitor the inflammatory pain in small animals. We reported the use of motion analysis to monitor gait changes in a rat model of degenerative tendon injury. Intratendinous injection of collagenase into the left patellar tendon of Sprague Dawley rat was used to induce degenerative tendon injury, while an equal volume of saline was injected in the control groups. Motion analyses with a high speed video camera were performed on all rats at pre-injury, 2, 4, 8, 12 or 16 weeks post injection. In the end-point study, the rats were sacrificed to obtain tendon samples for histological examination after motion analyses. In the follow-up study, repeated motion analyses were performed on another group of collagenase-treated and saline-treated rats. The results showed that rats with injured patellar tendon exhibited altered walking gait as compared to the controls. The change in double stance duration in the collagenase-treated rats was reversible by administration of buprenorphrine (p=0.029), it suggested that the detected gait changes were associated with pain. Comparisons of end-point and follow-up studies revealed the confounding effects of training, which led to higher gait velocities and probably a different adaptive response to tendon pain in the trained rats. The results showed that motion analysis could be used to measure activity-related chronic tendon pain.

Morus alba L. Stem Extract Attenuates Pain and Articular Cartilage Damage in the Anterior Cruciate Ligament Transection-Induced Rat Model of Osteoarthritis.

PubMed

Khunakornvichaya, Arada; Lekmeechai, Sujinna; Pham, Phi Phuong; Himakoun, Wanwisa; Pitaksuteepong, Tasana; Morales, Noppawan Phumala; Hemstapat, Warinkarn

2016-01-01

This study was designed to investigate the anti-nociceptive effect of Morus alba stem extract as well as its cartilage protective effect in the anterior cruciate ligament transection (ACLT)-induced rat model of osteoarthritis (OA). The anti-nociceptive effect of this plant extract was determined by measuring hind limb weight bearing, while the severity of cartilage damage to the knee joints was evaluated using the modified Mankin grading system. Oral administration of M. alba stem extract (56 and 560 mg/kg) significantly attenuated joint pain as indicated by a significant (p < 0.05) increase in the values of percent weight borne on the operated hind limb for the OA-induced groups that received M. alba stem extract at 56 and 560 mg/kg when compared to those of the vehicle-treated OA-induced group. In addition, a significant improvement in the Mankin score was also observed in rats treated with 560 mg/kg M. alba stem extract, which was in agreement with its pain-relieving effect. The results showed that M. alba stem extract exhibited an anti-nociceptive effect as well as cartilage protection in the ACLT-induced rat model of OA, supporting its potential use as a therapeutic treatment for OA. © 2016 S. Karger AG, Basel.

Pressure application measurement (PAM): a novel behavioural technique for measuring hypersensitivity in a rat model of joint pain.

PubMed

Barton, Nicola J; Strickland, Iain T; Bond, Susan M; Brash, Harry M; Bate, Simon T; Wilson, Alex W; Chessell, Iain P; Reeve, Alison J; McQueen, Daniel S

2007-06-15

Chronic joint pain affects physical well being and can lead to severe psychological and social problems, therefore successful long-term management is highly sought-after. No current behavioural measures of pain used in pre-clinical models mimic the clinical dolorimeter, which provides an objective measure of joint hypersensitivity. In this study we aim to use a novel behavioural readout alongside an established measure to mimic the multifactorial measurements taken in the clinic. Using the pressure application measurement (PAM) device a gradually increasing squeeze was applied across the knee joint of rats until the animal gave an indication of pain or discomfort. PAM and the incapacitance tester were used to detect joint hypersensitivity in a well-established rodent model of adjuvant-induced arthritis. Subsequently, the analgesic effects of prednisolone (1, 3 or 10 mg kg(-1)), morphine (3 mg kg(-1)) and celecoxib (15 mg kg(-1)) were assessed. Both PAM and the incapacitance tester detected a reversal of hypersensitivity 1h post-drug administration. Furthermore, the two readouts were highly correlated, and power analysis indicated that PAM was highly reproducible. In conclusion, PAM provides a novel, accurate behavioural tool for detecting a primary mechanical hypersensitivity in a rat model of chronic inflammatory joint pain.

Differential expression of miRNAs in the nervous system of a rat model of bilateral sciatic nerve chronic constriction injury.

PubMed

Li, Haixia; Shen, Le; Ma, Chao; Huang, Yuguang

2013-07-01

Chronic neuropathic pain is associated with global changes in gene expression in different areas of the nociceptive pathway. MicroRNAs (miRNAs) are small (~22 nt long) non-coding RNAs, which are able to regulate hundreds of different genes post-transcriptionally. The aim of this study was to determine the miRNA expression patterns in the different regions of the pain transmission pathway using a rat model of human neuropathic pain induced by bilateral sciatic nerve chronic constriction injury (bCCI). Using microarray analysis and quantitative reverse transcriptase-PCR, we observed a significant upregulation in miR-341 expression in the dorsal root ganglion (DRG), but not in the spinal dorsal horn (SDH), hippocampus or anterior cingulate cortex (ACC), in the rats with neuropathic pain compared to rats in the naïve and sham-operated groups. By contrast, the expression of miR-203, miR-181a-1* and miR-541* was significantly reduced in the SDH of rats with neuropathic pain. Our data indicate that miR-341 is upregulated in the DRG, whereas miR-203, miR-181a-1* and miR-541* are downregulated in the SDH under neuropathic pain conditions. Thus, the differential expression of miRNAs in the nervous system may play a role in the development of chronic pain. These observations may aid in the development of novel treatment methods for neuropathic pain, which may involve miRNA gene therapy in local regions.

Anti-allodynic effect of mangiferin in neuropathic rats: Involvement of nitric oxide-cyclic GMP-ATP sensitive K+ channels pathway and serotoninergic system.

PubMed

de Los Monteros-Zuñiga, Antonio Espinosa; Izquierdo, Teresa; Quiñonez-Bastidas, Geovanna Nallely; Rocha-González, Héctor Isaac; Godínez-Chaparro, Beatriz

The neurobiology of neuropathic pain is caused by injury in the central or peripheral nervous system. Recent evidence points out that mangiferin shows anti-nociceptive effect in inflammatory pain. However, its role in inflammatory and neuropathic pain and the possible mechanisms of action are not yet established. The purpose of this study was to determine the possible anti-allodynic effect of mangiferin in rats with spinal nerve ligation (SNL). Furthermore, we sought to investigate the possible mechanisms of action that contribute to these effects. Mechanical allodynia to stimulation with the von Frey filaments was measured by the up and down method. Intrathecal administration of mangiferin prevented, in a dose-dependent fashion, SNL-induced mechanical allodynia. Mangiferin-induced anti-allodynia was prevented by the intrathecal administration of L-NAME (100μg/rat, non-selective nitric oxide synthase inhibitor), ODQ (10μg/rat, inhibitor of guanylate-cyclase) and glibenclamide (50μg/rat, channel blocker of ATP-sensitive K + channels). Moreover, methiothepin (30μg/rat, non-selective 5-HT receptor antagonist), WAY-100635 (6μg/rat, selective 5-HT 1A receptor antagonist), SB-224289 (5μg/rat, selective 5-HT 1B receptor antagonist), BRL-15572 (4μg/rat, selective 5-HT 1D receptor antagonist) and SB-659551 (6μg/rat, selective 5-HT 5A receptor antagonist), but not naloxone (50μg/rat, non-selective opioid receptor antagonist), were able to prevent mangiferin-induced anti-allodynic effect. These data suggest that the anti-allodynic effect induced by mangiferin is mediated at least in part by the serotoninergic system, involving the activation of 5-HT 1A/1B/1D/5A receptors, as well as the nitric oxide-cyclic GMP-ATP-sensitive K + channels pathway, but not by the opioidergic system, in the SNL model of neuropathic pain in rats. Copyright © 2016. Published by Elsevier Inc.

Differential Effectiveness of Clinically-Relevant Analgesics in a Rat Model of Chemotherapy-Induced Mucositis.

PubMed

Whittaker, Alexandra L; Lymn, Kerry A; Wallace, Georgia L; Howarth, Gordon S

2016-01-01

Chemotherapy-induced intestinal mucositis is characterized by pain and a pro-inflammatory tissue response. Rat models are frequently used in mucositis disease investigations yet little is known about the presence of pain in these animals, the ability of analgesics to ameliorate the condition, or the effect that analgesic administration may have on study outcomes. This study investigated different classes of analgesics with the aim of determining their analgesic effects and impact on research outcomes of interest in a rat model of mucositis. Female DA rats were allocated to 8 groups to include saline and chemotherapy controls (n = 8). Analgesics included opioid derivatives (buprenorphine; 0.05mg/kg and tramadol 12.5mg/kg) and NSAID (carprofen; 15mg/kg) in combination with either saline or 5-Fluorouracil (5-FU; 150mg/kg). Research outcome measures included daily clinical parameters, pain score and gut histology. Myeloperoxidase assay was performed to determine gut inflammation. At the dosages employed, all agents had an analgesic effect based on behavioural pain scores. Jejunal myeloperoxidase activity was significantly reduced by buprenorphine and tramadol in comparison to 5-FU control animals (53%, p = 0.0004 and 58%, p = 0.0001). Carprofen had no ameliorating effect on myeloperoxidase levels. None of the agents reduced the histological damage caused by 5-FU administration although tramadol tended to increase villus length even when administered to healthy animals. These data provide evidence that carprofen offers potential as an analgesic in this animal model due to its pain-relieving efficacy and minimal effect on measured parameters. This study also supports further investigation into the mechanism and utility of opioid agents in the treatment of chemotherapy-induced mucositis.

Electroacupuncture alleviates affective pain in an inflammatory pain rat model

PubMed Central

Zhang, Yu; Meng, Xianze; Li, Aihui; Xin, Jiajia; Berman, Brian M.; Lao, Lixing; Tan, Ming; Ren, Ke; Zhang, Rui-Xin

2011-01-01

Pain has both sensory-discriminative and emotional-affective dimensions. Previous studies demonstrate that electroacupuncture (EA) alleviates the sensory dimension but do not address the affective. An inflammatory pain rat model, produced by a complete Freund adjuvant (CFA) injection into the hind paw, was combined with a conditioned place avoidance (CPA) test to determine whether EA inhibits spontaneous pain-induced affective response and, if so, to study the possibility that rostral anterior cingulate cortex (rACC) opioids underlie this effect. Male Sprague-Dawley rats (250–275g, Harlan) were used. The rats showed place aversion (i.e. affective pain) by spending less time in a pain-paired compartment after conditioning than during a preconditioning test. Systemic non-analgesic morphine (0.5 and 1.0 mg/ kg, i.p.) inhibited the affective reaction, suggesting that the affective dimension is underpinned by mechanisms different from those of the sensory dimension of pain. Morphine at 0.5 and at 1 mg/kg did not induce reward. Rats given EA treatment before pain-paired conditioning at GB 30 showed no aversion to the pain-paired compartment, indicating that EA inhibited the affective dimension. EA treatment did not produce reward or aversive effect. Intra-rACC administration of D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr amide (CTOP), a selective mu opioid receptor antagonist, but not norbinaltorphimine (nor-BNI), a selective kappa opioid receptor antagonist, blocked EA inhibition of the affective dimension. These data demonstrate that EA activates opioid receptors in the rACC to inhibit pain-induced affective responses and that EA may be an effective therapy for both the sensory-discriminative and the affective dimensions of pain. PMID:22323370

AMPAkines have novel analgesic properties in rat models of persistent neuropathic and inflammatory pain.

PubMed

Le, Alexander M; Lee, Michelle; Su, Chen; Zou, Anthony; Wang, Jing

2014-11-01

Novel analgesics that do not suppress the respiratory drive are urgently needed. Glutamate signaling through α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors plays important roles in central pain circuits. AMPAkines augment AMPA receptor function and have been shown to stimulate the respiratory drive to oppose opioid-induced hypoventilation. However, their role in chronic pain states remains unknown. The authors studied AMPAkines (CX546 and CX516) in rat spared nerve injury (SNI) model of neuropathic pain and Complete Freund's Adjuvant (CFA) model of inflammatory pain. They measured the effect of AMPAkines on mechanical and cold allodynia. They also evaluated their effect on depressive symptoms of pain using the forced swim test, as time of immobility on this test has been used as a measure for behavioral despair, a feature of depression. The authors found that CX546, compared with dimethyl sulfoxide (DMSO) control, reduced both mechanical and sensory allodynia in SNI (DMSO group, n = 9; CX546 group, n = 11) and CFA models (both DMSO and CX546 groups, n = 9). They found that CX546, compared with control, also reduced depressive symptoms of pain by decreasing immobility on the forced swim test in both SNI (both DMSO and CX546 groups, n = 8) and CFA models (both DMSO and CX546 groups, n = 10). Finally, they found that CX516, compared with control, also reduced mechanical and cold allodynia in the SNI model (both DMSO and CX516 groups, n = 10). AMPAkines alleviate pain hypersensitivity as well as depression-like behavior associated with long-lasting nerve injury and inflammatory insult.

Effects of exogenous galanin on neuropathic pain state and change of galanin and its receptors in DRG and SDH after sciatic nerve-pinch injury in rat.

PubMed

Xu, Xiaofeng; Yang, Xiangdong; Zhang, Ping; Chen, Xiuying; Liu, Huaxiang; Li, Zhenzhong

2012-01-01

A large number of neuroanatomical, neurophysiologic, and neurochemical mechanisms are thought to contribute to the development and maintenance of neuropathic pain. However, mechanisms responsible for neuropathic pain have not been completely delineated. It has been demonstrated that neuropeptide galanin (Gal) is upregulated after injury in the dorsal root ganglion (DRG) and spinal dorsal horn (SDH) where it plays a predominantly antinociceptive role. In the present study, sciatic nerve-pinch injury rat model was used to determine the effects of exogenous Gal on the expression of the Gal and its receptors (GalR1, GalR2) in DRG and SDH, the alterations of pain behavior, nerve conduction velocity (NCV) and morphology of sciatic nerve. The results showed that exogenous Gal had antinociceptive effects in this nerve-pinch injury induced neuropathic pain animal model. It is very interesting that Gal, GalR1 and GalR2 change their expression greatly in DRG and SDH after nerve injury and intrathecal injection of exougenous Gal. Morphological investigation displays a serious damage after nerve-pinch injury and an amendatory regeneration after exogenous Gal treatment. These findings imply that Gal, via activation of GalR1 and/or GalR2, may have neuroprotective effects in reducing neuropathic pain behaviors and improving nerve regeneration after nerve injury.

Wen-Luo-Tong Prevents Glial Activation and Nociceptive Sensitization in a Rat Model of Oxaliplatin-Induced Neuropathic Pain.

PubMed

Deng, Bo; Jia, Liqun; Pan, Lin; Song, Aiping; Wang, Yuanyuan; Tan, Huangying; Xiang, Qing; Yu, Lili; Ke, Dandan

2016-01-01

One of the main dose-limiting complications of the chemotherapeutic agent oxaliplatin (OXL) is painful neuropathy. Glial activation and nociceptive sensitization may be responsible for the mechanism of neuropathic pain. The Traditional Chinese Medicine (TCM) Wen-luo-tong (WLT) has been widely used in China to treat chemotherapy induced neuropathic pain. However, there is no study on the effects of WLT on spinal glial activation induced by OXL. In this study, a rat model of OXL-induced chronic neuropathic pain was established and WLT was administrated. Pain behavioral tests and morphometric examination of dorsal root ganglia (DRG) were conducted. Glial fibrillary acidic protein (GFAP) immunostaining was performed, glial activation was evaluated, and the excitatory neurotransmitter substance P (SP) and glial-derived proinflammatory cytokine tumor necrosis factor-α (TNF-α) were analyzed. WLT treatment alleviated OXL-induced mechanical allodynia and mechanical hyperalgesia. Changes in the somatic, nuclear, and nucleolar areas of neurons in DRG were prevented. In the spinal dorsal horn, hypertrophy and activation of GFAP-positive astrocytes were averted, and the level of GFAP mRNA decreased significantly. Additionally, TNF-α mRNA and protein levels decreased. Collectively, these results indicate that WLT reversed both glial activation in the spinal dorsal horn and nociceptive sensitization during OXL-induced chronic neuropathic pain in rats.

Glycinergic dysfunction in a subpopulation of dorsal horn interneurons in a rat model of neuropathic pain

PubMed Central

Imlach, Wendy L.; Bhola, Rebecca F.; Mohammadi, Sarasa A.; Christie, Macdonald J.

2016-01-01

The development of neuropathic pain involves persistent changes in signalling within pain pathways. Reduced inhibitory signalling in the spinal cord following nerve-injury has been used to explain sensory signs of neuropathic pain but specific circuits that lose inhibitory input have not been identified. This study shows a specific population of spinal cord interneurons, radial neurons, lose glycinergic inhibitory input in a rat partial sciatic nerve ligation (PNL) model of neuropathic pain. Radial neurons are excitatory neurons located in lamina II of the dorsal horn, and are readily identified by their morphology. The amplitude of electrically-evoked glycinergic inhibitory post-synaptic currents (eIPSCs) was greatly reduced in radial neurons following nerve-injury associated with increased paired-pulse ratio. There was also a reduction in frequency of spontaneous IPSCs (sIPSCs) and miniature IPSCs (mIPSC) in radial neurons without significantly affecting mIPSC amplitude. A subtype selective receptor antagonist and western blots established reversion to expression of the immature glycine receptor subunit GlyRα2 in radial neurons after PNL, consistent with slowed decay times of IPSCs. This study has important implications as it identifies a glycinergic synaptic connection in a specific population of dorsal horn neurons where loss of inhibitory signalling may contribute to signs of neuropathic pain. PMID:27841371

Coregulation of endoplasmic reticulum stress and oxidative stress in neuropathic pain and disinhibition of the spinal nociceptive circuitry.

PubMed

Ge, Yanhu; Jiao, Yingfu; Li, Peiying; Xiang, Zhenghua; Li, Zhi; Wang, Long; Li, Wenqian; Gao, Hao; Shao, Jiayun; Wen, Daxiang; Yu, Weifeng

2018-05-01

The accumulation of unfolded or misfolded proteins in the endoplasmic reticulum (ER) lumen leads to ER stress, which is related to cellular reactive oxygen species production. Neuropathic pain may result from spinal dorsal horn (SDH) ER stress. In this study, we examined the cause-effect relationship between ER stress and neuropathic pain using the spinal nerve ligation (SNL) rat model. We showed that ER stress was mutually promotive with oxidative stress during the process. We also tested the hypothesis that spinal sensitization arose from reduced activities of GABA-ergic interneurons and that spinal sensitization was mediated by SDH ER stress. Other important findings in this study including the following: (1) nociceptive behavior was alleviated in SNL rat as long as tauroursodeoxycholic acid injections were repeated to inhibit ER stress; (2) inducing SDH ER stress in healthy rat resulted in mechanical hyperalgesia; (3) blocking protein disulfide isomerase pharmacologically reduced ER stress and nociceptive behavior in SNL rat; (4) cells in the dorsal horn with elevated ER stress were mainly neurons; and (5) whole-cell recordings made in slide preparations revealed significant inhibition of GABA-ergic interneuron activity in the dorsal horn with ER stress vs in the healthy dorsal horn. Taken together, results of the current study demonstrate that coregulation of ER stress and oxidative stress played an important role in neuropathic pain process. Inhibiting SDH ER stress could be a potential novel strategy to manage neuropathic pain.

Restoring Spinal Noradrenergic Inhibitory Tone Attenuates Pain Hypersensitivity in a Rat Model of Parkinson's Disease

PubMed Central

Wang, Bing; Chen, Li-Hua

2016-01-01

In the present study, we investigated whether restoring descending noradrenergic inhibitory tone can attenuate pain in a PD rat model, which was established by stereotaxic infusion of 6-hydroxydopamine (6-OHDA) into the bilateral striatum (CPu). PD rats developed thermal and mechanical hypersensitivity at the 4th week after surgery. HPLC analysis showed that NE content, but not dopamine or 5-HT, significantly decreased in lumbar spinal cord in PD rats. Additional noradrenergic depletion by injection of N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) aggravated pain hypersensitivity in PD rats. At the 5th week after injection of 6-OHDA, systemic treatment with pharmacological norepinephrine (NE) precursor droxidopa (L-DOPS) or α2 adrenoceptor agonist clonidine significantly attenuated thermal and mechanical pain hypersensitivity in PD rats. Furthermore, application of norepinephrine (NE) and 5-hydroxytryptamine (5-HT) reuptake inhibitors duloxetine, but not 5-HT selective reuptake inhibitors sertraline, significantly inhibited thermal and mechanical pain hypersensitivity in PD rats. Systemic administration of Madopar (L-DOPA) or the D2/D3 agonist pramipexole slightly inhibited the thermal, but not mechanical, hypersensitivity in PD rats. Thus, our study revealed that impairment of descending noradrenergic system may play a key role in PD-associated pain and restoring spinal noradrenergic inhibitory tone may serve as a novel strategy to manage PD-associated pain. PMID:27747105

Localized Sympathectomy Reduces Mechanical Hypersensitivity by Restoring Normal Immune Homeostasis in Rat Models of Inflammatory Pain

PubMed Central

Xie, Wenrui; Chen, Sisi; Strong, Judith A.; Li, Ai-Ling; Lewkowich, Ian P.

2016-01-01

Some forms of chronic pain are maintained or enhanced by activity in the sympathetic nervous system (SNS), but attempts to model this have yielded conflicting findings. The SNS has both pro- and anti-inflammatory effects on immunity, confounding the interpretation of experiments using global sympathectomy methods. We performed a “microsympathectomy” by cutting the ipsilateral gray rami where they entered the spinal nerves near the L4 and L5 DRG. This led to profound sustained reductions in pain behaviors induced by local DRG inflammation (a rat model of low back pain) and by a peripheral paw inflammation model. Effects of microsympathectomy were evident within one day, making it unlikely that blocking sympathetic sprouting in the local DRGs or hindpaw was the sole mechanism. Prior microsympathectomy greatly reduced hyperexcitability of sensory neurons induced by local DRG inflammation observed 4 d later. Microsympathectomy reduced local inflammation and macrophage density in the affected tissues (as indicated by paw swelling and histochemical staining). Cytokine profiling in locally inflamed DRG showed increases in pro-inflammatory Type 1 cytokines and decreases in the Type 2 cytokines present at baseline, changes that were mitigated by microsympathectomy. Microsympathectomy was also effective in reducing established pain behaviors in the local DRG inflammation model. We conclude that the effect of sympathetic fibers in the L4/L5 gray rami in these models is pro-inflammatory. This raises the possibility that therapeutic interventions targeting gray rami might be useful in some chronic inflammatory pain conditions. SIGNIFICANCE STATEMENT Sympathetic blockade is used for many pain conditions, but preclinical studies show both pro- and anti-nociceptive effects. The sympathetic nervous system also has both pro- and anti-inflammatory effects on immune tissues and cells. We examined effects of a very localized sympathectomy. By cutting the gray rami to the spinal nerves near the lumbar sensory ganglia, we avoided widespread sympathetic denervation. This procedure profoundly reduced mechanical pain behaviors induced by a back pain model and a model of peripheral inflammatory pain. One possible mechanism was reduction of inflammation in the sympathetically denervated regions. This raises the possibility that therapeutic interventions targeting gray rami might be useful in some inflammatory conditions. PMID:27535916

Merging the Structural Motifs of Functionalized Amino Acids and α-Aminoamides: Compounds with Significant Anticonvulsant Activities

PubMed Central

Salomé, Christophe; Salomé-Grosjean, Elise; Stables, James P.; Kohn, Harold

2010-01-01

Functional amino acids (FAAs) and α-aminoamides (AAAs) are two classes of antiepileptic drugs (AEDs) that exhibit pronounced anticonvulsant activities. We combined key structural pharmacophores present in FAAs and AAAs to generate a new series of compounds and document that select compounds exhibit activity superior to either the prototypical FAA (lacosamide) or the prototypical AAA (safinamide) in the maximal electroshock (MES) seizure model in rats. A representative compound, (R)-N-4′-((3″-fluoro)benzyloxy)benzyl 2-acetamido-3-methoxypropionamide ((R)-10), was tested in the MES (mice, ip), MES (rat, po), psychomotor 6 Hz (32 mA) (mice, ip), and hippocampal kindled (rat, ip) seizure tests providing excellent protection with ED50 values of 13, 14, ~10 mg/kg, and 12 mg/kg, respectively. In the rat sciatic nerve ligation model (ip), (R)-10 (12 mg/kg) provided an 11.2-fold attenuation of mechanical allodynia. In the mouse biphasic formalin pain model (ip), (R)-10 (15 mg/kg) reduced pain responses in the acute and the chronic inflammatory phases. PMID:20394379

Merging the structural motifs of functionalized amino acids and alpha-aminoamides: compounds with significant anticonvulsant activities.

PubMed

Salomé, Christophe; Salomé-Grosjean, Elise; Stables, James P; Kohn, Harold

2010-05-13

Functional amino acids (FAAs) and alpha-aminoamides (AAAs) are two classes of antiepileptic drugs (AEDs) that exhibit pronounced anticonvulsant activities. We combined key structural pharmacophores present in FAAs and AAAs to generate a new series of compounds and document that select compounds exhibit activity superior to either the prototypical FAA (lacosamide) or the prototypical AAA (safinamide) in the maximal electroshock (MES) seizure model in rats. A representative compound, (R)-N-4'-((3''-fluoro)benzyloxy)benzyl 2-acetamido-3-methoxypropionamide ((R)-10), was tested in the MES (mice, ip), MES (rat, po), psychomotor 6 Hz (32 mA) (mice, ip), and hippocampal kindled (rat, ip) seizure tests providing excellent protection with ED(50) values of 13, 14, approximately 10 mg/kg, and 12 mg/kg, respectively. In the rat sciatic nerve ligation model (ip), (R)-10 (12 mg/kg) provided an 11.2-fold attenuation of mechanical allodynia. In the mouse biphasic formalin pain model (ip), (R)-10 (15 mg/kg) reduced pain responses in the acute and the chronic inflammatory phases.

The Rat Grimace Scale: A partially automated method for quantifying pain in the laboratory rat via facial expressions

PubMed Central

2011-01-01

We recently demonstrated the utility of quantifying spontaneous pain in mice via the blinded coding of facial expressions. As the majority of preclinical pain research is in fact performed in the laboratory rat, we attempted to modify the scale for use in this species. We present herein the Rat Grimace Scale, and show its reliability, accuracy, and ability to quantify the time course of spontaneous pain in the intraplantar complete Freund's adjuvant, intraarticular kaolin-carrageenan, and laparotomy (post-operative pain) assays. The scale's ability to demonstrate the dose-dependent analgesic efficacy of morphine is also shown. In addition, we have developed software, Rodent Face Finder®, which successfully automates the most labor-intensive step in the process. Given the known mechanistic dissociations between spontaneous and evoked pain, and the primacy of the former as a clinical problem, we believe that widespread adoption of spontaneous pain measures such as the Rat Grimace Scale might lead to more successful translation of basic science findings into clinical application. PMID:21801409

Effect of styrene maleic acid WIN55,212-2 micelles on neuropathic pain in a rat model.

PubMed

Linsell, Oliver; Brownjohn, Philip W; Nehoff, Hayley; Greish, Khaled; Ashton, John C

2015-05-01

Cannabinoid receptor agonists are moderately effective at reducing neuropathic pain but are limited by psychoactivity. We developed a styrene maleic acid (SMA) based on the cannabinoid WIN 55,212-2 (WIN) and tested in a rat model of neuropathic pain and in the rotarod test. We hypothesized that miceller preparation can ensure prolonged plasma half-life being above the renal threshold of excretion. Furthermore, SMA-WIN could potentially reduce the central nervous system effects of encapsulated WIN by limiting its transport across the blood-brain barrier. Using the chronic constriction injury model of sciatic neuropathy, the SMA-WIN micelles were efficacious in the treatment of neuropathic pain for a prolonged period compared to control (base WIN). Attenuation of chronic constriction injury-induced mechanical allodynia occurred for up to 8 h at a dose of 11.5 mg/kg of SMA-WIN micelles. To evaluate central effects on motor function, the rotarod assessment was utilized. Results showed initial impairment caused by SMA-WIN micelles to be identical to WIN control for up to 1.5 h. Despite this, the SMA-WIN micelle formulation was able to produce prolonged analgesia over a time when there was decreased impairment in the rotarod test compared with base WIN.

Spontaneous Trigeminal Allodynia in Rats: A Model of Primary Headache

PubMed Central

Oshinsky, Michael L.; Sanghvi, Menka M.; Maxwell, Christina R.; Gonzalez, Dorian; Spangenberg, Rebecca J.; Cooper, Marnie; Silberstein, Stephen D.

2014-01-01

Animal models are essential for studying the pathophysiology of headache disorders and as a screening tool for new therapies. Most animal models modify a normal animal in an attempt to mimic migraine symptoms. They require manipulation to activate the trigeminal nerve or dural nociceptors. At best, they are models of secondary headache. No existing model can address the fundamental question: How is a primary headache spontaneously initiated? In the process of obtaining baseline periorbital von Frey thresholds in a wild-type Sprague-Dawley rat, we discovered a rat with spontaneous episodic trigeminal allodynia (manifested by episodically changing periorbital pain threshold). Subsequent mating showed that the trait is inherited. Animals with spontaneous trigeminal allodynia allow us to study the pathophysiology of primary recurrent headache disorders. To validate this as a model for migraine, we tested the effects of clinically proven acute and preventive migraine treatments on spontaneous changes in rat periorbital sensitivity. Sumatriptan, ketorolac, and dihydroergotamine temporarily reversed the low periorbital pain thresholds. Thirty days of chronic valproic acid treatment prevented spontaneous changes in trigeminal allodynia. After discontinuation, the rats returned to their baseline of spontaneous episodic threshold changes. We also tested the effects of known chemical human migraine triggers. On days when the rats did not have allodynia and showed normal periorbital von Frey thresholds, glycerol trinitrate and calcitonin gene related peptide induced significant decreases in the periorbital pain threshold. This model can be used as a predictive model for drug development and for studies of putative biomarkers for headache diagnosis and treatment. PMID:22963523

Correlation of intact sensibility and neuropathic pain-related behaviors in eight inbred and outbred rat strains and selection lines.

PubMed

Shir, Y; Zeltser, R; Vatine, J J; Carmi, G; Belfer, I; Zangen, A; Overstreet, D; Raber, P; Seltzer, Z

2001-02-01

In some rat strains, total hindpaw denervation triggers autotomy, a behavior of self mutilation presumably related to neuropathic pain. Partial sciatic ligation (PSL) in rats produces tactile allodynia and heat hyperalgesia but not autotomy. Our aims in this study were to examine: (1) whether sensibility of intact rats to noxious and non-noxious stimuli is strain-dependent; (2) whether sensibility of intact rats could predict levels of autotomy, or of allodynia and hyperalgesia in the PSL model; and (3) whether autotomy levels are correlated with levels of allodynia or hyperalgesia. Here we report that in two inbred rat strains (Lewis and Fisher 344), two outbred rat strains (Sabra and Sprague-Dawley) and four selection lines of rats (Genetically Epilepsy-Prone Rats, High Autotomy, Low Autotomy and Flinders Sensitive Line), tactile sensitivity and response duration to noxious heat of intact animals were strain-dependent. Levels of autotomy following hindpaw denervation and of allodynia and hyperalgesia in the PSL model were also strain-dependent. Thus, these traits are determined in part by genetic factors. Sensory sensibility of intact rats was not correlated with levels of autotomy following total denervation, or allodynia and hyperalgesia following partial denervation. We suggest that preoperative sensibility of intact rats is not a predictor of levels of neuropathic disorders following nerve injury. Likewise, no correlation was found between autotomy, allodynia and hyperalgesia, suggesting that neuropathic pain behaviors triggered by nerve injury of different etiologies are mediated by differing mechanisms.

Activation of Corticostriatal Circuitry Relieves Chronic Neuropathic Pain

PubMed Central

Lee, Michelle; Manders, Toby R.; Eberle, Sarah E.; Su, Chen; D'amour, James; Yang, Runtao; Lin, Hau Yueh; Deisseroth, Karl; Froemke, Robert C.

2015-01-01

Neural circuits that determine the perception and modulation of pain remain poorly understood. The prefrontal cortex (PFC) provides top-down control of sensory and affective processes. While animal and human imaging studies have shown that the PFC is involved in pain regulation, its exact role in pain states remains incompletely understood. A key output target for the PFC is the nucleus accumbens (NAc), an important component of the reward circuitry. Interestingly, recent human imaging studies suggest that the projection from the PFC to the NAc is altered in chronic pain. The function of this corticostriatal projection in pain states, however, is not known. Here we show that optogenetic activation of the PFC produces strong antinociceptive effects in a rat model (spared nerve injury model) of persistent neuropathic pain. PFC activation also reduces the affective symptoms of pain. Furthermore, we show that this pain-relieving function of the PFC is likely mediated by projections to the NAc. Thus, our results support a novel role for corticostriatal circuitry in pain regulation. PMID:25834050

Adolescent peer-rejection persistently alters pain perception and CB1 receptor expression in female rats.

PubMed

Schneider, Peggy; Hannusch, Christin; Schmahl, Christian; Bohus, Martin; Spanagel, Rainer; Schneider, Miriam

2014-02-01

Peer-interactions are particularly important during adolescence and teenagers display enhanced sensitivity toward rejection by peers. Social rejection has been shown to induce alterations in pain perception in humans. However, the neurobiological consequences of adolescent social rejection have yet to be extensively characterized, and no appropriate animal model is available. Here, we propose inadequate playful interactions in adolescent rats as a novel animal model for social peer-rejection and examine potential long-term consequences into adulthood. Acute social pairing of female adolescent Wistar rats with an age-matched rat from the less playful Fischer344 strain was found to alter social play and decrease pain reactivity, indicating Fischer rats as inadequate social partners for Wistar animals. Therefore, in a second experiment, adolescent female Wistar rats were either reared with another Wistar rat (adequate social rearing; control) or with a Fischer rat (inadequate social rearing; play-deprived). Beginning on day 50, all Wistar rats were group housed with same-strain partners and tested for behavioral, neurobiological and endocrine differences in adulthood. Playful peer-interactions were decreased during adolescence in play-deprived animals, without affecting social contact behavior. Consequently, adult play-deprived rats showed decreased pain sensitivity and increased startle reactivity compared to controls, but did not differ in activity, anxiety-related behavior or social interaction. Both groups also differed in their endocrine stress-response, and expression levels of the cannabinoid CB1 receptor were increased in the thalamus, whereas FAAH levels were decreased in the amygdala. The present animal model therefore represents a novel approach to assess the long-term consequences of peer-rejection during adolescence. Copyright © 2013 Elsevier B.V. and ECNP. All rights reserved.

Central Sensitization and Neuropathic Features of Ongoing Pain in a Rat Model of Advanced Osteoarthritis.

PubMed

Havelin, Joshua; Imbert, Ian; Cormier, Jennifer; Allen, Joshua; Porreca, Frank; King, Tamara

2016-03-01

Osteoarthritis (OA) pain is most commonly characterized by movement-triggered joint pain. However, in advanced disease, OA pain becomes persistent, ongoing and resistant to treatment with nonsteroidal anti-inflammatory drugs (NSAIDs). The mechanisms underlying ongoing pain in advanced OA are poorly understood. We recently showed that intra-articular (i.a.) injection of monosodium iodoacetate (MIA) into the rat knee joint produces concentration-dependent outcomes. Thus, a low dose of i.a. MIA produces NSAID-sensitive weight asymmetry without evidence of ongoing pain and a high i.a. MIA dose produces weight asymmetry and NSAID-resistant ongoing pain. In the present study, palpation of the ipsilateral hind limb of rats treated 14 days previously with high, but not low, doses of i.a. MIA produced expression of the early oncogene, FOS, in the spinal dorsal horn. Inactivation of descending pain facilitatory pathways using a microinjection of lidocaine within the rostral ventromedial medulla induced conditioned place preference selectively in rats treated with the high dose of MIA. Conditioned place preference to intra-articular lidocaine was blocked by pretreatment with duloxetine (30 mg/kg, intraperitoneally at -30 minutes). These observations are consistent with the likelihood of a neuropathic component of OA that elicits ongoing, NSAID-resistant pain and central sensitization that is mediated, in part, by descending modulatory mechanisms. This model provides a basis for exploration of underlying mechanisms promoting neuropathic components of OA pain and for the identification of mechanisms that might guide drug discovery for treatment of advanced OA pain without the need for joint replacement. Difficulty in managing advanced OA pain often results in joint replacement therapy in these patients. Improved understanding of mechanisms driving NSAID-resistant ongoing OA pain might facilitate development of alternatives to joint replacement therapy. Our findings suggest that central sensitization and neuropathic features contribute to NSAID-resistant ongoing OA joint pain. Copyright © 2016 American Pain Society. Published by Elsevier Inc. All rights reserved.

Mechanisms mediating vibration-induced chronic musculoskeletal pain analyzed in the rat.

PubMed

Dina, Olayinka A; Joseph, Elizabeth K; Levine, Jon D; Green, Paul G

2010-04-01

While occupational exposure to vibration is a common cause of acute and chronic musculoskeletal pain, eliminating exposure produces limited symptomatic improvement, and reexposure precipitates rapid recurrence or exacerbation. To evaluate mechanisms underlying these pain syndromes, we have developed a model in the rat, in which exposure to vibration (60-80Hz) induces, in skeletal muscle, both acute mechanical hyperalgesia as well as long-term changes characterized by enhanced hyperalgesia to a proinflammatory cytokine or reexposure to vibration. Exposure of a hind limb to vibration-produced mechanical hyperalgesia measured in the gastrocnemius muscle of the exposed hind limb, which persisted for approximately 2 weeks. When nociceptive thresholds had returned to baseline, exposure to a proinflammatory cytokine or reexposure to vibration produced markedly prolonged hyperalgesia. The chronic prolongation of vibration- and cytokine-hyperalgesia was prevented by spinal intrathecal injection of oligodeoxynucleotide (ODN) antisense to protein kinase Cepsilon, a second messenger in nociceptors implicated in the induction and maintenance of chronic pain. Vibration-induced hyperalgesia was inhibited by spinal intrathecal administration of ODN antisense to receptors for the type-1 tumor necrosis factor-alpha (TNFalpha) receptor. Finally, in TNFalpha-pretreated muscle, subsequent vibration-induced hyperalgesia was markedly prolonged. These studies establish a model of vibration-induced acute and chronic musculoskeletal pain, and identify the proinflammatory cytokine TNFalpha and the second messenger protein kinase Cepsilon as targets against which therapies might be directed to prevent and/or treat this common and very debilitating chronic pain syndrome. Copyright 2010 American Pain Society. All rights reserved.

Towards Development of a Dermal Pain Model: In Vitro Activation of Rat and Human Transient Receptor Potential Ankyrin Repeat 1 and Safe Dermal Injection of o-Chlorobenzylidene Malononitrile to Rat.

PubMed

Annas, Anita; Berg, Anna-Lena; Nyman, Eva; Meijer, Thomas; Lundgren, Viveka; Franzén, Bo; Ståhle, Lars

2015-12-01

During clinical development of analgesics, it is important to have access to pharmacologically specific human pain models. o-Chlorobenzylidene malononitrile (CS) is a selective and potent agonist of the transient receptor potential ankyrin repeat 1 (TRPA1), which is a transducer molecule in nociceptors sensing reactive chemical species. While CS has been subject to extensive toxicological investigations in animals and human beings, its effects on intradermal or subcutaneous injection have not previously been reported. We have investigated the potential of CS to be used as an agonist on TRPA1 in human experimental pain studies. A calcium influx assay was used to confirm the capacity of CS to activate TRPA1 with >100,000 times the selectivity over the transient receptor potential vanilloid receptor 1. CS dose-dependently (EC50 0.9 μM) released calcitonin gene-related peptide in rat dorsal root ganglion cultures, supporting involvement in pain signalling. In a local tolerance study, injection of a single intradermal dose of 20 mM CS to rats resulted in superficial, circular crusts at the injection sites after approximately 4 days. The histopathology evaluation revealed a mild, acute inflammatory reaction in the epidermis and dermis at the intradermal CS injection site 1 day after administration. After 14 days, the epidermal epithelium was fully restored. The symptoms were not considered to be adverse, and it is suggested that doses up to 20 μL of 20 mM CS can be safely administered to human beings. In conclusion, our data support development of a CS human dermal pain model. © 2015 Nordic Association for the Publication of BCPT (former Nordic Pharmacological Society).

Evaluation of a novel biodegradable thermosensitive keto-hydrogel for improving postoperative pain in a rat model.

PubMed

Wu, Meng-Huang; Shih, Ming-Hung; Hsu, Wei-Bin; Dubey, Navneet Kumar; Lee, Wen-Fu; Lin, Tsai-Yu; Hsieh, Meng-Yow; Chen, Chin-Fu; Peng, Kuo-Ti; Huang, Tsung-Jen; Shi, Chung-Sheng; Guo, Ren-Shyang; Cai, Chang-Jhih; Chung, Chiu-Yen; Wong, Chung-Hang

2017-01-01

This study evaluates the sustained analgesic effect of ketorolac-eluting thermosensitive biodegradable hydrogel in the plantar incisional pain model of the rat hind-paw. A ketorolac-embedded 2, 2'-Bis (2-oxazolin) (BOX) linking methoxy-poly(ethylene glycol) and poly(lactide-co-glycolide) (mPEG-PLGA) diblock copolymer (BOX copolymer) was synthesized as keto-hydrogel based on optimal sol-gel phase transition and in vitro drug release profile. The effect of keto-hydrogel on postoperative pain (POP) was assessed using the established plantar incisional pain model in hind-paw of rats and compared to that of ketorolac solution. Pain and sensory threshold, as well as pain scoring, were evaluated with behavioral tests by means of anesthesiometer and incapacitance apparatus, respectively. Pro-inflammatory cytokine levels (TNF-α, IL-6, VEGF, and IL-1β) around incisional wounds were measured by ELISA. Tissue histology was assessed using hematoxylin and eosin and Masson's trichrome staining. Ten mg/mL (25 wt%) keto-hydrogel showed a sol-gel transition at 26.4°C with a 10-day sustained drug release profile in vitro. Compared to ketorolac solution group, the concentration of ketorolac in tissue fluid was higher in the keto-hydrogel group during the first 18 h of application. Keto-hydrogel elevated pain and sensory threshold, increased weight-bearing capacity, and significantly reduced the levels of TNF-α, IL-6, and IL-1β while enhanced VEGF in tissue fluid. Histologic analysis reveals greater epithelialization and collagen deposition around wound treated with keto-hydrogel. In conclusion, our study suggests that keto-hydrogel is an ideal compound to treat POP with a secondary gain of improved incisional wound healing.

Rubus occidentalis analgesic effect in a rat model of incisional pain.

PubMed

Choi, Geun Joo; Kang, Hyun; Kim, Won Joong; Kwon, Ji Wung; Kim, Beom Gyu; Choi, Yoo Shin; Cha, Young Joo; Ko, Jin Soo

2016-11-01

The purpose of this study was to evaluate the analgesic effect of Rubus occidentalis extract (ROE) in a rat model of incisional pain. The involved mechanisms and proinflammatory cytokine response were also examined. To investigate the analgesic effect, rats were intraperitoneally administered with normal saline or various doses of ROE before or after a plantar incision. To evaluate the involved mechanism, rats were intraperitoneally administered yohimbine, dexmedetomidine, prazosin, naloxone, atropine, or mecamylamine after a plantar incision; ROE was then administered intraperitoneally. The mechanical withdrawal threshold (MWT) was tested with von Frey filaments at various time points. To determine the inflammatory response, serum levels of interleukin (IL)-1β or IL-6 were measured. The MWTs significantly increased at 15 min after postincisional administration of 300 mg/kg ROE when compared with those in the control group. This elevation was observed for up to 45 min. Overall, MWTs increased in proportion to ROE dosage; however, ROEs administered before the incision produced no significant change in the MWT. The analgesic effect of ROE was significantly antagonized by mecamylamine, naloxone, and yohimbine, and agonized by dexmedetomidine. Administration of ROE inhibited the postincisional increase in serum IL-1β and IL-6. Intraperitoneal administration of ROE after surgery induces antinociceptive effects in a rat model of postoperative pain, and its effects on mechanical hyperalgesia may be associated with α 2 -adrenergic, nicotinic cholinergic, and opioid receptors. Copyright © 2016 Elsevier Inc. All rights reserved.

Evaluating Intra-Articular Drug Delivery for the Treatment of Osteoarthritis in a Rat Model

PubMed Central

Allen, Kyle D.; Adams, Samuel B.

2010-01-01

Osteoarthritis (OA) is a degenerative joint disease that can result in joint pain, loss of joint function, and deleterious effects on activity levels and lifestyle habits. Current therapies for OA are largely aimed at symptomatic relief and may have limited effects on the underlying cascade of joint degradation. Local drug delivery strategies may provide for the development of more successful OA treatment outcomes that have potential to reduce local joint inflammation, reduce joint destruction, offer pain relief, and restore patient activity levels and joint function. As increasing interest turns toward intra-articular drug delivery routes, parallel interest has emerged in evaluating drug biodistribution, safety, and efficacy in preclinical models. Rodent models provide major advantages for the development of drug delivery strategies, chiefly because of lower cost, successful replication of human OA-like characteristics, rapid disease development, and small joint volumes that enable use of lower total drug amounts during protocol development. These models, however, also offer the potential to investigate the therapeutic effects of local drug therapy on animal behavior, including pain sensitivity thresholds and locomotion characteristics. Herein, we describe a translational paradigm for the evaluation of an intra-articular drug delivery strategy in a rat OA model. This model, a rat interleukin-1β overexpression model, offers the ability to evaluate anti-interleukin-1 therapeutics for drug biodistribution, activity, and safety as well as the therapeutic relief of disease symptoms. Once the action against interleukin-1 is confirmed in vivo, the newly developed anti-inflammatory drug can be evaluated for evidence of disease-modifying effects in more complex preclinical models. PMID:19943805

Intervertebral disc degeneration-induced expression of pain-related molecules: glial cell-derived neurotropic factor as a key factor.

PubMed

Jung, Woon-Won; Kim, Hyun-Sook; Shon, Jong-Ryeul; Lee, Min; Lee, Sang-Heon; Sul, Donggeun; Na, Heung Sik; Kim, Joo Han; Kim, Byung-Jo

2011-10-01

Discogenic low back pain has been shown to develop into chronic intractable pain due to an unknown pathogenesis. To study the mechanism of discogenic pain, we analyzed the serial expression of pain-related molecules in the dorsal root ganglia (DRG) and thalamus using a newly developed rat model of disc degeneration. Ten microliters of complete Freund's adjuvant was injected into the L5-6 disc of male Sprague-Dawley rats for 10 minutes using a 26-gauge needle. Using a behavioral test, rats with significant pain were selected and subsequently serial gene expression of pain-related molecules in the DRG and the thalamus was analyzed by reverse transcriptase polymerase chain reaction. The expression of tumor necrosis factor-α and interleukin-1β significantly increased at 4 and 8 weeks in the DRG of rats with pain. Furthermore, interleukin-6 was significantly increased at 4 weeks in the DRG; however, these cytokines did not show a significant change in the thalamus. Calcitonin gene-related peptide and substance P were significantly increased in DRG at 4 and 8 weeks and in the thalamus at 2 and 4 weeks. The level of nerve growth factor-β did not significantly increase in the DRG or thalamus, whereas glial cell line-derived neurotropic factor (GDNF) was significantly increased at 2 weeks and was sustained through 8 weeks in both the DRG and thalamus. The disc degeneration rat model described herein led to significant pain of a chronic nature. The gradual and persistent increase of GDNF in both the thalamus and DRG suggests that GDNF might be a key factor in the development of intractable, chronic discogenic pain.

[The role of brain-derived neurotrophic factor in pain facilitation and spinal mechanism in rat model of bone cancer pain].

PubMed

Wang, Li-na; Yang, Jian-ping; Ji, Fu-hai; Wang, Xiu-yun; Zuo, Jian-ling; Xu, Qi-nian; Jia, Xiao-ming; Zhou, Jing; Ren, Chun-guang; Li, Wei

2011-05-10

To investigate the role of brain-derived neurotrophic factor (BDNF) in pain facilitation and spinal mechanisms in the rat model of bone cancer pain. The bone cancer pain model was developed by inoculated Walker 256 mammary gland carcinoma cells into the tibia medullary cavity. Sixty SD female rats were divided into 5 groups (n = 12 each) randomly; group I: control group (sham operation); group II: model group; group III: control group + anti-BDNF intrathecal (i.t.); group IV: model group + control IgG i.t.; group V: model group + anti-BDNF i.t.. Anti-BDNF or control IgG was injected i.t. during 7 to 9th day. Von-Frey threshold was measured one day before operation and every 2 days after operation. On the 9th day after threshold tested, rats were sacrificed after i.t. injection of either anti-BDNF or control IgG, the lumbar 4-6 spinal cord was removed. The expression of the spinal BDNF and the phosphorylation of extracellular signal-regulated protein kinase 1/2 (p-ERK1/2) were detected by immunohistochemistry assay and Western-Blot. Co-expression pattern of BDNF and p-ERK1/2 were determined by double-labeling immunofluorescence. We demonstrated the coexistence of BDNF and p-ERK1/2 in the spinal cord of rats. From the 7 to 9th day after operation, von-Frey threshold in groups II and IV was significantly lower than that in group I and group V (P < 0.01), group V was remarkly higher than that in group IV (P < 0.01). The spinal BDNF and p-ERK1/2 expression in group II or IV were significantly increased compared with that in group I or V (P < 0.01), intrathecal anti-BDNF was significantly suppressed BDNF and p-ERK1/2 expression (P < 0.01). BDNF and p-ERK1/2 was coexistence in the spinal cord of rats, and it maybe involved in the bone cancer pain.

Role of Kv 4.3 in vibration-induced muscle pain in the rat

PubMed Central

Conner, Lindsay; Alvarez, Pedro; Bogen, Oliver; Levine, Jon D.

2015-01-01

We hypothesized that changes in the expression of Kv4.3 contribute to the mechanical hyperalgesia induced by vibration injury, a rodent model for hand-arm vibration syndrome in humans. Here we show that the exposure of the gastrocnemius muscle to vibration injury induces muscle hyperalgesia that is accompanied by a significant down-regulation of Kv4.3 in affected sensory nerve fibers in dorsal root ganglia (DRG). We additionally demonstrate that the intrathecal administration of antisense oligonucleotides for Kv4.3 mRNA itself induces muscle hyperalgesia in the rat. Our results suggest that attenuation in the expression of Kv4.3 may contribute to neuropathic pain in people affected by hand-arm vibration syndrome. PMID:26721612

Preclinical characterization of three transient receptor potential vanilloid receptor 1 antagonists for early use in human intradermal microdose analgesic studies.

PubMed

Sjögren, E; Halldin, M M; Stålberg, O; Sundgren-Andersson, A K

2018-05-01

The transient receptor potential vanilloid receptor 1 (TRPV1) is a nonselective cation channel involved in the mediation of peripheral pain to the central nervous system. As such, the TRPV1 is an accessible molecular target that lends itself well to the understanding of nociceptive signalling. This study encompasses preclinical investigations of three molecules with the prospect to establish them as suitable analgesic model compounds in human intradermal pain relief studies. The inhibitory effectiveness was evaluated by means of in vitro assays, TRPV1 expressing Chinese hamster ovary cells (CHO-K1) and rat dorsal root ganglion cultures in fluorescent imaging plate reader and whole cell patch clamp systems, as well as in vivo by capsaicin-evoked pain-related behavioural response studies in rat. Secondary pharmacology, pharmacokinetics and preclinical safety were also assessed. In vitro, all three compounds were effective at inhibiting capsaicin-activated TRPV1. The concentration producing 50% inhibition (IC 50 ) determined was in the range of 3-32 nmol/L and 10-501 nmol/L using CHO-K1 and dorsal root ganglion cultures, respectively. In vivo, all compounds showed dose-dependent reduction in capsaicin-evoked pain-related behavioural responses in rat. None of the three compounds displayed any significant activity on any of the secondary targets tested. The compounds were also shown to be safe from a toxicological, drug metabolism and pharmacokinetic perspective, for usage in microgram doses in the human skin. The investigated model compounds displayed ideal compound characteristics as pharmacological and translational tools to address efficacy on the human native TRPV1 target in human skin in situ. This work details the pharmaceutical work-up of three TRPV1-active investigational compounds, to obtain regulatory approval, for subsequent use in humans. This fast and cost-effective preclinical development path may impact research beyond the pain management area, as it allows human target engagement information gathering early in drug development. © 2018 European Pain Federation - EFIC®.

Role of Kv4.3 in Vibration-Induced Muscle Pain in the Rat.

PubMed

Conner, Lindsay B; Alvarez, Pedro; Bogen, Oliver; Levine, Jon D

2016-04-01

We hypothesized that changes in the expression of voltage-gated potassium channel (Kv) 4.3 contribute to the mechanical hyperalgesia induced by vibration injury, in a rodent model for hand-arm vibration syndrome in humans. Here we show that the exposure of the gastrocnemius muscle to vibration injury induces muscle hyperalgesia that is accompanied by a significant downregulation of Kv4.3 in affected sensory nerve fibers in dorsal root ganglia. We additionally show that the intrathecal administration of antisense oligonucleotides for Kv4.3 messenger RNA itself induces muscle hyperalgesia in the rat. Our results suggest that attenuation in the expression of Kv4.3 may contribute to neuropathic pain in people affected by hand-arm vibration syndrome. Our findings establish Kv4.3 as a potential molecular target for the treatment of hand-arm vibration syndrome. Copyright © 2016 American Pain Society. Published by Elsevier Inc. All rights reserved.

Mechanisms Mediating Vibration-induced Chronic Musculoskeletal Pain Analyzed in the Rat

PubMed Central

Dina, Olayinka A.; Joseph, Elizabeth K.; Levine, Jon D.; Green, Paul G.

2009-01-01

While occupational exposure to vibration is a common cause of acute and chronic musculoskeletal pain, eliminating exposure produces limited symptomatic improvement, and re-exposure precipitates rapid recurrence or exacerbation. To evaluate mechanisms underlying these pain syndromes, we have developed a model in the rat, in which exposure to vibration (60–80 Hz) induces, in skeletal muscle, both acute mechanical hyperalgesia as well as long-term changes characterized by enhanced hyperalgesia to a pro-inflammatory cytokine or re-exposure to vibration. Exposure of a hind limb to vibration produced mechanical hyperalgesia measured in the gastrocnemius muscle of the exposed hind limb, which persisted for ~2 weeks. When nociceptive thresholds had returned to baseline, exposure to a pro-inflammatory cytokine or re-exposure to vibration produced markedly prolonged hyperalgesia. The chronic prolongation of vibration- and cytokine-hyperalgesia induced by vibration was prevented by spinal intrathecal injection of oligodeoxynucleotide (ODN) antisense to protein kinase Cε, a second messenger in nociceptors implicated in the induction and maintenance of chronic pain. Vibration-induced hyperalgesia was inhibited by spinal intrathecal administration of ODN antisense to receptors for the type-1 tumor necrosis factor-α (TNFα) receptor. Finally, in TNFα-pretreated muscle, subsequent vibration-induced hyperalgesia was markedly prolonged. Perspective These studies establish a model of vibration-induced acute and chronic musculoskeletal pain, and identify the proinflammatory cytokine TNFα and the second messenger PKCε as targets against which therapies might be directed to prevent and/or treat this common and very debilitating chronic pain syndrome. PMID:19962353

Histopathological classification criteria of rat model of chronic prostatitis/chronic pelvic pain syndrome.

PubMed

Wang, Xianjin; Zhong, Shan; Xu, Tianyuan; Xia, Leilei; Zhang, Xiaohua; Zhu, Zhaowei; Zhang, Minguang; Shen, Zhoujun

2015-02-01

A variety of murine models of experimental prostatitis that mimic the phenotype of human chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) have been developed. However, there is still a lack of explicit diagnosis criteria about those animal model. Our study is to establish histopathological classification criteria, which will be conducive to evaluate the animal models. We firstly established a rat model of experimental autoimmune prostatitis that is considered a valid model for CP/CPPS. For modelling, male Sprague-Dawley rats were immunized with autologous prostate tissue homogenate supernatant emulsified with complete Freund's adjuvant by subcutaneous injection into abdominal flank and simultaneously immunized with pertussis-diphtheria-tetanus vaccine by intraperitoneal injection. Three immunizations were administered semimonthly. At the 45th day, animals were killed, and prostate tissues were examined for morphology. Histologically, the prostate tissues were characterized by lymphoproliferation, atrophy of acini, and chronic inflammatory cells infiltration in the stromal connective tissue around the acini or ducts. Finally, we built histopathological classification criteria incorporating inflammation locations (mesenchyme, glands, periglandular tissues), ranges (focal, multifocal, diffuse), and grades (grade I-IV). To verify the effectiveness and practicability of the histopathological classification criteria, we conducted the treatment study with one of the alpha blockers, tamsulosin. The histopathological classification criteria of rat model of CP/CPPS will serve for further research of the pathogenesis and treatment strategies of the disease.

Intraarticularly-Injected Mesenchymal Stem Cells Stimulate Anti-Inflammatory Molecules and Inhibit Pain Related Protein and Chondrolytic Enzymes in a Monoiodoacetate-Induced Rat Arthritis Model

PubMed Central

Ichiseki, Toru; Shimasaki, Miyako; Ueda, Yoshimichi; Tsuchiya, Masanobu; Souma, Daisuke; Kaneuji, Ayumi; Kawahara, Norio

2018-01-01

Persistent inflammation is well known to promote the progression of arthropathy. mesenchymal stem cells (MSCs) have been shown to possess anti-inflammatory properties and tissue differentiation potency. Although the experience so far with the intraarticular administration of mesenchymal stem cell (MSC) to induce cartilage regeneration has been disappointing, MSC implantation is now being attempted using various surgical techniques. Meanwhile, prevention of osteoarthritis (OA) progression and pain control remain important components of the treatment of early-stage OA. We prepared a shoulder arthritis model by injecting monoiodoacetate (MIA) into a rat shoulder, and then investigated the intraarticular administration of MSC from the aspects of the cartilage protective effect associated with their anti-inflammatory property and inhibitory effect on central sensitization of pain. When MIA was administered in this rat shoulder arthritis model, anti-Calcitonin Gene Related Peptide (CGRP) was expressed in the joint and C5 spinal dorsal horn. Moreover, expression of A disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5), a marker of joint cartilage injury, was similarly elevated following MIA administration. When MSC were injected intraarticularly after MIA, the expression of CGRP in the spinal dorsal horn was significantly deceased, indicating suppression of the central sensitization of pain. The expression of ADAMTS 5 in joint cartilage was also significantly inhibited by MSC administration. In contrast, a significant increase in the expression of TNF-α stimulated gene/protein 6 (TSG-6), an anti-inflammatory and cartilage protective factor shown to be produced and secreted by MSC intraarticularly, was found to extend to the cartilage tissue following MSC administration. In this way, the intraarticular injection of MSC inhibited the central sensitization of pain and increased the expression of the anti-inflammatory and cartilage protective factor TSG-6. As the least invasive conservative strategies possible are desirable in the actual clinical setting, the intraarticular administration of MSC, which appears to be effective for the treatment of pain and cartilage protection in early-stage arthritis, may achieve these aims. PMID:29315262

Local Infiltration of Analgesics at Surgical Wound to Reduce Postoperative Pain After Laparotomy in Rats.

PubMed

Kroin, Jeffrey S; Li, Jinyuan; Moric, Mario; Birmingham, Brian W; Tuman, Kenneth J; Buvanendran, Asokumar

There is an increasing use of local infiltration analgesia (LIA) to reduce postoperative pain. Despite widespread use of LIA, wide variations in drug combinations and concomitant use of systemic analgesics have made it difficult to determine the optimal drug combinations for LIA. Using a previously validated rat laparotomy model, the optimal LIA combination of medications to reduce postoperative pain was determined. Laparotomy was performed in an adult rat model under isoflurane anesthesia. During surgery, combinations of bupivacaine, ketorolac, and dexamethasone were injected over the sutured muscle wound before skin closing, and compared to saline (placebo). The same medications were injected systemically as controls. Postoperative pain was assessed by measuring spontaneous rearing activity. A high-dose 3-drug LIA combination (50 μL of bupivacaine 0.75%, ketorolac 6.0 mg/mL, and dexamethasone 2.0 mg/mL) increased rearing (decreased pain) at 2 hours (P = 0.0032) postsurgery compared to saline. However, the same 3 drugs injected systemically had a similar analgesic effect (P = 0.0002). Bupivacaine 0.75% alone was not effective for LIA. When low-dose (9-fold reduction) 3-drug LIA combination was used, LIA increased rearing (P = 0.0034) whereas the same 3 drugs injected systemically had no effect. Low-dose LIA ketorolac/dexamethasone (2-drug combination) also increased rearing (P = 0.0393). Our animal study suggests that clinical trials with low-dose LIA combinations of local anesthetic, nonsteroidal anti-inflammatory drug, and corticosteroid may be useful for reducing postoperative pain after laparotomy.

Analgesic effects of intrathecally-administered 3 alpha-hydroxy-5 alpha-pregnan-20-one in a rat mechanical visceral pain model.

PubMed

Winfree, C J; Coombs, D W; DeLeo, J A; Colburn, R W

1992-01-01

Recent studies in animals have demonstrated that the steroid, 3 alpha-hydroxy-5 alpha-pregnan-20-one (3A5P), is a potent analgesic when given intracerebroventricularly. Several studies in humans report that spinal steroids are effective in the treatment of chronic low-back pain when given in combination with morphine. The spinal antinociceptive effect of steroids, in particular a progesterone metabolite has not been studied in a visceral pain model. The experiments in the following study were designed to test, first, if the intrathecally-administered (i.t.) steroid, 3A5P, has analgesic properties in a mechanical visceral nociceptive assay, and second, if the intrathecal coadministration of this steroid and morphine is more effective than either therapy alone. Our mechanical visceral pain model (VPM) consists of a chronic indwelling duodenal balloon catheter implanted in the rat. The balloon is inflated to elicit a writhing response. Protection values are defined as the percentage of rats in each group which did not writhe. In this model, 3A5P was found to provide a dose-independent, though significant (p less than 0.01), antinociception when administered alone (33-67% protection vs. 0-25% for controls). Yet, protection offered by the coadministration of 3A5P and morphine (79%) was not significantly greater than that offered by morphine alone (85%). Unlike a dose and time-dependent response observed in a thermal cutaneous nociceptive assay, the antinociception of 3A5P was not dose-dependent when challenged with a mechanical visceral noxious stimulus.

Negative allosteric modulation of the mGlu7 receptor reduces visceral hypersensitivity in a stress-sensitive rat strain

PubMed Central

Moloney, Rachel D.; Golubeva, Anna V.; O'Connor, Richard M.; Kalinichev, Mikhail; Dinan, Timothy G.; Cryan, John F.

2015-01-01

Glutamate, the main excitatory neurotransmitter in the central nervous system, exerts its effect through ionotropic and metabotropic receptors. Of these, group III mGlu receptors (mGlu 4, 6, 7, 8) are among the least studied due to a lack of pharmacological tools. mGlu7 receptors, the most highly conserved isoform, are abundantly distributed in the brain, especially in regions, such as the amygdala, known to be crucial for the emotional processing of painful stimuli. Visceral hypersensitivity is a poorly understood phenomenon manifesting as an increased sensitivity to visceral stimuli. Glutamate has long been associated with somatic pain processing leading us to postulate that crossover may exist between these two modalities. Moreover, stress has been shown to exacerbate visceral pain. ADX71743 is a novel, centrally penetrant, negative allosteric modulator of mGlu7 receptors. Thus, we used this tool to explore the possible involvement of this receptor in the mediation of visceral pain in a stress-sensitive model of visceral hypersensitivity, namely the Wistar Kyoto (WKY) rat. ADX71743 reduced visceral hypersensitivity in the WKY rat as exhibited by increased visceral sensitivity threshold with concomitant reductions in total number of pain behaviours. Moreover, AD71743 increased total distance and distance travelled in the inner zone of the open field. These findings show, for what is to our knowledge, the first time, that mGlu7 receptor signalling plays a role in visceral pain processing. Thus, negative modulation of the mGlu7 receptor may be a plausible target for the amelioration of stress-induced visceral pain where there is a large unmet medical need. PMID:26844237

Pharmacology of modality-specific transient receptor potential vanilloid-1 antagonists that do not alter body temperature.

PubMed

Reilly, Regina M; McDonald, Heath A; Puttfarcken, Pamela S; Joshi, Shailen K; Lewis, LaGeisha; Pai, Madhavi; Franklin, Pamela H; Segreti, Jason A; Neelands, Torben R; Han, Ping; Chen, Jun; Mantyh, Patrick W; Ghilardi, Joseph R; Turner, Teresa M; Voight, Eric A; Daanen, Jerome F; Schmidt, Robert G; Gomtsyan, Arthur; Kort, Michael E; Faltynek, Connie R; Kym, Philip R

2012-08-01

The transient receptor potential vanilloid-1 (TRPV1) channel is involved in the development and maintenance of pain and participates in the regulation of temperature. The channel is activated by diverse agents, including capsaicin, noxious heat (≥ 43°C), acidic pH (< 6), and endogenous lipids including N-arachidonoyl dopamine (NADA). Antagonists that block all modes of TRPV1 activation elicit hyperthermia. To identify efficacious TRPV1 antagonists that do not affect temperature antagonists representing multiple TRPV1 pharmacophores were evaluated at recombinant rat and human TRPV1 channels with Ca(2+) flux assays, and two classes of antagonists were identified based on their differential ability to inhibit acid activation. Although both classes of antagonists completely blocked capsaicin- and NADA-induced activation of TRPV1, select compounds only partially inhibited activation of the channel by protons. Electrophysiology and calcitonin gene-related peptide release studies confirmed the differential pharmacology of these antagonists at native TRPV1 channels in the rat. Comparison of the in vitro pharmacological properties of these TRPV1 antagonists with their in vivo effects on core body temperature confirms and expands earlier observations that acid-sparing TRPV1 antagonists do not significantly increase core body temperature. Although both classes of compounds elicit equivalent analgesia in a rat model of knee joint pain, the acid-sparing antagonist tested is not effective in a mouse model of bone cancer pain.

Negative allosteric modulation of the mGlu7 receptor reduces visceral hypersensitivity in a stress-sensitive rat strain.

PubMed

Moloney, Rachel D; Golubeva, Anna V; O'Connor, Richard M; Kalinichev, Mikhail; Dinan, Timothy G; Cryan, John F

2015-01-01

Glutamate, the main excitatory neurotransmitter in the central nervous system, exerts its effect through ionotropic and metabotropic receptors. Of these, group III mGlu receptors (mGlu 4, 6, 7, 8) are among the least studied due to a lack of pharmacological tools. mGlu7 receptors, the most highly conserved isoform, are abundantly distributed in the brain, especially in regions, such as the amygdala, known to be crucial for the emotional processing of painful stimuli. Visceral hypersensitivity is a poorly understood phenomenon manifesting as an increased sensitivity to visceral stimuli. Glutamate has long been associated with somatic pain processing leading us to postulate that crossover may exist between these two modalities. Moreover, stress has been shown to exacerbate visceral pain. ADX71743 is a novel, centrally penetrant, negative allosteric modulator of mGlu7 receptors. Thus, we used this tool to explore the possible involvement of this receptor in the mediation of visceral pain in a stress-sensitive model of visceral hypersensitivity, namely the Wistar Kyoto (WKY) rat. ADX71743 reduced visceral hypersensitivity in the WKY rat as exhibited by increased visceral sensitivity threshold with concomitant reductions in total number of pain behaviours. Moreover, AD71743 increased total distance and distance travelled in the inner zone of the open field. These findings show, for what is to our knowledge, the first time, that mGlu7 receptor signalling plays a role in visceral pain processing. Thus, negative modulation of the mGlu7 receptor may be a plausible target for the amelioration of stress-induced visceral pain where there is a large unmet medical need.

A novel method for delivering ramped cooling reveals rat behaviours at innocuous and noxious temperatures: A comparative study of human psychophysics and rat behaviour.

PubMed

Dunham, James P; Hulse, Richard P; Donaldson, Lucy F

2015-07-15

Thermal sensory testing in rodents informs human pain research. There are important differences in the methodology for delivering thermal stimuli to humans and rodents. This is particularly true in cold pain research. These differences confound extrapolation and de-value nociceptive tests in rodents. We investigated cooling-induced behaviours in rats and psychophysical thresholds in humans using ramped cooling stimulation protocols. A Peltier device mounted upon force transducers simultaneously applied a ramped cooling stimulus whilst measuring contact with rat hind paw or human finger pad. Rat withdrawals and human detection, discomfort and pain thresholds were measured. Ramped cooling of a rat hind paw revealed two distinct responses: Brief paw removal followed by paw replacement, usually with more weight borne than prior to the removal (temperature inter-quartile range: 19.1 °C to 2.8 °C). Full withdrawal was evoked at colder temperatures (inter quartile range: -11.3 °C to -11.8 °C). The profile of human cool detection threshold and cold pain threshold were remarkably similar to that of the rat withdrawals behaviours. Previous rat cold evoked behaviours utilise static temperature stimuli. By utilising ramped cold stimuli this novel methodology better reflects thermal testing in patients. Brief paw removal in the rat is driven by non-nociceptive afferents, as is the perception of cooling in humans. This is in contrast to the nociceptor-driven withdrawal from colder temperatures. These findings have important implications for the interpretation of data generated in older cold pain models and consequently our understanding of cold perception and pain. Copyright © 2015. Published by Elsevier B.V.

Pharmacological kynurenine 3-monooxygenase enzyme inhibition significantly reduces neuropathic pain in a rat model.

PubMed

Rojewska, Ewelina; Piotrowska, Anna; Makuch, Wioletta; Przewlocka, Barbara; Mika, Joanna

2016-03-01

Recent studies have highlighted the involvement of the kynurenine pathway in the pathology of neurodegenerative diseases, but the role of this system in neuropathic pain requires further extensive research. Therefore, the aim of our study was to examine the role of kynurenine 3-monooxygenase (Kmo), an enzyme that is important in this pathway, in a rat model of neuropathy after chronic constriction injury (CCI) to the sciatic nerve. For the first time, we demonstrated that the injury-induced increase in the Kmo mRNA levels in the spinal cord and the dorsal root ganglia (DRG) was reduced by chronic administration of the microglial inhibitor minocycline and that this effect paralleled a decrease in the intensity of neuropathy. Further, minocycline administration alleviated the lipopolysaccharide (LPS)-induced upregulation of Kmo mRNA expression in microglial cell cultures. Moreover, we demonstrated that not only indirect inhibition of Kmo using minocycline but also direct inhibition using Kmo inhibitors (Ro61-6048 and JM6) decreased neuropathic pain intensity on the third and the seventh days after CCI. Chronic Ro61-6048 administration diminished the protein levels of IBA-1, IL-6, IL-1beta and NOS2 in the spinal cord and/or the DRG. Both Kmo inhibitors potentiated the analgesic properties of morphine. In summary, our data suggest that in neuropathic pain model, inhibiting Kmo function significantly reduces pain symptoms and enhances the effectiveness of morphine. The results of our studies show that the kynurenine pathway is an important mediator of neuropathic pain pathology and indicate that Kmo represents a novel pharmacological target for the treatment of neuropathy. Copyright © 2015 Elsevier Ltd. All rights reserved.

Behavioral and anatomical characterization of the bilateral sciatic nerve chronic constriction (bCCI) injury: correlation of anatomic changes and responses to cold stimuli.

PubMed

Datta, Sukdeb; Chatterjee, Koel; Kline, Robert H; Wiley, Ronald G

2010-01-27

Unilateral constrictive sciatic nerve injury (uCCI) is a common neuropathic pain model. However, the bilateral constrictive injury (bCCI) model is less well studied, and shows unique characteristics. In the present study, we sought to correlate effects of bCCI on nocifensive responses to cold and mechanical stimuli with selected dorsal horn anatomic markers. bCCI or sham ligation of both rat sciatic nerves were followed up to 90 days of behavioural testing. Additional rats sacrificed at 15, 30 and 90 days were used for anatomic analyses. Behavioural tests included hindpaw withdrawal responses to topical acetone, cold plate testing, an operant thermal preference task and hindpaw withdrawal thresholds to mechanical probing. All nocifensive responses to cold increased and remained enhanced for >45 days. Mechanical withdrawal thresholds decreased for 25 days only. Densitometric analyses of immunoperoxidase staining in the superficial dorsal horn at L4-5 revealed decreased cholecystokinin (CCK) staining at all times after bCCI, decreased mu opiate receptor (MOR) staining, maximal at 15 days, increased neuropeptide Y (NPY) staining only at days 15 and 30, and increased neurokinin-1 receptor (NK-1R) staining at all time points, maximal at 15 days. Correlation analyses at 45 days post-bCCI, were significant for individual rat nocifensive responses in each cold test and CCK and NK-1R, but not for MOR or NPY. These results confirm the usefulness of cold testing in bCCI rats, a new approach using CCI to model neuropathic pain, and suggest a potential value of studying the roles of dorsal horn CCK and substance P in chronic neuropathic pain. Compared to human subjects with neuropathic pain, responses to cold stimuli in rats with bCCI may be a useful model of neuropathic pain.

Administration of a co-crystal of tramadol and celecoxib in a 1:1 molecular ratio produces synergistic antinociceptive effects in a postoperative pain model in rats.

PubMed

Merlos, Manuel; Portillo-Salido, Enrique; Brenchat, Alex; Aubel, Bertrand; Buxens, Jordi; Fisas, Angels; Codony, Xavier; Romero, Luz; Zamanillo, Daniel; Vela, José Miguel

2018-06-19

Drug combination for the treatment of pain is common clinical practice. Co-crystal of Tramadol-Celecoxib (CTC) consists of two active pharmaceutical ingredients (APIs), namely the atypical opioid tramadol and the preferential cyclooxygenase-2 inhibitor celecoxib, at a 1:1 molecular ratio. In this study, a non-formulated 'raw' form of CTC administered in suspension (referred to as ctc susp ) was compared with both tramadol and celecoxib alone in a rat plantar incision postoperative pain model. For comparison, the strong opioids morphine and oxycodone, and a tramadol plus acetaminophen combination at a molecular ratio of 1:17 were also tested. Isobolographic analyses showed that ctc susp exerted synergistic mechanical antiallodynic (experimental ED 50 =2.0±0.5mg/kg, i.p.; theoretical ED 50 =3.8±0.4mg/kg, i.p.) and thermal (experimental ED 50 =2.3±0.5mg/kg, i.p.; theoretical ED 50 =9.8±0.8mg/kg, i.p.) antihyperalgesic effects in the postoperative pain model. In contrast, the tramadol and acetaminophen combination showed antagonistic effects on both mechanical allodynia and thermal hyperalgesia. No synergies between tramadol and celecoxib on locomotor activity, motor coordination, ulceration potential and gastrointestinal transit were observed after the administration of ctc susp . Overall, rat efficacy and safety data revealed that ctc susp provided synergistic analgesic effects compared with each API alone, without enhancing adverse effects. Moreover, ctc susp showed similar efficacy but improved safety ratio (80, measured as gastrointestinal transit vs postoperative pain ED 50 ratios) compared with the strong opioids morphine (2.5) and oxycodone (5.8). The overall in vivo profile of ctc susp supports the further investigation of CTC in the clinical management of moderate-to-severe acute pain as an alternative to strong opioids. Copyright © 2018. Published by Elsevier B.V.

Sympathetic regulation and anterior cingulate cortex volume are altered in a rat model of chronic back pain.

PubMed

Touj, Sara; Houle, Sébastien; Ramla, Djamel; Jeffrey-Gauthier, Renaud; Hotta, Harumi; Bronchti, Gilles; Martinoli, Maria-Grazia; Piché, Mathieu

2017-06-03

Chronic pain is associated with autonomic disturbance. However, specific effects of chronic back pain on sympathetic regulation remain unknown. Chronic pain is also associated with structural changes in the anterior cingulate cortex (ACC), which may be linked to sympathetic dysregulation. The aim of this study was to determine whether sympathetic regulation and ACC surface and volume are affected in a rat model of chronic back pain, in which complete Freund Adjuvant (CFA) is injected in back muscles. Sympathetic regulation was assessed with renal blood flow (RBF) changes induced by electrical stimulation of a hind paw, while ACC structure was examined by measuring cortical surface and volume. RBF changes and ACC volume were compared between control rats and rats injected with CFA in back muscles segmental (T10) to renal sympathetic innervation or not (T2). In rats with CFA, chronic inflammation was observed in the affected muscles in addition to increased nuclear factor-kappa B (NF-kB) protein expression in corresponding spinal cord segments (p=0.01) as well as decreased ACC volume (p<0.05). In addition, intensity-dependent decreases in RBF during hind paw stimulation were attenuated by chronic pain at T2 (p's<0.05) and T10 (p's<0.05), but less so at T10 compared with T2 (p's<0.05). These results indicate that chronic back pain alters sympathetic functions through non-segmental mechanisms, possibly by altering descending regulatory pathways from ACC. Yet, segmental somato-sympathetic reflexes may compete with non-segmental processes depending on the back region affected by pain and according to the segmental organization of the sympathetic nervous system. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

Antinociceptive Effect of Ghrelin in a Rat Model of Irritable Bowel Syndrome Involves TRPV1/Opioid Systems.

PubMed

Mao, Yuqing; Li, Zhengyang; Chen, Kan; Yu, Huafang; Zhang, Shaoren; Jiang, Miao; Ma, Yuanhua; Liang, Chunli; Liu, Hongyan; Li, Huanqing; Hua, Qian; Zhou, Hao; Sun, Yonghong; Fan, Xiaoming

2017-01-01

Irritable bowel syndrome (IBS), defined as recurrent abdominal pain and changes in bowel habits, seriously affects quality of life and ability to work. Ghrelin is a brain-gut hormone, which has been reported to show antinociceptive effects in peripheral pain. We investigated the effect of ghrelin on visceral hypersensitivity and pain in a rat model of IBS. Maternal deprivation (MD) was used to provide a stress-induced model of IBS in Wistar rats. Colorectal distension (CRD) was used to detect visceral sensitivity, which was evaluated by abdominal withdrawal reflex (AWR) scores. Rats that were confirmed to have visceral hypersensitivity after MD were injected with ghrelin (10 µg/kg) subcutaneously twice a week from weeks 7 to 8. [D-Lys3]-GHRP-6 (100 nmol/L) and naloxone (100 nmol/L) were administered subcutaneously to block growth hormone secretagogue receptor 1α (GHS-R1α) and opioid receptors, respectively. Expression of transient receptor potential vanilloid type 1 (TRPV1) and µ and κ opioid receptors (MOR and KOR) in colon, dorsal root ganglion (DRG) and cerebral cortex tissues were detected by western blotting, quantitative real-time polymerase chain reaction (qRT-PCR), immunohistochemical analyses and immunofluorescence. Ghrelin treatment increased expression of opioid receptors and inhibited expression of TRPV1 in colon, dorsal root ganglion (DRG) and cerebral cortex. The antinociceptive effect of ghrelin in the rat model of IBS was partly blocked by both the ghrelin antagonist [D-Lys3]-GHRP-6 and the opioid receptor antagonist naloxone. The results indicate that ghrelin exerted an antinociceptive effect, which was mediated via TRPV1/opioid systems, in IBS-induced visceral hypersensitivity. Ghrelin might potentially be used as a new treatment for IBS. © 2017 The Author(s). Published by S. Karger AG, Basel.

Electroacupuncture attenuates mechanical allodynia by suppressing the spinal JNK1/2 pathway in a rat model of inflammatory pain.

PubMed

Du, Jun-Ying; Fang, Jian-Qiao; Liang, Yi; Fang, Jun-Fan

2014-09-01

Electroacupuncture (EA) has a substantial analgesic effect on inflammatory pain induced by complete Freund's adjuvant (CFA). The activation of the c-Jun N-terminal kinase 1/2 (JNK1/2) signal transduction pathway in the spinal cord is associated with inflammatory pain. However, the relationship between EA's analgesic effect and the JNK1/2 signal transduction pathway in the inflammatory pain remain unclear. In the present study, we used the established rat model of CFA-induced inflammatory pain to investigate the role of the spinal JNK1/2 pathway in EA-mediated analgesia. We observed a decrease in paw withdrawal thresholds and an increase in paw edema at 1 and 3 days after injecting CFA into the right hindpaw. CFA, 3 days after injection, upregulated expression of phospho-c-Jun N-terminal kinase1/2 (p-JNK1/2) protein and its downstream targets, the transcriptional regulators p-c-Jun and activator protein-1 (AP-1), as well as cyclooxygenase-2 (COX-2) and the transient receptor potential vanilloid 1 (TRPV1). EA significantly alleviated CFA-induced inflammatory pain. In addition, EA reduced p-JNK1/2 protein levels and COX-2 mRNA expressions, a degree of down-regulated p-c-Jun protein level and AP-1 DNA binding activity in the spinal dorsal horn of CFA-administered animals, but it had no effect on TRPV1 mRNA expression. Furthermore, EA and the JNK inhibitor SP600125 synergistically inhibited CFA-induced hyperalgesia and suppressed the COX-2 mRNA expression in the spinal dorsal horn. Our findings indicate that EA alleviates inflammatory pain behavior, at least in part, by reducing COX-2 expression in the spinal cord via the JNK1/2 signaling pathway. Inactivation of the spinal JNK1/2 signal transduction pathway maybe the potential mechanism of EA's antinociception in the inflammatory pain model. Copyright © 2014 Elsevier Inc. All rights reserved.

Upregulation of the sodium channel NaVβ4 subunit and its contributions to mechanical hypersensitivity and neuronal hyperexcitability in a rat model of radicular pain induced by local DRG inflammation

PubMed Central

Xie, Wenrui; Tan, Zhi-Yong; Barbosa, Cindy; Strong, Judith A.; Cummins, Theodore R.; Zhang, Jun-Ming

2016-01-01

High frequency spontaneous firing in myelinated sensory neurons plays a key role in initiating pain behaviors in several different models, including the radicular pain model in which the rat lumbar dorsal root ganglia (DRG) are locally inflamed. The sodium channel isoform NaV1.6 contributes to pain behaviors and spontaneous activity in this model. Among all the isoforms in adult DRG, NaV1.6 is the main carrier of TTX-sensitive resurgent Na currents that allow high-frequency firing. Resurgent currents flow after a depolarization or action potential, as a blocking particle exits the pore. In most neurons the regulatory β4 subunit is potentially the endogenous blocker. We used in vivo siRNA mediated knockdown of NaVβ4 to examine its role in the DRG inflammation model. NaVβ4 but not control siRNA almost completely blocked mechanical hypersensitivity induced by DRG inflammation. Microelectrode recordings in isolated whole DRGs showed that NaVβ4 siRNA blocked the inflammation-induced increase in spontaneous activity of Aβ neurons, and reduced repetitive firing and other measures of excitability. NaVβ4 was preferentially expressed in larger diameter cells; DRG inflammation increased its expression and this was reversed by NaVβ4 siRNA, based on immunohistochemistry and Western blotting. NaVβ4 siRNA also reduced immunohistochemical NaV1.6 expression. Patch clamp recordings of TTX-sensitive Na currents in acutely cultured medium diameter DRG neurons showed that DRG inflammation increased transient and especially resurgent current; effects blocked by NaVβ4 siRNA. NaVβ4 may represent a more specific target for pain conditions that depend on myelinated neurons expressing NaV1.6. PMID:26785322

Behavioral and anatomical characterization of the bilateral sciatic nerve chronic constriction (bCCI) injury: correlation of anatomic changes and responses to cold stimuli

PubMed Central

2010-01-01

Background Unilateral constrictive sciatic nerve injury (uCCI) is a common neuropathic pain model. However, the bilateral constrictive injury (bCCI) model is less well studied, and shows unique characteristics. In the present study, we sought to correlate effects of bCCI on nocifensive responses to cold and mechanical stimuli with selected dorsal horn anatomic markers. bCCI or sham ligation of both rat sciatic nerves were followed up to 90 days of behavioural testing. Additional rats sacrificed at 15, 30 and 90 days were used for anatomic analyses. Behavioural tests included hindpaw withdrawal responses to topical acetone, cold plate testing, an operant thermal preference task and hindpaw withdrawal thresholds to mechanical probing. Results All nocifensive responses to cold increased and remained enhanced for >45 days. Mechanical withdrawal thresholds decreased for 25 days only. Densitometric analyses of immunoperoxidase staining in the superficial dorsal horn at L4-5 revealed decreased cholecystokinin (CCK) staining at all times after bCCI, decreased mu opiate receptor (MOR) staining, maximal at 15 days, increased neuropeptide Y (NPY) staining only at days 15 and 30, and increased neurokinin-1 receptor (NK-1R) staining at all time points, maximal at 15 days. Correlation analyses at 45 days post-bCCI, were significant for individual rat nocifensive responses in each cold test and CCK and NK-1R, but not for MOR or NPY. Conclusions These results confirm the usefulness of cold testing in bCCI rats, a new approach using CCI to model neuropathic pain, and suggest a potential value of studying the roles of dorsal horn CCK and substance P in chronic neuropathic pain. Compared to human subjects with neuropathic pain, responses to cold stimuli in rats with bCCI may be a useful model of neuropathic pain. PMID:20105332

Intrathecal transplantation of neuroblastoma cells decreases heat hyperalgesia and cold allodynia in a rat model of neuropathic pain.

PubMed

De la Calle, J L; Mena, M A; González-Escalada, J R; Paíno, C L

2002-11-30

Intrathecal grafting of cells as biological pumps to deliver monoamines, endorphins, and/or trophic factors, has been shown to be effective in treating chronic pain both in experimental animals and in clinical trials. We have tested whether intrathecal implantation of neuroblastoma cells reduces heat hyperalgesia and cold allodynia in a rat model of neuropathic pain induced by chronic constriction injury (CCI) of the sciatic nerve. Behavioral tests and cerebrospinal fluid (CSF) collection were performed before CCI, 1 week later (after which, vehicle or NB69 cells were intrathecally injected) and at 4, 7, and 14 days post-injection. Both CSF sampling and injection of the cells were performed by direct lumbar puncture. Intrathecal grafting of 4 x 10(6) NB69 neuroblastoma cells reduced to basal levels the nociceptive response to heat in nerve-injured hindpaws, while the response of control limbs remained unchanged. Similarly, the allodynic response to cold elicited by acetone evaporation decreased in the animals implanted with NB69 cells. An increase in the concentrations of dopamine and serotonin metabolites of around 150% was observed in the CSF of animals that received grafts of NB69 cells. These data suggest that the monoamines released by NB69 cells in the intrathecal space produce analgesia to neuropathic pain in rats. Copyright 2002 Elsevier Science Inc.

Reduced epidermal thickness, nerve degeneration and increased pain-related behavior in rats with diabetes type 1 and 2.

PubMed

Boric, Matija; Skopljanac, Ivan; Ferhatovic, Lejla; Jelicic Kadic, Antonia; Banozic, Adriana; Puljak, Livia

2013-11-01

To examine the mechanisms contributing to pain genesis in diabetic neuropathy, we investigated epidermal thickness and number of intraepidermal nerve fibers in rat foot pad of the animal model of diabetes type 1 and type 2 in relation to pain-related behavior. Male Sprague-Dawley rats were used. Diabetes type 1 was induced with intraperitoneal injection of streptozotocin (STZ) and diabetes type 2 was induced with a combination of STZ and high-fat diet. Control group for diabetes type 1 was fed with regular laboratory chow, while control group for diabetes type 2 received high-fat diet. Body weights and blood glucose levels were monitored to confirm induction of diabetes. Pain-related behavior was analyzed using thermal (hot, cold) and mechanical stimuli (von Frey fibers, number of hyperalgesic responses). Two months after induction of diabetes, glabrous skin samples from plantar surface of the both hind paws were collected. Epidermal thickness was evaluated with hematoxylin and eosin staining. Intraepidermal nerve fibers quantification was performed after staining skin with polyclonal antiserum against protein gene product 9.5. We found that induction of diabetes type 1 and type 2 causes significant epidermal thinning and loss of intraepidermal nerve fibers in a rat model, and both changes were more pronounced in diabetes type 1 model. Significant increase of pain-related behavior two months after induction of diabetes was observed only in a model of diabetes type 1. In conclusion, animal models of diabetes type 1 and diabetes type 2 could be used in pharmacological studies, where cutaneous changes could be used as outcome measures for predegenerative markers of neuropathies. Copyright © 2013 Elsevier B.V. All rights reserved.

Alleviating neuropathic pain mechanical allodynia by increasing Cdh1 in the anterior cingulate cortex.

PubMed

Tan, Wei; Yao, Wen-Long; Hu, Rong; Lv, You-You; Wan, Li; Zhang, Chuan-Han; Zhu, Chang

2015-09-12

Plastic changes in the anterior cingulate cortex (ACC) are critical in the pathogenesis of pain hypersensitivity caused by injury to peripheral nerves. Cdh1, a co-activator subunit of anaphase-promoting complex/cyclosome (APC/C) regulates synaptic differentiation and transmission. Based on this, we hypothesised that the APC/C-Cdh1 played an important role in long-term plastic changes induced by neuropathic pain in ACC. We employed spared nerve injury (SNI) model in rat and found Cdh1 protein level in the ACC was down-regulated 3, 7 and 14 days after SNI surgery. We detected increase in c-Fos expression, numerical increase of organelles, swollen myelinated fibre and axon collapse of neuronal cells in the ACC of SNI rat. Additionally, AMPA receptor GluR1 subunit protein level was up-regulated on the membrane through a pathway that involves EphA4 mediated by APC/C-Cdh1, 3 and 7 days after SNI surgery. To confirm the effect of Cdh1 in neuropathic pain, Cdh1-expressing lentivirus was injected into the ACC of SNI rat. Intra-ACC treatment with Cdh1-expressing lentivirus vectors elevated Cdh1 levels, erased synaptic strengthening, as well as alleviating established mechanical allodynia in SNI rats. We also found Cdh1-expressing lentivirus normalised SNI-induced redistribution of AMPA receptor GluR1 subunit in ACC by regulating AMPA receptor trafficking. These results provide evidence that Cdh1 in ACC synapses may offer a novel therapeutic strategy for treating chronic neuropathic pain.

HDAC inhibitor TSA ameliorates mechanical hypersensitivity and potentiates analgesic effect of morphine in a rat model of bone cancer pain by restoring μ-opioid receptor in spinal cord.

PubMed

Hou, Xinran; Weng, Yingqi; Ouyang, Bihan; Ding, Zhuofeng; Song, Zongbin; Zou, Wangyuan; Huang, Changsheng; Guo, Qulian

2017-08-15

Bone cancer pain (BCP) is a common complication with inadequate management in patients suffering from advanced cancer. Histone deacetylase inhibitors showed significant analgesic effect in multiple inflammatory and neuropathic pain models, but their effect in bone cancer pain has never been explored. In this study, we utilized a BCP rat model with intra-tibial inoculation of Walker 256 mammary gland carcinoma cells, which developed progressive mechanical hypersensitivity but not thermal hypersensitivity. Intrathecal application of trichostatin A (TSA), a classic pan-HDAC inhibitor, ameliorated tactile hypersensitivity and enhanced the analgesic effect of morphine in BCP rats. The analgesic effect of TSA was blocked by co-administration of CTAP, a specific MOR antagonist, confirming the involvement of mu-opioid receptor (MOR). A reduction of MOR expression was observed in the lumbar spinal cord of BCP rats and TSA treatment was able to partially reverse it. In vitro study in PC12 cells also demonstrated the dose-dependent enhancement of MOR expression by TSA treatment. Taking all into consideration, we could draw the conclusion that HDAC inhibitor TSA ameliorates mechanical hypersensitivity and potentiates analgesic effect of morphine in BCP rats, probably by restoring MOR expression in spinal cord. Copyright © 2017 Elsevier B.V. All rights reserved.

[The changes of monocarboxylate transporter-2 in spinal cord horn in a rat model of chronic inflammatory pain].

PubMed

He, Jian-hua; Xu, Li; Shen, Yu; Kong, Ming-jian; Shi, Lin-yu; Ma, Zheng-liang

2015-01-01

To investigate the changes in the levels of monocarboxylate transporter-2 in spinal cord horn in a rat model of chronic inflammatory pain. Male SD rats weighting 180 - 220 g were randomly divided into two groups(n = 48): normal saline group (NS group), complete Freund's adjuvant group (CFA group). Rats were given injections of CFA 100 µl in left hind paw in group CFA, and an equal volume of saline was given injection in group NS. Mechanical withdraw threshold(MWT) and thermal withdraw latency(TWL) were measured at before injection(T0 and 3 h, 1 d, 3 d, 7 d, 14 d, and 21 d after injection(T1-7). Four rats were chosen from each group at T0-7 and sacrificed, and L4-5 segments of the spinal cord horn were removed for measurement of the expression of monocarboxylate transporter-2 by Western blot analysis. In CFA group, mechanical hyperalgesia and allodynia appeared on the 3 h after CFA injection, then until the day 14. The expression of monocarboxylate transporter-2 in the spinal dorsal horn of rats in CFA group was significantly higher than that in normal control group at T1-6(P <0.05). The protein level of monocarboxylate transporter-2 was apparently correlated with MWT and TWL(P <0.01 and P <0.05) in CFA group. The level of monocarboxylate transporter-2 in spinal dorsal horn is significantly increased in a rat model of chronic inflammatory pain and the change may involve in the formation and maintenance of central sensitization in spinal cord of chronic inflammatory uain.

Motor Cortex Stimulation Reverses Maladaptive Plasticity Following Spinal Cord Injury

DTIC Science & Technology

2012-09-01

pp 74–85. Austin: Landes Biosciences. 3. Abstracts o Mechanisms of Pain Relief Following Motor Cortex Stimulation: An fMRI Study. Society for...Neuroscience Meeting. Washington, DC. 2012. o Resting State fMRI in a Rat Model of Spinal Cord Injury Neuropathic Pain: A Longitudinal Study. Society...2601–2610. 16. Stefanacci L, Reber P, Costanza J, Wong E, Buxton R, Zola S, Squire L, Albright T. fMRI of monkey visual cortex. Neuron 1998;20:1051

Changes in erectile organ structure and function in a rat model of chronic prostatitis/chronic pelvic pain syndrome.

PubMed

Wang, X-J; Xia, L-L; Xu, T-Y; Zhang, X-H; Zhu, Z-W; Zhang, M-G; Liu, Y; Xu, C; Zhong, S; Shen, Z-J

2016-04-01

There is a growing recognition of the association between chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) and erectile dysfunction (ED); however, most of the reports are based on questionnaires which cannot distinguish between organic and functional ED. The purpose of this study was to determine the exact relationship between CP/CPPS and ED, and to investigate the changes in erectile organ structure and function in a rat model of CP/CPPS. We established a rat model of experimental autoimmune prostatitis (EAP), which is a valid model for CP/CPPS. Erectile function in EAP and normal rats was comparable after cavernous nerve electrostimulation. The serum testosterone and oestradiol levels, ultrastructure of the corpus cavernosum and expression of endothelial nitric oxide synthase and neuronal nitric oxide synthase in the two groups were similar; however, there was a decrease in smooth muscle-to-collagen ratio and alpha-smooth muscle actin expression and an increase in transforming growth factor-beta 1 expression was observed in EAP rats. Thus, organic ED may not exist in EAP rats. We speculate that ED complained by patients with CP/CPPS may be psychological, which could be caused by impairment in the quality of life; however, further studies are needed to fully understand the potential mechanisms underlying the penile fibrosis in EAP rats. © 2015 Blackwell Verlag GmbH.

Investigation of the effect of traditional Chinese medicine on pain and inflammation in chronic nonbacterial prostatitis in rats.

PubMed

Liu, Y-J; Song, G-H; Liu, G T

2016-08-01

According to traditional Chinese medicine, the symptoms of chronic nonbacterial prostatitis/chronic pelvic pain syndrome (CNP/CPPS) may be treated using a cocktail of herbs that stimulate blood circulation ('activating blood circulation formula'). We investigated the effect of three doses of this formula on a rat model of CNP/CPPS. Male Wistar rats were injected with a saline extract of male sex accessory glands on days 0 and 30 to induce prostatitis and then treated daily by gavage between days 32 and 60. Treatment with low, medium and high doses of activating blood circulation formula resulted in an almost total rescue of paw withdrawal threshold at day 60, and treatment with the highest dose also significantly decreased prostate inflammation (assessed histopathologically). We further observed elevated serum prostaglandin E2 levels in the CNP/CPPS model which decreased upon high-dose treatment, and increased Cox-2 expression in the prostate and spinal cord dorsal horn which was rescued in both tissues in the high-dose group and in the prostate in the medium-dose group. These results shed light on a possible mechanism by which activating blood circulation therapy may alleviate pain in a rat model of CNP/CPPS by downregulating Cox-2 expression in the spinal cord, thereby raising the pain threshold. Further research will be needed to fully characterise the mechanism by which activating blood circulation therapy produces this therapeutic effect. © 2016 Blackwell Verlag GmbH.

Effect of electroacupuncture on the cervicospinal P2X7 receptor/fractalkine/CX3CR1 signaling pathway in a rat neck-incision pain model.

PubMed

Gao, Y H; Li, C W; Wang, J Y; Tan, L H; Duanmu, C L; Jing, X H; Chang, X R; Liu, J L

2017-06-01

Increasing evidence supports that acupuncture intervention is an effective approach for intraoperative and postoperative pain. Neuron-microglia crosstalk, mediated by the purinergic P2X7 receptor (R)/fractalkine/CX3CR1 cascade in the spinal cord dorsal horn, plays a pivotal role in pain processing. However, its involvement in the analgesic effect of electroacupuncture (EA) remains unclear. In this study, a rat neck-incision pain model was established by making a longitudinal incision along the midline of the neck and subsequent repeated mechanical stimulation. EA stimulation was applied to bilateral LI18, LI4-PC6, or ST36-GB34. The thermal pain threshold, cervicospinal ATP concentration, expression levels of purinergic P2XR and P2YR subunits mRNAs, and fractalkine, CX3CR1 and p38 MAPK proteins, were detected separately. The neck incision induced strong thermal hyperalgesia and upregulation of spinal ATP within 48 h. No significant change was found in thermal hyperalgesia after a single session of EA intervention. However, a single session of EA dramatically enhanced the neck incision-induced upregulation of ATP and upregulated the expression of P2X7R, which was reversed by two sessions of EA. Two sessions of EA at bilateral LI18 or LI4-PC6 attenuated hyperalgesia significantly, accompanied with downregulation of P2X7R/fractalkine/ CX3CR1 signaling after three sessions of EA. EA stimulation of LI18 or LI4-PC6 alleviates thermal hyperalgesia in neck-incision pain rats, which may be associated with its effects in regulating the neck incision-induced increase of ATP and P2X7R and subsequently suppressing fractalkine/CX3CR1 signaling in the cervical spinal cord.

Further characterisation of a rat model of varicella zoster virus (VZV)-associated pain

PubMed Central

Hasnie, F. S.; Breuer, J.; Parker, S.; Wallace, V.; Blackbeard, J.; Lever, I.; Kinchington, P.R.; Dickenson, A. H.; Pheby, T.; Rice, A. S. C.

2007-01-01

Persistent herpes zoster-associated pain is a significant clinical problem and an area of largely unmet therapeutic need. Progress in elucidating the underlying pathophysiology of zoster-associated pain and related co-morbidity behaviour, in addition to appropriately targeted drug development has been hindered by the lack of an appropriate animal model. This study further characterises a recently developed rat model of zoster-associated hypersensitivity and investigates (a) response to different viral strains; (b) relationship between viral inoculum concentration (‘dose’) and mechanical hypersensitivity (‘response’); (c) attenuation of virus-associated mechanical hypersensitivity by clinically useful analgesic drugs; and (d) measurement of pain co-morbidity (anxiety-like behaviour) and pharmacological intervention in the open field paradigm (in parallel with models of traumatic peripheral nerve injury). VZV was propagated on fibroblast cells before subcutaneous injection into the glabrous footpad of the left hind limb of adult male Wistar rats. Control animals received injection of uninfected fibroblast cells. Hind-limb reflex withdrawal thresholds to mechanical, noxious thermal and cooling stimuli were recorded at specified intervals post-infection. Infection with all viral strains was associated with a dose-dependent mechanical hypersensitivity but not a thermal or cool hypersensitivity. Systemic treatment with intraperitoneal (i.p.) morphine (2.5mg/kg), amitriptyline (10mg/kg), gabapentin (30mg/kg), (S)-(+)-ibuprofen (20mg/kg) and the cannnabinoid WIN55,212-2 (2mg/kg) but not the antiviral, acyclovir (50mg/kg), was associated with a reversal of mechanical paw withdrawal thresholds. In the open field paradigm, virus-infected and nerve-injured animals demonstrated an anxiety-like pattern of ambulation (reduced entry into the central area of the open arena) which was positively correlated with mechanical hypersensitivity. This may reflect pain-related comorbidity. Further, anxiety-like behaviour was attenuated by acute i.p. administration of gabapentin (30mg/kg) in nerve-injured, but not virus-infected animals. This model will prove useful in elucidating the pathophysiology of zoster-associated pain and provide a tool for pre-clinical screening of analgesic drugs. PMID:17197105

Low dose native type II collagen prevents pain in a rat osteoarthritis model

PubMed Central

2013-01-01

Background Osteoarthritis is the most widespread joint-affecting disease. Patients with osteoarthritis experience pain and impaired mobility resulting in marked reduction of quality of life. A progressive cartilage loss is responsible of an evolving disease difficult to treat. The characteristic of chronicity determines the need of new active disease modifying drugs. Aim of the present research is to evaluate the role of low doses of native type II collagen in the rat model of osteoarthritis induced by sodium monoiodoacetate (MIA). Methods 1, 3 and 10 mg kg-1 porcine native type II collagen were daily per os administered for 13 days starting from the day of MIA intra-articular injection. Results On day 14, collagen-treated rats showed a significant prevention of pain threshold alterations induced by MIA. Evaluation were performed on paws using mechanical noxious (Paw pressure test) or non-noxious (Electronic Von Frey test) stimuli, and a decrease of articular pain was directly measured on the damaged joint (PAM test). The efficacy of collagen in reducing pain was as higher as the dose was lowered. Moreover, a reduced postural unbalance, measured as hind limb weight bearing alterations (Incapacitance test), and a general improvement of motor activity (Animex test) were observed. Finally, the decrease of plasma and urine levels of CTX-II (Cross Linked C-Telopeptide of Type II Collagen), a biomarker of cartilage degradation, suggests a collagen-dependent decrease of structural joint damage. Conclusions These results describe the preclinical efficacy of low dosages of native type II collagen as pain reliever by a mechanism that involves a protective effect on cartilage. PMID:23915264

CJ-13610, an orally active inhibitor of 5-lipoxygenase is efficacious in preclinical models of pain.

PubMed

Cortes-Burgos, Luz A; Zweifel, Ben S; Settle, Steven L; Pufahl, Robert A; Anderson, Gary D; Hardy, Medora M; Weir, Dana E; Hu, George; Happa, Fernando A; Stewart, Zachary; Muthian, Shanmugam; Graneto, Matthew J; Masferrer, Jaime L

2009-09-01

Zileuton, a redox and iron chelator 5-lipoxygenase (5-LOX) inhibitor and, leukotriene receptor antagonists are presently used clinically in the long term treatment of asthma. Recent data implicate 5-LOX pathway in pain signaling. We report 5-LOX expression in the central nervous system (CNS) and analyze the pain efficacy of a new class of non redox, non iron chelating 5-LOX inhibitor. CJ-13610, 4-(3-(4-(2-methyl-1H-imidazol-1-yl) phenylthio) phenyl)-tetrahydro-2H-pyran-4-carboxamide, demonstrated antihyperalgesic activity in inflammatory pain models including the acute carrageenan model and the chronic inflammatory model using complete Freund's adjuvant. Following complete Freund's adjuvant stimulus leukotrieneB(4) concentration in the brain was elevated (9+/-1 ng/g, mean+/-S.E.M.) by about 3 times that of the control group (3+/-0.11, mean+/-S.E.M.). Hyperalgesia and leukotrieneB(4) concentration were both reversed following CJ-13610 treatment. Furthermore, we demonstrate CJ-13610 efficacy against osteoarthritis like pain using the rat medial meniscal transection model. CJ-13610 at oral doses of 0.6, 2 and 6 mg/kg/day reversed two modalities of pain in this model; tactile allodynia and weight bearing differential. Taken together, these data suggest that 5-LOX pathway and the leukotriene products are important mediators of pain.

Persistent Pain Maintains Morphine-Seeking Behavior after Morphine Withdrawal through Reduced MeCP2 Repression of Glua1 in Rat Central Amygdala

PubMed Central

Hou, Yuan-Yuan; Cai, You-Qing

2015-01-01

As long-term opioids are increasingly used for control of chronic pain, how pain affects the rewarding effect of opioids and hence risk of prescription opioid misuse and abuse remains a healthcare concern and a challenging issue in current pain management. In this study, using a rat model of morphine self-administration, we investigated the molecular mechanisms underlying the impact of pain on operant behavior of morphine intake and morphine seeking before and after morphine withdrawal. We found that rats with persistent pain consumed a similar amount of daily morphine to that in control rats without pain, but maintained their level-pressing behavior of morphine seeking after abstinence of morphine at 0.2 mg/kg, whereas this behavior was gradually diminished in control rats. In the central nucleus of amygdala (CeA), a limbic structure critically involved in the affective dimension of pain, proteins of GluA1 subunits of glutamate AMPA receptors were upregulated during morphine withdrawal, and viral knockdown of CeA GluA1 eliminated the morphine-seeking behavior in withdrawn rats of the pain group. Chromatin immunoprecipitation analysis revealed that the methyl CpG-binding protein 2 (MeCP2) was enriched in the promoter region of Gria1 encoding GluA1 and this enrichment was significantly attenuated in withdrawn rats of the pain group. Furthermore, viral overexpression of CeA MeCP2 repressed the GluA1 level and eliminated the maintenance of morphine-seeking behavior after morphine withdrawal. These results suggest direct MeCp2 repression of GluA1 function as a likely mechanism for morphine-seeking behavior maintained by long-lasting affective pain after morphine withdrawal. PMID:25716866

Nociceptin/orphanin FQ peptide receptor antagonist JTC-801 reverses pain and anxiety symptoms in a rat model of post-traumatic stress disorder.

PubMed

Zhang, Y; Simpson-Durand, C D; Standifer, K M

2015-01-01

Single-prolonged stress (SPS), a rat model of post-traumatic stress disorder (PTSD), also induces long-lasting hyperalgesia associated with hypocortisolism and elevated nociceptin/orphanin FQ (N/OFQ) levels in serum and CSF. Here, we determined the effect of JTC-801 (N-(4-amino-2-methylquinolin-6-yl)-2-(4-ethylphenoxymethyl) benzamide monohydrochloride), a nociceptin/orphanin FQ peptide (NOP) receptor antagonist, on symptoms of pain and anxiety in rats after SPS exposure, and examined N/OFQ-NOP receptor system changes. Male Sprague Dawley rats received JTC-801 (6 mg kg(-1) i.p., once daily) during days 7-21 of SPS. The ability of JTC-801 to inhibit N/OFQ-stimulated [(35) S]-GTPγS binding was confirmed in rat brain membranes. Anxiety-like behaviour and pain sensitivity were monitored by changes in elevated plus maze performance and withdrawal responses to thermal and mechanical stimuli. Serum corticosterone and N/OFQ content in CSF, serum and brain tissues were determined by radioimmunoassay; NOP receptor protein and gene expression in amygdala, hippocampus and periaqueductal grey (PAG) were examined by immunoblotting and real-time PCR respectively. JTC-801 treatment reversed SPS-induced mechanical allodynia, thermal hyperalgesia, anxiety-like behaviour and hypocortisolism. Elevated N/OFQ levels in serum, CSF, PAG and hippocampus at day 21 of SPS were blocked by JTC-801; daily JTC-801 treatment also reversed NOP receptor protein and mRNA up-regulation in amygdala and PAG. JTC-801 reversed SPS-induced anxiety- and pain-like behaviours, and NOP receptor system up-regulation. These findings suggest that N/OFQ plays an important role in hyperalgesia and allodynia maintenance after SPS. NOP receptor antagonists may provide effective treatment for co-morbid PTSD and pain. This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2. © 2014 The British Pharmacological Society.

Radiotherapy Suppresses Bone Cancer Pain through Inhibiting Activation of cAMP Signaling in Rat Dorsal Root Ganglion and Spinal Cord.

PubMed

Zhu, Guiqin; Dong, Yanbin; He, Xueming; Zhao, Ping; Yang, Aixing; Zhou, Rubing; Ma, Jianhua; Xie, Zhong; Song, Xue-Jun

2016-01-01

Radiotherapy is one of the major clinical approaches for treatment of bone cancer pain. Activation of cAMP-PKA signaling pathway plays important roles in bone cancer pain. Here, we examined the effects of radiotherapy on bone cancer pain and accompanying abnormal activation of cAMP-PKA signaling. Female Sprague-Dawley rats were used and received tumor cell implantation (TCI) in rat tibia (TCI cancer pain model). Some of the rats that previously received TCI treatment were treated with X-ray radiation (radiotherapy). Thermal hyperalgesia and mechanical allodynia were measured and used for evaluating level of pain caused by TCI treatment. PKA mRNA expression in dorsal root ganglion (DRG) was detected by RT-PCR. Concentrations of cAMP, IL-1β, and TNF-α as well as PKA activity in DRG and the spinal cord were measured by ELISA. The results showed that radiotherapy significantly suppressed TCI-induced thermal hyperalgesia and mechanical allodynia. The level of PKA mRNA in DRG, cAMP concentration and PKA activity in DRG and in the spinal cord, and concentrations of IL-1β and TNF-α in the spinal cord were significantly reduced by radiotherapy. In addition, radiotherapy also reduced TCI-induced bone loss. These findings suggest that radiotherapy may suppress bone cancer pain through inhibition of activation of cAMP-PKA signaling pathway in DRG and the spinal cord.

DEET potentiates the development and persistence of anticholinesterase dependent chronic pain signs in a rat model of Gulf War Illness pain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flunker, L.K., E-mail: lflunker@dental.ufl.edu

Exposure to DEET (N,N-diethyl-meta-toluamide) may have influenced the pattern of symptoms observed in soldiers with GWI (Gulf War Illness; Haley and Kurt, 1997). We examined how the addition of DEET (400 mg/kg; 50% topical) to an exposure protocol of permethrin (2.6 mg/kg; topical), chlorpyrifos (CP; 120 mg/kg), and pyridostigmine bromide (PB;13 mg/kg) altered the emergence and pattern of pain signs in an animal model of GWI pain (). Rats underwent behavioral testing before, during and after a 4 week exposure: 1) hindlimb pressure withdrawal threshold; 2) ambulation (movement distance and rate); and 3) resting duration. Additional studies were conducted tomore » assess the influence of acute DEET (10–100 μM) on muscle and vascular nociceptor K{sub v}7, K{sub DR}, Na{sub v}1.8 and Na{sub v}1.9. We report that a 50% concentration of DEET enhanced the development and persistence of pain-signs. Rats exposed to all 4 compounds exhibited ambulation deficits that appeared 5–12 weeks post-exposure and persisted through weeks 21–24. Rats exposed to only three agents (CP or PB excluded), did not fully develop ambulation deficits. When PB was excluded, rats also developed rest duration pain signs, in addition to ambulation deficits. There was no evidence that physiological doses of DEET acutely modified nociceptor K{sub v}7, K{sub DR}, Na{sub v}1.8 or Na{sub v}1.9 activities. Nevertheless, DEET augmented protocols decreased the conductance of K{sub v}7 expressed in vascular nociceptors harvested from chronically exposed rats. We concluded that DEET enhanced the development and persistence of pain behaviors, but the anticholinesterases CP and PB played a determinant role. - Highlights: • DEET accelerated and prolonged pain-like behaviors in a rat model of Gulf War Illness. • The development of pain behaviors were dependent upon chlorpyrifos and pyridostigmine. • Conductance of vascular nociceptor Kv7 was diminished 12 weeks following exposures. • DEET did not have any acute influence on nociceptor Kv7, Nav1.8, Nav1.9 or KDR.« less

Sex differences in pain-related behavior and expression of calcium/calmodulin-dependent protein kinase II in dorsal root ganglia of rats with diabetes type 1 and type 2.

PubMed

Ferhatovic, Lejla; Banozic, Adriana; Kostic, Sandra; Sapunar, Damir; Puljak, Livia

2013-06-01

Sex differences in pain-related behavior and expression of calcium/calmodulin dependent protein kinase II (CaMKII) in dorsal root ganglia were studied in rat models of Diabetes mellitus type 1 (DM1) and type 2 (DM2). DM1 was induced with 55mg/kg streptozotocin, and DM2 with a combination of high-fat diet and 35mg/kg of streptozotocin. Pain-related behavior was analyzed using thermal and mechanical stimuli. The expression of CaMKII was analyzed with immunofluorescence. Sexual dimorphism in glycemia, and expression of CaMKII was observed in the rat model of DM1, but not in DM2 animals. Increased expression of total CaMKII (tCaMKII) in small-diameter dorsal root ganglia neurons, which are associated with nociception, was found only in male DM1 rats. None of the animals showed increased expression of the phosphorylated alpha CaMKII isoform in small-diameter neurons. The expression of gamma and delta isoforms of CaMKII remained unchanged in all analyzed animal groups. Different patterns of glycemia and tCaMKII expression in male and female model of DM1 were not associated with sexual dimorphism in pain-related behavior. The present findings do not suggest sex-related differences in diabetic painful peripheral neuropathy in male and female diabetic rats. Copyright © 2012 Elsevier GmbH. All rights reserved.

Long-Term Effects of Neonatal Pain and Stress on Reactivity of the Nociceptive System.

PubMed

Butkevich, I P; Mikhailenko, V A

2016-10-01

The influence of inflammatory pain and/or weaning stress at different terms of neonatal development on functional activity of the nociceptive system during adulthood was studied in rats. Repeated stress in 1-2-day-old rat pups (a premature baby model) enhanced pain sensitivity to peripheral inflammation in both males and females. Repeated inflammatory pain experienced by male pups aged 1-2 or 7-8 days (models of preterm and full-term baby), even in presence of mother, enhanced pain behavior under conditions of repeated inflammatory pain in adulthood. Pain sensitivity in adult animals before (hot plate test) and after formation of the inflammatory focus (formalin test) depended on the age when the animals were subjected to the injury, type of exposure, and on animal sex. The priority data obtained by us will help to understand the mechanisms of long-term effects of early injuries and are important for pediatricians and neonatologists.

Pregabalin reduces acute inflammatory and persistent pain associated with nerve injury and cancer in rat models of orofacial pain.

PubMed

Hummig, Wagner; Kopruszinski, Caroline Machado; Chichorro, Juliana Geremias

2014-01-01

To assess the analgesic effect of pregabalin in orofacial models of acute inflammatory pain and of persistent pain associated with nerve injury and cancer, and so determine its effectiveness in controlling orofacial pains having different underlying mechanisms. Orofacial capsaicin and formalin tests were employed in male Wistar rats to assess the influence of pregabalin (or vehicle) pretreatment in acute pain models, and the results from these experiments were analyzed by one-way analysis of variance (ANOVA) followed by Newman Keuls post-hoc test. Pregabalin (or vehicle) treatment was also tested on the facial heat hyperalgesia that was evaluated in rats receiving injection of the inflammatory irritant carrageenan into the upper lip, as well as after constriction of the infraorbital nerve (a model of trigeminal neuropathic pain), or after inoculation of tumor cells into the facial vibrissal pad; two-way repeated measures ANOVA followed by Newman-Keuls post-hoc test was used to analyze data from these experiments. Facial grooming induced by capsaicin was abolished by pretreatment with pregabalin at 10 and 30 mg/kg. However, pregabalin failed to modify the first phase of the formalin response, but reduced the second phase at both doses (10 and 30 mg/kg). In addition, treatment of rats with pregabalin reduced the heat hyperalgesia induced by carrageenan, as well as by nerve injury and facial cancer. Pregabalin produced a marked antinociceptive effect in rat models of facial inflammatory pain as well as in facial neuropathic and cancer pain models, suggesting that it may represent an important agent for the clinical control of orofacial pain.

Efficacy of Various Analgesics on Shoulder Function and Rotator Cuff Tendon-to-Bone Healing in a Rat (Rattus norvegicus) Model

PubMed Central

Caro, Adam C; Tucker, Jennica J; Yannascoli, Sarah M; Dunkman, Andrew A; Thomas, Stephen J; Soslowsky, Louis J

2014-01-01

Although relief of postoperative pain is an imperative aspect of animal welfare, analgesics that do not interfere with the scientific goals of the study must be used. Here we compared the efficacy of different analgesic agents by using an established rat model of supraspinatus tendon healing and a novel gait-analysis system. We hypothesized that different analgesic agents would all provide pain relief in this model but would cause differences in tendon-to-bone healing and gait parameters. Buprenorphine, ibuprofen, tramadol–gabapentin, and acetaminophen were compared with a no-analgesia control group. Gait measures (stride length and vertical force) on the operative forelimb differed between the control group and both the buprenorphine (2 and 4 d postsurgery) and ibuprofen (2 d postsurgery) groups. Step length was different in the control group as compared with the tramadol–gabapentin (2 d after surgery), buprenorphine (2 and 4 d after surgery), and ibuprofen (2 d after surgery) groups. Regarding tendon-to-bone healing, the ibuprofen group showed less stiffness at the insertion site; no other differences in tendon-to-bone healing were detected. In summary, the analgesics evaluated were associated with differences in both animal gait and tendon-to-bone healing. This information will be useful for improving the management of postsurgical pain without adversely affecting tissue healing. Given its ability to improve gait without impeding healing, we recommend use of buprenorphine for postsurgical pain management in rats. In addition, our gait-analysis system can be used to evaluate new analgesics. PMID:24602546

Postoperative Analgesia Due to Sustained-Release Buprenorphine, Sustained-Release Meloxicam, and Carprofen Gel in a Model of Incisional Pain in Rats (Rattus norvegicus)

PubMed Central

Seymour, Travis L; Adams, Sean C; Felt, Stephen A; Jampachaisri, Katechan; Yeomans, David C; Pacharinsak, Cholawat

2016-01-01

Postoperative analgesia in laboratory rats is complicated by the frequent handling associated with common analgesic dosing requirements. Here, we evaluated sustained-release buprenorphine (Bup-SR), sustained-release meloxicam (Melox-SR), and carprofen gel (CG) as refinements for postoperative analgesia. The aim of this study was to investigate whether postoperative administration of Bup-SR, Melox-SR, or CG effectively controls behavioral mechanical and thermal hypersensitivity in a rat model of incisional pain. Rats were randomly assigned to 1 of 5 treatment groups: saline, 1 mL/kg SC BID; buprenorphine HCl (Bup HCl), 0.05 mg/kg SC BID; Bup-SR, 1.2 mg/kg SC once; Melox-SR, 4 mg/kg SC once; and CG, 2 oz PO daily. Mechanical and thermal hypersensitivity were tested daily from day–1 through 4. Bup HCl and Bup-SR attenuated mechanical and thermal hypersensitivity on days 1 through 4. Melox-SR and CG attenuated mechanical hypersensitivity–but not thermal hypersensitivity–on days 1 through 4. Plasma concentrations, measured by using UPLC with mass spectrometry, were consistent between both buprenorphine formulations. Gross pathologic examination revealed no signs of toxicity in any group. These findings suggest that postoperative administration of Bup HCl and Bup-SR—but not Melox-SR or CG—effectively attenuates mechanical and thermal hypersensitivity in a rat model of incisional pain. PMID:27177563

Transplantation of Reprogrammed Autologous Stem Cells for Chronic Pain and Drug Abuse

DTIC Science & Technology

2012-10-01

Hyperalgesia and Mechanical Allodynia by Curcumin in a Rat Model of Partial Thickness Thermal Injury Clifford, John Evaluation Of A Non-Invasive System Of...Thermal Injury Garza, Thomas Biochemical Correlates for the Analgesic Action Of Curcumin : A Naturally occurring Anti-inflammatory Agent Greer, Angie

Postoperative Analgesia Due to Sustained-Release Buprenorphine, Sustained-Release Meloxicam, and Carprofen Gel in a Model of Incisional Pain in Rats (Rattus norvegicus).

PubMed

Seymour, Travis L; Adams, Sean C; Felt, Stephen A; Jampachaisri, Katechan; Yeomans, David C; Pacharinsak, Cholawat

2016-01-01

Postoperative analgesia in laboratory rats is complicated by the frequent handling associated with common analgesic dosing requirements. Here, we evaluated sustained-release buprenorphine (Bup-SR), sustained-release meloxicam (Melox-SR), and carprofen gel (CG) as refinements for postoperative analgesia. The aim of this study was to investigate whether postoperative administration of Bup-SR, Melox-SR, or CG effectively controls behavioral mechanical and thermal hypersensitivity in a rat model of incisional pain. Rats were randomly assigned to 1 of 5 treatment groups: saline, 1 mL/kg SC BID; buprenorphine HCl (Bup HCl), 0.05 mg/kg SC BID; Bup-SR, 1.2 mg/kg SC once; Melox-SR, 4 mg/kg SC once; and CG, 2 oz PO daily. Mechanical and thermal hypersensitivity were tested daily from day-1 through 4. Bup HCl and Bup-SR attenuated mechanical and thermal hypersensitivity on days 1 through 4. Melox-SR and CG attenuated mechanical hypersensitivity-but not thermal hypersensitivity-on days 1 through 4. Plasma concentrations, measured by using UPLC with mass spectrometry, were consistent between both buprenorphine formulations. Gross pathologic examination revealed no signs of toxicity in any group. These findings suggest that postoperative administration of Bup HCl and Bup-SR-but not Melox-SR or CG-effectively attenuates mechanical and thermal hypersensitivity in a rat model of incisional pain.

Comparison of dorsal root ganglion gene expression in rat models of traumatic and HIV-associated neuropathic pain

PubMed Central

Maratou, Klio; Wallace, Victoria C.J.; Hasnie, Fauzia S.; Okuse, Kenji; Hosseini, Ramine; Jina, Nipurna; Blackbeard, Julie; Pheby, Timothy; Orengo, Christine; Dickenson, Anthony H.; McMahon, Stephen B.; Rice, Andrew S.C.

2009-01-01

To elucidate the mechanisms underlying peripheral neuropathic pain in the context of HIV infection and antiretroviral therapy, we measured gene expression in dorsal root ganglia (DRG) of rats subjected to systemic treatment with the anti-retroviral agent, ddC (Zalcitabine) and concomitant delivery of HIV-gp120 to the rat sciatic nerve. L4 and L5 DRGs were collected at day 14 (time of peak behavioural change) and changes in gene expression were measured using Affymetrix whole genome rat arrays. Conventional analysis of this data set and Gene Set Enrichment Analysis (GSEA) was performed to discover biological processes altered in this model. Transcripts associated with G protein coupled receptor signalling and cell adhesion were enriched in the treated animals, while ribosomal proteins and proteasome pathways were associated with gene down-regulation. To identify genes that are directly relevant to neuropathic mechanical hypersensitivity, as opposed to epiphenomena associated with other aspects of the response to a sciatic nerve lesion, we compared the gp120 + ddC-evoked gene expression with that observed in a model of traumatic neuropathic pain (L5 spinal nerve transection), where hypersensitivity to a static mechanical stimulus is also observed. We identified 39 genes/expressed sequence tags that are differentially expressed in the same direction in both models. Most of these have not previously been implicated in mechanical hypersensitivity and may represent novel targets for therapeutic intervention. As an external control, the RNA expression of three genes was examined by RT-PCR, while the protein levels of two were studied using western blot analysis. PMID:18606552

Visualizing Nerve Injury in a Neuropathic Pain Model with [18F]FTC-146 PET/MRI.

PubMed

Shen, Bin; Behera, Deepak; James, Michelle L; Reyes, Samantha T; Andrews, Lauren; Cipriano, Peter W; Klukinov, Michael; Lutz, Amanda Brosius; Mavlyutov, Timur; Rosenberg, Jarrett; Ruoho, Arnold E; McCurdy, Christopher R; Gambhir, Sanjiv S; Yeomans, David C; Biswal, Sandip; Chin, Frederick T

2017-01-01

The ability to locate nerve injury and ensuing neuroinflammation would have tremendous clinical value for improving both the diagnosis and subsequent management of patients suffering from pain, weakness, and other neurologic phenomena associated with peripheral nerve injury. Although several non-invasive techniques exist for assessing the clinical manifestations and morphological aspects of nerve injury, they often fail to provide accurate diagnoses due to limited specificity and/or sensitivity. Herein, we describe a new imaging strategy for visualizing a molecular biomarker of nerve injury/neuroinflammation, i.e. , the sigma-1 receptor (S1R), in a rat model of nerve injury and neuropathic pain. The two-fold higher increase of S1Rs was shown in the injured compared to the uninjured nerve by Western blotting analyses. With our novel S1R-selective radioligand, [ 18 F]FTC-146 (6-(3-[ 18 F]fluoropropyl)-3-(2-(azepan-1-yl)ethyl)benzo[ d ]thiazol-2(3H)-one), and positron emission tomography-magnetic resonance imaging (PET/MRI), we could accurately locate the site of nerve injury created in the rat model. We verified the accuracy of this technique by ex vivo autoradiography and immunostaining, which demonstrated a strong correlation between accumulation of [ 18 F]FTC-146 and S1R staining. Finally, pain relief could also be achieved by blocking S1Rs in the neuroma with local administration of non-radioactive [ 19 F]FTC-146. In summary, [ 18 F]FTC-146 S1R PET/MR imaging has the potential to impact how we diagnose, manage and treat patients with nerve injury, and thus warrants further investigation.

Transdermal cannabidiol reduces inflammation and pain-related behaviours in a rat model of arthritis

PubMed Central

Hammell, D.C.; Zhang, L.P.; Ma, F.; Abshire, S.M.; McIlwrath, S.L.; Stinchcomb, A.L.; Westlund, K.N.

2015-01-01

Background Current arthritis treatments often have side-effects attributable to active compounds as well as route of administration. Cannabidiol (CBD) attenuates inflammation and pain without side-effects, but CBD is hydrophobic and has poor oral bioavailability. Topical drug application avoids gastrointestinal administration, first pass metabolism, providing more constant plasma levels. Methods This study examined efficacy of transdermal CBD for reduction in inflammation and pain, assessing any adverse effects in a rat complete Freund’s adjuvant-induced monoarthritic knee joint model. CBD gels (0.6, 3.1, 6.2 or 62.3 mg/day) were applied for 4 consecutive days after arthritis induction. Joint circumference and immune cell invasion in histological sections were measured to indicate level of inflammation. Paw withdrawal latency (PWL) in response to noxious heat stimulation determined nociceptive sensitization, and exploratory behaviour ascertained animal’s activity level. Results Measurement of plasma CBD concentration provided by transdermal absorption revealed linearity with 0.6–6.2 mg/day doses. Transdermal CBD gel significantly reduced joint swelling, limb posture scores as a rating of spontaneous pain, immune cell infiltration and thickening of the synovial membrane in a dose-dependent manner. PWL recovered to near baseline level. Immunohistochemical analysis of spinal cord (CGRP, OX42) and dorsal root ganglia (TNFα) revealed dose-dependent reductions of pro-inflammatory biomarkers. Results showed 6.2 and 62 mg/day were effective doses. Exploratory behaviour was not altered by CBD indicating limited effect on higher brain function. Conclusions These data indicate that topical CBD application has therapeutic potential for relief of arthritis pain-related behaviours and inflammation without evident side-effects. PMID:26517407

Activation of spinal and supraspinal cannabinoid-1 receptors lead to antinociception in a rat model of neuropathic spinal cord injury pain

PubMed Central

Hama, Aldric; Sagen, Jacqueline

2011-01-01

Activation of CNS cannabinoid subtype-1 (CB1) receptors has been shown to mediate the antinociceptive and other effects of systemically administered CB receptor agonists. The endogenous peptide CB receptor ligand hemopressin (HE) has previously demonstrated an antinociceptive effect in rats with a hind paw inflammation, without exhibiting characteristic CB1 receptor-mediated side-effects. The current study evaluated the effect of intrathecal (i.t.) and intracerebroventricular (i.c.v.) injection of HE in a rat model of neuropathic spinal cord injury (SCI) pain. The non-subtype selective CB receptor agonist WIN 55,212-2 was also centrally administered in SCI rats as a comparator. Four weeks following an acute compression of the mid-thoracic spinal cord, rats displayed markedly decreased hind paw withdrawal thresholds, indicative of below-level neuropathic pain. Central administration of WIN 55,212-2 significantly increased withdrawal thresholds, whereas HE did not. Hemopressin has been reported to block CB1 receptors in vitro, similar to the CB1 receptor antagonist rimonabant. Pretreatment with rimonabant completely blocked the antinociceptive effect of centrally administered WIN 55,212-2, but pretreatment with HE did not. While the data confirm that activation of either supraspinal or spinal CB1 receptors leads to significant antinociception in SCI rats, the current data do not support an antinociceptive effect from an acute blockade of central CB1 receptors, HE’s putative antinociceptive mechanism, in neuropathic SCI rats. Although such a mechanism could be useful in other models of pain with a significant inflammatory component, the current data indicate that activation of CB1 receptors is needed to ameliorate neuropathic SCI pain. PMID:21813113

CJ-023,423, a novel, potent and selective prostaglandin EP4 receptor antagonist with antihyperalgesic properties.

PubMed

Nakao, Kazunari; Murase, Akio; Ohshiro, Hiroyuki; Okumura, Takako; Taniguchi, Kana; Murata, Yoko; Masuda, Masatoshi; Kato, Tomoki; Okumura, Yoshiyuki; Takada, Junji

2007-08-01

The prostaglandin (PG) EP(4) receptor subtype is expressed by peripheral sensory neurons. Although a potential role of EP(4) receptor in pain has been suggested, a limited number of selective ligands have made it difficult to explore the physiological functions of EP(4) or its potential as a new analgesic target. Here, we describe the in vitro and in vivo pharmacology of a novel EP(4) receptor antagonist, N-[({2-[4-(2-ethyl-4,6-dimethyl-1H-imidazo [4,5-c] pyridin-1-yl) phenyl]ethyl}amino) carbonyl]-4-methylbenzenesulfonamide (CJ-023,423). In vitro, CJ-023,423 inhibits [(3)H]PGE(2) binding to both human and rat EP(4) receptors with K(i) of 13 +/- 4 and 20 +/- 1 nM, respectively. CJ-023,423 is highly selective for the human EP(4) receptor over other human prostanoid receptor subtypes. It also inhibits PGE(2)-evoked elevation in intracellular cAMP at the human and rat EP(4) receptors with pA(2) of 8.3 +/- 0.03 and 8.2 +/- 0.2 nM, respectively. In vivo, oral administration of CJ-023,423 significantly reduces thermal hyperalgesia induced by intraplantar injection of PGE(2) (ED(50) = 12.8 mg/kg). CJ-023,423 is also effective in models of acute and chronic inflammatory pain. CJ-023,423 significantly reduces mechanical hyperalgesia in the carrageenan model. Furthermore, CJ-023,423 significantly reverses complete Freund's adjuvant-induced chronic inflammatory pain response. Taken together, the present data indicate that CJ-023,423, a highly potent and selective antagonist of both human and rat EP(4) receptors, produces antihyperalgesic effects in animal models of inflammatory pain. Thus, specific blockade of the EP(4) receptor signaling may represent a novel therapeutic approach for the treatment of inflammatory pain.

Ablating spinal NK1-bearing neurons eliminates the development of pain & reduces spinal neuronal hyperexcitability & inflammation from mechanical joint injury in the rat

PubMed Central

Weisshaar, Christine L.; Winkelstein, Beth A.

2014-01-01

The facet joint is a common source of pain especially from mechanical injury. Although chronic pain is associated with altered spinal glial and neuronal responses, the contribution of specific spinal cells to joint pain are not understood. This study used the neurotoxin [Sar9,Met(O2)11]-substance P-saporin (SSP-SAP) to selectively eliminate spinal cells expressing neurokinin-1 receptor (NK1R) in a rat model of painful facet joint injury to determine the role of those spinal neurons in pain from facet injury. Following spinal administration of SSP-SAP or its control (blank-SAP), a cervical facet injury was imposed and behavioral sensitivity assessed. Spinal extracellular recordings were made on day 7 to classify neurons and quantify evoked firing. Spinal glial activation and IL1α expression also were evaluated. SSP-SAP prevented the development of mechanical hyperalgesia that is induced by joint injury and reduced NK1R expression and mechanically-evoked neuronal firing in the dorsal horn. SSP-SAP also prevented a shift toward wide dynamic range neurons that is seen after injury. Spinal astrocytic activation and IL1α expression were reduced to sham levels with SSP-SAP treatment. These results suggest that spinal NK1R-bearing cells are critical in initiating spinal nociception and inflammation associated with a painful mechanical joint injury. Perspective Results demonstrate that cells expressing NK1R in the spinal cord are critical for the development of joint pain and spinal neuroplasticity and inflammation after trauma to the joint. These findings have utility for understanding mechanisms of joint pain and developing potential targets to treat pain. PMID:24389017

Behavioral, cellular and molecular maladaptations covary with exposure to pyridostigmine bromide in a rat model of gulf war illness pain.

PubMed

Cooper, B Y; Flunker, L D; Johnson, R D; Nutter, T J

2018-08-01

Many veterans of Operation Desert Storm (ODS) struggle with the chronic pain of Gulf War Illness (GWI). Exposure to insecticides and pyridostigmine bromide (PB) have been implicated in the etiology of this multisymptom disease. We examined the influence of 3 (DEET (N,N-diethyl-meta-toluamide), permethrin, chlorpyrifos) or 4 GW agents (DEET, permethrin, chlorpyrifos, pyridostigmine bromide (PB)) on the post-exposure ambulatory and resting behaviors of rats. In three independent studies, rats that were exposed to all 4 agents consistently developed both immediate and delayed ambulatory deficits that persisted at least 16 weeks after exposures had ceased. Rats exposed to a 3 agent protocol (PB excluded) did not develop any ambulatory deficits. Cellular and molecular studies on nociceptors harvested from 16WP (weeks post-exposure) rats indicated that vascular nociceptor Na v 1.9 mediated currents were chronically potentiated following the 4 agent protocol but not following the 3 agent protocol. Muscarinic linkages to muscle nociceptor TRPA1 were also potentiated in the 4 agent but not the 3 agent, PB excluded, protocol. Although K v 7 activity changes diverged from the behavioral data, a K v 7 opener, retigabine, transiently reversed ambulation deficits. We concluded that PB played a critical role in the development of pain-like signs in a GWI rat model and that shifts in Na v 1.9 and TRPA1 activity were critical to the expression of these pain behaviors. Copyright © 2018 Elsevier Inc. All rights reserved.

Mangiferin attenuates contusive spinal cord injury in rats through the regulation of oxidative stress, inflammation and the Bcl‑2 and Bax pathway.

PubMed

Luo, Yang; Fu, Changfeng; Wang, Zhenyu; Zhang, Zhuo; Wang, Hongxia; Liu, Yi

2015-11-01

Mangiferin has antioxidant, antiviral, apoptosis regulating, anti‑inflammatory, antitumor and antidiabetic effects, which can also inhibit osteoclast formation and bone resorption. However, whether mangiferin ameliorates the neurological pain of spinal cord injury (SCI) in ratS remains to be elucidated. The present study investigated the therapeutic effects of mangiferin on neurological function, the water content of spinal cord, oxidative stress, the expression of inflammatory cytokines and the protein expression of Bcl‑2/Bax in a SCI rat model. In the present study, the Basso, Beattie and Bresnahan scores, and the water content of the spinal cord were used to analyze the therapeutic effects of mangiferin on neurological pain in the SCI rat. The concentrations of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and the serum levels of glutathione peroxidase (GSH‑PX), nuclear factor‑κB p65 unit, tumor necrosis factor‑α, interleukin (IL)‑1β, IL‑6 and caspase‑3/9 were detected using commercial kits. The expression levels of Bcl‑2 and Bax were measured using western blot analysis. The results demonstrated that administrating mangiferin began to ameliorate neurological function and the water content of the spinal cord in the SCI rat. The mangiferin‑treated group were found to have lower oxidative stress activity and lower expression levels of inflammatory cytokines, compared with the SCI rat. In addition, mangiferin significantly reduced the protein expression of Bax and promoted the protein expression of Bcl-2 in the SCI rat model. Finally, mangiferin markedly suppressed the expression of caspase‑3/9, indicating that the protective action of mangiferin may be associated with anti‑apoptosis activation. In conclusion, mangiferin attenuated contusive SCI in the rats through regulating oxidative stress, inflammation and the Bcl‑2 and Bax pathway.

Antihyperalgesic effect of a Cannabis sativa extract in a rat model of neuropathic pain: mechanisms involved.

PubMed

Comelli, Francesca; Giagnoni, Gabriella; Bettoni, Isabella; Colleoni, Mariapia; Costa, Barbara

2008-08-01

This study aimed to give a rationale for the employment of phytocannabinoid formulations to treat neuropathic pain. It was found that a controlled cannabis extract, containing multiple cannabinoids, in a defined ratio, and other non-cannabinoid fractions (terpenes and flavonoids) provided better antinociceptive efficacy than the single cannabinoid given alone, when tested in a rat model of neuropathic pain. The results also demonstrated that such an antihyperalgesic effect did not involve the cannabinoid CB1 and CB2 receptors, whereas it was mediated by vanilloid receptors TRPV1. The non-psychoactive compound, cannabidiol, is the only component present at a high level in the extract able to bind to this receptor: thus cannabidiol was the drug responsible for the antinociceptive behaviour observed. In addition, the results showed that after chronic oral treatment with cannabis extract the hepatic total content of cytochrome P450 was strongly inhibited as well as the intestinal P-glycoprotein activity. It is suggested that the inhibition of hepatic metabolism determined an increased bioavailability of cannabidiol resulting in a greater effect. However, in the light of the well known antioxidant and antiinflammatory properties of terpenes and flavonoids which could significantly contribute to the therapeutic effects, it cannot be excluded that the synergism observed might be achieved also in the absence of the cytochrome P450 inhibition.

Augmented chondroprotective effect of coadministration of celecoxib and rebamipide in the monosodium iodoacetate rat model of osteoarthritis.

PubMed

Moon, Su-Jin; Park, Jin-Sil; Jeong, Jeong-Hee; Yang, Eun-Ji; Park, Mi-Kyung; Kim, Eun-Kyung; Park, Sung-Hwan; Kim, Ho-Youn; Cho, Mi-La; Min, Jun-Ki

2013-01-01

Osteoarthritis (OA) is a degenerative joint disease characterized by the progressive loss of articular cartilage and chronic pain. Although cyclooxygenase-2 (COX-2) inhibitors such as celecoxib are recommended to patients at high risk of gastrointestinal (GI) adverse events, COX-2 inhibitors do not completely prevent GI adverse events. Rebamipide, a gastroprotective agent, has anti-inflammatory properties and acts as an oxygen radical scavenger. The aim of this study was to investigate the in vivo effects of coadministration of rebamipide and celecoxib in an OA rat model. OA was induced by intra-articular injection of monosodium iodoacetate. Oral administration of rebamipide was initiated on the day of OA induction. In this study, rebamipide showed antinociceptive properties and attenuated cartilage degeneration. Rebamipide reduced the expression of matrix metalloproteinase 13, interleukin-1β, inducible nitric oxide synthase, and nitrotyrosine in OA cartilage. OA rats treated with celecoxib in combination with rebamipide demonstrated a higher pain threshold than those treated with monotherapy. Histological examination also showed that the joints from OA animals treated with combination therapy demonstrated less cartilage damage than those of animals treated with monotherapy. We showed that the potential benefit of combination therapy with celecoxib and rebamipide on pain and cartilage degeneration in OA.

Preemptive Caffeine Administration Blocks the Increase in Postoperative Pain Caused by Previous Sleep Loss in the Rat: A Potential Role for Preoptic Adenosine A2A Receptors in Sleep-Pain Interactions.

PubMed

Hambrecht-Wiedbusch, Viviane S; Gabel, Maya; Liu, Linda J; Imperial, John P; Colmenero, Angelo V; Vanini, Giancarlo

2017-09-01

Sleep and pain are reciprocally related, but the precise mechanisms underlying this relationship are poorly understood. This study used a rat model of surgical pain to examine the effect of previous sleep loss on postoperative pain and tested the hypothesis that preoptic adenosinergic mechanisms regulate sleep-pain interactions. Relative to ad libitum sleep, 6 hours of total sleep deprivation prior to a surgical incision significantly enhanced postoperative mechanical hypersensitivity in the affected paw and prolonged the time to recovery from surgery. There were no sex-specific differences in these measures. There were also no changes in adrenocorticotropic hormone and corticosterone levels after sleep deprivation, suggesting that this effect was not mediated by the stress associated with the sleep perturbation. Systemic administration of the nonselective adenosine receptor antagonist caffeine at the onset of sleep deprivation prevented the sleep deprivation-induced increase in postoperative hypersensitivity. Microinjection of the adenosine A2A receptor antagonist ZM 241385 into the median preoptic nucleus (MnPO) blocked the increase in surgical pain levels and duration caused by prior sleep deprivation and eliminated the thermal hyperalgesia induced by sleep deprivation in a group of nonoperated (i.e., without surgical incision) rats. These data show that even a brief sleep disturbance prior to surgery worsens postoperative pain and are consistent with our hypothesis that adenosine A2A receptors in the MnPO contribute to regulate these sleep-pain interactions. © Sleep Research Society 2017. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please e-mail journals.permissions@oup.com.

Injectable Nanocomposite Analgesic Delivery System for Musculoskeletal Pain Management.

PubMed

Khanal, Manakamana; Gohil, Shalini V; Kuyinu, Emmanuel; Kan, Ho-Man; Knight, Brittany E; Baumbauer, Kyle M; Lo, Kevin W-H; Walker, Joseph; Laurencin, Cato T; Nair, Lakshmi S

2018-05-24

Musculoskeletal pain is a major health issue which results from surgical procedures (i.e. total knee and/ or hip replacements and rotator cuff repairs), as well as from non-surgical conditions (i.e. sympathetically-mediated pain syndrome and occipital neuralgia). Local anesthetics, opioids or corticosteroids are currently used for the pain management of musculoskeletal conditions. Even though local anesthetics are highly preferred, the need for multiple administration presents significant disadvantages. Development of unique delivery systems that can deliver local anesthetics at the injection site for prolonged time could significantly enhance the therapeutic efficacy and patient comfort. The goal of the present study is to evaluate the efficacy of an injectable local anesthetic nanocomposite carrier to provide sustained analgesic effect. The nanocomposite carrier was developed by encapsulating ropivacaine, a local anesthetic, in lipid nanocapsules (LNC-Rop), and incorporating the nanocapsules in enzymatically crosslinked glycol chitosan (0.3GC) hydrogels. Cryo Scanning Electron Microscopic (Cryo SEM) images showed the ability to distribute the LNCs within the hydrogel without adversely affecting their morphology. The study demonstrated the feasibility to achieve sustained release of lipophilic molecules from the nanocomposite carrier in vitro and in vivo. A rat chronic constriction injury (CCI) pain model was used to evaluate the efficacy of the nanocomposite carrier using thermal paw withdrawal latency (TWL). The nanocomposite carriers loaded with ropivacaine and dexamethasone showed significant improvement in pain response compared to the control groups for at least 7 days. The study demonstrated the clinical potential of these nanocomposite carriers for post-operative and neuropathic pain. Acute or chronic pain associated with musculoskeletal conditions is considered a major health issue, with healthcare costs totaling several billion dollars. The opioid crisis presents a pressing clinical need to develop alternative and effective approaches to treat musculoskeletal pain. The goal of this study was to develop a long-acting injectable anesthetic formulation which can sustain a local anesthetic effect for a prolonged time. This in turn could increase the quality of life and rehabilitation outcome of patients, and decrease opioid consumption. The developed injectable nanocomposite demonstrated the feasibility to achieve prolonged pain relief in a rat chronic constriction injury (CCI) model. Copyright © 2018. Published by Elsevier Ltd.

The role of trigeminal nucleus caudalis orexin 1 receptors in orofacial pain transmission and in orofacial pain-induced learning and memory impairment in rats.

PubMed

Kooshki, Razieh; Abbasnejad, Mehdi; Esmaeili-Mahani, Saeed; Raoof, Maryam

2016-04-01

It is widely accepted that the spinal trigeminal nuclear complex, especially the subnucleus caudalis (Vc), receives input from orofacial structures. The neuropeptides orexin-A and -B are expressed in multiple neuronal systems. Orexin signaling has been implicated in pain-modulating system as well as learning and memory processes. Orexin 1 receptor (OX1R) has been reported in trigeminal nucleus caudalis. However, its roles in trigeminal pain modulation have not been elucidated so far. This study was designed to investigate the role of Vc OX1R in the modulation of orofacial pain as well as pain-induced learning and memory deficits. Orofacial pain was induced by subcutaneous injection of capsaicin in the right upper lip of the rats. OX1R agonist (orexin-A) and antagonist (SB-334867-A) were microinjected into Vc prior capsaicin administration. After recording nociceptive times, learning and memory was investigated using Morris water maze (MWM) test. The results indicated that, orexin-A (150 pM/rat) significantly reduced the nociceptive times, while SB334867-A (80 nM/rat) exaggerated nociceptive behavior in response to capsaicin injection. In MWM test, capsaicin-treated rats showed a significant learning and memory impairment. Moreover, SB-334867-A (80 nM/rat) significantly exaggerated learning and memory impairment in capsaicin-treated rats. However, administration of orexin-A (100 pM/rat) prevented learning and memory deficits. Taken together, these results indicate that Vc OX1R was at least in part involved in orofacial pain transmission and orexin-A has also a beneficial inhibitory effect on orofacial pain-induced deficits in abilities of spatial learning and memory. Copyright © 2016 Elsevier Inc. All rights reserved.

Sex differences underlying orofacial varicella zoster associated pain in rats.

PubMed

Stinson, Crystal; Deng, Mohong; Yee, Michael B; Bellinger, Larry L; Kinchington, Paul R; Kramer, Phillip R

2017-05-17

Most people are initially infected with varicella zoster virus (VZV) at a young age and this infection results in chickenpox. VZV then becomes latent and reactivates later in life resulting in herpes zoster (HZ) or "shingles". Often VZV infects neurons of the trigeminal ganglia to cause ocular problems, orofacial disease and occasionally a chronic pain condition termed post-herpetic neuralgia (PHN). To date, no model has been developed to study orofacial pain related to varicella zoster. Importantly, the incidence of zoster associated pain and PHN is known to be higher in women, although reasons for this sex difference remain unclear. Prior to this work, no animal model was available to study these sex-differences. Our goal was to develop an orofacial animal model for zoster associated pain which could be utilized to study the mechanisms contributing to this sex difference. To develop this model VZV was injected into the whisker pad of rats resulting in IE62 protein expression in the trigeminal ganglia; IE62 is an immediate early gene in the VZV replication program. Similar to PHN patients, rats showed retraction of neurites after VZV infection. Treatment of rats with gabapentin, an agent often used to combat PHN, ameliorated the pain response after whisker pad injection. Aversive behavior was significantly greater for up to 7 weeks in VZV injected rats over control inoculated rats. Sex differences were also seen such that ovariectomized and intact female rats given the lower dose of VZV showed a longer affective response than male rats. The phase of the estrous cycle also affected the aversive response suggesting a role for sex steroids in modulating VZV pain. These results suggest that this rat model can be utilized to study the mechanisms of 1) orofacial zoster associated pain and 2) the sex differences underlying zoster associated pain.

Resveratrol attenuates bone cancer pain through regulating the expression levels of ASIC3 and activating cell autophagy.

PubMed

Zhu, Haili; Ding, Jieqiong; Wu, Ji; Liu, Tingting; Liang, Jing; Tang, Qiong; Jiao, Ming

2017-11-01

Bone cancer pain (BCP) is one of the most common pains in patients with malignant cancers. The mechanism underlying BCP is largely unknown. Our previous studies and the increasing evidence both have shown that acid-sensing ion channels 3 (ASIC3) is an important protein in the pathological pain state in some pain models. We hypothesized that the expression change of ASIC3 might be one of the factors related to BCP. In this study, we established the BCP model through intrathecally injecting rat mammary gland carcinoma cells (MRMT-1) into the left tibia of Sprague-Dawley female rats, and found that the BCP rats showed bone destruction, increased mechanical pain sensitivities and up-regulated ASIC3 protein expression levels in L4-L6 dorsal root ganglion. Then, resveratrol, which was intraperitoneally injected into the BCP rats on post-operative Day 21, dose-dependently increased the paw withdrawal threshold of BCP rats, reversed the pain behavior, and had an antinociceptive effect on BCP rats. In ASIC3-transfected SH-SY5Y cells, the ASIC3 protein expression levels were regulated by resveratrol in a dose- and time-dependent manner. Meanwhile, resveratrol also had an antinociceptive effect in ASIC3-mediated pain rat model. Furthermore, resveratrol also enhanced the phosphorylation of AMPK, SIRT1, and LC3-II levels in ASIC3-transfected SH-SY5Y cells, indicating that resveratrol could activate the AMPK-SIRT1-autophagy signal pathway in ASIC3-transfected SH-SY5Y cells. In BCP rats, SIRT1 and LC3-II were also down-regulated. These findings provide new evidence for the use of resveratrol as a therapeutic treatment during BCP states. © The Author 2017. Published by Oxford University Press on behalf of the Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

A novel inhibitor of active protein kinase G attenuates chronic inflammatory and osteoarthritic pain.

PubMed

Sung, Ying-Ju; Sofoluke, Nelson; Nkamany, Mary; Deng, Shixian; Xie, Yuli; Greenwood, Jeremy; Farid, Ramy; Landry, Donald W; Ambron, Richard T

2017-05-01

Activating PKG-1α induces a long-term hyperexcitability (LTH) in nociceptive neurons. Since the LTH correlates directly with chronic pain in many animal models, we tested the hypothesis that inhibiting PKG-1α would attenuate LTH-mediated pain. We first synthesized and characterized compound N46 (N-((3R,4R)-4-(4-(2-fluoro-3-methoxy-6-propoxybenzoyl)benzamido)pyrrolidin-3-yl)-1H-indazole-5-carboxamide). N46 inhibits PKG-1α with an IC50 of 7.5 nmol, was highly selective when tested against a panel of 274 kinases, and tissue distribution studies indicate that it does not enter the CNS. To evaluate its antinociceptive potential, we used 2 animal models in which the pain involves both activated PKG-1α and LTH. Injecting complete Freund's adjuvant (CFA) into the rat hind paw causes a thermal hyperalgesia that was significantly attenuated 24 hours after a single intravenous injection of N46. Next, we used a rat model of osteoarthritic knee joint pain and found that a single intra-articular injection of N46 alleviated the pain 14 days after the pain was established and the relief lasted for 7 days. Thermal hyperalgesia and osteoarthritic pain are also associated with the activation of the capsaicin-activated transient receptor protein vanilloid-1 (TRPV1) channel. We show that capsaicin activates PKG-1α in nerves and that a subcutaneous delivery of N46 attenuated the mechanical and thermal hypersensitivity elicited by exposure to capsaicin. Thus, PKG-1α appears to be downstream of the transient receptor protein vanilloid-1. Our studies provide proof of concept in animal models that a PKG-1α antagonist has a powerful antinociceptive effect on persistent, already existing inflammatory pain. They further suggest that N46 is a valid chemotype for the further development of such antagonists.

Nociceptive neuronal Fc-gamma receptor I is involved in IgG immune complex induced pain in the rat.

PubMed

Jiang, Haowu; Shen, Xinhua; Chen, Zhiyong; Liu, Fan; Wang, Tao; Xie, Yikuan; Ma, Chao

2017-05-01

Antigen-specific immune diseases such as rheumatoid arthritis are often accompanied by pain and hyperalgesia. Our previous studies have demonstrated that Fc-gamma-receptor type I (FcγRI) is expressed in a subpopulation of rat dorsal root ganglion (DRG) neurons and can be directly activated by IgG immune complex (IgG-IC). In this study we investigated whether neuronal FcγRI contributes to antigen-specific pain in the naïve and rheumatoid arthritis model rats. In vitro calcium imaging and whole-cell patch clamp recordings in dissociated DRG neurons revealed that only the small-, but not medium- or large-sized DRG neurons responded to IgG-IC. Accordingly, in vivo electrophysiological recordings showed that intradermal injection of IgG-IC into the peripheral receptive field could sensitize only the C- (but not A-) type sensory neurons and evoke action potential discharges. Pain-related behavioral tests showed that intradermal injection of IgG-IC dose-dependently produced mechanical and thermal hyperalgesia in the hindpaw of rats. These behavioral effects could be alleviated by localized administration of non-specific IgG or an FcγRI antibody, but not by mast cell stabilizer or histamine antagonist. In a rat model of antigen-induced arthritis (AIA) produced by methylated bovine serum albumin, FcγRI were found upregulated exclusively in the small-sized DRG neurons. In vitro calcium imaging revealed that significantly more small-sized DRG neurons responded to IgG-IC in the AIA rats, although there was no significant difference between the AIA and control rats in the magnitude of calcium changes in the DRG neurons. Moreover, in vivo electrophysiological recordings showed that C-nociceptive neurons in the AIA rats exhibited a greater incidence of action potential discharges and stronger responses to mechanical stimuli after IgG-IC was injected to the receptive fields. These results suggest that FcγRI expressed in the peripheral nociceptors might be directly activated by IgG-IC and contribute to antigen-specific pain in pathological conditions. Copyright © 2017 Elsevier Inc. All rights reserved.

Analgesic Effect of the Newly Developed S(+)-Flurbiprofen Plaster on Inflammatory Pain in a Rat Adjuvant-Induced Arthritis Model.

PubMed

Sugimoto, Masanori; Toda, Yoshihisa; Hori, Miyuki; Mitani, Akiko; Ichihara, Takahiro; Sekine, Shingo; Hirose, Takuya; Endo, Hiromi; Futaki, Nobuko; Kaku, Shinsuke; Otsuka, Noboru; Matsumoto, Hideo

2016-02-01

Preclinical Research This article describes the properties of a novel topical NSAID (Nonsteroidal anti-inflammatory drug) patch, SFPP (S(+)-flurbiprofen plaster), containing the potent cyclooxygenase (COX) inhibitor, S(+)-flurbiprofen (SFP). The present studies were conducted to confirm human COX inhibition and absorption of SFP and to evaluate the analgesic efficacy of SFPP in a rat adjuvant-induced arthritis (AIA) model. COX inhibition by SFP, ketoprofen and loxoprofen was evaluated using human recombinant COX proteins. Absorption of SFPP, ketoprofen and loxoprofen from patches through rat skin was assessed 24 h after application. The AIA model was induced by injecting Mycobacterium tuberculosis followed 20 days later by the evaluation of the prostaglandin PGE2 content of the inflamed paw and the pain threshold. SFP exhibited more potent inhibitory activity against COX-1 (IC50  = 8.97 nM) and COX-2 (IC50  = 2.94 nM) than the other NSAIDs evaluated. Absorption of SFP was 92.9%, greater than that of ketoprofen and loxoprofen from their respective patches. Application of SFPP decreased PGE2 content from 15 min to 6 h and reduced paw hyperalgesia compared with the control, ketoprofen and loxoprofen patches. SFPP showed analgesic efficacy, and was superior to the ketoprofen and loxoprofen patches, which could be through the potent COX inhibitory activity of SFP and greater skin absorption. The results suggested SFPP can be expected to exert analgesic effect clinically. © 2016 The Authors Drug Development Research Published by Wiley Periodicals, Inc.

The effects of alpha2-adrenoceptor agents on anti-hyperalgesic effects of carbamazepine and oxcarbazepine in a rat model of inflammatory pain.

PubMed

Vucković, Sonja M; Tomić, Maja A; Stepanović-Petrović, Radica M; Ugresić, Nenad; Prostran, Milica S; Bosković, Bogdan

2006-11-01

In this study, the effects of yohimbine (alpha2-adrenoceptor antagonist) and clonidine (alpha2-adrenoceptor agonist) on anti-hyperalgesia induced by carbamazepine and oxcarbazepine in a rat model of inflammatory pain were investigated. Carbamazepine (10-40 mg/kg; i.p.) and oxcarbazepine (40-160 mg/kg; i.p.) caused a significant dose-dependent reduction of the paw inflammatory hyperalgesia induced by concanavalin A (Con A, intraplantarly) in a paw pressure test in rats. Yohimbine (1-3 mg/kg; i.p.) significantly depressed the anti-hyperalgesic effects of carbamazepine and oxcarbazepine, in a dose- and time-dependent manner. Both drug mixtures (carbamazepine-clonidine and oxcarbazepine-clonidine) administered in fixed-dose fractions of the ED50 (1/2, 1/4 and 1/8) caused significant and dose-dependent reduction of the hyperalgesia induced by Con A. Isobolographic analysis revealed a significant synergistic (supra-additive) anti-hyperalgesic effect of both combinations tested. These results indicate that anti-hyperalgesic effects of carbamazepine and oxcarbazepine are, at least partially, mediated by activation of adrenergic alpha2-receptors. In addition, synergistic interaction for anti-hyperalgesia between carbamazepine and clonidine, as well as oxcarbazepine and clonidine in a model of inflammatory hyperalgesia, was demonstrated.

Nociceptin/orphanin FQ peptide receptor antagonist JTC-801 reverses pain and anxiety symptoms in a rat model of post-traumatic stress disorder

PubMed Central

Zhang, Y; Simpson-Durand, C D; Standifer, K M

2015-01-01

BACKGROUND AND PURPOSE Single-prolonged stress (SPS), a rat model of post-traumatic stress disorder (PTSD), also induces long-lasting hyperalgesia associated with hypocortisolism and elevated nociceptin/orphanin FQ (N/OFQ) levels in serum and CSF. Here, we determined the effect of JTC-801 (N-(4-amino-2-methylquinolin-6-yl)-2-(4-ethylphenoxymethyl) benzamide monohydrochloride), a nociceptin/orphanin FQ peptide (NOP) receptor antagonist, on symptoms of pain and anxiety in rats after SPS exposure, and examined N/OFQ-NOP receptor system changes. EXPERIMENTAL APPROACH Male Sprague Dawley rats received JTC-801 (6 mg kg−1 i.p., once daily) during days 7–21 of SPS. The ability of JTC-801 to inhibit N/OFQ-stimulated [35S]-GTPγS binding was confirmed in rat brain membranes. Anxiety-like behaviour and pain sensitivity were monitored by changes in elevated plus maze performance and withdrawal responses to thermal and mechanical stimuli. Serum corticosterone and N/OFQ content in CSF, serum and brain tissues were determined by radioimmunoassay; NOP receptor protein and gene expression in amygdala, hippocampus and periaqueductal grey (PAG) were examined by immunoblotting and real-time PCR respectively. KEY RESULTS JTC-801 treatment reversed SPS-induced mechanical allodynia, thermal hyperalgesia, anxiety-like behaviour and hypocortisolism. Elevated N/OFQ levels in serum, CSF, PAG and hippocampus at day 21 of SPS were blocked by JTC-801; daily JTC-801 treatment also reversed NOP receptor protein and mRNA up-regulation in amygdala and PAG. CONCLUSION AND IMPLICATIONS JTC-801 reversed SPS-induced anxiety- and pain-like behaviours, and NOP receptor system up-regulation. These findings suggest that N/OFQ plays an important role in hyperalgesia and allodynia maintenance after SPS. NOP receptor antagonists may provide effective treatment for co-morbid PTSD and pain. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2 PMID:24666365

Analgesic Effect of the Newly Developed S(+)‐Flurbiprofen Plaster on Inflammatory Pain in a Rat Adjuvant‐Induced Arthritis Model

PubMed Central

Toda, Yoshihisa; Hori, Miyuki; Mitani, Akiko; Ichihara, Takahiro; Sekine, Shingo; Hirose, Takuya; Endo, Hiromi; Futaki, Nobuko; Kaku, Shinsuke; Otsuka, Noboru; Matsumoto, Hideo

2016-01-01

ABSTRACT Preclinical Research This article describes the properties of a novel topical NSAID (Nonsteroidal anti‐inflammatory drug) patch, SFPP (S(+)‐flurbiprofen plaster), containing the potent cyclooxygenase (COX) inhibitor, S(+)‐flurbiprofen (SFP). The present studies were conducted to confirm human COX inhibition and absorption of SFP and to evaluate the analgesic efficacy of SFPP in a rat adjuvant‐induced arthritis (AIA) model. COX inhibition by SFP, ketoprofen and loxoprofen was evaluated using human recombinant COX proteins. Absorption of SFPP, ketoprofen and loxoprofen from patches through rat skin was assessed 24 h after application. The AIA model was induced by injecting Mycobacterium tuberculosis followed 20 days later by the evaluation of the prostaglandin PGE2 content of the inflamed paw and the pain threshold. SFP exhibited more potent inhibitory activity against COX‐1 (IC50 = 8.97 nM) and COX‐2 (IC50 = 2.94 nM) than the other NSAIDs evaluated. Absorption of SFP was 92.9%, greater than that of ketoprofen and loxoprofen from their respective patches. Application of SFPP decreased PGE2 content from 15 min to 6 h and reduced paw hyperalgesia compared with the control, ketoprofen and loxoprofen patches. SFPP showed analgesic efficacy, and was superior to the ketoprofen and loxoprofen patches, which could be through the potent COX inhibitory activity of SFP and greater skin absorption. The results suggested SFPP can be expected to exert analgesic effect clinically. Drug Dev Res 76 : 20–28, 2016. © 2016 Wiley Periodicals, Inc. PMID:26763139

Clinically relevant behavioral endpoints in a recurrent nitroglycerin migraine model in rats.

PubMed

Sufka, Kenneth J; Staszko, Stephanie M; Johnson, Ainslee P; Davis, Morgan E; Davis, Rachel E; Smitherman, Todd A

2016-01-01

This research sought to further validate the rat nitroglycerin (NTG) migraine model by comparing the effects of single versus recurrent NTG episodes on behavioral endpoints that mirror ICHD-3 diagnostic criteria for migraine, and to determine if the altered behavioral endpoints are reduced after administration of sumatriptan. Separate cohorts of rats were administered NTG (10 mg/kg/2 ml) or saline (Experiment 1: single injection; Experiment 2: repeated injections; Experiment 3: repeated injections with sumatriptan [0.0, 0.3 and 1.0 mg/kg/ml] rescue. Behavioral endpoints were assessed 2 h after final NTG administration and included time in light/dark chambers for photophobia and activity, pain facial ratings, and cool (5 °C) and warm (46 °C) tail dip. The first two experiments demonstrated that repeated (n = 5) but not single NTG injections produced photophobia, decreased activity, and yielded less weight gain than saline injections. Experiment 3 showed that sumatriptan attenuated hypoactivity, reduced facial expressions of pain, and reversed weight alterations in a dose-dependent manner. These findings identify numerous clinical homologies of a recurrent NTG rat migraine model that may be useful for screening novel pharmacotherapies.

Minocycline attenuates bone cancer pain in rats by inhibiting NF-κB in spinal astrocytes.

PubMed

Song, Zhen-Peng; Xiong, Bing-Rui; Guan, Xue-Hai; Cao, Fei; Manyande, Anne; Zhou, Ya-Qun; Zheng, Hua; Tian, Yu-Ke

2016-06-01

To investigate the mechanisms underlying the anti-nociceptive effect of minocycline on bone cancer pain (BCP) in rats. A rat model of BCP was established by inoculating Walker 256 mammary carcinoma cells into tibial medullary canal. Two weeks later, the rats were injected with minocycline (50, 100 μg, intrathecally; or 40, 80 mg/kg, ip) twice daily for 3 consecutive days. Mechanical paw withdrawal threshold (PWT) was used to assess pain behavior. After the rats were euthanized, spinal cords were harvested for immunoblotting analyses. The effects of minocycline on NF-κB activation were also examined in primary rat astrocytes stimulated with IL-1β in vitro. BCP rats had marked bone destruction, and showed mechanical tactile allodynia on d 7 and d 14 after the operation. Intrathecal injection of minocycline (100 μg) or intraperitoneal injection of minocycline (80 mg/kg) reversed BCP-induced mechanical tactile allodynia. Furthermore, intraperitoneal injection of minocycline (80 mg/kg) reversed BCP-induced upregulation of GFAP (astrocyte marker) and PSD95 in spinal cord. Moreover, intraperitoneal injection of minocycline (80 mg/kg) reversed BCP-induced upregulation of NF-κB, p-IKKα and IκBα in spinal cord. In IL-1β-stimulated primary rat astrocytes, pretreatment with minocycline (75, 100 μmol/L) significantly inhibited the translocation of NF-κB to nucleus. Minocycline effectively alleviates BCP by inhibiting the NF-κB signaling pathway in spinal astrocytes.

Superior analgesic effect of H-Dmt-D-Arg-Phe-Lys-NH2 ([Dmt1]DALDA), a multifunctional opioid peptide, compared to morphine in a rat model of neuropathic pain.

PubMed

Shimoyama, Megumi; Schiller, Peter W; Shimoyama, Naohito; Toyama, Satoshi; Szeto, Hazel H

2012-11-01

H-Dmt-D-Arg-Phe-Lys-NH(2) ([Dmt(1)]DALDA) is a synthetic tetrapeptide with extraordinary selectivity for the mu-opioid receptor and is an extremely potent analgesic. [Dmt(1) ]DALDA is unusual in the way that the greater part of its analgesic potency appears to be produced by its actions in the spinal cord. Furthermore, [Dmt(1) ]DALDA inhibits norepinephrine re-uptake and is a mitochondria-targeted antioxidant. Such characteristics may make [Dmt(1)]DALDA particularly effective against neuropathic pain. The present study was designed to compare the effects of [Dmt(1)]DALDA and morphine on thermal hyperalgesia in an experimental neuropathic pain model. Neuropathic pain was induced in rats by surgical ligation of the L5 spinal nerve, and thermal pain thresholds were assessed by latencies of paw withdrawal to radiant heat. The increase in paw withdrawal latency was greater after the administration of [Dmt(1) ]DALDA than that of morphine in neuropathic rats at doses that were equianalgesic in naïve animals. We conclude that [Dmt(1)]DALDA is more effective than morphine against thermal hyperalgesia in this experimental model of neuropathic pain. © 2012 John Wiley & Sons A/S.

Effects of low energy shock wave therapy on inflammatory moleculars, bladder pain, and bladder function in a rat cystitis model.

PubMed

Wang, Hung-Jen; Lee, Wei-Chia; Tyagi, Pradeep; Huang, Chao-Cheng; Chuang, Yao-Chi

2017-08-01

Low energy shock wave (LESW) is known to facilitate tissue regeneration with analgesic and anti-inflammatory effects. We examined the effects of LESW on the expression of inflammatory molecules, pain behavior, and bladder function in a rat cystitis model. Control and experimental animals were injected with saline or cyclophosphamide (CYP; 75 mg/kg intraperitoneally) on day 1 and 4. After lower midline incision, the bladders were exposed to LESW (300 pulses, 0.12 mJ/mm 2 ) or sham operation on day 2. In study 1 (N = 12, 4 for each group), the nociceptive effects of CYP were evaluated for 30 min by behavioral assessment on day 4 one hour after CYP injection. In study 2 (N = 21, 7 for each group), continuous cystometry (CMG) was performed on day 8. The bladder was harvested after behavioral assessment or CMG for histology and Western blotting. CYP-induced upregulation of COX2 and IL6 expression, caused pain behavior (eye closing and hypolocomotion), and bladder inflammation was noted on days 4 and 8 along with bladder hyperactivity. LESW treatment reduced pain behavior and downregulated the NGF expression (33.3%, P < 0.05) on day 4 and IL6 (40.9%, P < 0.05). LESW treatment suppressed bladder overactivity (intercontraction interval 77.8% increase, P < 0.05) by decreasing inflammation and COX2 (38.6%, P < 0.05) expression and NGF expression (25.2%, P = 0.0812). CYP-induced bladder pain, inflammation, and overactivity involves activation of IL6, NGF, and COX2 expression. These changes are suppressed by LESW, indicating it as a potential candidate for relieving bladder inflammatory conditions and overactivity. © 2016 Wiley Periodicals, Inc.

Central Action of Peripherally Applied Botulinum Toxin Type A on Pain and Dural Protein Extravasation in Rat Model of Trigeminal Neuropathy

PubMed Central

Filipović, Boris; Matak, Ivica; Bach-Rojecky, Lidija; Lacković, Zdravko

2012-01-01

Background Infraorbital nerve constriction (IoNC) is an experimental model of trigeminal neuropathy. We investigated if IoNC is accompanied by dural extravasation and if botulinum toxin type A (BoNT/A) can reduce pain and dural extravasation in this model. Methodology/Principal Findings Rats which developed mechanical allodynia 14 days after the IoNC were injected with BoNT/A (3.5 U/kg) into vibrissal pad. Allodynia was tested by von Frey filaments and dural extravasation was measured as colorimetric absorbance of Evans blue - plasma protein complexes. Presence of dural extravasation was also examined in orofacial formalin-induced pain. Unilateral IoNC, as well as formalin injection, produced bilateral dural extravasation. Single unilateral BoNT/A injection bilaterally reduced IoNC induced dural extravasation, as well as allodynia (lasting more than 2 weeks). Similarly, BoNT/A reduced formalin-induced pain and dural extravasation. Effects of BoNT/A on pain and dural extravasation in IoNC model were dependent on axonal transport through sensory neurons, as evidenced by colchicine injections (5 mM, 2 µl) into the trigeminal ganglion completely preventing BoNT/A effects. Conclusions/Significance Two different types of pain, IoNC and formalin, are accompanied by dural extravasation. The lasting effect of a unilateral injection of BoNT/A in experimental animals suggests that BoNT/A might have a long-term beneficial effect in craniofacial pain associated with dural neurogenic inflammation. Bilateral effects of BoNT/A and dependence on retrograde axonal transport suggest a central site of its action. PMID:22238656

A cross-circulated bicephalic model of head transplantation.

PubMed

Li, Peng-Wei; Zhao, Xin; Zhao, Yun-Long; Wang, Bing-Jian; Song, Yang; Shen, Zi-Long; Jiang, Hong-Jun; Jin, Hai; Canavero, Sergio; Ren, Xiao-Ping

2017-06-01

A successful cephalosomatic anastomosis ("head transplant") requires, among others, the ability to control long-term immune rejection and avoidance of ischemic events during the head transference phase. We developed a bicephalic model of head transplantation to study these aspects. The thoracic aorta and superior vena cava of a donor rat were anastomosed with the carotid artery and extracorporeal veins of a recipient rat by vascular grafts. Before thoracotomy in the donor rat, the axillary artery and vein of the donor were connected to the carotid and the extracranial vein of the third rat through a silicone tube. The silicone tube was passed through a peristaltic pump to ensure donor brain tissue blood supply. There is no ischemia reperfusion injury in donor brain tissue analyzed by electroencephalogram. Postoperative donor has pain reflex and corneal reflex. Peristaltic pump application can guarantee the blood supply of donor brain tissue per unit time, while the application of temperature change device to the silicone tube can protect the brain tissue hypothermia, postoperative experimental data show that there is no brain tissue ischemia during the whole operation. The application of vascular grafting can also provide the possibility of long-term survival of the model. © 2017 John Wiley & Sons Ltd.

A Chinese Herbal Decoction, Shaoyao-Gancao Tang, Exerts Analgesic Effect by Down-Regulating the TRPV1 Channel in a Rat Model of Arthritic Pain.

PubMed

Sui, Feng; Zhou, Hai-Yu; Meng, Jing; Du, Xin-Liang; Sui, Yun-Peng; Zhou, Zhi-Kun; Dong, Cheng; Wang, Zhu-Ju; Wang, Wei-Hao; Dai, Li; Ma, Hai; Huo, Hai-Ru; Jiang, Ting-Liang

2016-01-01

Shaoyao-Gancao Tang (SGT) is one of the most frequently used compound formulas in the treatment of pain-related diseases in the medical practice of traditional Chinese medicine (TCM). To investigate the anti-inflammatory and antinociceptive effects, as well as to uncover the molecular mechanism of SGT, the rat pain model of arthritis was experimentally induced by single unilateral injection of rats' left hind paw with Freund's complete adjuvant (FCA). SGT was orally administered to the rats daily at three doses individually for a period of 16 days post-model induction. Swollen degrees and pain thresholds of the rats in different groups were measured for evaluation of the anti-inflammatory and anti-nociceptive effects of SGT. Furthermore, the mRNA and protein expression levels of transient receptor potential ion channel protein vanilloid receptor 1 (TRPV1) channel as well as its calcium-mediating function in the isolated DRG neurons were further detected to provide indexes for exploration of the molecular mechanisms mediating anti-arthritic activities of SGT. As a result, FCA injection induced significant allodynia, inflammation and edema, accompanied by a significant increase in both expression and calcium-mediating function of the TRPV1 channel. Pharmacologically, oral administration of SGT at a high or middle dose demonstrated a significant relief from the above-mentioned pathological conditions in a dose-dependent manner. Simultaneously the mRNA and protein expressional levels of TRPV1 channel, as well as its calcium-mediating function, were down-regulated greatly. These findings suggest that SGT possesses a significant analgesic and anti-inflammatory effect on arthritis rats; its therapeutic activities might be achieved through reversing the elevated expression and function of TRPV1 channel evoked by FCA.

Cardamonin (2',4'-dihydroxy-6'-methoxychalcone) isolated from Boesenbergia rotunda (L.) Mansf. inhibits CFA-induced rheumatoid arthritis in rats.

PubMed

Voon, Fui-Ling; Sulaiman, Mohd Roslan; Akhtar, Muhammad Nadeem; Idris, Mohamad Fauzi; Akira, Ahmad; Perimal, Enoch Kumar; Israf, Daud Ahmad; Ming-Tatt, Lee

2017-01-05

Boesenbergia rotunda (L.) Mansf. had been traditionally used as herbs to treat pain and rheumatism. Cardamonin (2',4'-dihydroxy-6'-methoxychalcone) is a compound isolated from Boesenbergia rotunda (L.) Mansf.. Previous study had shown the potential of cardamonin in inhibiting the release of pro-inflammatory cytokines such as tumour necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) in vitro. Thus, the possible therapeutic effect of cardamonin in the rheumatoid arthritis (RA) joints is postulated. This study was performed to investigate the anti-arthritic properties of cardamonin in rat model of induced RA, particularly on the inflammatory and pain response of RA. Rheumatoid arthritis paw inflammation was induced by intraplantar (i.pl.) injection of complete Freund's adjuvant (CFA) in Sprague Dawley rats. Using four doses of cardamonin (0.625, 1.25, 2.5, and 5.0mg/kg), anti-arthritic activity was evaluated through the paw edema, mechanical allodynia and thermal hyperalgesia responses. Enzyme-linked immunosorbent assay (ELISA) was carried out to evaluate the plasma level of TNF-α, IL-1β, and IL-6. Histological slides were prepared from the harvested rat paws to observe the arthritic changes in the joints. Behavioral, biochemical, and histological studies showed that cardamonin demonstrated significant inhibition on RA-induced inflammatory and pain responses as well as progression of joint destruction in rats. ELISA results showed that there was significant inhibition in TNF-α, IL-1β, and IL-6 levels in plasma of the cardamonin-treated RA rats. Overall, cardamonin possesses potential anti-arthritic properties in CFA-induced RA rat model. Copyright © 2016 Elsevier B.V. All rights reserved.

Role of Complement in a Rat Model of Paclitaxel-Induced Peripheral Neuropathy.

PubMed

Xu, Jijun; Zhang, Lingjun; Xie, Mian; Li, Yan; Huang, Ping; Saunders, Thomas L; Fox, David A; Rosenquist, Richard; Lin, Feng

2018-06-15

Chemotherapy-induced peripheral neuropathy (CIPN) is a painful and debilitating side effect of cancer chemotherapy with an unclear pathogenesis. Consequently, the available therapies for this neuropathic pain syndrome are inadequate, leading to a significantly reduced quality of life in many patients. Complement, a key component of the innate immune system, has been associated with neuroinflammation, a potentially important trigger of some types of neuropathic pain. However, the role of complement in CIPN remains unclear. To address this issue, we developed a C3 knockout (KO) rat model and induced CIPN in these KO rats and wild-type littermates via the i.p. administration of paclitaxel, a chemotherapeutic agent associated with CIPN. We then compared the severity of mechanical allodynia, complement activation, and intradermal nerve fiber loss between the groups. We found that 1) i.p. paclitaxel administration activated complement in wild-type rats, 2) paclitaxel-induced mechanical allodynia was significantly reduced in C3 KO rats, and 3) the paclitaxel-induced loss of intradermal nerve fibers was markedly attenuated in C3 KO rats. In in vitro studies, we found that paclitaxel-treated rat neuronal cells activated complement, leading to cellular injury. Our findings demonstrate a previously unknown but pivotal role of complement in CIPN and suggest that complement may be a new target for the development of novel therapeutics to manage this painful disease. Copyright © 2018 by The American Association of Immunologists, Inc.

The refined biomimetic NeuroDigm GEL™ model of neuropathic pain in a mature rat

PubMed Central

Hannaman, Mary R.; Fitts, Douglas A.; Doss, Rose M.; Weinstein, David E.; Bryant, Joseph L.

2017-01-01

Background: Many humans suffering with chronic neuropathic pain have no objective evidence of an etiological lesion or disease. Frequently their persistent pain occurs after the healing of a soft tissue injury. Based on clinical observations over time, our hypothesis was that after an injury in mammals the process of tissue repair could cause chronic neural pain. Our objectives were to create the delayed onset of neuropathic pain in rats with minimal nerve trauma using a physiologic hydrogel, and characterize the rats’ responses to known analgesics and a targeted biologic. Methods: In mature male Sprague Dawley rats (age 9.5 months) a percutaneous implant of tissue-derived hydrogel was placed in the musculofascial tunnel of the distal tibial nerve. Subcutaneous morphine (3 mg/kg), celecoxib (10 mg/kg), gabapentin (25 mg/kg) and duloxetine (10 mg/kg) were each screened in the model three times each over 5 months after pain behaviors developed. Sham and control groups were used in all screenings. A pilot study followed in which recombinant human erythropoietin (200 units) was injected by the GEL™ neural procedure site. Results: The GEL group gradually developed mechanical hypersensitivity lasting months. Morphine, initially effective, had less analgesia over time. Celecoxib produced no analgesia, while gabapentin and duloxetine at low doses demonstrated profound analgesia at all times tested. The injected erythropoietin markedly decreased bilateral pain behavior that had been present for over 4 months, p ≤ 0.001. Histology of the GEL group tibial nerve revealed a site of focal neural remodeling, with neural regeneration, as found in nerve biopsies of patients with neuropathic pain. Conclusion: The refined NeuroDigm GEL™ model induces a neural response resulting in robust neuropathic pain behavior. The analgesic responses in this model reflect known responses of humans with neuropathic pain. The targeted recombinant human erythropoietin at the ectopic neural lesion appears to alleviate the persistent pain behavior in the GEL™ model rodents. PMID:28620451

Bisphosphonates inhibit pain, bone loss, and inflammation in a rat tibia fracture model of complex regional pain syndrome

PubMed Central

Wang, Liping; Guo, Tian-Zhi; Wei, Tzuping; Li, Wen-wu; Shi, Xiaoyou; Clark, J David; Kingery, Wade S

2016-01-01

BACKGROUND Bisphosphonates are used to prevent the bone loss and fractures associated with osteoporosis, bone metastases, multiple myeloma, and osteogenis deformans. Distal limb fractures cause regional bone loss with cutaneous inflammation and pain in the injured limb that can develop into complex regional pain syndrome (CRPS). Clinical trials have reported that anti-resorptive bisphosphonates can prevent fracture-induced bone loss, inhibit serum inflammatory cytokine levels, and alleviate CRPS pain. Previously we observed that the inhibition of inflammatory cytokines or adaptive immune responses attenuated the development of pain behavior in a rat fracture model of CRPS and we hypothesized that bisphosphonates could prevent pain behavior, trabecular bone loss, post-fracture cutaneous cytokine up-regulation, and adaptive immune responses in this CRPS model. METHODS Rats underwent tibia fracture and cast immobilization for 4 weeks and were chronically administered either subcutaneously perfused alendronate or oral zoledronate. Behavioral measurements included hindpaw von Frey allodynia, unweighting, warmth, and edema. Bone microarchitecture was measured by uCT and bone cellular activity was evaluated by static and dynamic histomorphometry. Spinal cord Fos immunostaining was performed and skin cytokine (TNF, IL-1, IL-6) and nerve growth factor (NGF) levels were determined by EIA. Skin and sciatic nerve immunoglobulin levels were determined by EIA. RESULTS Tibia fracture rats developed hindpaw allodynia, unweighting, warmth, and edema, increased spinal Fos expression, trabecular bone loss in the lumbar vertebra and bilateral distal femurs as measured by uCT, increased trabecular bone resorption and osteoclast surface with decreased bone formation rates, increased cutaneous inflammatory cytokine and NGF expression and elevated immunocomplex deposition in skin and nerve. Alendronate (60 μg/kg/day s.c.) or zoledronate (3 mg/kg/day p.o.) treatment for 28 days, started at the time of fracture, completely inhibited the development of hindpaw allodynia and reduced hindpaw unweighting by 44 ± 13% and 58 ± 5%, respectively. Orally administered zoledronate (3 mg/kg/day for 21 days) treatment also completely reversed established allodynia and unweighting when started at 4-weeks post-fracture. Histomorphometric and uCT analysis demonstrated that both the 3 and 60 μg/kg/day alendronate treatments reversed trabecular bone loss (a 88 ± 25% and 188 ± 39% increase in the ipsilateral distal femur BV/TV, respectively) and blocked the increase in osteoclast numbers and erosion surface observed in bilateral distal femurs and in L5 vertebra of the fracture rats. Alendronate treatment inhibited fracture-induced increases in hindpaw inflammatory mediators, reducing post-fracture levels of TNF by 43 ± 9%, IL-1 by 60 ± 9%, IL-6 by 56 ± 14%, and NGF by 37 ± 14%, but had no effect on increased spinal cord Fos expression, or skin and sciatic nerve immunocomplex deposition. CONCLUSIONS Collectively, these results indicate that bisphosphonate therapy inhibits pain, osteoclast activation, trabecular bone loss, and cutaneous inflammation in the rat fracture model of CRPS, data supporting the hypothesis that bisphosphonate therapy can provide effective multimodal treatment for CRPS. PMID:27636578

[Study on relationship of dose-effect and time-effect of APA microencapsulated bovine chromaffin cells on pain treatment].

PubMed

Hui, Jianfeng; Li, Tao; Du, Zhi; Song, Jichang

2011-12-01

This study was to investigate the relationship of dose-effect and time-effect of Alginate-Polylysine-Alginate (APA) microencapsulated bovine chromaffin cells on the treatment of pain model rats. Using a rat model of painful peripheral neuropathy, the antinociceptive effects of APA microencapsulated bovine cells transplanted into the subarachnoid space was evaluated by cold allodynia test and hot hyperalgesia test. Compared with control group, the withdrawal difference with cell number 50 thousands groups, 100 thousands groups and 200 thousands groups was reduced (P < 0.05), and the difference decreased with the cells increases, indicating a significant analgesic effect. There was no significant difference between 400 thousands groups and 200 thousands groups. This analgesic effect maintained longer than 12 weeks. There was a positive correlation between the analgesic effect and the quantity of APA microencapsulated bovine chromaffin cells which were transplanted to treat pain model rats, and the effective antinociception remained longer than 12 weeks.

An evaluation of the antinociceptive effects of Phα1β, a neurotoxin from the spider Phoneutria nigriventer, and ω-conotoxin MVIIA, a cone snail Conus magus toxin, in rat model of inflammatory and neuropathic pain.

PubMed

de Souza, Alessandra Hubner; Castro, Célio J; Rigo, Flavia Karine; de Oliveira, Sara Marchesan; Gomez, Renato Santiago; Diniz, Danuza Montijo; Borges, Marcia Helena; Cordeiro, Marta Nascimento; Silva, Marco Aurélio Romano; Ferreira, Juliano; Gomez, Marcus Vinicius

2013-01-01

Voltage-sensitive calcium channels (VSCCs) underlie cell excitability and are involved in the mechanisms that generate and maintain neuropathic and inflammatory pain. We evaluated in rats the effects of two VSCC blockers, ω-conotoxin MVIIA and Phα1β, in models of inflammatory and neuropathic pain induced with complete Freund's adjuvant (CFA) and chronic constrictive injury (CCI), respectively. We also evaluated the effects of the toxins on capsaicin-induced Ca(2+) influx in dorsal root ganglion (DRG) neurons obtained from rats exposed to both models of pain. A single intrathecal injection of Phα1β reversibly inhibits CFA and CCI-induced mechanical hyperalgesia longer than a single injection of ω-conotoxin MVIIA. Phα1β and MVIIA also inhibited capsaicin-induced Ca(2+) influx in DRG neurons. The inhibitory effect of Phα1β on capsaicin-induced calcium transients in DRG neurons was greater in the CFA model of pain, while the inhibitory effect of ω-conotoxin MVIIA was greater in the CCI model. The management of chronic inflammatory and neuropathic pain is still a major challenge for clinicians. Phα1β, a reversible inhibitor of VSCCs with a preference for N-type Ca(2+) channels, has potential as a novel therapeutic agent for inflammatory and neuropathic pain. Clinical studies are necessary to establish the role of Phα1β in the treatment of chronic pain.

Sciatic endometriosis induces mechanical hypersensitivity, segmental nerve damage, and robust local inflammation in rats

PubMed Central

Chen, S.; Xie, W.; Strong, J. A.; Jiang, J.; Zhang, J.-M.

2015-01-01

Background Endometriosis is a common cause of pain including radicular pain. Ectopic endometrial tissue may directly affect peripheral nerves including the sciatic, which has not been modelled in animals. Methods We developed a rat model for sciatic endometriosis by grafting a piece of autologous uterine tissue around the sciatic nerve. Control animals underwent a similar surgery but received a graft of pelvic fat tissue. Results The uterine grafts survived and developed fluid filled cysts; the adjacent nerve showed signs of swelling and damage. Mechanical and cold hypersensitivity and allodynia of the ipsilateral hindpaw developed gradually over the first two weeks after the surgery, peaked at 2 to 5 weeks, and was almost resolved by 7 weeks. Control animals showed only minor changes in these pain behaviors. Histological signs of inflammation in the uterine graft and in the adjacent nerve were observed at 3 weeks but were resolving by 7 weeks. In vivo fiber recording showed increased spontaneous activity, especially of C fibers, in sciatic nerve proximal to the uterine graft. Several pro-inflammatory cytokines including interluekin-18, VEGF, fractalkine, and MIP-1α, were elevated in the uterine graft plus sciatic nerve samples, compared to samples from normal nerve or nerve plus fat graft. Growth associated protein 43 (GAP43), a marker of regenerating nerve fibers, was observed in the adjacent sciatic nerve as well as in the uterine graft. Conclusions This model shared many features with other rat models of endometriosis, but also had some unique features more closely related to neuropathic pain models. PMID:26688332

Anti-allodynic effect of NW-1029, a novel Na(+) channel blocker, in experimental animal models of inflammatory and neuropathic pain.

PubMed

Veneroni, O; Maj, R; Calabresi, M; Faravelli, L; Fariello, R G; Salvati, P

2003-03-01

NW-1029, a benzylamino propanamide derivative, was selected among several molecules of this chemical class on the basis of its affinity for the [(3)H]batracotoxin ligand displacement of the Na(+) channel complex and also on the basis of its voltage and use-dependent inhibitory action on the Na(+) currents of the rat DRG (dorsal root ganglia) sensory neuron. This study evaluated the analgesic activity of NW-1029 in animal models of inflammatory and neuropathic pain (formalin test in mice, complete Freund's adjuvant and chronic constriction injury in rats) as well as in acute pain test (hot-plate and tail-flick in rats). Orally administered NW-1029 dose-dependently reduced cumulative licking time in the early and late phase of the formalin test (ED(50)=10.1 mg/kg in the late phase). In the CFA model, NW-1029 reversed mechanical allodynia (von Frey test) after both i.p. and p.o. administration (ED(50)=0.57 and 0.53 mg/kg), respectively. Similarly, NW-1029 reversed mechanical allodynia in the CCI model after both i.p. and p.o. administration yielding an ED(50) of 0.89 and 0.67 mg/kg, respectively. No effects were observed in the hot-plate and tail-flick tests up to 30 mg/kg p.o. The compound orally administered (0.1-10 mg/kg) was well tolerated, without signs of neurological impairment up to high doses (ED(50)=470 and 245 mg/kg in rat and mice Rotarod test, respectively). These results indicate that NW-1029 has anti-nociceptive properties in models of inflammatory and neuropathic pain.

Antineuropathic Profile of N-Palmitoylethanolamine in a Rat Model of Oxaliplatin-Induced Neurotoxicity

PubMed Central

Di Cesare Mannelli, Lorenzo; Pacini, Alessandra; Corti, Francesca; Boccella, Serena; Luongo, Livio; Esposito, Emanuela; Cuzzocrea, Salvatore; Maione, Sabatino; Calignano, Antonio; Ghelardini, Carla

2015-01-01

Neurotoxicity is a main side effect of the anticancer drug oxaliplatin. The development of a neuropathic syndrome impairs quality of life and potentially results in chemotherapy dose reductions and/or early discontinuation. In the complex pattern of molecular and morphological alterations induced by oxaliplatin in the nervous system, an important activation of glia has been preclinically evidenced. N-Palmitoylethanolamine (PEA) modulates glial cells and exerts antinociceptive effects in several animal models. In order to improve the therapeutic chances for chemotherapy-dependent neuropathy management, the role of PEA was investigated in a rat model of oxaliplatin-induced neuropathy (2.4 mg kg-1 daily, intraperitoneally). On day 21, a single administration of PEA (30 mg kg-1 i.p.) was able to reduce oxaliplatin-dependent pain induced by mechanical and thermal stimuli. The repeated treatment with PEA (30 mg kg-1 daily i.p. for 21 days, from the first oxaliplatin injection) prevented lowering of pain threshold as well as increased pain on suprathreshold stimulation. Ex vivo histological and molecular analysis of dorsal root ganglia, peripheral nerves and spinal cord highlighted neuroprotective effects and glia-activation prevention induced by PEA repeated administration. The protective effect of PEA resulted in the normalization of the electrophysiological activity of the spinal nociceptive neurons. Finally, PEA did not alter the oxaliplatin-induced mortality of the human colon cancer cell line HT-29. The efficacy of PEA in neuropathic pain control and in preventing nervous tissue alteration candidates this endogenous compound as disease modifying agent. These characteristics, joined to the safety profile, suggest the usefulness of PEA in chemotherapy-induced neuropathy. PMID:26039098

Dual effects of Rho-kinase inhibitors on a rat model of inflammatory pain.

PubMed

Paiva-Lima, Patricia; Bakhle, Y S; Francischi, Janetti Nogueira

2014-01-01

Rho-kinases (ROCKs), a family of small GTP-dependent enzymes, are involved in a range of pain models, and their inhibition typically leads to antinociceptive effects. To study the effects of inhibiting ROCKs using two known inhibitors, Y27632 and HA1077 (fasudil), administered locally, on nociception and paw edema in rats. A range of doses of Y27632 or HA1077 (2.5 μg to 1000 μg) were injected locally into rat paws alone or in combination with carrageenan, a known proinflammatory stimulus. Nociceptive responses to mechanical stimuli and increased paw volume, reflecting edema formation, were measured at 2 h and 3 h, using a Randall-Selitto apparatus and a hydroplethysmometer, respectively. Animals treated with either ROCK inhibitor showed biphasic nociceptive effects, with lower doses being associated with pronociceptive, and higher doses with antinociceptive responses. In contrast, a monophasic dose-dependent increase in edema was observed in the same animals. Local injection of 8-bromo-cyclic (c)GMP, an activator of the nitric oxide⁄cGMP⁄protein kinase G pathway, also produced biphasic effects on nociceptive responses in rat paws; however, low doses were antinociceptive and high doses were pronociceptive. Local administration of cytochalasin B, an inhibitor of actin polymerization and a downstream mediator of ROCK activity, reversed the antinociceptive effect of Y27632. The results of the present study suggest that ROCKs participate in the local mechanisms associated with nociception⁄antinociception and inflammation, with a possible involvement of the nitric oxide⁄cGMP⁄protein kinase G pathway. Also, drug effects following local administration may differ markedly from the effects following systemic administration. Finally, separate treatment of pain and edema may be needed to maximize clinical benefit in inflammatory pain.

Nefopam hydrochloride loaded microspheres for post-operative pain management: synthesis, physicochemical characterization and in-vivo evaluation.

PubMed

Sharma, Neelam; Arora, Sandeep; Madan, Jitender

2018-02-01

Once-daily oral dosage of nefopam hydrochloride loaded sustained release microspheres (NPH-MS) was investigated as novel therapeutic strategy for post-operative pain management. Microspheres were synthesized using poly-3-hydroxybutyrate and poly-(ɛ-caprolactone) by double emulsion solvent evaporation technique. NPH-MS were characterized through FTIR, PXRD and SEM. In-vitro drug release study revealed sustained behavior till 24 h. Haemolysis was <5% which signified haemocompatibility of formulation. ED50 in rat tail-flick anti-nociceptive test was found ∼18.12 mg/kg. In post-operative pain model, reversal of mechanical allodynia and thermal hyperalgesia by NPH-MS was statistically significant (p < .001) as compared with NPH till 24 h post-dose.

Up-regulation of CXCR4 expression contributes to persistent abdominal pain in rats with chronic pancreatitis.

PubMed

Zhu, Hong-Yan; Liu, Xuelian; Miao, Xiuhua; Li, Di; Wang, Shusheng; Xu, Guang-Yin

2017-01-01

Background Pain in patients with chronic pancreatitis is critical hallmark that accompanied inflammation, fibrosis, and destruction of glandular pancreas. Many researchers have demonstrated that stromal cell-derived factor 1 (also named as CXCL12) and its cognate receptor C-X-C chemokine receptor type 4 (CXCR4) involved in mediating neuropathic and bone cancer pain. However, their roles in chronic pancreatic pain remain largely unclear. Methods Chronic pancreatitis was induced by intraductal injection of trinitrobenzene sulfonic acid to the pancreas. Von Frey filament tests were conducted to evaluate pancreas hypersensitivity of rat. Expression of CXCL12, CXCR4, NaV1.8, and pERK in rat dorsal root ganglion was detected by Western blot analyses. Dorsal root ganglion neuronal excitability was assessed by electrophysiological recordings. Results We showed that both CXCL12 and CXCR4 were dramatically up-regulated in the dorsal root ganglion in trinitrobenzene sulfonic acid-induced chronic pancreatitis pain model. Intrathecal application with AMD3100, a potent and selective CXCR4 inhibitor, reversed the hyperexcitability of dorsal root ganglion neurons innervating the pancreas of rats following trinitrobenzene sulfonic acid injection. Furthermore, trinitrobenzene sulfonic acid-induced extracellular signal-regulated kinase activation and Nav1.8 up-regulation in dorsal root ganglias were reversed by intrathecal application with AMD3100 as well as by blockade of extracellular signal-regulated kinase activation by intrathecal U0126. More importantly, the trinitrobenzene sulfonic acid-induced persistent pain was significantly suppressed by CXCR4 and extracellular signal-regulated kinase inhibitors. Conclusions The present results suggest that the activation of CXCL12-CXCR4 signaling might contribute to pancreatic pain and that extracellular signal-regulated kinase-dependent Nav1.8 up-regulation might lead to hyperexcitability of the primary nociceptor neurons in rats with chronic pancreatitis.

[6]-gingerol and [6]-shogaol, active ingredients of the traditional Japanese medicine hangeshashinto, relief oral ulcerative mucositis-induced pain via action on Na+ channels.

PubMed

Hitomi, Suzuro; Ono, Kentaro; Terawaki, Kiyoshi; Matsumoto, Chinami; Mizuno, Keita; Yamaguchi, Kiichiro; Imai, Ryota; Omiya, Yuji; Hattori, Tomohisa; Kase, Yoshio; Inenaga, Kiyotoshi

2017-03-01

The traditional Japanese herbal medicine hangeshashinto (HST) has beneficial effects for the treatment of oral ulcerative mucositis (OUM) in cancer patients. However, the ingredient-based mechanism that underlies its pain-relieving activity remains unknown. In the present study, to clarify the analgesic mechanism of HST on OUM-induced pain, we investigated putative HST ingredients showing antagonistic effects on Na + channels in vitro and in vivo. A screen of 21 major ingredients using automated patch-clamp recordings in channel-expressing cells showed that [6]-gingerol and [6]-shogaol, two components of a Processed Ginger extract, considerably inhibited voltage-activated Na + currents. These two ingredients inhibited the stimulant-induced release of substance P and action potential generation in cultured rat sensory neurons. A submucosal injection of a mixture of [6]-gingerol and [6]-shogaol increased the mechanical withdrawal threshold in healthy rats. In a rat OUM model, OUM-induced mechanical pain was alleviated 30min after the swab application of HST despite the absence of anti-bacterial and anti-inflammatory actions in the OUM area. A swab application of a mixture of [6]-gingerol and [6]-shogaol induced sufficient analgesia of OUM-induced mechanical or spontaneous pain when co-applied with a Ginseng extract containing abundant saponin. The Ginseng extract demonstrated an acceleration of substance permeability into the oral ulcer tissue without an analgesic effect. These findings suggest that Na + channel blockage by gingerol/shogaol plays an essential role in HST-associated analgesia of OUM-induced pain. This pharmacological mechanism provides scientific evidence supporting the use of this herbal medicine in patients suffering from OUM-induced pain. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of lappaconitine on neuropathic pain mediated by P2X3 receptor in rat dorsal root ganglion.

PubMed

Ou, Shan; Zhao, Yan-Dong; Xiao, Zhi; Wen, Hui-Zhong; Cui, Jian; Ruan, Huai-Zhen

2011-04-01

ATP facilitates initiation and transmission of the neuropathic pain at the dorsal root ganglion (DRG) level via the P2X receptors, especially the subtype P2X(3). Lappaconitine (LA) is an active principle isolated from Chinese herbal medicine and possesses analgesic effect. The aim of this study was to investigate the effect of LA on chronic constriction injury (CCI)-induced neuropathic pain mediated by P2X(3) receptor in the DRG neurons. In the presence of CCI and/or LA, the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured and P2X(3) receptor expression in the DRG neurons was evaluated by immunohistochemistry and Western blotting. Following intrathecal administration of P2X(3) receptor oligonucleotide, the effect of LA on pain thresholds was assessed. Furthermore, the effect of LA on the P2X(3) receptor agonists ATP- and α,β-meATP-induced inward currents (I(ATP) and I(α,β-meATP)) in the acutely dissociated rat DRG neurons was investigated by whole cell patch-clamp. The results included: (1) There showed reduction of pain thresholds, enhancement of I(ATP) and I(α,β-meATP) and up-regulation of P2X(3) receptor expression in rat DRG neurons when neuropathic pain occurred. (2) In the presence of LA, the decreased pain thresholds, the up-regulated P2X(3) receptor expression and the enhanced I(ATP) and I(α,β-meATP) were reversible in the CCI rats. (3) The down-regulated P2X(3) receptor expression with pretreatment of P2X(3) receptor antisense oligonucleotide significantly attenuated the analgesic effect of LA. These results indicate that the analgesic effect of LA involves decrease of expression and sensitization of the P2X(3) receptors of the rat DRG neurons following CCI. Copyright © 2011 Elsevier Ltd. All rights reserved.

MiR-203 involves in neuropathic pain development and represses Rap1a expression in nerve growth factor differentiated neuronal PC12 cells.

PubMed

Li, Haixia; Huang, Yuguang; Ma, Chao; Yu, Xuerong; Zhang, Zhiyong; Shen, Le

2015-01-01

Although microRNAs (miRNAs) have been shown to play a role in numerous biological processes, their function in neuropathic pain is not clear. The rat bilateral sciatic nerve chronic constriction injury (bCCI) is an established model of neuropathic pain, so we examined miRNA expression and function in the spinal dorsal horn in bCCI rats. Microarray and real-time polymerase chain reaction were used to examine the expression of miRNA in nerve system of bCCI rats, and the targets of miRNA were predicted by bioinformatic approaches. The function of specific miRNA was estimated through the methods of gene engineering. This study revealed substantially (∼10-fold) decreased miR-203 expression in the spinal dorsal horns but not the dorsal root ganglions, hippocampus, or anterior cingulate cortexes of bCCI rats. Rap1a protein expression was upregulated in bCCI rat spinal dorsal horns. We further verified that miR-203 directly targeted the 3'-untranslated region of the rap1a gene, thereby decreasing rap1a protein expression in neuron-like cells. Rap1a has diverse neuronal functions and their perturbation is responsible for several mental disorders. For example, Rap1a/MEK/ERK is involved in peripheral sensitization. These data suggest a potential role for miR-203 in regulating neuropathic pain development, and Rap1a is a validated target gene in vitro. Results from our study and others indicate the possibility that Rap1a may be involved in pain. We hope that these results can provide support for future research into miR-203 in gene therapy for neuropathic pain.

Effect of oxidative stress induced by intracranial iron overload on central pain after spinal cord injury.

PubMed

Meng, Fan Xing; Hou, Jing Ming; Sun, Tian Sheng

2017-02-08

Central pain (CP) is a common clinical problem in patients with spinal cord injury (SCI). Recent studies found the pathogenesis of CP was related to the remodeling of the brain. We investigate the roles of iron overload and subsequent oxidative stress in the remodeling of the brain after SCI. We established a rat model of central pain after SCI. Rats were divided randomly into four groups: SCI, sham operation, SCI plus deferoxamine (DFX) intervention, and SCI plus nitric oxide synthase (NOS) inhibitor treatment. Pain behavior was observed and thermal pain threshold was measured regularly, and brain levels of iron, transferrin receptor 1 (TfR1), ferritin (Fn), and lactoferrin (Lf), were detected in the different groups 12 weeks after establishment of the model. Rats demonstrated self-biting behavior after SCI. Furthermore, the latent period of thermal pain was reduced and iron levels in the hind limb sensory area, hippocampus, and thalamus increased after SCI. Iron-regulatory protein (IRP) 1 levels increased in the hind limb sensory area, while Fn levels decreased. TfR1 mRNA levels were also increased and oxidative stress was activated. Oxidative stress could be inhibited by ferric iron chelators and NOS inhibitors. SCI may cause intracranial iron overload through the NOS-iron-responsive element/IRP pathway, resulting in central pain mediated by the oxidative stress response. Iron chelators and oxidative stress inhibitors can effectively relieve SCI-associated central pain.

Establishment of model of visceral pain due to colorectal distension and its behavioral assessment in rats

PubMed Central

Yang, Jian-Ping; Yao, Ming; Jiang, Xing-Hong; Wang, Li-Na

2006-01-01

AIM: To establish a visceral pain model via colorectal distension (CRD) and to evaluate the efficiency of behavioral responses of CRD by measuring the score of abdominal withdrawal reflex (AWR) in rats. METHODS: Thirty-eight male SD rats weighing 180-240g were used to establish the visceral pain model. The rat was inserted intra-anally with a 7 cm long flexible latex balloon under ether anesthesia, and colorectal distensions by inflating the balloon with air were made 30 min after recovering from the anesthesia. Five AWR scores (AWR0 to AWR4) were used to assess the intensity of noxious visceral stimuli. It was regarded as the threshold of the minimal pressure (kPa) for abdominal flatting was induced by colorectal distension. RESULTS: A vigorous AWR to distension of the descending colon and rectum was found in 100% of the awake rats tested. The higher the pressure of distension, the higher the score of AWR. The distension pressures of 0, 2.00, 3.33, 5.33 and 8.00 kPa produced different AWR scores (P < 0.05). The pain threshold of AWR was constant for up to 80 min after the initial windup (first 1-3 distensions), the mean threshold was 3.69 ± 0.35 kPa. Systemic administration of morphine sulfate elevated the threshold of visceral pain in a dose-dependent and naloxone reversible manner. CONCLUSION: Scoring the AWR during colorectal distensions can assess the intensity of noxious visceral stimulus. Flatting of abdomen (AWR 3) to CRD as the visceral pain threshold is clear, constant and reliable. This pain model and its behavioral assessment are good for research on visceral pain and analgesics. PMID:16718770

Minocycline attenuates bone cancer pain in rats by inhibiting NF-κB in spinal astrocytes

PubMed Central

Song, Zhen-peng; Xiong, Bing-rui; Guan, Xue-hai; Cao, Fei; Manyande, Anne; Zhou, Ya-qun; Zheng, Hua; Tian, Yu-ke

2016-01-01

Aim: To investigate the mechanisms underlying the anti-nociceptive effect of minocycline on bone cancer pain (BCP) in rats. Methods: A rat model of BCP was established by inoculating Walker 256 mammary carcinoma cells into tibial medullary canal. Two weeks later, the rats were injected with minocycline (50, 100 μg, intrathecally; or 40, 80 mg/kg, ip) twice daily for 3 consecutive days. Mechanical paw withdrawal threshold (PWT) was used to assess pain behavior. After the rats were euthanized, spinal cords were harvested for immunoblotting analyses. The effects of minocycline on NF-κB activation were also examined in primary rat astrocytes stimulated with IL-1β in vitro. Results: BCP rats had marked bone destruction, and showed mechanical tactile allodynia on d 7 and d 14 after the operation. Intrathecal injection of minocycline (100 μg) or intraperitoneal injection of minocycline (80 mg/kg) reversed BCP-induced mechanical tactile allodynia. Furthermore, intraperitoneal injection of minocycline (80 mg/kg) reversed BCP-induced upregulation of GFAP (astrocyte marker) and PSD95 in spinal cord. Moreover, intraperitoneal injection of minocycline (80 mg/kg) reversed BCP-induced upregulation of NF-κB, p-IKKα and IκBα in spinal cord. In IL-1β-stimulated primary rat astrocytes, pretreatment with minocycline (75, 100 μmol/L) significantly inhibited the translocation of NF-κB to nucleus. Conclusion: Minocycline effectively alleviates BCP by inhibiting the NF-κB signaling pathway in spinal astrocytes. PMID:27157092

The anti-NGF antibody muMab 911 both prevents and reverses pain behaviour and subchondral osteoclast numbers in a rat model of osteoarthritis pain.

PubMed

Xu, L; Nwosu, L N; Burston, J J; Millns, P J; Sagar, D R; Mapp, P I; Meesawatsom, P; Li, L; Bennett, A J; Walsh, D A; Chapman, V

2016-09-01

Nerve growth factor (NGF) has a pivotal role in peripheral hyperalgesia and inflammation; anti-NGF antibodies attenuate pain responses in inflammatory pain models, and in people with osteoarthritis (OA) or low back pain. The aim of this study was to characterise the peripheral mechanisms contributing to the analgesic effects of anti-NGF antibody treatment in an established model of joint pain, which mimics key clinical features of OA. Effects of preventative vs therapeutic treatment with an anti-NGF antibody (monoclonal antibody 911: muMab 911 (10 mg/kg, s.c.)) on pain behaviour (weight bearing asymmetry and hindpaw withdrawal thresholds (PWT)), cartilage damage, synovitis and numbers of subchondral osteoclasts were investigated in the monosodium iodoacetate (MIA) model. Potential direct effects of NGF on receptor activator of nuclear factor kappa-B ligand (RANKL) mediated osteoclastogenesis were investigated in cultured human osteoclasts. Intra-articular MIA injection resulted in significant pain behaviour, cartilage damage, synovitis and increased numbers of subchondral osteoclasts. Both preventative and therapeutic treatment with muMab 911 significantly prevented, or reversed, MIA-induced pain behaviour, but did not alter cartilage or synovial pathology quantified at the end of the treatment period. NGF did not facilitate RANKL driven osteoclast differentiation in vitro, but preventative or therapeutic muMab 911 reduced numbers of TRAP positive osteoclasts in the subchondral bone. We demonstrate that anti-NGF antibody treatment attenuates OA pain behaviour despite permitting cartilage damage and synovitis. Indirect effects on subchondral bone remodelling may contribute to the analgesic effects of NGF blockade. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Minocycline reduces mechanical allodynia and depressive-like behaviour in type-1 diabetes mellitus in the rat.

PubMed

Amorim, Diana; Puga, Sónia; Bragança, Rui; Braga, António; Pertovaara, Antti; Almeida, Armando; Pinto-Ribeiro, Filipa

2017-06-01

A common and devastating complication of diabetes mellitus is painful diabetic neuropathy (PDN) that can be accompanied by emotional disorders such as depression. A few studies have suggested that minocycline that inhibits microglia may attenuate pain hypersensitivity in PDN. Moreover, a recent study reported that minocycline has an acute antidepressive-like effect in diabetic animals. Here we studied whether (i) prolonged minocycline treatment suppresses pain behaviour in PDN, (ii) the minocycline effect varies with submodality of pain, and (iii) the suppression of pain behaviour by prolonged minocycline treatment is associated with antidepressive-like effect. The experiments were performed in streptozotocin-induced rat model of type-1 diabetes. Pain behaviour was evoked by innocuous (monofilaments) and noxious (paw pressure) mechanical stimulation, innocuous cold (acetone drops) and noxious heat (radiant heat). Depression-like behaviour was assessed using forced swimming test. Minocycline treatment (daily 80mg/kg per os) of three-week duration started four weeks after induction of diabetes. Diabetes induced mechanical allodynia and hyperalgesia, cold allodynia, heat hypoalgesia, and depression-like behaviour. Minocycline treatment significantly attenuated mechanical allodynia and depression-like behaviour, while it failed to produce significant changes in mechanical hyperalgesia, cold allodynia or heat hypoalgesia. The results indicate that prolonged per oral treatment with minocycline has a sustained mechanical antiallodynic and antidepressive-like effect in PDN. These results support the proposal that minocycline might provide a treatment option for attenuating sensory and comorbid emotional symptoms in chronic PDN. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of arginine vasopressin in the nucleus raphe magnus on antinociception in the rat.

PubMed

Yang, Jun; Chen, Jian-Min; Liu, Wen-Yan; Song, Cao-You; Wang, Cheng-Hai; Lin, Bao-Cheng

2006-09-01

Previous work has shown that arginine vasopressin (AVP) regulates antinociception through brain nuclei rather than the spinal cord and peripheral organs. The present study investigated the nociceptive effect of AVP in the nucleus raphe magnus (NRM) of the rat. Microinjection of AVP into the NRM increased pain threshold in a dose-dependent manner, while local administration of AVP-receptor antagonist-d(CH2)5Tyr(Et)DAVP decreased the pain threshold. Pain stimulation elevated AVP concentration in the NRM perfuse liquid. NRM pretreatment with AVP-receptor antagonist completely reversed AVP's effect on pain threshold in the NRM. The data suggest that AVP in the NRM is involved in antinociception.

Use of Liposomal Bupivacaine for Postoperative Analgesia in an Incisional Pain Model in Rats (Rattus norvegicus)

PubMed Central

Kang, Stacey C; Jampachaisri, Katechan; Seymour, Travis L; Felt, Stephen A; Pacharinsak, Cholawat

2017-01-01

The local anesthetic bupivacaine is valuable for perioperative analgesia, but its use in the postoperative period is limited by its short duration of action. Here, we evaluated the application of a slow-release liposomal formulation of bupivacaine for postoperative analgesia. The aim was to assess whether liposomal bupivacaine effectively attenuates postoperative mechanical and thermal hypersensitivity in a rat model of incisional pain. Rats (n = 36) were randomly assigned to 1 of 5 treatment groups: saline, 1 mL/kg SC every 12 h for 2 d; buprenorphine HCl, 0.05 mg/kg SC every 12 h for 2 d (Bup HCl); 0.5% bupivacaine, 2 mg/kg SC local infiltration once (Bupi); liposomal bupivacaine, 1 mg/kg SC local infiltration once (Exp1); and liposomal bupivacaine, 6 mg/kg SC local infiltration once (Exp6). Mechanical and thermal hypersensitivity were evaluated daily on days –1, 0, 1, 2, 3, and 4. The saline group exhibited both hypersensitivities through all 4 evaluated postoperative days. Bup HCl attenuated mechanical hypersensitivity for 2 d and thermal hypersensitivity for 1 d. Bupi attenuated only thermal hypersensitivity for 4 d. Rats in the Exp1 group showed attenuation of both mechanical and thermal hypersensitivity for 4 d, and those in the Exp6 group had attenuation of mechanical hypersensitivity on day 0 and thermal hypersensitivity for 4 d. These data suggest that a single local infiltration of liposomal bupivacaine at a dose of 1 mg/kg SC effectively attenuates postoperative mechanical and thermal hypersensitivity for 4 d in a rat model of incisional pain. PMID:28905717

Involvement of spinal orexin A in the electroacupuncture analgesia in a rat model of post-laparotomy pain.

PubMed

Feng, Xiao-Ming; Mi, Wen-Li; Xia, Fang; Mao-Ying, Qi-Liang; Jiang, Jian-Wei; Xiao, Sheng; Wang, Zhi-Fu; Wang, Yan-Qing; Wu, Gen-Cheng

2012-11-22

Orexin A (OXA, hypocretin/hcrt 1) is a newly discovered potential analgesic substance. However, whether OXA is involved in acupuncture analgesia remains unknown. The present study was designed to investigate the involvement of spinal OXA in electroacupuncture (EA) analgesia. A modified rat model of post-laparotomy pain was adopted and evaluated. Von Frey filaments were used to measure mechanical allodynia of the hind paw and abdomen. EA at 2/15 Hz or 2/100 Hz was performed once on the bilateral ST36 and SP6 for 30 min perioperatively. SB-334867, a selective orexin 1 receptor (OX1R) antagonist with a higher affinity for OXA than OXB, was intrathecally injected to observe its effect on EA analgesia. OXA at 0.3 nmol and EA at 2/15 Hz produced respective analgesic effects on the model (P<0.05). Pre-surgical intrathecal administered of SB-334867 30 nmol antagonized OXA analgesia and attenuated the analgesic effect of EA (P<0.05). However, SB-334867 did not block fentanyl-induced analgesia (P>0.05). In addition, naloxone, a selective opioid receptor antagonist, failed to antagonize OXA-induced analgesia (P>0.05). The results of the present study indicate the involvement of OXA in EA analgesia via OX1R in an opioid-independent way.

Forced treadmill running suppresses postincisional pain and inhibits upregulation of substance P and cytokines in rat dorsal root ganglion.

PubMed

Chen, Yu-Wen; Tzeng, Jann-Inn; Lin, Min-Fei; Hung, Ching-Hsia; Wang, Jhi-Joung

2014-08-01

Exercise causes a variety of psychophysical effects (eg, alterations in pain sensation). Tissue injury induces mediator releases in the spinal cord resulting in pain hypersensitivity; however, the contribution of the dorsal root ganglion (DRG) is poorly understood. In this study, we tested if forced treadmill running can attenuate postoperative pain and alter substance P (SP) or proinflammatory cytokine level in the DRG by using a rat model of skin/muscle incision and retraction (SMIR). We evaluated mechanical sensitivity to von Frey stimuli (6 and 15 g) and expression of SP, interleukin-1β, and interleukin-6 in the DRG of sham-operated sedentary rats, SMIR sedentary rats, sham-operated rats with forced treadmill running, and SMIR rats with forced treadmill running. At postoperative day 8, trained rats ran for 5 days per week for 4 weeks on a treadmill 70 minutes/d with an intensity of 18 m/min. On postoperative day 6, SMIR sedentary rats displayed a significant mechanical hypersensitivity that persisted until postoperative day 35. By comparison, SMIR-operated rats, which received forced treadmill running, exhibited a quick recovery from mechanical hypersensitivity. SMIR sedentary rats showed an upregulation of SP, interleukin-1β, and interleukin-6 in the DRG at postoperative days 14 and 28, whereas SMIR-operated rats receiving forced treadmill running reversed this upregulation at postoperative day 28. We concluded that forced treadmill running alleviated persistent postincisional pain caused by SMIR surgery. This appears to be protective against postoperative pain, which probably relates to the downturn in excess SP, interleukin-1β, and interleukin-6 in the DRG. Controlling the expression of SP, interleukin-6, and interleukin-1β in the DRG can help manage postoperative pain. This finding could potentially help clinicians and physical therapists who seek to examine how exercise may attenuate postsurgical pain and its mechanism. Copyright © 2014 American Pain Society. Published by Elsevier Inc. All rights reserved.

Evidence for a central mechanism of action of S-(+)-ketoprofen.

PubMed

Díaz-Reval, María Irene; Ventura-Martínez, Rosa; Déciga-Campos, Myrna; Terrón, José A; Cabré, Francesc; López-Muñoz, Francisco Javier

2004-01-12

It has been observed that some non-steroidal anti-inflammatory drugs (NSAIDs) may act through several mechanisms, in addition to central inhibition of prostaglandin synthesis. These other mechanisms include the L-arginine-nitric oxide (L-arginine-NO) pathway, as well as endogenous opiate and serotonergic mechanisms. Some of these mechanisms can explain the efficacy of NSAIDs in chronic pain conditions such as rheumatoid arthritis. The present study was designed to elucidate the involvement of the above pathways/mechanisms in the antinociceptive effect of S-(+)-ketoprofen at supraspinal and spinal levels. S-(+)-ketoprofen induced dose-dependent antinociception in the pain-induced functional impairment model in the rat. The antinociceptive effect of S-(+)-ketoprofen was not altered by i.t. or intracerebroventricula (i.c.v.) pre-treatment with L-arginine (29.6 microg/site) and L-nitro-arginine-monomethylester (L-NAME) (21.1 microg/site) and neither was the effect of S-(+)-ketoprofen modified by the opiate antagonist, naloxone (1 mg/kg, s.c.). In marked contrast, both i.c.v. administration of the 5-hydroxytryptamine (5-HT)(1)/5-HT(2)/5-HT(7) receptor antagonist, methiothepin (1.5 microg/site), and i.t. administration of the 5-HT(3)/5-HT(4) receptor antagonist, tropisetron (0.9 microg/site), significantly inhibited the S-(+)-ketoprofen-induced antinociceptive effect. These data suggest that the antinociceptive response to S-(+)-ketoprofen involves serotoninergic mechanisms via both supraspinal 5-HT(1)/5-HT(2)/5-HT(7) receptors and 5-HT(3) receptors located at spinal level. A role of the L-arginine-NO and opiate systems in S-(+)-ketoprofen-induced antinociception in the pain-induced functional impairment model in the rat model seems unlikely.

Use of Liposomal Bupivacaine for Postoperative Analgesia in an Incisional Pain Model in Rats (Rattus norvegicus).

PubMed

Kang, Stacey C; Jampachaisri, Katechan; Seymour, Travis L; Felt, Stephen A; Pacharinsak, Cholawat

2017-01-01

The local anesthetic bupivacaine is valuable for perioperative analgesia, but its use in the postoperative period is limited by its short duration of action. Here, we evaluated the application of a slow-release liposomal formulation of bupivacaine for postoperative analgesia. The aim was to assess whether liposomal bupivacaine effectively attenuates postoperative mechanical and thermal hypersensitivity in a rat model of incisional pain. Rats (n = 36) were randomly assigned to 1 of 5 treatment groups: saline, 1 mL/kg SC every 12 h for 2 d; buprenorphine HCl, 0.05 mg/kg SC every 12 h for 2 d (Bup HCl); 0.5% bupivacaine, 2 mg/kg SC local infiltration once (Bupi); liposomal bupivacaine, 1 mg/kg SC local infiltration once (Exp1); and liposomal bupivacaine, 6 mg/kg SC local infiltration once (Exp6). Mechanical and thermal hypersensitivity were evaluated daily on days -1, 0, 1, 2, 3, and 4. The saline group exhibited both hypersensitivities through all 4 evaluated postoperative days. Bup HCl attenuated mechanical hypersensitivity for 2 d and thermal hypersensitivity for 1 d. Bupi attenuated only thermal hypersensitivity for 4 d. Rats in the Exp1 group showed attenuation of both mechanical and thermal hypersensitivity for 4 d, and those in the Exp6 group had attenuation of mechanical hypersensitivity on day 0 and thermal hypersensitivity for 4 d. These data suggest that a single local infiltration of liposomal bupivacaine at a dose of 1 mg/kg SC effectively attenuates postoperative mechanical and thermal hypersensitivity for 4 d in a rat model of incisional pain.

P2X₇ receptor of rat dorsal root ganglia is involved in the effect of moxibustion on visceral hyperalgesia.

PubMed

Liu, Shuangmei; Shi, Qingming; Zhu, Qicheng; Zou, Ting; Li, Guilin; Huang, An; Wu, Bing; Peng, Lichao; Song, Miaomiao; Wu, Qin; Xie, Qiuyu; Lin, Weijian; Xie, Wei; Wen, Shiyao; Zhang, Zhedong; Lv, Qiulan; Zou, Lifang; Zhang, Xi; Ying, Mofeng; Li, Guodong; Liang, Shangdong

2015-06-01

Irritable bowel syndrome (IBS) and inflammatory bowel disease often display visceral hypersensitivity. Visceral nociceptors after inflammatory stimulation generate afferent nerve impulses through dorsal root ganglia (DRG) transmitting to the central nervous system. ATP and its activated-purinergic 2X7 (P2X7) receptor play an important role in the transmission of nociceptive signal. Purinergic signaling is involved in the sensory transmission of visceral pain. Moxibustion is a therapy applying ignited mugwort directly or indirectly at acupuncture points or other specific parts of the body to treat diseases. Heat-sensitive acupoints are the corresponding points extremely sensitive to moxa heat in disease conditions. In this study, we aimed to investigate the relationship between the analgesic effect of moxibustion on a heat-sensitive acupoint "Dachangshu" and the expression levels of P2X7 receptor in rat DRG after chronic inflammatory stimulation of colorectal distension. Heat-sensitive moxibustion at Dachangshu acupoint inhibited the nociceptive signal transmission by decreasing the upregulated expression levels of P2X7 mRNA and protein in DRG induced by visceral pain, and reversed the abnormal expression of glial fibrillary acidic protein (GFAP, a marker of satellite glial cells) in DRG. Consequently, abdominal withdrawal reflex (AWR) score in a visceral pain model was reduced, and the pain threshold was elevated. Therefore, heat-sensitive moxibustion at Dachangshu acupoint can produce a therapeutic effect on IBS via inhibiting the nociceptive transmission mediated by upregulated P2X7 receptor.

The probiotic Bifidobacterium infantis 35624 displays visceral antinociceptive effects in the rat.

PubMed

McKernan, D P; Fitzgerald, P; Dinan, T G; Cryan, J F

2010-09-01

Irritable bowel syndrome (IBS) is characterized by recurrent abdominal pain and altering bowel habit with a high percentage of patients displaying comorbid anxiety. Growing clinical and preclinical evidence suggests that probiotic agents may restore the altered brain-gut communication in IBS. In this study, we evaluated the efficacy of repeated treatment with three different probiotics in reducing visceral pain in visceral normosensitive (Sprague-Dawley [SD]) and visceral hypersensitive (Wistar-Kyoto [WKY]) rat strains. Following 14 days oral gavage of Lactobacillus salivarius UCC118, Bifidobacterium infantis 35624, or Bifidobacterium breve UCC2003 both SD and WKY rats were exposed to a novel stress, the open field arena and their behavior was recorded. Subsequently, the effects of probiotics on visceral nociceptive responses were analyzed by recording pain behaviors during colorectal distension (CRD). It was found that there was a difference in the open field behavior between strains but none of the probiotic treatment altered behavior within each strain. Interestingly, the probiotic B. infantis 35624 but not others tested significantly reduced CRD-induced visceral pain behaviors in both rat strains. It significantly increased the threshold pressure of the first pain behavior and also reduced the total number pain behaviors during CRD. These data confirm that probiotics such as B. infantis 35624 are effective in reducing visceral pain and may be effective in treating certain symptoms of IBS.

Effect of intraarticular tramadol administration in the rat model of knee joint inflammation.

PubMed

Garlicki, Jarosław; Dorazil-Dudzik, Magdalena; Wordliczek, Jerzy; Przewłocka, Barbara

2006-01-01

Local administration of exogenous opioids may cause effective analgesia without adverse symptoms from the central nervous system. Experiments show that peripheral antinociceptive effect of opioids is observed especially in inflammatory pain. The aim of the research was to estimate the effect of tramadol on nociceptive process at the level of peripheral nervous system, after its local administration in the model of knee joint inflammation. Tramadol was administered intraarticulary into the rat knee joint, before the inflammation as a preemptive analgesia and, for comparison, after the intraarticular injection of carrageenan. The research determined the influence of tramadol injection on pain threshold for thermal stimuli, development of inflammatory processes using the measurement of joint edema and motor function following the induction of knee joint inflammation in the rat. Functional assessment of knee joint with inflammation, in terms of rats' mobility and body position as well as joint loading and mobility were studied. The results of the experiments show that local administration of tramadol induces antinociceptive effect. The effect of tramadol, which elicits also a decrease in inflammatory edema, appears not only after its administration after carrageenan when inflammation was already present, but also in the case of its injection prior to carrageenan in the scheme of preemptive analgesia. The results of the described research show that not only morphine but also another opioid, tramadol, widely used in clinical practice, inhibits nociception, edema and functional impairment of the paw after its local application directly to the inflamed knee joint.

Mastering tricyclic ring systems for desirable functional cannabinoid activity

PubMed Central

Petrov, Ravil R.; Knight, Lindsay; Chen, Shao-Rui; Wager-Miller, Jim; McDaniel, Steven W.; Diaz, Fanny; Barth, Francis; Pan, Hui-Lin; Mackie, Ken; Cavasotto, Claudio N.; Diaz, Philippe

2013-01-01

There is growing interest in using cannabinoid receptor 2 (CB2) agonists for the treatment of neuropathic pain and other indications. In continuation of our ongoing program aiming for the development of new small molecule cannabinoid ligands, we have synthesized a novel series of carbazole and γ-carboline derivatives. The affinities of the newly synthesized compounds were determined by a competitive radioligand displacement assay for human CB2 cannabinoid receptor and rat CB1 cannabinoid receptor. Functional activity and selectivity at human CB1 and CB2 receptors were characterized using receptor internalization and [35S]GTP-γ-S assays. The structure-activity relationship and optimization studies of the carbazole series have led to the discovery of a non-selective CB1 and CB2 agonist, compound 4. Our subsequent research efforts to increase CB2 selectivity of this lead compound have led to the discovery of CB2 selective compound 64, which robustly internalized CB2 receptors. Compound 64 had potent inhibitory effects on pain hypersensitivity in a rat model of neuropathic pain. Other potent and CB2 receptor–selective compounds, including compounds 63 and 68, and a selective CB1 agonist, compound 74 were also discovered. In addition, we identified the CB2 ligand 35 which failed to promote CB2 receptor internalization and inhibited compound CP55,940-induced CB2 internalization despite a high CB2 receptor affinity. The present study provides novel tricyclic series as a starting point for further investigations of CB2 pharmacology and pain treatment. PMID:24125850

Periaqueductal gray knockdown of V2, not V1a and V1b receptor influences nociception in the rat. yj6676@yahoo.com.

PubMed

Yang, Jun; Yang, Yu; Chen, Jian-Min; Wang, Gen; Xu, Hong-Tao; Liu, Wen-Yan; Lin, Bao-Cheng

2007-01-01

Our pervious study has proved that arginine vasopressin (AVP) in periaqueductal gray (PAG) plays a role in antinociception. After establishing a model of local special gene knockdown, the nociceptive effect of vasopressin receptor subunit in PAG was investigated in the rat. Microinjection of short-interfering RNA (siRNA) into PAG, which targeted vasopressin receptor subtypes (V(1a), V(1b) and V(2)), locally weakened the associated mRNA expression and depressed the related receptor synthesis in a dose-dependent manner, in which the significant inhibitive effect occurred on from 7th day to 14th day following 1microg or 2microg siRNA administration. PAG knockdown of V(2) receptor gene markedly decreased pain threshold in from 6th day to 13th day after siRNA administration, whereas local knockdown of either V(1a) or V(1b) receptor gene could not influence pain threshold. The data suggest that V(2) rather than V(1a) and V(1b) receptor in PAG involves in nociception.

Forebrain Mechanisms of Nociception and Pain: Analysis through Imaging

NASA Astrophysics Data System (ADS)

Casey, Kenneth L.

1999-07-01

Pain is a unified experience composed of interacting discriminative, affective-motivational, and cognitive components, each of which is mediated and modulated through forebrain mechanisms acting at spinal, brainstem, and cerebral levels. The size of the human forebrain in relation to the spinal cord gives anatomical emphasis to forebrain control over nociceptive processing. Human forebrain pathology can cause pain without the activation of nociceptors. Functional imaging of the normal human brain with positron emission tomography (PET) shows synaptically induced increases in regional cerebral blood flow (rCBF) in several regions specifically during pain. We have examined the variables of gender, type of noxious stimulus, and the origin of nociceptive input as potential determinants of the pattern and intensity of rCBF responses. The structures most consistently activated across genders and during contact heat pain, cold pain, cutaneous laser pain or intramuscular pain were the contralateral insula and anterior cingulate cortex, the bilateral thalamus and premotor cortex, and the cerebellar vermis. These regions are commonly activated in PET studies of pain conducted by other investigators, and the intensity of the brain rCBF response correlates parametrically with perceived pain intensity. To complement the human studies, we developed an animal model for investigating stimulus-induced rCBF responses in the rat. In accord with behavioral measures and the results of human PET, there is a progressive and selective activation of somatosensory and limbic system structures in the brain and brainstem following the subcutaneous injection of formalin. The animal model and human PET studies should be mutually reinforcing and thus facilitate progress in understanding forebrain mechanisms of normal and pathological pain.

DAMGO in the central amygdala alleviates the affective dimension of pain in a rat model of inflammatory hyperalgesia.

PubMed

Zhang, R-X; Zhang, M; Li, A; Pan, L; Berman, B M; Ren, K; Lao, L

2013-11-12

Pain has sensory-discriminative and emotional-affective dimensions. Recent studies show that the affective component can be assessed with a conditioned place avoidance (CPA) test. We hypothesized that systemic morphine before a post-conditioning test would more potently attenuate the affective aspect compared to the sensory component and that [d-Ala2-N-Me-Phe4, Gly-ol5]-enkephalin (DAMGO), a μ-selective opioid receptor agonist, injected into the central nucleus of the amygdala (CeA) would reduce established CPA. A rat model of inflammatory pain, produced by a complete Freund adjuvant (CFA) injection into the hind paw, was combined with a CPA test. Three experiments were performed on adult male Sprague-Dawley rats. Systemic morphine (0.5 or 1.0mg/kg) in Experiment 1, intrathecal (i.t.) morphine (2.5 μg/rat) in Experiment 2, and intra-CeA DAMGO (7.7-15.4 ng/0.4 μl) in Experiment 3 were given to CFA-injected rats (n=6-8/group) prior to a post-conditioning test. Saline-injected rats were used as control. Time spent in a pain-paired compartment was recorded twice, before conditioning and after a post-conditioning test. Paw withdrawal latency (PWL) to a noxious thermal stimulus was measured before experiment at day-1 and after the post-conditioning test; hyperalgesia was defined as a decrease in PWL. The data showed that CFA-injected rats had significantly negative CPA compared to those of saline-injected rats (P<0.05). Low-dosage systemic morphine significantly (P<0.05) reduced CFA-induced CPA but had no effect on PWL. I.t. morphine did not inhibit the display of CPA but significantly increased PWL, suppressing hyperalgesia (P<0.05). Intra-CeA DAMGO significantly inhibited the display of CPA compared to saline (P<0.05) but had no effect on PWL. The data demonstrate that morphine attenuates the affective component more powerfully than it does the sensory and suggests that the sensory and the emotional-affective dimensions are underpinned by different mechanisms. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

Osthole, a herbal compound, alleviates nucleus pulposus-evoked nociceptive responses through the suppression of overexpression of acid-sensing ion channel 3 (ASIC3) in rat dorsal root ganglion

PubMed Central

He, Qiu-Lan; Chen, Yuling; Qin, Jian; Mo, Sui-Lin; Wei, Ming; Zhang, Jin-Jun; Li, Mei-Na; Zou, Xue-Nong; Zhou, Shu-Feng; Chen, Xiao-Wu; Sun, Lai-Bao

2012-01-01

Summary Background Osthole (Ost), a natural coumarin derivative, has been shown to inhibit many pro-inflammatory mediators and block voltage-gated Na+ channels. During inflammation, acidosis is an important pain inducer which activates nociceptors by gating depolarizing cationic channels, such as acid-sensing ion channel 3 (ASIC3). The aim of this study was to examine the effects of Ost on nucleus pulposus-evoked nociceptive responses and ASIC3 over-expression in the rat dorsal root ganglion, and to investigate the possible mechanism. Material/Methods Radicular pain was generated with application of nucleus pulposus (NP) to nerve root. Mechanical allodynia was evaluated using von Frey filaments with logarithmically incremental rigidity to calculate the 50% probability thresholds for mechanical paw withdrawal. ASIC3 protein expression in dorsal root ganglions (DRGs) was assessed with Western blot and immunohistochemistry. Membrane potential (MP) shift of DRG neurons induced by ASIC3-sensitive acid (pH6.5) was determined by DiBAC4 (3) fluorescence intensity (F.I.). Results The NP-evoked mechanical hyperalgesia model showed allodynia for 3 weeks, and ASIC3 expression was up-regulated in DRG neurons, reaching peak on Day 7. Epidural administration of Ost induced a remarkable and prolonged antinociceptive effect, accompanied by an inhibition of over-expressed ASIC3 protein and of abnormal shift of MP. Amiloride (Ami), an antagonist of ASIC3, strengthened the antinociceptive effect of Ost. Conclusions Up-regulation of ASIC3 expression may be associated with NP-evoked mechanical hyperalgesia. A single epidural injection of Ost decreased ASIC3 expression in DGR neurons and the pain in the NP-evoked mechanical hyperalgesia model. Osthole may be of great benefit for preventing chronic pain status often seen in lumbar disc herniation (LDH). PMID:22648244

Orofacial inflammatory pain affects the expression of MT1 and NADPH-d in rat caudal spinal trigeminal nucleus and trigeminal ganglion

PubMed Central

Huang, Fang; He, Hongwen; Fan, Wenguo; Liu, Yongliang; Zhou, Hongyu; Cheng, Bin

2013-01-01

Very little is known about the role of melatonin in the trigeminal system, including the function of melatonin receptor 1. In the present study, adult rats were injected with formaldehyde into the right vibrissae pad to establish a model of orofacial inflammatory pain. The distribution of melatonin receptor 1 and nicotinamide adenine dinucleotide phosphate diaphorase in the caudal spinal trigeminal nucleus and trigeminal ganglion was determined with immunohistochemistry and histochemistry. The results show that there are significant differences in melatonin receptor 1 expression and nicotinamide adenine dinucleotide phosphate diaphorase expression in the trigeminal ganglia and caudal spinal nucleus during the early stage of orofacial inflammatory pain. Our findings suggest that when melatonin receptor 1 expression in the caudal spinal nucleus is significantly reduced, melatonin's regulatory effect on pain is attenuated. PMID:25206619

The multiplicity of spinal AA-5-HT anti-nociceptive action in a rat model of neuropathic pain.

PubMed

Malek, Natalia; Kostrzewa, Magdalena; Makuch, Wioletta; Pajak, Agnieszka; Kucharczyk, Mateusz; Piscitelli, Fabiana; Przewlocka, Barbara; Di Marzo, Vincenzo; Starowicz, Katarzyna

2016-09-01

There is considerable evidence to support the role of anandamide (AEA), an endogenous ligand of cannabinoid receptors, in neuropathic pain modulation. AEA also produces effects mediated by other biological targets, of which the transient receptor potential vanilloid type 1 (TRPV1) has been the most investigated. Both, inhibition of AEA breakdown by fatty acid amide hydrolase (FAAH) and blockage of TRPV1 have been shown to produce anti-nociceptive effects. Recent research suggests the usefulness of dual-action compounds, which may afford greater anti-allodynic efficacy. Therefore, in the present study, we examined the effect of N-arachidonoyl-serotonin (AA-5-HT), a blocker of FAAH and TRPV1, in a rat model of neuropathic pain after intrathecal administration. We found that treatment with AA-5-HT increased the pain threshold to mechanical and thermal stimuli, with highest effect at the dose of 500nM, which was most strongly attenuated by AM-630, CB2 antagonist, administration. The single action blockers PF-3845 (1000nM, for FAAH) and I-RTX (1nM, for TRPV1) showed lower efficacy than AA-5-HT. Moreover AA-5-HT (500nM) elevated AEA and palmitoylethanolamide (PEA) levels. Among the possible targets of these mediators, only the mRNA levels of CB2, GPR18 and GPR55, which are believed to be novel cannabinoid receptors, were upregulated in the spinal cord and/or DRG of CCI rats. It was previously reported that AA-5-HT acts in CB1 and TRPV1-dependent manner after systemic administration, but here for the first time we show that AA-5-HT action at the spinal level involves CB2, with potential contributions from GRP18 and/or GPR55 receptors. Copyright © 2016 Elsevier Ltd. All rights reserved.

Tramadol and Propentofylline Coadministration Exerted Synergistic Effects on Rat Spinal Nerve Ligation-Induced Neuropathic Pain

PubMed Central

Wang, Huan; Wang, Wei; Zhang, Hui; Liu, Rui; Xu, Li-Xian; Mei, Xiao-Peng

2013-01-01

Neuropathic pain is an intractable clinical problem. Drug treatments such as tramadol have been reported to effectively decrease neuropathic pain by inhibiting the activity of nociceptive neurons. It has also been reported that modulating glial activation could also prevent or reverse neuropathic pain via the administration of a glial modulator or inhibitor, such as propentofylline. Thus far, there has been no clinical strategy incorporating both neuronal and glial participation for treating neuropathic pain. Therefore, the present research study was designed to assess whether coadministration of tramadol and propentofylline, as neuronal and glial activation inhibitors, respectively, would exert a synergistic effect on the reduction of rat spinal nerve ligation (SNL)-induced neuropathic pain. Rats underwent SNL surgery to induce neuropathic pain. Pain behavioral tests were conducted to ascertain the effect of drugs on SNL-induced mechanical allodynia with von-Frey hairs. Proinflammatory factor interleukin-1β (IL-1β) expression was also detected by Real-time RT-PCR. Intrathecal tramadol and propentofylline administered alone relieved SNL-induced mechanical allodynia in a dose-dependent manner. Tramadol and propentofylline coadministration exerted a more potent effect in a synergistic and dose dependent manner than the intrathecal administration of either drug alone. Real-time RT-PCR demonstrated IL-1β up-expression in the ipsilateral spinal dorsal horn after the lesion, which was significantly decreased by tramadol and propentofylline coadministration. Inhibiting proinflammatory factor IL-1β contributed to the synergistic effects of tramadol and propentofylline coadministration on rat peripheral nerve injury-induced neuropathic pain. Thus, our study provided a rationale for utilizing a novel strategy for treating neuropathic pain by blocking the proinflammatory factor related pathways in the central nervous system. PMID:24009718

HDAC inhibition inhibits brachial plexus avulsion induced neuropathic pain.

PubMed

Zhao, Yingbo; Wu, Tianjian

2018-05-09

Introduction Neuropathic pain induced by brachial plexus avulsion (BPA) is a pathological condition. We hypothesized that inhibition of histone deacetylase (HDAC) could suppress BPA-induced neuropathic pain through inhibition of transient reception potential (TRP) overexpression and protein kinase B (Akt) mediated mammalian target of rapamycin (mTOR) activation. Methods We generated a rat BPA model, administered HDAC inhibitor Tricostatin A (TSA) for 7 days post-surgery and assessed the effects on HDAC expression, Akt phosphorylation, neuroinflammation and mTOR activation. Results TSA treatment alleviated BPA induced mechanical hyperalgesia, suppressed Akt phosphorylation and increased HDAC. We found suppressed pro-inflammatory cytokine levels, TRP cation channel subfamily V member 1 (TRPV1) and TRP melastatin 8 (TRPM8) expression and mTOR activity in TSA treated BPA rats. Discussion Our results suggest that altered HDAC and Akt signaling are involved in BPA-induced neuropathic pain and that inhibition of HDAC could be an effective therapeutic approach in reducing neuropathic pain. This article is protected by copyright. All rights reserved. © 2018 Wiley Periodicals, Inc.

Endomorphin-2 Inhibition of Substance P Signaling within Lamina I of the Spinal Cord Is Impaired in Diabetic Neuropathic Pain Rats

PubMed Central

Wan, Fa-Ping; Bai, Yang; Kou, Zhen-Zhen; Zhang, Ting; Li, Hui; Wang, Ya-Yun; Li, Yun-Qing

2017-01-01

Opiate analgesia in the spinal cord is impaired in diabetic neuropathic pain (DNP), but until now the reason is unknown. We hypothesized that it resulted from a decreased inhibition of substance P (SP) signaling within the dorsal horn of the spinal cord. To investigate this possibility, we evaluated the effects of endomorphin-2 (EM2), an endogenous ligand of the μ-opioid receptor (MOR), on SP release within lamina I of the spinal dorsal horn (SDH) in rats with DNP. We established the DNP rat model and compared the analgesic efficacy of EM2 between inflammation pain and DNP rat models. Behavioral results suggested that the analgesic efficacy of EM2 was compromised in the condition of painful diabetic neuropathy. Then, we measured presynaptic SP release induced by different stimulating modalities via neurokinin-1 receptor (NK1R) internalization. Although there was no significant change in basal and evoked SP release between control and DNP rats, EM2 failed to inhibit SP release by noxious mechanical and thermal stimuli in DNP but not in control and inflammation pain model. We also observed that EM2 decreased the number of FOS-positive neurons within lamina I of the SDH but did not change the amount of FOS/NK1R double-labeled neurons. Finally, we identified a remarkable decrease in MORs within the primary afferent fibers and dorsal root ganglion (DRG) neurons by Western blot (WB) and immunohistochemistry (IHC). Taken together, these data suggest that reduced presynaptic MOR expression might account for the loss of the inhibitory effect of EM2 on SP signaling, which might be one of the neurobiological foundations for decreased opioid efficacy in the treatment of DNP. PMID:28119567

Pharmacological interaction between oxcarbazepine and two COX inhibitors in a rat model of inflammatory hyperalgesia.

PubMed

Stepanović-Petrović, Radica M; Tomić, Maja A; Vučković, Sonja M; Poznanović, Goran; Ugrešić, Nenad D; Prostran, Milica Š; Bošković, Bogdan

2011-01-01

Oxcarbazepine, ibuprofen and etodolac have efficacy in inflammatory pain. The combination of different drugs activates both central and peripheral pain inhibitory pathways to induce additive or synergistic antinociception, and this interaction may allow lower doses of each drug combined and improve the safety profile, with lower side-effects. This study aimed to examine the effects of oxcarbazepine-ibuprofen and oxcarbazepine-etodolac combinations, in a rat model of inflammatory hyperalgesia, and determine the type of interaction between drugs. Rats were intraplantarly injected with carrageenan (0.1 ml, 1%) and the hyperalgesia was assessed by modified paw pressure test. The anti-hyperalgesic effects of oxcarbazepine, ibuprofen and etodolac and oxcarbazepine-ibuprofen and oxcarbazepine-etodolac combinations were examined. Drugs were co-administered in a fixed-dose fractions of the ED₅₀ and the type of interaction was determined by isobolographic analysis. Oxcarbazepine (40-160 mg/kg; p.o.), ibuprofen (10-120 mg/kg; p.o.) and etodolac (5-20 mg/kg; p.o.) produced a significant, dose-dependent anti-hyperalgesia in carrageenan-injected rats. ED₅₀ values (mean±SEM) for oxcarbazepine, ibuprofen and etodolac were 88.17±3.65, 47.07±10.27 and 13.05±1.42 mg/kg, respectively. Oxcarbazepine-ibuprofen and oxcarbazepine-etodolac combinations induced significant and dose-dependent anti-hyperalgesia. Isobolographic analysis revealed that oxcarbazepine exerts a synergistic interaction with ibuprofen, with almost 4-fold reduction of doses of both drugs in combination. In contrast, there was an additive interaction with etodolac. Synergistic interaction of oxcarbazepine with ibuprofen and its additive interaction with etodolac provide new information about the combination pain treatment and could be explored further in patients with inflammatory pain. Adverse effect analysis of the combinations is necessary to verify possible clinical use of the mixtures. Copyright © 2010 Elsevier Inc. All rights reserved.

Decreased voltage-gated potassium currents in rat dorsal root ganglion neurons after chronic constriction injury.

PubMed

Xiao, Yun; Wu, Yang; Zhao, Bo; Xia, Zhongyuan

2016-01-20

Voltage-gated potassium channels (KV) regulate pain transmission by controlling neuronal excitability. Changes in KV expression patterns may thus contribute toward hyperalgesia following nerve injury. The aim of this study was to characterize KV current density in dorsal root ganglion (DRG) neurons following chronic constriction injury (CCI) of the right sciatic nerve, a robust model of post-traumatic neuropathic pain. The study examined changes in small-diameter potassium ion currents (<30 µm) in neurons in the L4-L6 DRG following CCI by whole-cell patch-clamping and the association with post-CCI mechanical and thermal nociceptive thresholds. Compared with the control group, 7 days after CCI, the mechanical force and temperature required to elicit ipsilateral foot withdrawal decreased significantly, indicating tactile allodynia and thermal hyperalgesia. Post-CCI neurons had a significantly lower rheobase current and depolarized resting membrane potential than controls, suggesting KV current downregulation. Some ipsilateral DRG neurons also had spontaneous action potentials and repetitive firing. There was a 55% reduction in the total KV current density caused by a 55% decrease in the sustained delayed rectifier potassium ion current (IK) density and a 17% decrease in the transient A-type potassium ion current (IA) density. These results indicated that changes in DRG neuron IK and IA current density and concomitant afferent hyperexcitability may contribute toward neuropathic pain following injury. The rat CCI model may prove valuable for examining pathogenic mechanisms and potential therapies, such as KV channel modulators.

Adenovector GAD65 gene delivery into the rat trigeminal ganglion produces orofacial analgesia

PubMed Central

Vit, Jean-Philippe; Ohara, Peter T; Sundberg, Christopher; Rubi, Blanca; Maechler, Pierre; Liu, Chunyan; Puntel, Mariana; Lowenstein, Pedro; Castro, Maria; Jasmin, Luc

2009-01-01

Background Our goal is to use gene therapy to alleviate pain by targeting glial cells. In an animal model of facial pain we tested the effect of transfecting the glutamic acid decarboxylase (GAD) gene into satellite glial cells (SGCs) of the trigeminal ganglion by using a serotype 5 adenovector with high tropisms for glial cells. We postulated that GABA produced from the expression of GAD would reduce pain behavior by acting on GABA receptors on neurons within the ganglion. Results Injection of adenoviral vectors (AdGAD65) directly into the trigeminal ganglion leads to sustained expression of the GAD65 isoform over the 4 weeks observation period. Immunohistochemical analysis showed that adenovirus-mediated GAD65 expression and GABA synthesis were mainly in SGCs. GABAA and GABAB receptors were both seen in sensory neurons, yet only GABAA receptors decorated the neuronal surface. GABA receptors were not found on SGCs. Six days after injection of AdGAD65 into the trigeminal ganglion, there was a statistically significant decrease of pain behavior in the orofacial formalin test, a model of inflammatory pain. Rats injected with control virus (AdGFP or AdLacZ) had no reduction in their pain behavior. AdGAD65-dependent analgesia was blocked by bicuculline, a selective GABAA receptor antagonist, but not by CGP46381, a selective GABAB receptor antagonist. Conclusion Transfection of glial cells in the trigeminal ganglion with the GAD gene blocks pain behavior by acting on GABAA receptors on neuronal perikarya. PMID:19656360

Tramadol and propentofylline coadministration exerted synergistic effects on rat spinal nerve ligation-induced neuropathic pain.

PubMed

Zhang, Jin; Wu, Dan; Xie, Cheng; Wang, Huan; Wang, Wei; Zhang, Hui; Liu, Rui; Xu, Li-Xian; Mei, Xiao-Peng

2013-01-01

Neuropathic pain is an intractable clinical problem. Drug treatments such as tramadol have been reported to effectively decrease neuropathic pain by inhibiting the activity of nociceptive neurons. It has also been reported that modulating glial activation could also prevent or reverse neuropathic pain via the administration of a glial modulator or inhibitor, such as propentofylline. Thus far, there has been no clinical strategy incorporating both neuronal and glial participation for treating neuropathic pain. Therefore, the present research study was designed to assess whether coadministration of tramadol and propentofylline, as neuronal and glial activation inhibitors, respectively, would exert a synergistic effect on the reduction of rat spinal nerve ligation (SNL)-induced neuropathic pain. Rats underwent SNL surgery to induce neuropathic pain. Pain behavioral tests were conducted to ascertain the effect of drugs on SNL-induced mechanical allodynia with von-Frey hairs. Proinflammatory factor interleukin-1β (IL-1β) expression was also detected by Real-time RT-PCR. Intrathecal tramadol and propentofylline administered alone relieved SNL-induced mechanical allodynia in a dose-dependent manner. Tramadol and propentofylline coadministration exerted a more potent effect in a synergistic and dose dependent manner than the intrathecal administration of either drug alone. Real-time RT-PCR demonstrated IL-1β up-expression in the ipsilateral spinal dorsal horn after the lesion, which was significantly decreased by tramadol and propentofylline coadministration. Inhibiting proinflammatory factor IL-1β contributed to the synergistic effects of tramadol and propentofylline coadministration on rat peripheral nerve injury-induced neuropathic pain. Thus, our study provided a rationale for utilizing a novel strategy for treating neuropathic pain by blocking the proinflammatory factor related pathways in the central nervous system.

The Effects of a Co-Application of Menthol and Capsaicin on Nociceptive Behaviors of the Rat on the Operant Orofacial Pain Assessment Device

PubMed Central

Anderson, Ethan M.; Jenkins, Alan C.; Caudle, Robert M.; Neubert, John K.

2014-01-01

Background Transient receptor potential (TRP) cation channels are involved in the perception of hot and cold pain and are targets for pain relief in humans. We hypothesized that agonists of TRPV1 and TRPM8/TRPA1, capsaicin and menthol, would alter nociceptive behaviors in the rat, but their opposite effects on temperature detection would attenuate one another if combined. Methods Rats were tested on the Orofacial Pain Assessment Device (OPAD, Stoelting Co.) at three temperatures within a 17 min behavioral session (33°C, 21°C, 45°C). Results The lick/face ratio (L/F: reward licking events divided by the number of stimulus contacts. Each time there is a licking event a contact is being made.) is a measure of nociception on the OPAD and this was equally reduced at 45°C and 21°C suggesting they are both nociceptive and/or aversive to rats. However, rats consumed (licks) equal amounts at 33°C and 21°C but less at 45°C suggesting that heat is more nociceptive than cold at these temperatures in the orofacial pain model. When menthol and capsaicin were applied alone they both induced nociceptive behaviors like lower L/F ratios and licks. When applied together though, the licks at 21°C were equal to those at 33°C and both were significantly higher than at 45°C. Conclusions This suggests that the cool temperature is less nociceptive when TRPM8/TRPA1 and TRPV1 are co-activated. These results suggest that co-activation of TRP channels can reduce certain nociceptive behaviors. These data demonstrate that the motivational aspects of nociception can be influenced selectively by TRP channel modulation and that certain aspects of pain can be dissociated and therefore targeted selectively in the clinic. PMID:24558480

Modulation of Kv7 potassium channels by a novel opener pyrazolo[1,5-a]pyrimidin-7(4H)-one compound QO-58

PubMed Central

Zhang, F; Mi, Y; Qi, JL; Li, JW; Si, M; Guan, BC; Du, XN; An, HL; Zhang, HL

2013-01-01

Background and Purpose Modulation of Kv7/M channel function represents a relatively new strategy to treat neuronal excitability disorders such as epilepsy and neuropathic pain. We designed and synthesized a novel series of pyrazolo[1,5-a] pyrimidin-7(4H)-one compounds, which activate Kv7 channels. Here, we characterized the effects of the lead compound, QO-58, on Kv7 channels and investigated its mechanism of action. Experimental Approach A perforated whole-cell patch technique was used to record Kv7 currents expressed in mammalian cell lines and M-type currents from rat dorsal root ganglion neurons. The effects of QO-58 in a rat model of neuropathic pain, chronic constriction injury (CCI) of the sciatic nerve, were also examined. Key Results QO-58 increased the current amplitudes, shifted the voltage-dependent activation curve in a more negative direction and slowed the deactivation of Kv7.2/Kv7.3 currents. QO-58 activated Kv7.1, Kv7.2, Kv7.4 and Kv7.3/Kv7.5 channels with a more selective effect on Kv7.2 and Kv7.4, but little effect on Kv7.3. The mechanism of QO-58's activation of Kv7 channels was clearly distinct from that used by retigabine. A chain of amino acids, Val224Val225Tyr226, in Kv7.2 was important for QO-58 activation of this channel. QO-58 enhanced native neuronal M currents, resulting in depression of evoked action potentials. QO-58 also elevated the pain threshold of neuropathic pain in the sciatic nerve CCI model. Conclusions and Implications The results indicate that QO-58 is a potent modulator of Kv7 channels with a mechanism of action different from those of known Kv7 openers. Hence, QO-58 shows potential as a treatment for diseases associated with neuronal hyperexcitability. PMID:23013484

Spinal intracellular metabotropic glutamate receptor 5 (mGluR5) contributes to pain and c-fos expression in a rat model of inflammatory pain.

PubMed

Vincent, Kathleen; Wang, Shu Fan; Laferrière, André; Kumar, Naresh; Coderre, Terence J

2017-04-01

Metabotropic glutamate receptor 5 (mGluR5) is an excitatory G-protein-coupled receptor (GPCR) present in the spinal cord dorsal horn (SCDH) where it has a well-established role in pain. In addition to its traditional location on the cytoplasmic membrane, recent evidence shows that these receptors are present intracellularly on the nuclear membrane in the spinal cord dorsal horn and are implicated in neuropathic pain. Nuclear mGluR5 is a functional receptor that binds glutamate entering the cell through the neuronal glutamate transporter (GT) EAAT3 and activates transcription factor c-fos, whereas plasma membrane mGluR5 is responsible for c-jun activation. Here, we extend these findings to a model of inflammatory pain using complete Freund's adjuvant (CFA) and show that nuclear mGluR5 is also upregulated in the spinal cord dorsal horn following inflammation. We also show that pretreatment with an excitatory amino acid transporter (EAAT) inhibitor attenuates pain and decreases Fos, but not Jun, expression in complete Freund's adjuvant rats. In contrast, selective glial glutamate transporter inhibitors are pronociceptive and increase spinal glutamate concentrations. Additionally, we found that permeable mGluR5 antagonists are more effective at attenuating pain and Fos expression than nonpermeable group I mGluR antagonists. Taken together, these results suggest that under inflammatory conditions, intracellular mGluR5 is actively involved in the relay of nociceptive information in the spinal cord.

Adenovector GAD65 gene delivery into the rat trigeminal ganglion produces orofacial analgesia.

PubMed

Vit, Jean-Philippe; Ohara, Peter T; Sundberg, Christopher; Rubi, Blanca; Maechler, Pierre; Liu, Chunyan; Puntel, Mariana; Lowenstein, Pedro; Castro, Maria; Jasmin, Luc

2009-08-05

Our goal is to use gene therapy to alleviate pain by targeting glial cells. In an animal model of facial pain we tested the effect of transfecting the glutamic acid decarboxylase (GAD) gene into satellite glial cells (SGCs) of the trigeminal ganglion by using a serotype 5 adenovector with high tropisms for glial cells. We postulated that GABA produced from the expression of GAD would reduce pain behavior by acting on GABA receptors on neurons within the ganglion. Injection of adenoviral vectors (AdGAD65) directly into the trigeminal ganglion leads to sustained expression of the GAD65 isoform over the 4 weeks observation period. Immunohistochemical analysis showed that adenovirus-mediated GAD65 expression and GABA synthesis were mainly in SGCs. GABAA and GABAB receptors were both seen in sensory neurons, yet only GABAA receptors decorated the neuronal surface. GABA receptors were not found on SGCs. Six days after injection of AdGAD65 into the trigeminal ganglion, there was a statistically significant decrease of pain behavior in the orofacial formalin test, a model of inflammatory pain. Rats injected with control virus (AdGFP or AdLacZ) had no reduction in their pain behavior. AdGAD65-dependent analgesia was blocked by bicuculline, a selective GABAA receptor antagonist, but not by CGP46381, a selective GABAB receptor antagonist. Transfection of glial cells in the trigeminal ganglion with the GAD gene blocks pain behavior by acting on GABAA receptors on neuronal perikarya.

The involvement of peripheral alpha 2-adrenoceptors in the antihyperalgesic effect of oxcarbazepine in a rat model of inflammatory pain.

PubMed

Tomić, Maja A; Vucković, Sonja M; Stepanović-Petrović, Radica M; Ugresić, Nenad D; Paranos, Sonja Lj; Prostran, Milica S; Bosković, Bogdan

2007-11-01

We studied whether peripheral alpha2-adrenergic receptors are involved in the antihyperalgesic effects of oxcarbazepine by examining the effects of yohimbine (selective alpha2-adrenoceptor antagonist), BRL 44408 (selective alpha(2A)-adrenoceptor antagonist), MK-912 (selective alpha2C-adrenoceptor antagonist), and clonidine (alpha2-adrenoceptor agonist) on the antihyperalgesic effect of oxcarbazepine in the rat model of inflammatory pain. Rats were intraplantarly (i.pl.) injected with the proinflammatory compound concanavalin A (Con A). A paw-pressure test was used to determine: 1) the development of hyperalgesia induced by Con A; 2) the effects of oxcarbazepine (i.pl.) on Con A-induced hyperalgesia; and 3) the effects of i.pl. yohimbine, BRL 44408, MK-912 and clonidine on the oxcarbazepine antihyperalgesia. Both oxcarbazepine (1000-3000 nmol/paw; i.pl.) and clonidine (1.9-7.5 nmol/paw; i.pl.) produced a significant dose-dependent reduction of the paw inflammatory hyperalgesia induced by Con A. Yohimbine (260 and 520 nmol/paw; i.pl.), BRL 44408 (100 and 200 nmol/paw; i.pl.) and MK-912 (10 and 20 nmol/paw; i.pl.) significantly depressed the antihyperalgesic effects of oxcarbazepine (2000 nmol/paw; i.pl.) in a dose-dependent manner. The effects of antagonists were due to local effects since they were not observed after administration into the contralateral hindpaw. Oxcarbazepine and clonidine administered jointly in fixed-dose fractions of the ED(50) (1/4, 1/2, and 3/4) caused significant and dose-dependent reduction of hyperalgesia induced by Con A. Isobolographic analysis revealed an additive antihyperalgesic effect. Our results indicate that the peripheral alpha2A and alpha2C adrenoceptors could be involved in the antihyperalgesic effects of oxcarbazepine in a rat model of inflammatory hyperalgesia.

Analgesia induced by morphine microinjected into the nucleus raphe magnus: effects on tonic pain.

PubMed

Dualé, Christian; Sierralta, Fernando; Dallel, Radhouane

2007-07-01

One of the possible sites of action of the analgesic effect of morphine is the Nucleus Raphe Magnus, as morphine injected into this structure induces analgesia in transient pain models. In order to test if morphine in the Nucleus Raphe Magnus is also analgesic in a tonic pain model, 5 microg of morphine or saline (control) were microinjected into the Nucleus Raphe Magnus of the rat. Analgesic effects were assessed following nociceptive stimulation using transient heating of the tail (phasic pain) and subcutaneous orofacial injection of 1.5 % formalin (tonic pain). While morphine was strongly analgesic for the tail-flick response (p <0.0001 compared to control), analgesia on the response to formalin was also observed for both early (p = 0.007) and late responses (p = 0.02). However, the response to formalin was not completely blunted. These results suggest that the Nucleus Raphe Magnus is not the exclusive site of action of morphine-induced analgesia in clinical conditions.

Anti-nociceptive effects of Tanshinone IIA (TIIA) in a rat model of complete Freund's adjuvant (CFA)-induced inflammatory pain.

PubMed

Sun, Shukai; Yin, Yue; Yin, Xin; Cao, Fale; Luo, Daoshu; Zhang, Ting; Li, Yunqing; Ni, Longxing

2012-09-01

Inflammatory pain is an important clinical symptom. The levels of extracellular signal-regulated kinases (ERKs) and the levels of cytokines such as interleukin 1β (IL-1β), interleukin 6 (IL-6) and tumor necrosis factor-alpha (TNF-α) play important roles in inflammatory pain. Tanshinone IIA (TIIA) is an important component of Danshen, a traditional Chinese medicine that has been commonly used to treat cardiovascular disease. In this study, we investigated the potential anti-inflammatory nociceptive effects of TIIA on complete Freund's adjuvant (CFA)-induced inflammation and inflammatory pain in rats. The effects of TIIA on CFA-induced thermal and mechanical hypersensitivity were investigated using behavioral tests. The levels of ERKs, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and transient receptor potential vanilloid 1 (TRPV1) in the fifth segment of the lumbar spinal cord (L5) ganglia were detected by Western blot, and the levels of mRNA and protein production of IL1-β, IL-6 and TNF-α were detected by real-time reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immuno sorbent assay (ELISA). In this study, we found that TIIA attenuates the development of CFA-induced mechanical and thermal hypersensitivity. In addition, p-ERK and NF-κB expression levels were inhibited by TIIA, and the levels of the pro-inflammatory cytokines IL-1β, IL-6 and TNF-α were reduced. Finally, we found that the expression level of TRPV1 was significantly decreased after TIIA injection. This study demonstrated that TIIA has significant anti-nociceptive effects in a rat model of CFA-induced inflammatory pain. TIIA can inhibit the activation of ERK signaling pathways and the expression of pro-inflammatory cytokines. These results suggest that TIIA may be a potential anti-inflammatory and anti-nociceptive drug. Copyright © 2012 Elsevier Inc. All rights reserved.

The effects of levetiracetam, sumatriptan, and caffeine in a rat model of trigeminal pain: interactions in 2-component combinations.

PubMed

Tomić, Maja A; Pecikoza, Uroš B; Micov, Ana M; Popović, Božidar V; Stepanović-Petrović, Radica M

2015-06-01

Levetiracetam is an antiepileptic drug with analgesic efficacy shown in pain models and small clinical trials. Sumatriptan is used in acute migraine treatment. Caffeine is widely consumed in some beverages/foods and is also an adjuvant in analgesic formulations. We examined the effects of systemic levetiracetam, sumatriptan, and caffeine and their interactions in 2-component combinations in the rat orofacial formalin test, a model of trigeminal pain. Rats received a subcutaneous injection of formalin solution into the perinasal area, and the total time spent in nociceptive behavior (face rubbing) was quantified. The antinociceptive effect of drugs/drug combinations was assessed 1 hour after per os administration. The type of interaction between levetiracetam/sumatriptan and caffeine was examined by comparing the effects of a fixed, effective dose of levetiracetam/sumatriptan alone with the effects of the same dose applied with increasing, subeffective doses of caffeine. The type of interaction between levetiracetam and sumatriptan was determined by isobolographic analysis. Levetiracetam (1-50 mg/kg) and sumatriptan (0.5-5 mg/kg) produced significant and dose-dependent antinociceptive effects in both phases of the orofacial formalin test (P ≤ 0.001). Caffeine (7.5-100 mg/kg) produced significant antinociception in the second phase of the test (P = 0.04). Caffeine (1-7.5 mg/kg) significantly reduced the antinociceptive effects of levetiracetam (25 mg/kg) (first phase P = 0.002, second phase P < 0.001) and sumatriptan (2.5 mg/kg) (first phase P = 0.014, second phase P = 0.027); dose-dependent inhibition was observed in the second phase. Levetiracetam and sumatriptan exerted an additive interaction in the second phase of the orofacial formalin test. Results indicate that levetiracetam may be useful for treatment of pain in the trigeminal region. Dietary caffeine might decrease the effects of levetiracetam and sumatriptan; this needs to be considered in clinical settings. A levetiracetam-sumatriptan combination could also be useful in trigeminal pain treatment. Its efficacy and adverse effects should be examined clinically.

Bioactive Turmerosaccharides from Curcuma longa Extract (NR-INF-02): Potential Ameliorating Effect on Osteoarthritis Pain.

PubMed

Bethapudi, Bharathi; Murugan, Sasikumar; Illuri, Ramanaiah; Mundkinajeddu, Deepak; Velusami, Chandrasekaran Chinampudur

2017-10-01

Curcuma longa has long history of medicinal use in Ayurveda. A unique product NR-INF-02 was prepared from C. longa that was standardized to contain turmerosaccharides. The present study investigated the effect of turmerosaccharides rich fraction of NR-INF-02 on monosodium iodoacetate (MIA)-induced OA pain animal model that mimics human OA. Further, the analgesic effect of turmerosaccharides rich fraction was compared to turmerosaccharides less fraction of NR-INF-02. OA pain was chemically induced by intra-articular administration of single dose of 25 μl of 0.9% saline containing 0.3 mg MIA into the right knee of male albino Wistar rat. Turmerosaccharides rich fraction and turmerosaccharides less fraction (at 22.5, 45 and 90 mg/kg rat body weight dose levels) were administered as a single dose orally on day 5 of post-MIA injection. OA pain was measured using hind limb weight-bearing ability at 1, 3, 6, and 24 h post-test substance administration on day 5. Oral administration of turmerosaccharides rich fraction and turmerosaccharides less fraction (at 45 and 90 mg/kg) although significantly decreased the OA pain at all the intervals, the effect of turmerosaccharides rich fraction (57%) on OA pain was superior to turmerosaccharides less fraction (35%). Bioactive turmerosaccharides from C. longa extract contribute to the observed anti-arthritic effect in rats. Osteoarthritic pain was induced by intra-articular injection of MIA into the right kneeSingle administration of TRF/TLF on day 5 resulted in dose-dependent significant reduction of OA painTRF showed better analgesic activity than TLFTRF at 45 and 90 mg/kg has similar effects on OA pain as that of tramadolTurmerosaccharides identified as bioactive constituents of C. longa extract. Abbreviations used: MIA: Monosodium iodoacetate; i.ar: Intra-articular; OA: Osteoarthritis; TRF: Turmerosaccharides rich fraction; TLF: Turmerosaccharides less fraction; PGE2: Prostaglandin E2; ROS: Reactive oxygen species.

Hyperbaric oxygen attenuates neuropathic pain and reverses inflammatory signaling likely via the Kindlin-1/Wnt-10a signaling pathway in the chronic pain injury model in rats.

PubMed

Zhao, Baisong; Pan, Yongying; Xu, Haiping; Song, Xingrong

2017-12-01

Hyperbaric oxygen (HBO) therapy is proven to attenuate neuropathic pain in rodents. The goal of the present study was to determine the potential involvement of the Kindlin-1/Wnt-10a signaling pathway during astrocyte activation and inflammation in a rodent model of neuropathic pain. Rats were assigned into sham operation, chronic constriction injury (CCI), and CCI + HBO treatment groups. Neuropathic pain developed in rats following CCI of the sciatic nerve. Rats in the CCI + HBO group received HBO treatment for five consecutive days beginning on postoperative day 1. The mechanical withdrawal threshold (MWT) and the thermal withdrawal latency (TWL) tests were performed to determine mechanical and heat hypersensitivity of animals, respectively. Kindlin-1, Wnt-10a and β-catenin protein expression was examined by immunohistochemistry and Western blot analysis. Expression of tumor necrosis factor (TNF)-α was also determined by ELISA. Our findings demonstrated that HBO treatment significantly suppressed mechanical and thermal hypersensitivity in the CCI neuropathic pain model in rats. HBO therapy significantly reversed the up-regulation of Kindlin-1 in dorsal root ganglia (DRG), spinal cord, and hippocampus of CCI rats. CCI-induced astrocyte activation and increased levels of TNF-α were efficiently reversed by HBO (P < 0.05 vs. CCI). HBO also reversed Wnt-10a up-regulation induced by CCI in the DRG, spinal cord, and hippocampus (P < 0.05 vs. CCI). Our findings demonstrate that HBO attenuated CCI-induced rat neuropathic pain and inflammatory responses, possibly through regulation of the Kindlin-1/Wnt-10a signaling pathway.

Spontaneous Chronic Pain After Experimental Thoracotomy Revealed by Conditioned Place Preference: Morphine Differentiates Tactile Evoked Pain From Spontaneous Pain.

PubMed

Hung, Ching-Hsia; Wang, Jeffrey Chi-Fei; Strichartz, Gary R

2015-09-01

Chronic pain after surgery limits social activity, interferes with work, and causes emotional suffering. A major component of such pain is reported as resting or spontaneous pain with no apparent external stimulus. Although experimental animal models can simulate the stimulus-evoked chronic pain that occurs after surgery, there have been no studies of spontaneous chronic pain in such models. Here the conditioned place preference (CPP) paradigm was used to reveal resting pain after experimental thoracotomy. Male Sprague Dawley rats received a thoracotomy with 1-hour rib retraction, resulting in evoked tactile hypersensitivity, previously shown to last for at least 9 weeks. Intraperitoneal injections of morphine (2.5 mg/kg) or gabapentin (40 mg/kg) gave equivalent 2- to 3-hour-long relief of tactile hypersensitivity when tested 12 to 14 days postoperatively. In separate experiments, single trial CPP was conducted 1 week before thoracotomy and then 12 days (gabapentin) or 14 days (morphine) after surgery, followed the next day by 1 conditioning session with morphine or gabapentin, both versus saline. The gabapentin-conditioned but not the morphine-conditioned rats showed a significant preference for the analgesia-paired chamber, despite the equivalent effect of the 2 agents in relieving tactile allodynia. These results show that experimental thoracotomy in rats causes spontaneous pain and that some analgesics, such as morphine, that reduce evoked pain do not also relieve resting pain, suggesting that pathophysiological mechanisms differ between these 2 aspects of long-term postoperative pain. Perspective: Spontaneous pain, a hallmark of chronic postoperative pain, is demonstrated here in a rat model of experimental postthoracotomy pain, further validating the use of this model for the development of analgesics to treat such symptoms. Although stimulus-evoked pain was sensitive to systemic morphine, spontaneous pain was not, suggesting different mechanistic underpinnings. Copyright © 2015 American Pain Society. Published by Elsevier Inc. All rights reserved.

Chronic prostatitis/chronic pelvic pain syndrome impairs erectile function through increased endothelial dysfunction, oxidative stress, apoptosis, and corporal fibrosis in a rat model.

PubMed

Hu, Y; Niu, X; Wang, G; Huang, J; Liu, M; Peng, B

2016-11-01

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is an independent risk factor for the development of erectile dysfunction (ED). But the molecular mechanisms underlying the relationship between CP/CPPS and ED are still unclear. The aim of this study was to investigate the effect of CP/CPPS on erectile function in a rat model and the possible mechanisms. A rat model of experimental autoimmune prostatitis (EAP) was established to mimic human CP⁄CPPS. Then twenty 2-month-old male Sprague-Dawley rats were divided into EAP group and control group. Intracavernosal pressure (ICP) and mean arterial pressure (MAP) were measured during cavernous nerve electrostimulation, the ratio of max ICP/MAP was calculated. Blood was collected to measure the levels of serum C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6) and testosterone, respectively. The expression of endothelial nitric oxide synthase (eNOS), cyclic guanosine monophosphate (cGMP) levels, superoxide dismutase (SOD) activity and malondialdehyde (MDA) levels in corpus cavernosum were detected. We also evaluated the smooth muscle/collagen ratio and apoptotic index (AI). The ratio of max ICP/MAP in EAP group were significantly lower than that in control group. The levels of serum CRP, TNF-α, IL-1β, and IL-6 in EAP group were all significantly higher than these in control group. The expression of eNOS and cGMP levels in corpus cavernosum of EAP rats were significantly downregulated. Furthermore, decreased SOD activity and smooth muscle/collagen ratio, increased MDA levels and AI were found in corpus cavernosum of EAP rats. In conclusion, CP/CPPS impaired penile erectile function in a rat model. The declines of eNOS expression and cGMP levels in corpus cavernosum may be an important mechanism of CP/CPPS-induced ED. CP/CPPS also increased oxidative stress, cell apoptosis and decreased smooth muscle/collagen ratio in corpus cavernosum of rats, which were all important for erectile function. © 2016 American Society of Andrology and European Academy of Andrology.

Correlation between the cumulative analgesic effect of electroacupuncture intervention and synaptic plasticity of hypothalamic paraventricular nucleus neurons in rats with sciatica☆

PubMed Central

Xu, Qiuling; Liu, Tao; Chen, Shuping; Gao, Yonghui; Wang, Junying; Qiao, Lina; Liu, Junling

2013-01-01

In the present study, a rat model of chronic neuropathic pain was established by ligation of the sciatic nerve and a model of learning and memory impairment was established by ovariectomy to investigate the analgesic effect of repeated electroacupuncture stimulation at bilateral Zusanli (ST36) and Yanglingquan (GB34). In addition, associated synaptic changes in neurons in the paraventricular nucleus of the hypothalamus were examined. Results indicate that the thermal pain threshold (paw withdrawal latency) was significantly increased in rats subjected to 2-week electroacupuncture intervention compared with 2-day electroacupuncture, but the analgesic effect was weakened remarkably in ovariectomized rats with chronic constrictive injury. 2-week electroacupuncture intervention substantially reversed the chronic constrictive injury-induced increase in the synaptic cleft width and thinning of the postsynaptic density. These findings indicate that repeated electroacupuncture at bilateral Zusanli and Yanglingquan has a cumulative analgesic effect and can effectively relieve chronic neuropathic pain by remodeling the synaptic structure of the hypothalamic paraventricular nucleus. PMID:25206591

Sequential variation in brain functional magnetic resonance imaging after peripheral nerve injury: A rat study.

PubMed

Onishi, Okihiro; Ikoma, Kazuya; Oda, Ryo; Yamazaki, Tetsuro; Fujiwara, Hiroyoshi; Yamada, Shunji; Tanaka, Masaki; Kubo, Toshikazu

2018-04-23

Although treatment protocols are available, patients experience both acute neuropathic pain and chronic neuropathic pain, hyperalgesia, and allodynia after peripheral nerve injury. The purpose of this study was to identify the brain regions activated after peripheral nerve injury using functional magnetic resonance imaging (fMRI) sequentially and assess the relevance of the imaging results using histological findings. To model peripheral nerve injury in male Sprague-Dawley rats, the right sciatic nerve was crushed using an aneurysm clip, under general anesthesia. We used a 7.04T MRI system. T 2 * weighted image, coronal slice, repetition time, 7 ms; echo time, 3.3 ms; field of view, 30 mm × 30 mm; pixel matrix, 64 × 64 by zero-filling; slice thickness, 2 mm; numbers of slices, 9; numbers of average, 2; and flip angle, 8°. fMR images were acquired during electrical stimulation to the rat's foot sole; after 90 min, c-Fos immunohistochemical staining of the brain was performed in rats with induced peripheral nerve injury for 3, 6, and 9 weeks. Data were pre-processed by realignment in the Statistical Parametric Mapping 8 software. A General Linear Model first level analysis was used to obtain T-values. One week after the injury, significant changes were detected in the cingulate cortex, insular cortex, amygdala, and basal ganglia; at 6 weeks, the brain regions with significant changes in signal density were contracted; at 9 weeks, the amygdala and hippocampus showed activation. Histological findings of the rat brain supported the fMRI findings. We detected sequential activation in the rat brain using fMRI after sciatic nerve injury. Many brain regions were activated during the acute stage of peripheral nerve injury. Conversely, during the chronic stage, activation of the amygdala and hippocampus may be related to chronic-stage hyperalgesia, allodynia, and chronic neuropathic pain. Copyright © 2018 Elsevier B.V. All rights reserved.

Intrathecal Infusion of Hydrogen-Rich Normal Saline Attenuates Neuropathic Pain via Inhibition of Activation of Spinal Astrocytes and Microglia in Rats

PubMed Central

Sun, Xuejun; Xiang, Zhenghua; Yang, Liqun; Huang, Shengdong; Lu, Zhijie; Sun, Yuming; Yu, Wei-Feng

2014-01-01

Background Reactive oxygen and nitrogen species are key molecules that mediate neuropathic pain. Although hydrogen is an established antioxidant, its effect on chronic pain has not been characterized. This study was to investigate the efficacy and mechanisms of hydrogen-rich normal saline induced analgesia. Methodology/Principal findings In a rat model of neuropathic pain induced by L5 spinal nerve ligation (L5 SNL), intrathecal injection of hydrogen-rich normal saline relieved L5 SNL-induced mechanical allodynia and thermal hyperalgesia. Importantly, repeated administration of hydrogen-rich normal saline did not lead to tolerance. Preemptive treatment with hydrogen-rich normal saline prevented development of neuropathic pain behavior. Immunofluorochrome analysis revealed that hydrogen-rich normal saline treatment significantly attenuated L5 SNL-induced increase of 8-hydroxyguanosine immunoreactive cells in the ipsilateral spinal dorsal horn. Western blot analysis of SDS/PAGE-fractionated tyrosine-nitrated proteins showed that L5 SNL led to increased expression of tyrosine-nitrated Mn-containing superoxide dismutase (MnSOD) in the spinal cord, and hydrogen-rich normal saline administration reversed the tyrosine-nitrated MnSOD overexpression. We also showed that the analgesic effect of hydrogen-rich normal saline was associated with decreased activation of astrocytes and microglia, attenuated expression of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in the spinal cord. Conclusion/Significance Intrathecal injection of hydrogen-rich normal saline produced analgesic effect in neuropathic rat. Hydrogen-rich normal saline-induced analgesia in neuropathic rats is mediated by reducing the activation of spinal astrocytes and microglia, which is induced by overproduction of hydroxyl and peroxynitrite. PMID:24857932

The effect of the palmitoylethanolamide analogue, palmitoylallylamide (L-29) on pain behaviour in rodent models of neuropathy.

PubMed

Wallace, V C J; Segerdahl, A R; Lambert, D M; Vandevoorde, S; Blackbeard, J; Pheby, T; Hasnie, F; Rice, A S C

2007-08-01

Cannabinoids are associated with analgesia in acute and chronic pain states. A spectrum of central cannabinoid (CB(1)) receptor-mediated motor and psychotropic side effects limit their therapeutic potential. Here, we investigate the analgesic effect of the palmitoylethanolamide (PEA) analogue, palmitoylallylamide (L-29), which via inhibition of fatty acid amide hydrolase (FAAH) may potentiate endocannabinoids thereby avoiding psychotropic side effects. The in vivo analysis of the effect of L-29 on measures of pain behaviour in three rat models of neuropathic pain. Systemically administered L-29 (10 mg kg(-1)) reduced hypersensitivity to mechanical and thermal stimuli in the partial sciatic nerve injury (PSNI) model of neuropathic pain; and mechanical hypersensitivity in a model of antiretroviral (ddC)-associated hypersensitivity and a model of varicella zoster virus (VZV)-associated hypersensitivity. The effects of L-29 were comparable to those of gabapentin (50 mg kg(-1)). The CB(1) receptor antagonist SR141716a (1 mg kg(-1)) and the CB(2) receptor antagonist SR144528 (1 mg kg(-1)) reduced the effect of L-29 on hypersensitivity in the PSNI and ddC models, but not in the VZV model. The peroxisome proliferator-activated receptor-alpha antagonist, MK-886 (1 mg kg(-1)), partially attenuated the effect of L-29 on hypersensitivity in the PSNI model. L-29 (10 mg kg(-1)) significantly attenuated thigmotactic behaviour in the open field arena without effect on locomotor activity. L-29 produces analgesia in a range of neuropathic pain models. This presents L-29 as a novel analgesic compound that may target the endogenous cannabinoid system while avoiding undesirable side effects associated with direct cannabinoid receptor activation.

Neuronal expression of the ubiquitin ligase Nedd4-2 in rat dorsal root ganglia: modulation in the spared nerve injury model of neuropathic pain.

PubMed

Cachemaille, M; Laedermann, C J; Pertin, M; Abriel, H; Gosselin, R-D; Decosterd, I

2012-12-27

Neuronal hyperexcitability following peripheral nerve lesions may stem from altered activity of voltage-gated sodium channels (VGSCs), which gives rise to allodynia or hyperalgesia. In vitro, the ubiquitin ligase Nedd4-2 is a negative regulator of VGSC α-subunits (Na(v)), in particular Na(v)1.7, a key actor in nociceptor excitability. We therefore studied Nedd4-2 in rat nociceptors, its co-expression with Na(v)1.7 and Na(v)1.8, and its regulation in pathology. Adult rats were submitted to the spared nerve injury (SNI) model of neuropathic pain or injected with complete Freund's adjuvant (CFA), a model of inflammatory pain. L4 dorsal root ganglia (DRG) were analyzed in sham-operated animals, seven days after SNI and 48 h after CFA with immunofluorescence and Western blot. We observed Nedd4-2 expression in almost 50% of DRG neurons, mostly small and medium-sized. A preponderant localization is found in the non-peptidergic sub-population. Additionally, 55.7 ± 2.7% and 55.0 ± 3.6% of Nedd4-2-positive cells are co-labeled with Na(v)1.7 and Na(v)1.8 respectively. SNI significantly decreases the proportion of Nedd4-2-positive neurons from 45.9 ± 1.9% to 33.5 ± 0.7% (p<0.01) and the total Nedd4-2 protein to 44% ± 0.13% of its basal level (p<0.01, n=4 animals in each group, mean ± SEM). In contrast, no change in Nedd4-2 was found after peripheral inflammation induced by CFA. These results indicate that Nedd4-2 is present in nociceptive neurons, is downregulated after peripheral nerve injury, and might therefore contribute to the dysregulation of Na(v)s involved in the hyperexcitability associated with peripheral nerve injuries. Copyright © 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

Origins, actions and dynamic expression patterns of the neuropeptide VGF in rat peripheral and central sensory neurones following peripheral nerve injury

PubMed Central

Moss, Andrew; Ingram, Rachel; Koch, Stephanie; Theodorou, Andria; Low, Lucie; Baccei, Mark; Hathway, Gareth J; Costigan, Michael; Salton, Stephen R; Fitzgerald, Maria

2008-01-01

Background The role of the neurotrophin regulated polypeptide, VGF, has been investigated in a rat spared injury model of neuropathic pain. This peptide has been shown to be associated with synaptic strengthening and learning in the hippocampus and while it is known that VGFmRNA is upregulated in dorsal root ganglia following peripheral nerve injury, the role of this VGF peptide in neuropathic pain has yet to be investigated. Results Prolonged upregulation of VGF mRNA and protein was observed in injured dorsal root ganglion neurons, central terminals and their target dorsal horn neurons. Intrathecal application of TLQP-62, the C-terminal active portion of VGF (5–50 nmol) to naïve rats caused a long-lasting mechanical and cold behavioral allodynia. Direct actions of 50 nM TLQP-62 upon dorsal horn neuron excitability was demonstrated in whole cell patch recordings in spinal cord slices and in receptive field analysis in intact, anesthetized rats where significant actions of VGF were upon spontaneous activity and cold evoked responses. Conclusion VGF expression is therefore highly modulated in nociceptive pathways following peripheral nerve injury and can cause dorsal horn cell excitation and behavioral hypersensitivity in naïve animals. Together the results point to a novel and powerful role for VGF in neuropathic pain. PMID:19077191

Analgesic Effects of Tramadol, Tramadol–Gabapentin, and Buprenorphine in an Incisional Model of Pain in Rats (Rattus norvegicus)

PubMed Central

McKeon, Gabriel P; Pacharinsak, Cholawat; Long, Charles T; Howard, Antwain M; Jampachaisri, Katechan; Yeomans, David C; Felt, Stephen A

2011-01-01

Postoperative pain management in laboratory animals relies heavily on a limited number of drug classes, such as opioids and nonsteroidal antiinflammatory drugs. Here we evaluated the effects of saline, tramadol, tramadol with gabapentin, and buprenorphine (n = 6 per group) in a rat model of incisional pain by examining thermal hyperalgesia and weight-bearing daily for 6 d after surgery. All drugs were administered preemptively and continued for 2 consecutive days after surgery. Rats treated with saline or with tramadol only showed thermal hyperalgesia on days 1 through 4 and 1 through 3 after surgery, respectively. In contrast, buprenorphine-treated rats showed no thermal hyperalgesia on days 1 and 2 after surgery, and rats given tramadol with gabapentin showed reduced thermal hyperalgesia on days 2 and 4. For tests of weight-bearing, rats treated with saline or with tramadol only showed significantly less ipsilateral weight-bearing on day 1 after surgery, whereas rats given either buprenorphine or tramadol with gabapentin showed no significant change in ipsilateral weight-bearing after surgery. These data suggest that tramadol alone provides insufficient analgesia in this model of incisional pain; buprenorphine and, to a lesser extent, tramadol with gabapentin provide relief of thermal hyperalgesia and normalize weight-bearing. PMID:21439212

Effects of Sex and Stress on Trigeminal Neuropathic Pain-Like Behavior in Rats.

PubMed

Korczeniewska, Olga Anna; Khan, Junad; Tao, Yuanxiang; Eliav, Eli; Benoliel, Rafael

2017-01-01

To investigate the effects and interactions of sex and stress (provoked by chronic restraint [RS]) on pain-like behavior in a rat model of trigeminal neuropathic pain. The effects of sex and RS (carried out for 14 days as a model for stress) on somatosensory measures (reaction to pinprick, von Frey threshold) in a rat model of trigeminal neuropathic pain were examined. The study design was 2 × 4, with surgery (pain) and sham surgery (no pain) interacting with male restrained (RS) and unrestrained (nRS) rats and female RS and nRS rats. A total of 64 Sprague Dawley rats (32 males and 32 females) were used. Half of the animals in each sex group underwent RS, and the remaining half were left unstressed. Following the RS period, trigeminal neuropathic pain was induced by unilateral infraorbital nerve chronic constriction injury (IOCCI). Half of the animals in the RS group and half in the nRS group (both males and females) were exposed to IOCCI, and the remaining halves to sham surgery. Elevated plus maze (EPM) assessment and plasma interferon gamma (IFN-γ) levels were used to measure the effects of RS. Analysis of variance (ANOVA) was used to assess the effects of stress, sex, and their interactions on plasma IFN-γ levels, changes in body weight, EPM parameters, tactile allodynia, and mechanohyperalgesia. Pairwise comparisons were performed by using Tukey post hoc test corrected for multiple comparisons. Both male and female RS rats showed significantly altered exploratory behavior (as measured by EPM) and had significantly lower plasma IFN-γ levels than nRS rats. Rats exposed to RS gained weight significantly slower than the nRS rats, irrespective of sex. Following RS but before surgery, RS rats showed significant bilateral reductions in von Frey thresholds and significantly increased pinprick response difference scores compared to nRS rats, irrespective of sex. From 17 days postsurgery, RSIOCCI rats showed significantly reduced von Frey thresholds and significantly increased pinprick response difference scores compared to nRS-IOCCI rats, and the von Frey thresholds were significantly lower in females than in males. RS-sham females-but not RS-sham males-developed persistently reduced thresholds and increased pinprick response difference scores. RS produced an increased bilateral sensitivity to stimuli applied to the vibrissal pad following infraorbital nerve injury, irrespective of sex. This observed sensitivity subsequently persisted in RS-sham female rats but not in RS-sham male rats. Stress induced a significant but moderate increase in pain-like behavior in female rats compared to male rats. RS had no significant sex effects on IFN-γ levels, EPM parameters, or body weight gain. This suggests that stress may have a selective effect on pain-like behavior in both sexes, but the possible mechanisms are unclear.

Persistent Neural Membrane Protein Misregulation Following Neurotoxicant Exposure

DTIC Science & Technology

2015-12-01

pesticides may not have posed a significant detriment to the health of the troops, synergisms arising from multiple chemical exposures could have...develop from load bearing microinjuries. The Research Advisory Committee on Gulf War Illness (GWI) has determined that pesticides may have...whether a subset of the many pesticides and related GW chemicals that were used during the conflict could produce chronic pain behaviors in a rat model

Upregulated TLR3 Promotes Neuropathic Pain by Regulating Autophagy in Rat With L5 Spinal Nerve Ligation Model.

PubMed

Chen, Weijia; Lu, Zhijun

2017-02-01

Microglia, rapidly activated following peripheral nerve injury (PNI), accumulate within the spinal cord and adopt inflammation that contributes to development and maintenance of neuropathic pain. Microglia express functional Toll-like receptors (TLRs), which play pivotal roles in regulating inflammatory processes. However, little is known about the role of TLR3 in regulating neuropathic pain after PNI. Here TLR3 expression and autophagy activation was assayed in dorsal root ganglions and in microglia following PNI by using realtime PCR, western blot and immunohistochemistry. The role of TLR3/autophagy signaling in regulating tactile allodynia was evaluated by assaying paw mechanical withdrawal threshold and cold allodynia after intrathecal administration of Poly (I:C) and 3-methyladenine (3-MA). We found that L5 spinal nerve ligation (SNL) induces the expression of TLR3 in dorsal root ganglions and in primary rat microglia at the mRNA and protein level. Meanwhile, L5 SNL results in an increased activation of autophagy, which contributes to microglial activation and subsequent inflammatory response. Intrathecal administration of Poly (I:C), a TLR3 agonist, significantly increases the activation of microglial autophagy, whereas TLR3 knockdown markedly inhibits L5 SNL-induced microglial autophagy. Poly (I:C) treatment promotes the expression of proinflammatory mediators, whereas 3-MA (a specific inhibitor of autophagy) suppresses Poly (I:C)-induced secretion of proinflammatory cytokines. Autophagy inhibition further inhibits TLR3-mediated mechanical and cold hypersensitivity following SNL. These results suggest that inhibition of TLR3/autophagy signaling contributes to alleviate neurophathic pain triggered by SNL.

Decreased miR-199 augments visceral pain in patients with IBS through translational upregulation of TRPV1.

PubMed

Zhou, QiQi; Yang, Liuqing; Larson, Scott; Basra, Sapreet; Merwat, Shehzad; Tan, Alai; Croce, Carlo; Verne, G Nicholas

2016-05-01

Many patients with irritable bowel syndrome IBS not only have abdominal pain but also may suffer from visceral hypersensitivity and heighted visceral nociception. Moreover, IBS has few effective therapeutic agents and mechanisms of disease are unclear. Our goals were to (i) identify microRNA (miRNA) expression, signalling and targets in human colon (controls; patients with IBS); (ii) verify in vitro, IBS-associated changes in miRNAs, especially miR-199, which is complementary to the transient receptor potential vanilloid type 1 (TRPV1) gene; and (iii) determine whether modulating the expression of miRNAs in vivo, especially miR-199, reverses associated changes and pathological hallmarks of visceral hypersensitivity via TRPV1 signalling. We evaluated 45 patients with diarrhoea-predominant IBS (IBS-D) and 40 controls with (1) visceral pain severity score and (2) colonoscopy with biopsies. miRNA expression was evaluated in human colon following miRNA array analysis. Luciferase assays were done to confirm relationships between miR-199 and TRPV1 expression. A rat model of visceral hypersensitivity was used to study miR-199 and its target gene (TRPV1) expression in dorsal root ganglion (DRG) and colon in vivo. Gut miR-199a/b expression in IBS-D was significantly decreased, which correlated directly with both increased visceral pain scores and TRPV1 expression. In vivo upregulation of miR-199a by intraperitoneal injection of lenti-miR-199a precursors decreased visceral hypersensitivity via diminished TRPV1 signalling. Decreased colonic miR-199a/b correlates with visceral pain in patients with IBS-D. Similarly, reduced miR-199a expression in rat DRG and colon tissue is associated with heightened visceral hypersensitivity. In vivo upregulation of miR-199a decreases visceral pain via inhibition of TRPV1 signalling. Thus, miR-199 precursors may be promising therapeutic candidates for the treatment in patients with visceral pain. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Effect of electroacupuncture on thermal pain threshold and expression of calcitonin-gene related peptide, substance P and γ-aminobutyric acid in the cervical dorsal root ganglion of rats with incisional neck pain

PubMed Central

Qiao, Li-na; Liu, Jun-ling; Tan, Lian-hong; Yang, Hai-long; Zhai, Xu; Yang, Yong-sheng

2017-01-01

Objective Acupuncture therapy effectively reduces post-surgical pain, but its mechanism of action remains unclear. The aim of this study was to investigate whether expression of γ-aminobutyric acid (GABA) and the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) in the primary sensory neurons of cervical dorsal root ganglia (DRG) are involved in electroacupuncture (EA)-induced analgesia in a rat model of incisional neck pain. Methods The pain model was established by making a longitudinal midline neck incision in 60 rats. Another 15 rats underwent sham surgery (normal group). Post-incision, 15 rats remained untreated (model group) and 45 rats underwent EA (frequency 2/100 Hz, intensity 1 mA) at bilateral LI18, LI4-PC6 or ST36-GB34 (n=15 each) for 30 min at 4 hours, 24 hours, and 48 hours post-surgery, followed by thermal pain threshold (PT) measurement. 30 min later, the rats were euthanased and cervical (C3-6) DRGs removed for measurement of immunoreactivity and mRNA expression of SP/CGRP and the GABAergic neuronal marker glutamic acid decarboxylase 67 (GAD67). Results Thermal PT was significantly lower in the model group versus the normal group and increased in the LI18 and LI4-PC6 groups but not the ST36-GB34 group compared with the model group. Additionally, EA at LI18 and LI4-PC6 markedly suppressed neck incision-induced upregulation of mRNA/protein expression of SP/CGRP, and upregulated mRNA/protein expression of GAD67 in the DRGs of C3-6 segments. Conclusions EA at LI18/LI4-PC6 increases PT in rats with incisional neck pain, which is likely related to downregulation of pronociceptive mediators SP/CGRP and upregulation of the inhibitory transmitter GABA in the primary sensory neurons of cervical DRGs. PMID:28600329

Effect of electroacupuncture on thermal pain threshold and expression of calcitonin-gene related peptide, substance P and γ-aminobutyric acid in the cervical dorsal root ganglion of rats with incisional neck pain.

PubMed

Qiao, Li-Na; Liu, Jun-Ling; Tan, Lian-Hong; Yang, Hai-Long; Zhai, Xu; Yang, Yong-Sheng

2017-08-01

Acupuncture therapy effectively reduces post-surgical pain, but its mechanism of action remains unclear. The aim of this study was to investigate whether expression of γ-aminobutyric acid (GABA) and the neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) in the primary sensory neurons of cervical dorsal root ganglia (DRG) are involved in electroacupuncture (EA)-induced analgesia in a rat model of incisional neck pain. The pain model was established by making a longitudinal midline neck incision in 60 rats. Another 15 rats underwent sham surgery (normal group). Post-incision, 15 rats remained untreated (model group) and 45 rats underwent EA (frequency 2/100 Hz, intensity 1 mA) at bilateral LI18, LI4-PC6 or ST36-GB34 (n=15 each) for 30 min at 4 hours, 24 hours, and 48 hours post-surgery, followed by thermal pain threshold (PT) measurement. 30 min later, the rats were euthanased and cervical (C3-6) DRGs removed for measurement of immunoreactivity and mRNA expression of SP/CGRP and the GABAergic neuronal marker glutamic acid decarboxylase 67 (GAD67). Thermal PT was significantly lower in the model group versus the normal group and increased in the LI18 and LI4-PC6 groups but not the ST36-GB34 group compared with the model group. Additionally, EA at LI18 and LI4-PC6 markedly suppressed neck incision-induced upregulation of mRNA/protein expression of SP/CGRP, and upregulated mRNA/protein expression of GAD67 in the DRGs of C3-6 segments. EA at LI18/LI4-PC6 increases PT in rats with incisional neck pain, which is likely related to downregulation of pronociceptive mediators SP/CGRP and upregulation of the inhibitory transmitter GABA in the primary sensory neurons of cervical DRGs. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Neuroprotective Potential of Gentongping in Rat Model of Cervical Spondylotic Radiculopathy Targeting PPAR-γ Pathway.

PubMed

Sun, Wen; Zheng, Kang; Liu, Bin; Fan, Danping; Luo, Hui; Qu, Xiaoyuan; Li, Li; He, Xiaojuan; Yi, Jianfeng; Lu, Cheng

2017-01-01

Cervical spondylotic radiculopathy (CSR) is the most general form of spinal degenerative disease and is characterized by pain and numbness of the neck and arm. Gentongping (GTP) granule, as a classical Chinese patent medicine, has been widely used in curing CSR, whereas the underlying mechanism remains unclear. Therefore, the aim of this study is to explore the pharmacological mechanisms of GTP on CSR. The rat model of CSR was induced by spinal cord injury (SCI). Our results showed that GTP could significantly alleviate spontaneous pain as well as ameliorate gait. The HE staining and Western blot results showed that GTP could increase the quantity of motoneuron and enhance the activation of peroxisome proliferator-activated receptor gamma (PPAR- γ ) in the spinal cord tissues. Meanwhile, immunofluorescence staining analysis indicated that GTP could reduce the expression of TNF- α in the spinal cord tissues. Furthermore, the protein level of Bax was decreased whereas the protein levels of Bcl-2 and NF200 were increased after the GTP treatment. These findings demonstrated that GTP might modulate the PPAR- γ pathway by inhibiting the inflammatory response and apoptosis as well as by protecting the cytoskeletal integrity of the spinal cord, ultimately play a neuroprotective role in CSR.

A SNAP-25 cleaving chimera of botulinum neurotoxin /A and /E prevents TNFα-induced elevation of the activities of native TRP channels on early postnatal rat dorsal root ganglion neurons.

PubMed

Nugent, Marc; Yusef, Yamil R; Meng, Jianghui; Wang, Jiafu; Dolly, J Oliver

2018-06-12

Transient receptor potential (TRP) vallinoid 1 (TRPV1) and ankyrin 1 (TRPA1) are two transducing channels expressed on peripheral sensory nerves involved in pain sensation. Upregulation of their expression, stimulated by inflammatory cytokines and growth factors in animal pain models, correlate with the induction of nociceptive hyper-sensitivity. Herein, we firstly demonstrate by immuno-cytochemical labelling that TNFα augments the surface content of these channels on rat cultured dorsal root ganglion (DRG) neurons which, in turn, enhances the electrophysiological and functional responses of the latter to their specific agonists. A molecular basis underlying this TNFα-dependent enhancement was unveiled by pre-treating DRGs with a recently-published chimeric protein, consisting of the protease light chain (LC) of botulinum neurotoxin (BoNT) serotype E fused to full-length BoNT/A (LC/E-BoNT/A). This cleaves synaptosomal-associated protein of Mr 25k (SNAP-25) and reported previously to exhibit anti-nociceptive activity in a rat model of neuropathic pain. Low pM concentrations of this chimera were found to prevent the TNFα-stimulated delivery of TRPV1/A1 to the neuronal plasmalemma and, accordingly, decreased their incremental functional activities relative to those of control cells, an effect accompanied by SNAP-25 cleavage. Advantageously, LC/E-BoNT/A did not reduce the basal surface contents of the two channels or their pharmacological responses. Thus, use of multiple complementary methodologies provides evidence that LC/E-BoNT/A abolishes the TNFα-dependent augmented, but not resting, surface trafficking of TRPV1/A1. As TNFα is known to induce nociceptive hyper-sensitivity in vivo, our observed inhibition by LC/E-BoNT/A of its action in vitro could contribute to its potential alleviation of pain. Copyright © 2018 Elsevier Ltd. All rights reserved.

Mechanism of Chronic Pain in Rodent Brain Imaging

NASA Astrophysics Data System (ADS)

Chang, Pei-Ching

Chronic pain is a significant health problem that greatly impacts the quality of life of individuals and imparts high costs to society. Despite intense research effort in understanding of the mechanism of pain, chronic pain remains a clinical problem that has few effective therapies. The advent of human brain imaging research in recent years has changed the way that chronic pain is viewed. To further extend the use of human brain imaging techniques for better therapies, the adoption of imaging technique onto the animal pain models is essential, in which underlying brain mechanisms can be systematically studied using various combination of imaging and invasive techniques. The general goal of this thesis is to addresses how brain develops and maintains chronic pain in an animal model using fMRI. We demonstrate that nucleus accumbens, the central component of mesolimbic circuitry, is essential in development of chronic pain. To advance our imaging technique, we develop an innovative methodology to carry out fMRI in awake, conscious rat. Using this cutting-edge technique, we show that allodynia is assoicated with shift brain response toward neural circuits associated nucleus accumbens and prefrontal cortex that regulate affective and cognitive component of pain. Taken together, this thesis provides a deeper understanding of how brain mediates pain. It builds on the existing body of knowledge through maximizing the depth of insight into brain imaging of chronic pain.

Hippocampal GABAA Receptor and Pain Sensitivity during Estrous Cycle in the Rat

PubMed Central

Taherianfard, Mahnaz; Mosavi, Mahnaz

2011-01-01

Background: Estradiol and progesterone as well as hippocampal GABAA receptors are believed to play a role in the modulation of pain. The aim of present study was to investigate the effect of intrahippocampal injections of GABAA receptor agonist (muscimol) and GABAA receptor antagonist (picrotoxin) on pain sensitivity during estrous cycle. Methods: Pain sensitivity was evaluated in rats by formalin test during all stages of estrous cycle. Animals were divided into five groups including; 1- control (intact animal); 2- sham 1 receiving 0.75 µl artificial cerebrospinal fluids (ACSF); 3- sham 2 receiving 0.75 µl alcoholic ACSF; 4- experimental 1 receiving 250 or 500 µg/rat of muscimol in 0.75 µl vehicle, and 5- experimental 2 receiving 20 or 30 µg/rat picrotoxin in 0.75 µl vehicle. Data were analyzed by Kruskal-Wallis followed by Tucky's test for pairwise comparisons using a P value of ≤0.50 for statistical significance. Results: Muscimol significantly (P<0.05) decreased pain sensitivity in all stages of estrous cycle, and the analgesic effect was higher during proestrus and estrus stages of estrous cycle than that during metestrus and diestrus stages. Picrotoxin significantly (P<0.05) increased pain sensitivity in all stages of estrous cycle, and such a hyperalgesic effect was lower during proestrus and estrus stages of estrous cycle than that during metestrus and diestrus stages. Conclusion: The findings of the present study indicate that the role of hippocampal GABAA receptor in the control of the pain sensitivity can be modulated by variation in gonadal steroids during different stages of the estrous cycle. PMID:23115414

Identification and Functional Characterization of a Stable, Centrally Active Derivative of the Neurotensin (8–13) Fragment as a Potential First-in-Class Analgesic

PubMed Central

Hughes, Francis M.; Shaner, Brooke E.; May, Lisa A.; Zotian, Lyndsay; Brower, Justin O.; Woods, R. Jeremy; Cash, Michael; Morrow, Dustin; Massa, Fabienne; Mazella, Jean; Dix, Thomas A.

2010-01-01

The neurotensin hexapapetide fragment NT(8–13) is a potent analgesic when administered directly to the central nervous system, but does not cross the blood brain barrier. A total of 43 novel derivatives of NT(8–13) were evaluated with one, ABS212 (1), being most active in four rat models of pain when administered peripherally. Compound 1 binds to human neurotensin receptors 1 and 2 with IC50s of 10.6 and 54.2 nM, respectively and tolerance to the compound in a rat pain model did not develop after 12 days of daily administration. When administered peripherally, serum levels and neurotensin receptor binding potency of 1 peaked within 5 min and returned to baseline within 90–120 min, however analgesic activity remained near maximum for >240 min. This could be due to its metabolism into an active fragment; however, all 4- and 5-mer hydrolysis products were inactive. This pharmacokinetic/pharmacodynamic dichotomy is discussed. Compound 1 is a candidate for development as a first-in-class analgesic. PMID:20481538

Exercise following a short immobilization period is detrimental to tendon properties and joint mechanics in a rat rotator cuff injury model.

PubMed

Peltz, Cathryn D; Sarver, Joseph J; Dourte, Leann M; Würgler-Hauri, Carola C; Williams, Gerald R; Soslowsky, Louis J

2010-07-01

Rotator cuff tears are a common clinical problem that can result in pain and disability. Previous studies in a rat model showed enhanced tendon to bone healing with postoperative immobilization. The objective of this study was to determine the effect of postimmobilization activity level on insertion site properties and joint mechanics in a rat model. Our hypothesis was that exercise following a short period of immobilization will cause detrimental changes in insertion site properties compared to cage activity following the same period of immobilization, but that passive shoulder mechanics will not be affected. We detached and repaired the supraspinatus tendon of 22 Sprague-Dawley rats, and the injured shoulder was immobilized postoperatively for 2 weeks. Following immobilization, rats were prescribed cage activity or exercise for 12 weeks. Passive shoulder mechanics were determined, and following euthanasia, tendon cross-sectional area and mechanical properties were measured. Exercise following immobilization resulted in significant decreases compared to cage activity in range of motion, tendon stiffness, modulus, percent relaxation, and several parameters from both a structurally based elastic model and a quasi-linear viscoelastic model. Therefore, we conclude that after a short period of immobilization, increased activity is detrimental to both tendon mechanical properties and shoulder joint mechanics, presumably due to increased scar production. (c) 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc

Prior stress exposure increases pain behaviors in a rat model of full thickness thermal injury.

PubMed

Nyland, Jennifer E; McLean, Samuel A; Averitt, Dayna L

2015-12-01

Thermal burns among individuals working in highly stressful environments, such as firefighters and military Service Members, are common. Evidence suggests that pre-injury stress may exaggerate pain following thermal injury; however current animal models of burn have not evaluated the potential influence of pre-burn stress. This sham-controlled study evaluated the influence of prior stress exposure on post-burn thermal and mechanical sensitivity in male Sprague-Dawley rats. Rats were exposed to 20 min of inescapable swim stress or sham stress once per day for three days. Exposure to inescapable swim stress (1) increased the intensity and duration of thermal hyperalgesia after subsequent burn and (2) accelerated the onset of thermal hyperalgesia and mechanical allodynia after subsequent burn. This stress-induced exacerbation of pain sensitivity was reversed by pretreatment and concurrent treatment with the serotonin-norepinephrine reuptake inhibitor (SNRI) duloxetine. These data suggest a better understanding of mechanisms by which prior stress augments pain after thermal burn may lead to improved pain treatments for burn survivors. Copyright © 2015 Elsevier Ltd and ISBI. All rights reserved.

Synthesis and biological evaluation of compact, conformationally constrained bifunctional opioid agonist – neurokinin-1 antagonist peptidomimetics

PubMed Central

Guillemyn, Karel; Kleczkowska, Patrycia; Lesniak, Anna; Dyniewicz, Jolanta; Van der Poorten, Olivier; Van den Eynde, Isabelle; Keresztes, Attila; Varga, Eva; Lai, Josephine; Porreca, Frank; Chung, Nga N.; Lemieux, Carole; Mika, Joanna; Rojewska, Ewelina; Makuch, Wioletta; Van Duppen, Joost; Przewlocka, Barbara; Broeck, Jozef Vanden; Lipkowski, Andrzej W.; Schiller, Peter W.; Tourwé, Dirk; Ballet, Steven

2014-01-01

A reported mixed opioid agonist - neurokinin 1 receptor (NK1R) antagonist 4 (Dmt-D-Arg-Aba-Gly-(3’,5’-(CF3)2)NMe-benzyl) was modified to identify important features in both pharmacophores. The new dual ligands were tested in vitro and subsequently two compounds (lead structure 4 and one of the new analogues 22, Dmt-D-Arg-Aba-β-Ala-NMe-Bn) were selected for in vivo behavioral assays, which were conducted in acute (tail-flick) and neuropathic pain models (cold plate and von Frey) in rats. Compared to the parent opioid compound 33 (without NK1R pharmacophore), hybrid 22 was more active in the neuropathic pain models. Attenuation of neuropathic pain emerged from NK1R antagonism as demonstrated by the pure NK1R antagonist 6. Surprisingly, despite a lower in vitro activity at NK1R in comparison with 4, compound 22 was more active in the neuropathic pain models. Although potent analgesic effects were observed for 4 and 22, upon chronic administration, both manifested a tolerance profile similar to that of morphine and cross tolerance with morphine in a neuropathic pain model in rat. PMID:25544687

Periodontal CGRP contributes to orofacial pain following experimental tooth movement in rats.

PubMed

Long, Hu; Liao, Lina; Gao, Meiya; Ma, Wenqiang; Zhou, Yang; Jian, Fan; Wang, Yan; Lai, Wenli

2015-08-01

Calcitonin-related gene peptide (CGRP) plays an important role in orofacial inflammatory pain. The aim of this study was to determine whether periodontal CGRP contributes to orofacial pain induced by experimental tooth movement in rats. Male Sprague-Dawley rats were used in this study. Closed coil springs were used to deliver forces. Rats were euthanized on 0d, 1d, 3d, 5d, 7d, and 14d following experimental tooth movement. Then, alveolar bones were obtained for immunostaining of periodontal tissues against CGRP. Two hours prior to euthanasia on each day, orofacial pain levels were assessed through rat grimace scale. CGRP and olcegepant (CGRP receptor antagonist) were injected into periodontal tissues to verify the roles of periodontal CGRP in orofacial pain induced by experimental tooth movement. Periodontal CGRP expression levels and orofacial pain levels were elevated on 1d, 3d, 5d, and 7d following experimental tooth movement. The two indices were significantly correlated with each other and fitted into a dose-response model. Periodontal administration of CGRP could elevate periodontal CGRP expressions and exacerbate orofacial pain. Moreover, olcegepant administration could decrease periodontal CGRP expressions and alleviate orofacial pain. Therefore, periodontal CGRP plays an important role in pain transmission and modulation following experimental tooth movement. We suggest that it may participate in a positive feedback aiming to amplify orofacial pain signals. Copyright © 2015 Elsevier B.V. All rights reserved.

Stable, synthetic analogs of diadenosine tetraphosphate inhibit rat and human P2X3 receptors and inflammatory pain.

PubMed

Viatchenko-Karpinski, Viacheslav; Novosolova, Natalia; Ishchenko, Yevheniia; Azhar, M Ameruddin; Wright, Michael; Tsintsadze, Vera; Kamal, Ahmed; Burnashev, Nail; Miller, Andrew D; Voitenko, Nana; Giniatullin, Rashid; Lozovaya, Natalia

2016-01-01

A growing body of evidence suggests that ATP-gated P2X3 receptors (P2X3Rs) are implicated in chronic pain. We address the possibility that stable, synthetic analogs of diadenosine tetraphosphate (Ap4A) might induce antinociceptive effects by inhibiting P2X3Rs in peripheral sensory neurons. The effects of two stable, synthetic Ap4A analogs (AppNHppA and AppCH2ppA) are studied firstly in vitro on HEK293 cells expressing recombinant rat P2XRs (P2X2Rs, P2X3Rs, P2X4Rs, and P2X7Rs) and then using native rat brain cells (cultured trigeminal, nodose, or dorsal root ganglion neurons). Thereafter, the action of these stable, synthetic Ap4A analogs on inflammatory pain and thermal hyperalgesia is studied through the measurement of antinociceptive effects in formalin and Hargreaves plantar tests in rats in vivo. In vitro inhibition of rat P2X3Rs (not P2X2Rs, P2X4Rs nor P2X7Rs) is shown to take place mediated by high-affinity desensitization (at low concentrations; IC50 values 100-250 nM) giving way to only weak partial agonism at much higher concentrations (EC50 values ≥ 10 µM). Similar inhibitory activity is observed with human recombinant P2X3Rs. The inhibitory effects of AppNHppA on nodose, dorsal root, and trigeminal neuron whole cell currents suggest that stable, synthetic Ap4A analogs inhibit homomeric P2X3Rs in preference to heteromeric P2X2/3Rs. Both Ap4A analogs mediate clear inhibition of pain responses in both in vivo inflammation models. Stable, synthetic Ap4A analogs (AppNHppA and AppCH2ppA) being weak partial agonist provoke potent high-affinity desensitization-mediated inhibition of homomeric P2X3Rs at low concentrations. Therefore, both analogs demonstrate clear potential as potent analgesic agents for use in the management of chronic pain associated with heightened P2X3R activation. © The Author(s) 2016.

IL-1ra alleviates inflammatory hyperalgesia through preventing phosphorylation of NMDA receptor NR-1 subunit in rats.

PubMed

Zhang, Rui-Xin; Li, Aihui; Liu, Bing; Wang, Linbo; Ren, Ke; Zhang, Haiqing; Berman, Brian M; Lao, Lixing

2008-04-01

Although it has been shown that pro-inflammatory cytokines such as interleukin-1beta (IL-1beta) facilitate perception of noxious inputs at the spinal level, the mechanisms have not been understood. This study determined the cell type that produces IL-1beta, the co-localization of IL-1 receptor type I (IL-1RI) and Fos and NR1 in the spinal cord, and the effects of IL-1 receptor antagonist (IL-1ra) on NR1 phosphorylation and hyperalgesia in a rat model of inflammatory pain. Phosphorylation of NR1, an essential subunit of the NMDA receptor (NMDAR), is known to modulate NMDAR activity and facilitate pain. Hyperalgesia was induced by injecting complete Freund's adjuvant (CFA, 0.08ml, 40microg Mycobacterium tuberculosis) into one hind paw of each rat. Paw withdrawal latency (PWL) was tested before CFA (-48h) for baseline and 2 and 24h after CFA to assess hyperalgesia. IL-1ra was given (i.t.) 24h before CFA to block the action of basal IL-1beta and 2h prior to each of two PWL tests to block CFA-induced IL-1beta. Spinal cords were removed for double immunostaining of IL-1beta/neuronal marker and IL-1beta/glial cell markers, IL-1RI/Fos and IL-1RI/NR1, and for Western blot to measure NR1 phosphorylation. The data showed that: (1) astrocytes produce IL-1beta, (2) IL-1RI is localized in Fos- and NR1-immunoreactive neurons within the spinal dorsal horn, and (3) IL-1ra at 0.01mg/rat significantly increased PWL (P<0.05) and inhibited NR1 phosphorylation compared to saline control. The results suggest that spinal IL-1beta is produced by astrocytes and enhances NR1 phosphorylation to facilitate inflammatory pain.

Silencing the Kir4.1 potassium channel subunit in satellite glial cells of the rat trigeminal ganglion results in pain-like behavior in the absence of nerve injury.

PubMed

Vit, Jean-Philippe; Ohara, Peter T; Bhargava, Aditi; Kelley, Kanwar; Jasmin, Luc

2008-04-16

Growing evidence suggests that changes in the ion buffering capacity of glial cells can give rise to neuropathic pain. In the CNS, potassium ion (K+) buffering is dependent on the glia-specific inward rectifying K+ channel Kir4.1. We recently reported that the satellite glial cells that surround primary sensory neurons located in sensory ganglia of the peripheral nervous system also express Kir4.1, whereas the neurons do not. In the present study, we show that, in the rat trigeminal ganglion, the location of the primary sensory neurons for face sensation, specific silencing of Kir4.1 using RNA interference leads to spontaneous and evoked facial pain-like behavior in freely moving rats. We also show that Kir4.1 in the trigeminal ganglion is reduced after chronic constriction injury of the infraorbital nerve. These findings suggests that neuropathic pain can result from a change in expression of a single K+ channel in peripheral glial cells, raising the possibility of targeting Kir4.1 to treat pain in general and particularly neuropathic pain that occurs in the absence of nerve injury.

Stable, synthetic analogs of diadenosine tetraphosphate inhibit rat and human P2X3 receptors and inflammatory pain

PubMed Central

Viatchenko-Karpinski, Viacheslav; Novosolova, Natalia; Ishchenko, Yevheniia; Azhar, M Ameruddin; Wright, Michael; Tsintsadze, Vera; Kamal, Ahmed; Burnashev, Nail; Voitenko, Nana; Giniatullin, Rashid; Lozovaya, Natalia

2016-01-01

Background A growing body of evidence suggests that ATP-gated P2X3 receptors (P2X3Rs) are implicated in chronic pain. We address the possibility that stable, synthetic analogs of diadenosine tetraphosphate (Ap4A) might induce antinociceptive effects by inhibiting P2X3Rs in peripheral sensory neurons. Results The effects of two stable, synthetic Ap4A analogs (AppNHppA and AppCH2ppA) are studied firstly in vitro on HEK293 cells expressing recombinant rat P2XRs (P2X2Rs, P2X3Rs, P2X4Rs, and P2X7Rs) and then using native rat brain cells (cultured trigeminal, nodose, or dorsal root ganglion neurons). Thereafter, the action of these stable, synthetic Ap4A analogs on inflammatory pain and thermal hyperalgesia is studied through the measurement of antinociceptive effects in formalin and Hargreaves plantar tests in rats in vivo. In vitro inhibition of rat P2X3Rs (not P2X2Rs, P2X4Rs nor P2X7Rs) is shown to take place mediated by high-affinity desensitization (at low concentrations; IC50 values 100–250 nM) giving way to only weak partial agonism at much higher concentrations (EC50 values ≥ 10 µM). Similar inhibitory activity is observed with human recombinant P2X3Rs. The inhibitory effects of AppNHppA on nodose, dorsal root, and trigeminal neuron whole cell currents suggest that stable, synthetic Ap4A analogs inhibit homomeric P2X3Rs in preference to heteromeric P2X2/3Rs. Both Ap4A analogs mediate clear inhibition of pain responses in both in vivo inflammation models. Conclusions Stable, synthetic Ap4A analogs (AppNHppA and AppCH2ppA) being weak partial agonist provoke potent high-affinity desensitization-mediated inhibition of homomeric P2X3Rs at low concentrations. Therefore, both analogs demonstrate clear potential as potent analgesic agents for use in the management of chronic pain associated with heightened P2X3R activation. PMID:27030723

Enhanced excitability and down-regulated voltage-gated potassium channels in colonic drg neurons from neonatal maternal separation rats.

PubMed

Luo, Jia-Lie; Qin, Hong-Yan; Wong, Chun-Kit; Tsang, Suk-Ying; Huang, Yu; Bian, Zhao-Xiang

2011-05-01

Irritable bowel syndrome (IBS), characterized mainly by abdominal pain, is a functional bowel disorder. The present study aimed to examine changes in the excitability and the activity of the voltage-gated K(+) channel in dorsal root ganglia (DRG) neurons innervating the colon of rats subjected to neonatal maternal separation (NMS). Colonic DRG neurons from NMS rats as identified by FAST DiI™ labeling showed an increased cell size compared with those from nonhandled (NH) rats. Whole cell current-clamp recordings showed that colonic DRG neurons from NMS rats displayed: 1) depolarized resting membrane potential; 2) increased input resistance; 3) a dramatic reduction in rheobase; and 4) a significant increase in the number of action potentials evoked at twice rheobase. Whole cell voltage-clamp recordings revealed that neurons from both groups exhibited transient A-type (I(A)) and delayed rectifier (I(K)) K(+) currents. Compared with NH rat neurons, the averaged density of I(K) was significantly reduced in NMS rat neurons. Furthermore, the Kv1.2 expression was significantly decreased in NMS rat colonic DRG neurons. These results suggest that NMS increases the excitability of colonic DRG neurons mainly by suppressing the I(K) current, which is likely accounted for by the downregulation of the Kv1.2 expression and somal hypertrophy. This study demonstrates the alteration of delayed rectifier K current and Kv1.2 expression in DRG neurons from IBS model rats, representing a molecular mechanism underlying visceral pain and sensitization in IBS, suggesting the potential of Kv1.2 as a therapeutic target for the treatment of IBS. Copyright © 2011 American Pain Society. Published by Elsevier Inc. All rights reserved.

Aquaporins in Spinal Cord Injury: The Janus Face of AQP4

PubMed Central

Nesic, Olivera; Guest, James D.; Zivadinovic, Dragoslava; Narayana, Ponnada A.; Herrera, Juan J.; Grill, Raymond J.; Mokkapati, Venkata U.L.; Gelman, Benjamin B.; Lee, Julieann

2010-01-01

Although malfunction of spinal cord water channels (aquaporins, AQP) likely contributes to severe disturbances in ion/water homeostasis after spinal cord injury (SCI), their roles are still poorly understood. Here we report and discuss the potential significance of changes in the AQP4 expression in human SCI that generates GFAP-labeled astrocytes devoid of AQP4, and GFAP-labeled astroglia that overexpress AQP4. We used a rat model of contusion SCI to study observed changes in human SCI. AQP4-negative astrocytes are likely generated during the process of SCI-induced replacement of lost astrocytes, but their origin and role in SCI remains to be investigated. We found that AQP4-overexpression is likely triggered by hypoxia. Our transcriptional profiling of injured rat cords suggests that elevated AQP4-mediated water influx accompanies increased uptake of chloride and potassium ions which represents a protective astrocytic reaction to hypoxia. However, unbalanced water intake also results in astrocytic swelling that can contribute to motor impairment, but likely only in milder injuries. In severe rat SCI, a low abundance of AQP4-overexpressing astrocytes was found during the motor recovery phase. Our results suggest that severe rat contusion SCI is a better model to analyze AQP4 functions after SCI. We found that AQP4 increases in the chronic post-injury phase are associated with the development of pain-like behavior in SCI rats, while possible mechanisms underlying pain development may involve astrocytic swelling-induced glutamate release. In contrast, the formation and size of fluid-filled cavities occurring later after SCI does not appear to be affected by the extent of increased AQP4 levels. Therefore, the effect of therapeutic interventions targeting AQP4 will depend not only on the time interval after SCI or animal models, but also on the balance between protective role of increased AQP4 in hypoxia and deleterious effects of ongoing astrocytic swelling. PMID:20109536

Rescue of Impaired mGluR5-Driven Endocannabinoid Signaling Restores Prefrontal Cortical Output to Inhibit Pain in Arthritic Rats.

PubMed

Kiritoshi, Takaki; Ji, Guangchen; Neugebauer, Volker

2016-01-20

The medial prefrontal cortex (mPFC) serves executive functions that are impaired in neuropsychiatric disorders and pain. Underlying mechanisms remain to be determined. Here we advance the novel concept that metabotropic glutamate receptor 5 (mGluR5) fails to engage endocannabinoid (2-AG) signaling to overcome abnormal synaptic inhibition in pain, but restoring endocannabinoid signaling allows mGluR5 to increase mPFC output hence inhibit pain behaviors and mitigate cognitive deficits. Whole-cell patch-clamp recordings were made from layer V pyramidal cells in the infralimbic mPFC in rat brain slices. Electrical and optogenetic stimulations were used to analyze amygdala-driven mPFC activity. A selective mGluR5 activator (VU0360172) increased pyramidal output through an endocannabinoid-dependent mechanism because intracellular inhibition of the major 2-AG synthesizing enzyme diacylglycerol lipase or blockade of CB1 receptors abolished the facilitatory effect of VU0360172. In an arthritis pain model mGluR5 activation failed to overcome abnormal synaptic inhibition and increase pyramidal output. mGluR5 function was rescued by restoring 2-AG-CB1 signaling with a CB1 agonist (ACEA) or inhibitors of postsynaptic 2-AG hydrolyzing enzyme ABHD6 (intracellular WWL70) and monoacylglycerol lipase MGL (JZL184) or by blocking GABAergic inhibition with intracellular picrotoxin. CB1-mediated depolarization-induced suppression of synaptic inhibition (DSI) was also impaired in the pain model but could be restored by coapplication of VU0360172 and ACEA. Stereotaxic coadministration of VU0360172 and ACEA into the infralimbic, but not anterior cingulate, cortex mitigated decision-making deficits and pain behaviors of arthritic animals. The results suggest that rescue of impaired endocannabinoid-dependent mGluR5 function in the mPFC can restore mPFC output and cognitive functions and inhibit pain. Significance statement: Dysfunctions in prefrontal cortical interactions with subcortical brain regions, such as the amygdala, are emerging as important players in neuropsychiatric disorders and pain. This study identifies a novel mechanism and rescue strategy for impaired medial prefrontal cortical function in an animal model of arthritis pain. Specifically, an integrative approach of optogenetics, pharmacology, electrophysiology, and behavior is used to advance the novel concept that a breakdown of metabotropic glutamate receptor subtype mGluR5 and endocannabinoid signaling in infralimbic pyramidal cells fails to control abnormal amygdala-driven synaptic inhibition in the arthritis pain model. Restoring endocannabinoid signaling allows mGluR5 activation to increase infralimbic output hence inhibit pain behaviors and mitigate pain-related cognitive deficits. Copyright © 2016 the authors 0270-6474/16/360837-14$15.00/0.

Effect of spinal monoaminergic neuronal system dysfunction on pain threshold in rats, and the analgesic effect of serotonin and norepinephrine reuptake inhibitors.

PubMed

Tamano, Ryuta; Ishida, Mitsuhiro; Asaki, Toshiyuki; Hasegawa, Minoru; Shinohara, Shunji

2016-02-26

Dysfunction in the central serotonin (5-HT) and norepinephrine (NE) systems cause depression and pain. Descending spinal pain modulatory pathways are important in the analgesic mechanisms of antidepressants, particularly serotonin and norepinephrine reuptake inhibitors (SNRIs). While many non-clinical studies have demonstrated the roles of central monoaminergic systems in pain, there is little evidence to illuminate the direct contribution of spinal descending pain modulatory systems independently of depressive-like behavior. To examine the effects of dysfunction of spinal monoaminergic systems on pain sensitivity, we established a rat chronic pain model by administering lumbar-intrathecal reserpine to minimize its influence on brain. Lumbar-intrathecal reserpine evoked persistent mechanical hypersensitivity and corresponding reductions in spinal 5-HT and NE concentrations (from 767.2 to 241.6ng/g and from 455.9 to 41.7ng/g, respectively after reserpine 30nmol). Lumbar-intrathecal reserpine did not deplete brain monoamines or bring about depressive-like behavior in the forced swim test. Spinal monoamines depletion-induced pain sensitivity was ameliorated by lumbar-intrathecal administration of the SNRIs (duloxetine and milnacipran) in dose-dependent manners. These suggest that increased pain sensitivity could be induced by dysfunction solely of the descending pain modulatory system, regardless of depressive-like behavior, and lumbar-intrathecal administration of SNRIs could ameliorate the pain sensitivity which might be mediated by affecting the descending pain modulatory system in the spinal cord, not via their antidepressant effects. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Transient Receptor Potential Channel and Interleukin-17A Involvement in LTTL Gel Inhibition of Bone Cancer Pain in a Rat Model.

PubMed

Wang, Juyong; Zhang, Ruixin; Dong, Changsheng; Jiao, Lijing; Xu, Ling; Liu, Jiyong; Wang, Zhengtao; Lao, Lixing

2015-07-01

Cancer pain management is a challenge for which Chinese herbal medicine might be useful. To study the spinal mechanisms of the Chinese medicated gel Long-Teng-Tong-Luo (LTTL), a 7-herb compound, on bone cancer pain, a bone cancer pain model was made by inoculating the tibias of female rats with Walker 256 cells. LTTL gel or inert gel, 0.5 g/cm(2)/d, was applied to the skin of tumor-bearing tibias for 21 days beginning a day after the inoculation. Mechanical threshold and paw withdrawal latency to thermal stimulation was measured. Transient receptor potential (TRP) cation channels in lumbar dorsal root ganglia (DRG) were immunostained and counted, and lumbar spinal cord interleukin-17A (IL-17A) was measured with real-time polymerase chain reaction and enzyme-linked immunosorbent assay. TRP antagonists and interleukin (IL)-17A antibodies were intrathecally administered to determine their effects on bone cancer pain. The gel significantly (P < .05) alleviated cancer-induced mechanical allodynia and thermal hyperalgesia and inhibited cancer-enhanced expression of IL-17A in spinal astrocytes and the TRP subfamily members V1, A1, and V4 in lumbar DRG. Intrathecal TRP antagonists at 10 µg significantly (P < .05) attenuated mechanical allodynia, thermal hyperalgesia, and IL-17A expression, indicating that TRP channels facilitate spinal IL-17 expression and cancer pain. IL-17A antibodies inhibited cancer pain, suggesting that IL-17A promotes such pain. The data show that LTTL gel inhibits cancer pain, and this might be accounted for by the decrease in expression of DRG TRP channels and spinal astrocyte IL-17A. © The Author(s) 2015.

Widespread pain reliever profile of a flower extract of Tanacetum parthenium.

PubMed

Di Cesare Mannelli, Lorenzo; Tenci, Barbara; Zanardelli, Matteo; Maidecchi, Anna; Lugli, Andrea; Mattoli, Luisa; Ghelardini, Carla

2015-07-15

Tanacetum parthenium L., commonly called Feverfew, is known for anti-inflammatory and anti-migraine properties. Aimed to individuate new therapeutical strategies to control acute and persistent pain induced by different origins we tested two hydroalcoholic extracts obtained from Feverfew flowers and leaves, respectively. Extracts were characterized according to the European Pharmacopoeia monograph. Both the extracts were tested after acute per os administration in the dose range 30-1000 mg kg(-1). The anti-nociceptive properties were evaluated by the Writhing test in mice. The number of abdominal contractions was dose dependently reduced by the flower extract. It reduced mechanical hypersensitivity (Paw pressure test) related to the acute inflammatory phase induced by carrageenan similarly to diclofenac and ibuprofen. In the osteoarthritis model induced by intra articular injection of monoiodoacetate (MIA) the flower extract significantly increased the pain threshold peaking 30 min after treatment. Moreover, it was effective in the chronic constriction injury model of neuropathic pain showing activity similar to the anti-epileptic drug gabapentin. The flower extract activity was confirmed in rat models of chemotherapy-induced neuropathic pain. The mechanical hypersensitivity induced by repeated treatments with the anticancer drug oxaliplatin and with the antiviral dideoxycytidine was significantly reduced after a single injection of Feverfew flower extract. The leaf extract showed lesser efficacy and potency and it was devoid of any effect in carrageenan-, MIA- and chemotherapy-induced pain. The present Feverfew flower extract behaves as a potent pain reliever in acute, inflammatory, articular and neuropathic pain. It appears as a natural strategy potentially suitable for the treatment of different kinds of pain. Copyright © 2015 Elsevier GmbH. All rights reserved.

Attenuation of Activity in an Endogenous Analgesia Circuit by Ongoing Pain in the Rat

PubMed Central

Ferrari, Luiz F.; Gear, Robert W.; Levine, Jon D.

2010-01-01

Analgesic efficacy varies depending on the pain syndrome being treated. One reason for this may be a differential effect of individual pain syndromes on the function of endogenous pain control circuits at which these drugs act to produce analgesia. To test this hypothesis we examined the effects of diverse (i.e., ongoing inflammatory, neuropathic, or chronic widespread) pain syndromes on analgesia induced by activation of an opioid-mediated noxious stimulus-induced endogenous pain control circuit. This circuit was activated by subdermal capsaicin injection at a site remote from the site of nociceptive testing. Analgesia was not affected by carrageenan-induced inflammatory pain nor the early-phase of oxaliplatin neuropathy (a complication of cancer chemotherapy). However, the duration of analgesia was markedly shorter in the late-phase of oxaliplatin neuropathy and in alcoholic neuropathy. A model of fibromyalgia syndrome produced by chronic unpredictable stress and proinflammatory cytokines also shortened analgesia duration, but so did the same stress alone. Therefore, since chronic pain can activate neuroendocrine stress axes, we tested whether they are involved in the attenuation of analgesic duration induced by these pain syndromes. Rats in which the sympathoadrenal axis was ablated by adrenal medullectomy showed normal duration pain-induced analgesia in groups with either late-phase oxaliplatin neuropathy, alcoholic neuropathy, or exposure to sound stress. These results support the suggestion that pain syndromes can modulate activity in endogenous pain control circuits, and this effect is sympathoadrenal dependent. PMID:20943910

Spinal Changes of a Newly Isolated Neuropeptide Endomorphin-2 Concomitant with Vincristine-Induced Allodynia

PubMed Central

Huang, Ben-Qing; Liu, Ji-Dong; Liu, Hui; Zhang, Nan; Li, Li; Chen, Jian-Hua

2014-01-01

Chemotherapy-induced neuropathic pain (CNP) is the major dose-limiting factor in cancer chemotherapy. However, the neural mechanisms underlying CNP remain unclear. There is increasing evidence implicating the involvement of spinal endomorphin-2 (EM2) in neuropathic pain. In this study, we used a vincristine-evoked rat CNP model displaying mechanical allodynia and central sensitization, and observed a significant decrease in the expression of spinal EM2 in CNP. Also, while intrathecal administration of exogenous EM2 attenuated allodynia and central sensitization, the mu-opioid receptor antagonist β-funaltrexamine facilitated these events. We found that the reduction in spinal EM2 was mediated by increased activity of dipeptidylpeptidase IV, possibly as a consequence of chemotherapy-induced oxidative stress. Taken together, our findings suggest that a decrease in spinal EM2 expression causes the loss of endogenous analgesia and leads to enhanced pain sensation in CNP. PMID:24586889

Effect of artemisinin on neuropathic pain mediated by P2X4 receptor in dorsal root ganglia.

PubMed

Ying, Mofeng; Liu, Hui; Zhang, Tengling; Jiang, Chenxu; Gong, Yingxin; Wu, Bing; Zou, Lifang; Yi, Zhihua; Rao, Shenqiang; Li, Guilin; Zhang, Chunping; Jia, Tianyu; Zhao, Shanhong; Yuan, Huilong; Shi, Liran; Li, Lin; Liang, Shangdong; Liu, Shuangmei

2017-09-01

Neuropathic pain is a type of chronic pain caused by nervous system damage and dysfunction. The pathogenesis of chronic pain is complicated, and there are no effective therapies for neuropathic pain. Studies show that the P2X 4 receptor expressed in the satellite glial cells (SGCs) of dorsal root ganglia (DRG) is related to neuropathic pain. Artemisinin is a monomeric component extracted from traditional Chinese medicine and has a variety of important pharmacological effects and potential applications. This study observed the effect of artemisinin on neuropathic pain and delineated its possible mechanism. The chronic constriction injury (CCI) rat model was used in this study. The results demonstrated that artemisinin relieved pain behaviors in the CCI rats, inhibited the expression of P2X 4 receptor in the DRG, and decreased the ATP-activated currents in HEK293 cells transfected with P2X 4 plasmid. Dual-labeling immunofluorescence showed that the coexpression of P2X 4 receptor and glial fibrillary acidic protein (GFAP) in the DRG of CCI rats was increased compared to control rats. After CCI rats were treated with artemisinin, the coexpression of P2X 4 receptor and GFAP in the DRG was significantly decreased compared to the CCI group. This finding suggested that artemisinin could inhibit the nociceptive transmission mediated by P2X 4 receptor in the DRG SGCs and thus relieve pain behaviors in the CCI rats. Copyright © 2017 Elsevier Ltd. All rights reserved.

Topical Anti-Inflammatory and Analgesic Effects of Multiple Applications of S(+)-Flurbiprofen Plaster (SFPP) in a Rat Adjuvant-Induced Arthritis Model.

PubMed

Sugimoto, Masanori; Toda, Yoshihisa; Hori, Miyuki; Mitani, Akiko; Ichihara, Takahiro; Sekine, Shingo; Kaku, Shinsuke; Otsuka, Noboru; Matsumoto, Hideo

2016-06-01

Preclinical Research The aim of this study was to evaluate the efficacy of multiple applications of S(+)-flurbiprofen plaster (SFPP), a novel Nonsteroidal anti-inflammatory drug (NSAID) patch, for the alleviation of inflammatory pain and edema in rat adjuvant-induced arthritis (AIA) model as compared to other NSAID patches. The AIA model was induced by the injection of Mycobacterium butyricum and rats were treated with a patch (1.0 cm × 0.88 cm) containing each NSAID (SFP, ketoprofen, loxoprofen, diclofenac, felbinac, flurbiprofen, or indomethacin) applied to the paw for 6 h per day for 5 days. The pain threshold was evaluated using a flexion test of the ankle joint, and the inflamed paw edema was evaluated using a plethysmometer. cyclooxygenase (COX)-1 and COX-2 inhibition was evaluated using human recombinant proteins. Multiple applications of SFPP exerted a significant analgesic effect from the first day of application as compared to the other NSAID patches. In terms of paw edema, SFPP decreased edema from the second day after application, Multiple applications of SFPP were superior to those of other NSAID patches, in terms of the analgesic effect with multiple applications. These results suggest that SFPP may be a beneficial patch for providing analgesic and anti-inflammatory effects clinically. Drug Dev Res 77 : 206-211, 2016. © 2016 The Authors Drug Development Research Published by Wiley Periodicals, Inc. © 2016 The Authors Drug Development Research Published by Wiley Periodicals, Inc.

Upregulation of EMMPRIN (OX47) in Rat Dorsal Root Ganglion Contributes to the Development of Mechanical Allodynia after Nerve Injury.

PubMed

Wang, Qun; Sun, Yanyuan; Ren, Yingna; Gao, Yandong; Tian, Li; Liu, Yang; Pu, Yanan; Gou, Xingchun; Chen, Yanke; Lu, Yan

2015-01-01

Matrix metalloproteinases (MMPs) are widely implicated in inflammation and tissue remodeling associated with various neurodegenerative diseases and play an important role in nociception and allodynia. Extracellular Matrix Metalloproteinase Inducer (EMMPRIN) plays a key regulatory role for MMP activities. However, the role of EMMPRIN in the development of neuropathic pain is not clear. Western blotting, real-time quantitative RT-PCR (qRT-PCR), and immunofluorescence were performed to determine the changes of messenger RNA and protein of EMMPRIN/OX47 and their cellular localization in the rat dorsal root ganglion (DRG) after nerve injury. Paw withdrawal threshold test was examined to evaluate the pain behavior in spinal nerve ligation (SNL) model. The lentivirus containing OX47 shRNA was injected into the DRG one day before SNL. The expression level of both mRNA and protein of OX47 was markedly upregulated in ipsilateral DRG after SNL. OX47 was mainly expressed in the extracellular matrix of DRG. Administration of shRNA targeted against OX47 in vivo remarkably attenuated mechanical allodynia induced by SNL. In conclusion, peripheral nerve injury induced upregulation of OX47 in the extracellular matrix of DRG. RNA interference against OX47 significantly suppressed the expression of OX47 mRNA and the development of mechanical allodynia. The altered expression of OX47 may contribute to the development of neuropathic pain after nerve injury.

Interactive effects of acupuncture on pain and distress in major burns: An experiment with rats.

PubMed

Abali, Ayse Ebru; Cabioglu, Tugrul; Ozdemir, Handan; Haberal, Mehmet

2015-06-01

This study sought to investigate the interactive effects of acupuncture on pain and distress and the local progress in the burn wound in an experimental major burn model. Forty-eight male Sprague-Dawley rats were divided into six groups: S group (sham/observation during 7 days after injury); SA group (sham/acupuncture/observation during 7 days after injury); B1 group (burns/observation during 1h after injury); BA1 group (burns/acupuncture/observation during 1 h after injury); B7 group (burns/observation during 7 days after injury); and BA7 group (burns/acupuncture/observation during 7 days after injury). Pain and distress scores were evaluated throughout the study. The amounts of neutrophils and mononuclear cells were evaluated semiquantitatively, and the number of microvessels was evaluated quantitatively. Our data indicated that the average pain score of BA7 group was significantly lower than the other study groups. Histopathologic investigations indicate that the amounts of neutrophil and mononuclear cell and numbers of microvessels in the unburned skin were higher in acupuncture-applied groups. The number of microvessels in burn wounds of BA7 group was significantly higher than that of the other groups. Our data suggest that acupuncture provides low pain and distress scores in experimental rat model, and it contributes to wound healing with an enhanced angiogenesis during the acute phase of burns. Future clinical and experimental studies should be conducted to discern the benefits from acupuncture in pain management of burn patients. Copyright © 2014 Elsevier Ltd and ISBI. All rights reserved.

Electrophysiological evidence for voltage-gated calcium channel 2 (Cav2) modulation of mechano- and thermosensitive spinal neuronal responses in a rat model of osteoarthritis

PubMed Central

Rahman, W.; Patel, R.; Dickenson, A.H.

2015-01-01

Osteoarthritis (OA) remains one of the greatest healthcare burdens in western society, with chronic debilitating pain-dominating clinical presentation yet therapeutic strategies are inadequate in many patients. Development of better analgesics is contingent on improved understanding of the molecular mechanisms mediating OA pain. Voltage-gated calcium channels 2.2 (Cav2.2) play a critical role in spinal nociceptive transmission, therefore blocking Cav2.2 activity represents an attractive opportunity for OA pain treatment, but the only available licensed Cav2.2 antagonist ziconitide (PrilatTM) is of limited use. TROX-1 is an orally available, use dependent and state-selective Cav2 antagonist, exerting its analgesic effect primarily via Cav2.2 blockade, with an improved therapeutic window compared with ziconitide. Using a rat model of monosodium iodoacetate (MIA), 2 mg, induced OA we used in vivo electrophysiology to assess the effects of spinal or systemic administration of TROX-1 on the evoked activity of wide dynamic range spinal dorsal horn neurons in response to electrical, natural mechanical (dynamic brush and von Frey 2, 8, 26 and 6 g) and thermal (40, 45 and 45 °C) stimuli applied to the peripheral receptive field. MIA injection into the knee joint resulted in mechanical hypersensitivity of the ipsilateral hind paw and weight-bearing asymmetry. Spinal administration of TROX-1 (0.1 and 1 μg/50 μl) produced a significant dose-related inhibition of dynamic brush, mechanical (von Frey filament (vF) 8, 26 and 60 g) and noxious thermal-(45 and 48 °C) evoked neuronal responses in MIA rats only. Systemic administration of TROX-1 produced a significant inhibition of the mechanical-(vF 8, 26 and 60 g) evoked neuronal responses in MIA rats. TROX-1 did not produce any significant effect on any neuronal measure in Sham controls. Our in vivo electrophysiological results demonstrate a pathological state-dependent effect of TROX-1, which suggests an increased functional role of Cav2, likely Cav2.2, channels in mediating OA pain. PMID:26247695

Soluble Flt-1 improves the repair of ankle joint injury in rats

PubMed Central

Tian, Jing; Xie, Bing; Xiang, Liangbi; Zhao, Yong; Zhou, Dapeng

2016-01-01

The ankle injuries create great pain to a great number of patients worldwide. Past studies have focused on the development of practical treatments to relieve pain and improve recovery, but the molecular mechanisms underlying the ankle injuries, especially the local inflammation in the damaged ankle joint, have been rarely studied. Moreover, although reduction of production and secretion of pro-inflammatory cytokines may reduce the pain and promote the recovery, a practical approach is currently lacking. Here, we detected significantly higher levels of placental growth factor (PLGF) and pro-inflammatory cytokines in the joint fluid from the patients of acute ankle joint injury (AAJI). Interestingly, the levels of PLGF and pro-inflammatory cytokines in the joint fluid strongly correlated. In order to examine whether PLGF may regulate the production and secretion of pro-inflammatory cytokines in the injured joint, we used a rat carrageenan-induced ankle injury model for AAJI in humans. We injected soluble Flt-1 (sFlt-1) into the articular cavity of the injured ankle joint to block PLGF signaling and found that injection of sFlt-1 significantly improved the rat behavior in activity wheels test, which appeared to result from reduced secretion of the pro-inflammatory cytokines in the ankle joint. Thus, our study suggests that blocking PLGF signaling may be a novel therapeutic approach for treating AAJI in humans. PMID:27904694

Design, synthesis, and biological evaluation of 3,4-dihydroquinolin-2(1H)-one and 1,2,3,4-tetrahydroquinoline-based selective human neuronal nitric oxide synthase (nNOS) inhibitors.

PubMed

Ramnauth, Jailall; Speed, Joanne; Maddaford, Shawn P; Dove, Peter; Annedi, Subhash C; Renton, Paul; Rakhit, Suman; Andrews, John; Silverman, Sarah; Mladenova, Gabriela; Zinghini, Salvatore; Nair, Sheela; Catalano, Concettina; Lee, David K H; De Felice, Milena; Porreca, Frank

2011-08-11

Neuronal nitric oxide synthase (nNOS) inhibitors are effective in preclinical models of many neurological disorders. In this study, two related series of compounds, 3,4-dihydroquinolin-2(1H)-one and 1,2,3,4-tetrahydroquinoline, containing a 6-substituted thiophene amidine group were synthesized and evaluated as inhibitors of human nitric oxide synthase (NOS). A structure-activity relationship (SAR) study led to the identification of a number of potent and selective nNOS inhibitors. Furthermore, a few representative compounds were shown to possess druglike properties, features that are often difficult to achieve when designing nNOS inhibitors. Compound (S)-35, with excellent potency and selectivity for nNOS, was shown to fully reverse thermal hyperalgesia when given to rats at a dose of 30 mg/kg intraperitonieally (ip) in the L5/L6 spinal nerve ligation model of neuropathic pain (Chung model). In addition, this compound reduced tactile hyperesthesia (allodynia) after oral administration (30 mg/kg) in a rat model of dural inflammation relevant to migraine pain.

Topical Anti‐Inflammatory and Analgesic Effects of Multiple Applications of S(+)‐Flurbiprofen Plaster (SFPP) in a Rat Adjuvant‐Induced Arthritis Model

PubMed Central

Toda, Yoshihisa; Hori, Miyuki; Mitani, Akiko; Ichihara, Takahiro; Sekine, Shingo; Kaku, Shinsuke; Otsuka, Noboru; Matsumoto, Hideo

2016-01-01

Abstract Preclinical Research The aim of this study was to evaluate the efficacy of multiple applications of S(+)‐flurbiprofen plaster (SFPP), a novel Nonsteroidal anti‐inflammatory drug (NSAID) patch, for the alleviation of inflammatory pain and edema in rat adjuvant‐induced arthritis (AIA) model as compared to other NSAID patches. The AIA model was induced by the injection of Mycobacterium butyricum and rats were treated with a patch (1.0 cm × 0.88 cm) containing each NSAID (SFP, ketoprofen, loxoprofen, diclofenac, felbinac, flurbiprofen, or indomethacin) applied to the paw for 6 h per day for 5 days. The pain threshold was evaluated using a flexion test of the ankle joint, and the inflamed paw edema was evaluated using a plethysmometer. cyclooxygenase (COX)−1 and COX‐2 inhibition was evaluated using human recombinant proteins. Multiple applications of SFPP exerted a significant analgesic effect from the first day of application as compared to the other NSAID patches. In terms of paw edema, SFPP decreased edema from the second day after application, Multiple applications of SFPP were superior to those of other NSAID patches, in terms of the analgesic effect with multiple applications. These results suggest that SFPP may be a beneficial patch for providing analgesic and anti‐inflammatory effects clinically. Drug Dev Res 77 : 206–211, 2016. © 2016 The Authors Drug Development Research Published by Wiley Periodicals, Inc. PMID:27241582

Intrathecal administration of AYX2 DNA decoy produces a long-term pain treatment in rat models of chronic pain by inhibiting the KLF6, KLF9, and KLF15 transcription factors

PubMed Central

Klukinov, Michael; Harris, Scott; Manning, Donald C; Xie, Simon; Pascual, Conrado; Taylor, Bradley K; Donahue, Renee R; Yeomans, David C

2017-01-01

Background Nociception is maintained by genome-wide regulation of transcription in the dorsal root ganglia—spinal cord network. Hence, transcription factors constitute a promising class of targets for breakthrough pharmacological interventions to treat chronic pain. DNA decoys are oligonucleotides and specific inhibitors of transcription factor activities. A methodological series of in vivo–in vitro screening cycles was performed with decoy/transcription factor couples to identify targets capable of producing a robust and long-lasting inhibition of established chronic pain. Decoys were injected intrathecally and their efficacy was tested in the spared nerve injury and chronic constriction injury models of chronic pain in rats using repetitive von Frey testing. Results Results demonstrated that a one-time administration of decoys binding to the Kruppel-like transcription factors (KLFs) 6, 9, and 15 produces a significant and weeks–month long reduction in mechanical hypersensitivity compared to controls. In the spared nerve injury model, decoy efficacy was correlated to its capacity to bind KLF15 and KLF9 at a specific ratio, while in the chronic constriction injury model, efficacy was correlated to the combined binding capacity to KLF6 and KLF9. AYX2, an 18-bp DNA decoy binding KLF6, KLF9, and KLF15, was optimized for clinical development, and it demonstrated significant efficacy in these models. Conclusions These data highlight KLF6, KLF9, and KLF15 as transcription factors required for the maintenance of chronic pain and illustrate the potential therapeutic benefits of AYX2 for the treatment of chronic pain. PMID:28814144

Oxaliplatin regulates chemotherapy induced peripheral neuropathic pain in the dorsal horn and dorsal root ganglion via the Calcineurin/NFAT pathway.

PubMed

Huang, Wan; Huang, Jingxiu; Jiang, Yu; Huang, Xuanwei; Xing, Wei; He, Yaoxuan; Ouyang, Handong

2018-05-24

The aim of this study was to investigate the mechanism of oxaliplatin in the induction of neuropathic pain as a symptom of chemotherapy-induced peripheral neuropathy (CIPN). The CIPN rat model was induced with a one-time injection of oxaliplatin, and the paw withdrawal response was determined using von Frey filaments. The paw withdrawal threshold (PWT) value was recorded and the dorsal horn (DH) and dorsal root ganglion (DRG) tissues were collected. The mRNA and protein levels of calcineurin (CaN), nuclear factor of activated T cells (NFAT), and other relevant cytokines were determined. CaN and NFAT inhibition reagents, FK506 and 11R-VIVIT, were applied in order to investigate the functions of the CaN/NFAT pathway in the neuropathic pain processes. The levels of the downstream inflammatory cytokines, TNF-α and IL-1β, were assessed by ELISA. The application of oxaliplatin reduced the value of PWT by 4 times on days 7（4±1.33）and 14（5.13±3.07）compared with the control group(14±0.91; 13.67±0.76). After treatment, the CaN mRNA level decreased and that of NFAT increased in DH and DRG tissues (P<0.05). However, treatment with FK506 and 11R-VIVIT decreased the value of PWT that had increased after oxaliplatin treatment. The expression of downstream cytokines related to the CaN/NFAT pathway increased, including CCR2, COX2, p-ERK, and p-P38 (all p<0.05). In addition, when the CaN/NFAT pathway was activated, the concentration of TNFα increased to 40pg/mg in DH tissues and 60pg/mg in DRG tissues compared with the control group, while the concentration of IL-1β increased to over 60pg/mg in DH and DRG tissues. It was the first time to prove that oxaliplatin-induced neuropathic pain was correlated to the activation of the CaN/NFAT pathway in our rat model. This finding can provide a new direction for explore the mechanism of oxaliplatin-induced neuropathic pain. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

The Antinociceptive Effects of Tramadol and/or Gabapentin on Rat Neuropathic Pain Induced by a Chronic Constriction Injury.

PubMed

Corona-Ramos, Janette Nallely; De la O-Arciniega, Minarda; Déciga-Campos, Myrna; Medina-López, José Raúl; Domínguez-Ramírez, Adriana Miriam; Jaramillo-Morales, Osmar Antonio; Espinosa-Juárez, Josué Vidal; López-Muñoz, Francisco Javier

2016-08-01

Preclinical Research The current work evaluates the interaction between two commonly used drugs, tramadol (Tra) and gabapentin (Gbp). Dose-response curves (DRC) and isobolographic analysis were used to confirm their synergistic antihyperalgesic and anti-allodynic responses in a rat neuropathic pain model involving chronic constriction injury of the sciatic nerve and in von Frey and acetone tests. Tra and Gbp produced dose-dependent antihyperalgesic and anti-allodynic effects. Dose-response studies of combinations of Tra and Gbp in combination showed the DRC was leftward-shifted compared to the DRCs for each compound alone. One combination demonstrated both antihyperalgesic and anti-allodynic effects greater than those observed after individual administration. The remaining combinations demonstrated an additive effect. The Tra+Gbp combination demonstrated a potentiative effect with smaller doses of Tra. Additionally, it was determined lethal dose 50 (LD50 ) of Tra alone and tramadol + Gbp 10 using mice to 48 h post administration. The DRC (death) were similar for Tra alone and in Tra in combination, despite the improved effectiveness of Tra in the presence of GBP, 10 mg/kg. A combination of these drugs could be effective in neuropathic pain therapy because they can produce potentiative (at a low dose) or additive effects. Drug Dev Res 77 : 217-226, 2016.   © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Tannic acid modulates excitability of sensory neurons and nociceptive behavior and the Ionic mechanism.

PubMed

Zhang, Xuan; Zhang, Huiran; Zhou, Najing; Xu, Jiaxi; Si, Man; Jia, Zhanfeng; Du, Xiaona; Zhang, Hailin

2015-10-05

M/Kv7 K(+) channels, Ca(2+)-activated Cl(-) channels (CaCCs) and voltage gated Na(+) channels expressed in dorsal root ganglia (DRG) play an important role in nociception. Tannic acid has been proposed to be involved in multiple beneficial health effects; tannic acid has also been described to be analgesic. However the underlying mechanism is unknown. In this study, we investigated the effects of tannic acid on M/Kv7 K(+), Na(+) currents and CaCCs, and the effects on bradykinin-induced nociceptive behavior. A perforated patch technique was used. The bradykinin-induced rat pain model was used to assess the analgesic effect of tannic acid. We demonstrated that tannic acid enhanced M/Kv7 K(+) currents but inhibited bradykinin-induced activation of CaCC/TMEM16A currents in rat small DRG neurons. Tannic acid potentiated Kv7.2/7.3 and Kv7.2 currents expressed in HEK293B cells, with an EC50 of 7.38 and 5.40 µM, respectively. Tannic acid inhibited TTX-sensitive and TTX-insensitive currents of small DRG neurons with IC50 of 5.25 and 8.43 µM, respectively. Tannic acid also potently suppressed the excitability of small DRG neurons. Furthermore, tannic acid greatly reduced bradykinin-induced pain behavior of rats. This study thus demonstrates that tannic acid is an activator of M/Kv7 K(+) and an inhibitor of voltage-gated Na(+) channels and CaCC/TMEM16A, which may underlie its inhibitory effects on excitability of DRG neurons and its analgesic effect. Tannic acid could be a useful agent in treatment of inflammatory pain conditions such as osteoarthritis, rheumatic arthritis and burn pain. Copyright © 2015. Published by Elsevier B.V.

Sigma-1 Receptor Antagonist BD1047 Reduces Mechanical Allodynia in a Rat Model of Bone Cancer Pain through the Inhibition of Spinal NR1 Phosphorylation and Microglia Activation

PubMed Central

Zhu, Shanshan; Wang, Chenchen; Han, Yuan; Song, Chao; Hu, Xueming; Liu, Yannan

2015-01-01

Previous studies have demonstrated that sigma-1 receptor plays important roles in the induction phase of rodent neuropathic pain; however, whether it is involved in bone cancer pain (BCP) and the underlying mechanisms remain elusive. The aim of this study was to examine the potential role of the spinal sigma-1 receptor in the development of bone cancer pain. Walker 256 mammary gland carcinoma cells were implanted into the intramedullary space of the right tibia of Sprague-Dawley rats to induce ongoing bone cancer-related pain behaviors; our findings indicated that, on days 7, 10, 14, and 21 after operation, the expression of sigma-1 receptor in the spinal cord was higher in BCP rats compared to the sham rats. Furthermore, intrathecal injection of 120 nmol of sigma-1 receptor antagonist BD1047 on days 5, 6, and 7 after operation attenuated mechanical allodynia as well as the associated induction of c-Fos and activation of microglial cells, NR1, and the subsequent Ca2+-dependent signals of BCP rats. These results suggest that sigma-1 receptor is involved in the development of bone cancer pain and that targeting sigma-1 receptor may be a new strategy for the treatment of bone cancer pain. PMID:26696751

Dissecting the contribution of knee joint NGF to spinal nociceptive sensitization in a model of OA pain in the rat.

PubMed

Sagar, D R; Nwosu, L; Walsh, D A; Chapman, V

2015-06-01

Although analgesic approaches targeting nerve growth factor (NGF) for the treatment of osteoarthritis (OA) pain remain of clinical interest, neurophysiological mechanisms by which NGF contribute to OA pain remain unclear. We investigated the impact of local elevation of knee joint NGF on knee joint, vs remote (hindpaw), evoked responses of spinal neurones in a rodent model of OA pain. In vivo spinal electrophysiology was carried out in anaesthetised rats with established pain behaviour and joint pathology following intra-articular injection of monosodium iodoacetate (MIA), vs injection of saline. Neuronal responses to knee joint extension and flexion, mechanical punctate stimulation of the peripheral receptive fields over the knee and at a remote site (ipsilateral hind paw) were studied before, and following, intra-articular injection of NGF (10 μg/50 μl) or saline. MIA-injected rats exhibited significant local (knee joint) and remote (lowered hindpaw withdrawal thresholds) changes in pain behaviour, and joint pathology. Intra-articular injection of NGF significantly (P < 0.05) increased knee extension-evoked firing of spinal neurones and the size of the peripheral receptive fields of spinal neurones (100% increase) over the knee joint in MIA rats, compared to controls. Intra-articular NGF injection did not significantly alter responses of spinal neurones following noxious stimulation of the ipsilateral hind paw in MIA-injected rats. The facilitatory effects of intra-articular injection of NGF on spinal neurones receiving input from the knee joint provide a mechanistic basis for NGF mediated augmentation of OA knee pain, however additional mechanisms may contribute to the spread of pain to remote sites. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Effects of S 38093, an antagonist/inverse agonist of histamine H3 receptors, in models of neuropathic pain in rats.

PubMed

Chaumette, T; Chapuy, E; Berrocoso, E; Llorca-Torralba, M; Bravo, L; Mico, J A; Chalus, M; Eschalier, A; Ardid, D; Marchand, F; Sors, A

2018-01-01

Histamine H3 receptors are mainly expressed on CNS neurons, particularly along the nociceptive pathways. The potential involvement of these receptors in pain processing has been suggested using H3 receptor inverse agonists. The antinociceptive effect of S 38093, a novel inverse agonist of H3 receptors, has been evaluated in several neuropathic pain models in rat and compared with those of gabapentin and pregabalin. While S 38093 did not change vocalization thresholds to paw pressure in healthy rats, it exhibited a significant antihyperalgesic effect in the Streptozocin-induced diabetic (STZ) neuropathy model after acute and chronic administration and, in the chronic constriction injury (CCI) model only after chronic administration, submitted to the paw-pressure test. Acute S 38093 administration at all doses tested displayed a significant cold antiallodynic effect in a model of acute or repeated administration of oxaliplatin-induced neuropathy submitted to cold tail immersion, cold allodynia being the main side effect of oxaliplatin in patients. The effect of S 38093 increased following chronic administration (i.e. twice a day during 5 days) in the CCI and STZ models except in the oxaliplatin models where its effect was already maximal from the first administration The kinetics and size of effect of S 38093 were similar to gabapentin and/or pregabalin. Finally, the antinociceptive effect of S 38093 could be partially mediated by α2 adrenoreceptors desensitization in the locus coeruleus. These results highlight the interest of S 38093 to relieve neuropathic pain and warrant clinical trials especially in chemotherapeutic agent-induced neuropathic pain. S 38093, a new H3 antagonist/inverse agonist, displays antiallodynic and antihyperalgesic effect in neuropathic pain, especially in oxaliplatin-induced neuropathy after chronic administration. This effect of S 38093 in neuropathic pain could be partly mediated by α2 receptors desensitization in the locus coeruleus. © 2017 European Pain Federation - EFIC®.

ABT-627, an endothelin ET(A) receptor-selective antagonist, attenuates tactile allodynia in a diabetic rat model of neuropathic pain.

PubMed

Jarvis, M F; Wessale, J L; Zhu, C Z; Lynch, J J; Dayton, B D; Calzadilla, S V; Padley, R J; Opgenorth, T J; Kowaluk, E A

2000-01-24

Tactile allodynia, the enhanced perception of pain in response to normally non-painful stimulation, represents a common complication of diabetic neuropathy. The activation of endothelin ET(A) receptors has been implicated in diabetes-induced reductions in peripheral neurovascularization and concomitant endoneurial hypoxia. Endothelin receptor activation has also been shown to alter the peripheral and central processing of nociceptive information. The present study was conducted to evaluate the antinociceptive effects of the novel endothelin ET(A) receptor-selective antagonist, 2R-(4-methoxyphenyl)-4S-(1,3-benzodioxol-5-yl)-1-(N, N-di(n-butyl)aminocarbonyl-methyl)-pyrrolidine-3R-carboxylic acid (ABT-627), in the streptozotocin-induced diabetic rat model of neuropathic pain. Rats were injected with 75 mg/kg streptozotocin (i. p.), and drug effects were assessed 8-12 weeks following streptozotocin treatment to allow for stabilization of blood glucose levels (>/=240 mg/dl) and tactile allodynia thresholds (

Intervention of electroacupuncture on spinal p38 MAPK/ATF-2/VR-1 pathway in treating inflammatory pain induced by CFA in rats.

PubMed

Fang, Jian-Qiao; Du, Jun-Ying; Liang, Yi; Fang, Jun-Fan

2013-03-22

Previous studies have demonstrated that p38 MAPK signal transduction pathway plays an important role in the development and maintenance of inflammatory pain. Electroacupuncture (EA) can suppress the inflammatory pain. However, the relationship between EA effect and p38 MAPK signal transduction pathway in inflammatory pain remains poorly understood. It is our hypothesis that p38 MAPK/ATF-2/VR-1 and/or p38 MAPK/ATF-2/COX-2 signal transduction pathway should be activated by inflammatory pain in CFA-injected model. Meanwhile, EA may inhibit the activation of p38 MAPK signal transduction pathway. The present study aims to investigate that anti-inflammatory and analgesic effect of EA and its intervention on the p38 MAPK signal transduction pathway in a rat model of inflammatory pain. EA had a pronounced anti-inflammatory and analgesic effect on CFA-induced chronic inflammatory pain in rats. EA could quickly raise CFA-rat's paw withdrawal thresholds (PWTs) and maintain good and long analgesic effect, while it subdued the ankle swelling of CFA rats only at postinjection day 14. EA could down-regulate the protein expressions of p-p38 MAPK and p-ATF-2, reduced the numbers of p-p38 MAPK-IR cells and p-ATF-2-IR cells in spinal dorsal horn in CFA rats, inhibited the expressions of both protein and mRNA of VR-1, but had no effect on the COX-2 mRNA expression. The present study indicates that inhibiting the activation of spinal p38 MAPK/ATF-2/VR-1 pathway may be one of the main mechanisms via central signal transduction pathway in the process of anti-inflammatory pain by EA in CFA rats.

Intervention of electroacupuncture on spinal p38 MAPK/ATF-2/VR-1 pathway in treating inflammatory pain induced by CFA in rats

PubMed Central

2013-01-01

Background Previous studies have demonstrated that p38 MAPK signal transduction pathway plays an important role in the development and maintenance of inflammatory pain. Electroacupuncture (EA) can suppress the inflammatory pain. However, the relationship between EA effect and p38 MAPK signal transduction pathway in inflammatory pain remains poorly understood. It is our hypothesis that p38 MAPK/ATF-2/VR-1 and/or p38 MAPK/ATF-2/COX-2 signal transduction pathway should be activated by inflammatory pain in CFA-injected model. Meanwhile, EA may inhibit the activation of p38 MAPK signal transduction pathway. The present study aims to investigate that anti-inflammatory and analgesic effect of EA and its intervention on the p38 MAPK signal transduction pathway in a rat model of inflammatory pain. Results EA had a pronounced anti-inflammatory and analgesic effect on CFA-induced chronic inflammatory pain in rats. EA could quickly raise CFA-rat’s paw withdrawal thresholds (PWTs) and maintain good and long analgesic effect, while it subdued the ankle swelling of CFA rats only at postinjection day 14. EA could down-regulate the protein expressions of p-p38 MAPK and p-ATF-2, reduced the numbers of p-p38 MAPK-IR cells and p-ATF-2-IR cells in spinal dorsal horn in CFA rats, inhibited the expressions of both protein and mRNA of VR-1, but had no effect on the COX-2 mRNA expression. Conclusions The present study indicates that inhibiting the activation of spinal p38 MAPK/ATF-2/VR-1 pathway may be one of the main mechanisms via central signal transduction pathway in the process of anti-inflammatory pain by EA in CFA rats. PMID:23517865

Dissecting the contribution of knee joint NGF to spinal nociceptive sensitization in a model of OA pain in the rat

PubMed Central

Sagar, D.R.; Nwosu, L.; Walsh, D.A.; Chapman, V.

2015-01-01

Summary Objective Although analgesic approaches targeting nerve growth factor (NGF) for the treatment of osteoarthritis (OA) pain remain of clinical interest, neurophysiological mechanisms by which NGF contribute to OA pain remain unclear. We investigated the impact of local elevation of knee joint NGF on knee joint, vs remote (hindpaw), evoked responses of spinal neurones in a rodent model of OA pain. Design In vivo spinal electrophysiology was carried out in anaesthetised rats with established pain behaviour and joint pathology following intra-articular injection of monosodium iodoacetate (MIA), vs injection of saline. Neuronal responses to knee joint extension and flexion, mechanical punctate stimulation of the peripheral receptive fields over the knee and at a remote site (ipsilateral hind paw) were studied before, and following, intra-articular injection of NGF (10 μg/50 μl) or saline. Results MIA-injected rats exhibited significant local (knee joint) and remote (lowered hindpaw withdrawal thresholds) changes in pain behaviour, and joint pathology. Intra-articular injection of NGF significantly (P < 0.05) increased knee extension-evoked firing of spinal neurones and the size of the peripheral receptive fields of spinal neurones (100% increase) over the knee joint in MIA rats, compared to controls. Intra-articular NGF injection did not significantly alter responses of spinal neurones following noxious stimulation of the ipsilateral hind paw in MIA-injected rats. Conclusion The facilitatory effects of intra-articular injection of NGF on spinal neurones receiving input from the knee joint provide a mechanistic basis for NGF mediated augmentation of OA knee pain, however additional mechanisms may contribute to the spread of pain to remote sites. PMID:25623624

Home cage wheel running is an objective and clinically relevant method to assess inflammatory pain in male and female rats

PubMed Central

Kandasamy, Ram; Calsbeek, Jonas J.; Morgan, Michael M.

2016-01-01

Background The assessment of nociception in preclinical studies is undergoing a transformation from pain-evoked to pain-depressed tests to more closely mimic the effects of clinical pain. Many inflammatory pain-depressed behaviors (reward seeking, locomotion) have been examined, but these tests are limited because of confounds such as stress and difficulties in quantifying behavior. New Method The present study evaluates home cage wheel running as an objective method to assess the magnitude and duration of inflammatory pain in male and female rats. Results Injection of Complete Freund’s Adjuvant (CFA) into the right hindpaw to induce inflammatory pain almost completely inhibited wheel running for 2 days in males and females. Wheel running gradually returned to baseline levels within 12 days despite persistent mechanical hypersensitivity (von Frey test). Comparison with Existing Methods Continuously monitoring home cage wheel running improves on previous studies examining inflammatory pain-depressed wheel running because it is more sensitive to noxious stimuli, avoids the stress of removing the rat from its cage for testing, and provides a complete analysis of the time course for changes in nociception. Conclusions The present data indicate that home cage wheel running is a clinically relevant method to assess inflammatory pain in the rat. The decrease in activity caused by inflammatory pain and subsequent gradual recovery mimics the changes in activity caused by pain in humans. The tendency for pain-depressed wheel running to be greater in female than male rats is consistent with the tendency for women to be at greater risk of chronic pain than men. PMID:26891874

Rebamipide attenuates pain severity and cartilage degeneration in a rat model of osteoarthritis by downregulating oxidative damage and catabolic activity in chondrocytes.

PubMed

Moon, S-J; Woo, Y-J; Jeong, J-H; Park, M-K; Oh, H-J; Park, J-S; Kim, E-K; Cho, M-L; Park, S-H; Kim, H-Y; Min, J-K

2012-11-01

The objectives were to investigate the in vivo effects of treatment with rebamipide on pain severity and cartilage degeneration in an experimental model of rat osteoarthritis (OA) and to explore its mode of action. OA was induced in rats by intra-articular injection of monosodium iodoacetate (MIA). Oral administration of rebamipide was initiated on the day of MIA injection, 3 or 7 days after. Limb nociception was assessed by measuring the paw withdrawal latency and threshold. We analyzed the samples macroscopically and histomorphologically, and used immunohistochemistry to investigate the expression of matrix metalloproteinase-13 (MMP-13), interleukin-1β (IL-1β), hypoxia-inducible factor-2α (HIF-2α), inducible nitric oxide synthase (iNOS), and nitrotyrosine in knee joints. Real-time quantitative reverse transcription-polymerase chain reaction was used to quantify the mRNA for catabolic and anticatabolic factors in human OA chondrocytes. Rebamipide showed an antinociceptive property and attenuated cartilage degeneration. Rebamipide reduced the expression of MMP-13, IL-1β, HIF-2α, iNOS, and nitrotyrosine in OA cartilage in a dose-dependent manner. Nitrotyrosine expression in the subchondral bone region was decreased in the rebamipide-treated joints. mRNA expression of MMP-1, -3, and -13, and ADAMTS5 was attenuated in IL-1β-stimulated human OA chondrocytes. By contrast, rebamipide induced the mRNA expression of tissue inhibitor of metalloproteinase-1 and -3. The results show the inhibitory effects of rebamipide on pain production and cartilage degeneration in experimentally induced OA. The suppression of oxidative damage and the restoration of extracellular matrix homeostasis of articular chondrocyte suggest that rebamipide is a potential therapeutic strategy for OA. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

Silencing the Kir4.1 potassium channel subunit in satellite glial cells of the rat trigeminal ganglion results in pain-like behavior in the absence of nerve injury

PubMed Central

Vit, Jean-Philippe; Ohara, Peter T.; Bhargava, Aditi; Kelley, Kanwar; Jasmin, Luc

2008-01-01

Growing evidence suggests that changes in the ion buffering capacity of glial cells can give rise to neuropathic pain. In the CNS, potassium ion (K+) buffering is dependent on the glia-specific inward rectifying K+ channel Kir4.1. We recently reported that the satellite glial cells (SGCs) that surround primary sensory neurons located in sensory ganglia of the peripheral nervous system also express Kir4.1 while the neurons do not. In the present study we show that in the rat trigeminal ganglion, the location of the primary sensory neurons for face sensation, specific silencing of Kir4.1 using RNA interference leads to spontaneous and evoked facial pain-like behavior in freely moving rats. We also show that Kir4.1 in the trigeminal ganglion is reduced following chronic constriction injury of the infraorbital nerve. These findings suggests that neuropathic pain can result from a change in expression of a single K+ channel in peripheral glial cells, raising the possibility of targeting Kir4.1 to treat pain in general, and particularly neuropathic pain that occurs in the absence of nerve injury. PMID:18417695

Endogenous opioid mechanisms partially mediate P2X3/P2X2/3-related antinociception in rat models of inflammatory and chemogenic pain but not neuropathic pain.

PubMed

McGaraughty, Steve; Honore, Prisca; Wismer, Carol T; Mikusa, Joseph; Zhu, Chang Z; McDonald, Heath A; Bianchi, Bruce; Faltynek, Connie R; Jarvis, Michael F

2005-09-01

P2X3/P2X2/3 receptors have emerged as important components of nociception. However, there is limited information regarding the neurochemical systems that are affected by antagonism of the P2X3/P2X2/3 receptor and that ultimately contribute to the ensuing antinociception. In order to determine if the endogenous opioid system is involved in this antinociception, naloxone was administered just prior to the injection of a selective P2X3/P2X2/3 receptor antagonist, A-317491, in rat models of neuropathic, chemogenic, and inflammatory pain. Naloxone (1-10 mg kg(-1), i.p.), dose-dependently reduced the antinociceptive effects of A-317491 (1-300 micromol kg(-1), s.c.) in the CFA model of thermal hyperalgesia and the formalin model of chemogenic pain (2nd phase), but not in the L5-L6 spinal nerve ligation model of neuropathic allodynia. In comparison experiments, the same doses of naloxone blocked or attenuated the actions of morphine (2 or 8 mg kg(-1), s.c.) in each of these behavioral models. Injection of a peripheral opioid antagonist, naloxone methiodide (10 mg kg(-1), i.p.), did not affect A-317491-induced antinociception in the CFA and formalin assays, suggesting that the opioid component of this antinociception occurred within the CNS. Furthermore, this utilization of the central opioid system could be initiated by antagonism of spinal P2X3/P2X2/3 receptors since the antinociceptive actions of intrathecally delivered A-317491 (30 nmol) in the formalin model were reduced by both intrathecally (10-50 nmol) and systemically (10 mg kg(-1), i.p.) administered naloxone. This utilization of the opioid system was not specific to A-317491 since suramin-, a nonselective P2X receptor antagonist, induced antinociception was also attenuated by naloxone. In in vitro studies, A-317491 (3-100 microM) did not produce any agonist response at delta opioid receptors expressed in NG108-15 cells. A-317491 had been previously shown to be inactive at the kappa and mu opioid receptors. Furthermore, naloxone, at concentrations up to 1 mM, did not compete for [3H] A-317491 binding in 1321N1 cells expressing human P2X3 receptors. Taken together, these results indicate that antagonism of spinal P2X3/P2X2/3 receptors results in an indirect activation of the opioid system to alleviate inflammatory hyperalgesia and chemogenic nociception.

Intrathecal curcumin attenuates pain hypersensitivity and decreases spinal neuroinflammation in rat model of monoarthritis

PubMed Central

Chen, Jun-Jie; Dai, Lin; Zhao, Lin-Xia; Zhu, Xiang; Cao, Su; Gao, Yong-Jing

2015-01-01

Curcumin is a major component of turmeric and reportedly has anti-inflammatory and anti-oxidant effects. Neuroinflammation has been recognized to play an important role in the pathogenesis of various diseases in the central nervous system. Here we investigated the anti-nociceptive and anti-neuroinflammatory effect of curcumin on arthritic pain in rats. We found that repeated oral treatment with curcumin, either before or after complete Freund’s adjuvant (CFA) injection, dose-dependently attenuated CFA-induced mechanical allodynia and thermal hyperalgesia, but had no effect on joint edema. Repeated intrathecal injection of curcumin reversed CFA-induced pain hypersensitivity. Furthermore, such a curcumin treatment reduced CFA-induced activation of glial cells and production of inflammatory mediators [interleukin-1β (IL-1β), monocyte chemoattractant protein-1 (MCP-1), and monocyte inflammatory protein-1 (MIP-1α)] in the spinal cord. Curcumin also decreased lipopolysaccharide-induced production of IL-1β, tumor necrosis factor-α, MCP-1, and MIP-1α in cultured astrocytes and microglia. Our results suggest that intrathecal curcumin attenuates arthritic pain by inhibiting glial activation and the production of inflammatory mediators in the spinal cord, suggesting a new application of curcumin for the treatment of arthritic pain. PMID:25988362

Depressive-like symptoms in a reserpine-induced model of fibromyalgia in rats.

PubMed

Blasco-Serra, Arantxa; Escrihuela-Vidal, Francesc; González-Soler, Eva M; Martínez-Expósito, Fernando; Blasco-Ausina, M Carmen; Martínez-Bellver, Sergio; Cervera-Ferri, Ana; Teruel-Martí, Vicent; Valverde-Navarro, Alfonso A

2015-11-01

Since the pathogenesis of fibromyalgia is unknown, treatment options are limited, ineffective and in fact based on symptom relief. A recently proposed rat model of fibromyalgia is based on central depletion of monamines caused by reserpine administration. This model showed widespread musculoskeletal pain and depressive-like symptoms, but the methodology used to measure such symptoms has been criticized. Evidence relates the high prevalence of pain and depression in fibromyalgia to common pathogenic pathways, most probably focused on the monoaminergic system. The present study aims at a validation of the reserpine model of fibromyalgia. For this purpose, rats undergoing this model have been tested for depressive-like symptoms with a Novelty-Suppressed Feeding Test adaptation. Animals administered with reserpine and subjected to forced food deprivation performed a smaller number of incursions to the center of the open field, evidenced by a decrease in the per-minute rate of the rats' approaching, smelling or touching the food. They also took more time to eat from the central food than control rats. These NSFT findings suggest the presence of depressive-like disorders in this animal model of fibromyalgia. Copyright © 2015 Elsevier Inc. All rights reserved.

Intrathecal curcumin attenuates pain hypersensitivity and decreases spinal neuroinflammation in rat model of monoarthritis.

PubMed

Chen, Jun-Jie; Dai, Lin; Zhao, Lin-Xia; Zhu, Xiang; Cao, Su; Gao, Yong-Jing

2015-05-19

Curcumin is a major component of turmeric and reportedly has anti-inflammatory and anti-oxidant effects. Neuroinflammation has been recognized to play an important role in the pathogenesis of various diseases in the central nervous system. Here we investigated the anti-nociceptive and anti-neuroinflammatory effect of curcumin on arthritic pain in rats. We found that repeated oral treatment with curcumin, either before or after complete Freund's adjuvant (CFA) injection, dose-dependently attenuated CFA-induced mechanical allodynia and thermal hyperalgesia, but had no effect on joint edema. Repeated intrathecal injection of curcumin reversed CFA-induced pain hypersensitivity. Furthermore, such a curcumin treatment reduced CFA-induced activation of glial cells and production of inflammatory mediators [interleukin-1β (IL-1β), monocyte chemoattractant protein-1 (MCP-1), and monocyte inflammatory protein-1 (MIP-1α)] in the spinal cord. Curcumin also decreased lipopolysaccharide-induced production of IL-1β, tumor necrosis factor-α, MCP-1, and MIP-1α in cultured astrocytes and microglia. Our results suggest that intrathecal curcumin attenuates arthritic pain by inhibiting glial activation and the production of inflammatory mediators in the spinal cord, suggesting a new application of curcumin for the treatment of arthritic pain.

Evaluation of phenoxybenzamine in the CFA model of pain following gene expression studies and connectivity mapping.

PubMed

Chang, Meiping; Smith, Sarah; Thorpe, Andrew; Barratt, Michael J; Karim, Farzana

2010-09-16

We have previously used the rat 4 day Complete Freund's Adjuvant (CFA) model to screen compounds with potential to reduce osteoarthritic pain. The aim of this study was to identify genes altered in this model of osteoarthritic pain and use this information to infer analgesic potential of compounds based on their own gene expression profiles using the Connectivity Map approach. Using microarrays, we identified differentially expressed genes in L4 and L5 dorsal root ganglia (DRG) from rats that had received intraplantar CFA for 4 days compared to matched, untreated control animals. Analysis of these data indicated that the two groups were distinguishable by differences in genes important in immune responses, nerve growth and regeneration. This list of differentially expressed genes defined a "CFA signature". We used the Connectivity Map approach to identify pharmacologic agents in the Broad Institute Build02 database that had gene expression signatures that were inversely related ('negatively connected') with our CFA signature. To test the predictive nature of the Connectivity Map methodology, we tested phenoxybenzamine (an alpha adrenergic receptor antagonist) - one of the most negatively connected compounds identified in this database - for analgesic activity in the CFA model. Our results indicate that at 10 mg/kg, phenoxybenzamine demonstrated analgesia comparable to that of Naproxen in this model. Evaluation of phenoxybenzamine-induced analgesia in the current study lends support to the utility of the Connectivity Map approach for identifying compounds with analgesic properties in the CFA model.

Evaluation of the novel avocado/soybean unsaponifiable Arthrocen to alter joint pain and inflammation in a rat model of osteoarthritis.

PubMed

Goudarzi, Ramin; Reid, Allison; McDougall, Jason J

2018-01-01

Avocado/soybean unsaponifiables such as Arthrocen have been reported to reduce cartilage catabolism and chondrocytic synthesis of inflammatory mediators associated with osteoarthritis (OA). While there is some clinical evidence that avocado/soybean unsaponifiables can reduce OA pain, no preclinical studies have corroborated this observation. The present study determined whether addition of an avocado/soybean unsaponifiable (Arthrocen) to the drinking water of OA rats reduced direct and referred joint pain. OA was induced in male Wistar rats by intra-articular injection of sodium monoiodoacetate (MIA: 0.3mg) and animals were allowed to recover for 14 days. Arthrocen was added to the drinking water which was available to animals ad libitum. On day 30, joint pain was assessed by dynamic incapacitance while referred pain was determined by von Frey hair algesiometry. The joint damage induced by MIA injection was severe and was consistent with end-stage OA. Arthrocen consumption (approximately 35 mg/day) attenuated the joint oedema associated with MIA injection. Hindlimb weight bearing also significantly improved in Arthrocen-treated rats (P<0.05); however, von Frey hair mechanosensitivity was unaffected by this treatment. These data indicate that Arthrocen has the potential to reduce joint inflammation and pain associated with end-stage OA.

The effects of pre-emptive low-dose X-ray irradiation on MIA induced inflammatory pain in rats

NASA Astrophysics Data System (ADS)

Hahm, Suk-Chan; Lee, Go-Eun; Kim, Eun-Hye; Kim, Junesun; Lee, Taewoong; Lee, Wonho

2013-07-01

This study was performed to determine the effect of pre-emptive low-dose irradiation on the development of inflammatory pain and to characterize the potential mechanisms underlying this effect in osteoarthritis (OA) animal model. Whole-body X-irradiations with 0.1, 0.5, 1 Gy or sham irradiations were performed for 3 days before the induction of ostearthritis with monosodium iodoacetate (MIA) (40 µl, in saline) into the right knee joint in male Sprague Dawley rats. Behavioral tests for arthritic pain including evoked and non-evoked pain were conducted before and after MIA injection and inducible nitric-oxide synthase (iNOS) expression level was measured by western blot. Low-dose radiation significantly prevented the development of mechanical allodynia and thermal hyperalgesia and reduction in weight bearing that is regarded as a behavioral signs of non-evoked pain following MIA injection. Low-dose radiation significantly inhibited the increase in iNOS expression after MIA injection in spinal L3-5 segments in rat. These data suggest that low-dose X-irradiation is able to prevent the development of arthritic pain through modulation of iNOS expression in the spinal cord dorsal horn. Thus, low-dose radiotherapy could be substituted in part for treatment with drugs for patients with chronic inflammatory disease in clinical setting.

Effect of A-317491 delivered by glycolipid-like polymer micelles on endometriosis pain.

PubMed

Yuan, Ming; Ding, Shaojie; Meng, Tingting; Lu, Binbin; Shao, Shihong; Zhang, Xinmei; Yuan, Hong; Hu, Fuqiang

2017-01-01

Endometriosis is a common gynecological disease with a lack of effective clinical treatment. Current therapy often results in endometriosis pain recurrence and serious side effects. P2X 3 receptor, an adenosine triphosphate (ATP)-gated ion channel, might be implicated in endometriosis pain. In this study, chitosan oligosaccharide-g-stearic acid (CSOSA) polymer micelles-coated nanostructured lipid carriers (NLCs) were developed as a novel delivery system for A-317491, a selective P2X 3 receptor antagonist for endometriosis pain therapy. A-317491-loaded NLC (NLC/A-317491) could be coated by CSOSA micelles to form CSOSA/NLC/A-317491 nanoparticles. Pheochromocytoma PC12 cells, which highly expressed P2X 3 receptors, were used as a cell model, and the CSOSA/NLC/A-317491 partly blocked the Ca 2+ influx induced by ATP stimulation. In nude mouse and rat endometriotic models, CSOSA/NLC could accumulate into endometriotic lesions after vein injection. In endometriotic rats, CSOSA/NLC/A-317491 reversed mechanical and heat hyperalgesia with long-term efficacy, which might be attributed to the massive CSOSA/NLC/A-317491 distribution in the endometriotic lesions. In conclusion, A-317491 delivered by CSOSA/NLC nanoparticles attenuated endometriosis pain in rats, and CSOSA/NLC/A-317491 could be used as an effective treatment strategy for P2X 3 -targeted therapy in endometriosis pain.

E3 Ubiquitin Ligase c-cbl Inhibits Microglia Activation After Chronic Constriction Injury.

PubMed

Xue, Pengfei; Liu, Xiaojuan; Shen, Yiming; Ju, Yuanyuan; Lu, Xiongsong; Zhang, Jinlong; Xu, Guanhua; Sun, Yuyu; Chen, Jiajia; Gu, Haiyan; Cui, Zhiming; Bao, Guofeng

2018-06-22

E3 ubiquitin ligase c-Caritas B cell lymphoma (c-cbl) is associated with negative regulation of receptor tyrosine kinases, signal transduction of antigens and cytokine receptors, and immune response. However, the expression and function of c-cbl in the regulation of neuropathic pain after chronic constriction injury (CCI) are unknown. In rat CCI model, c-cbl inhibited the activation of spinal cord microglia and the release of pro-inflammatory factors including tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β) and interleukin 6 (IL-6), which alleviated mechanical and heat pain through down-regulating extracellular signal-regulated kinase (ERK) pathway. Additionally, exogenous TNF-α inhibited c-cbl protein level vice versa. In the primary microglia transfected with c-cbl siRNA, when treated with TNF-α or TNF-α inhibitor, the corresponding secretion of IL-1β and IL-6 did not change. In summary, CCI down-regulated c-cbl expression and induced the activation of microglia, then activated microglia released inflammatory factors via ERK signaling to cause pain. Our data might supply a novel molecular target for the therapy of CCI-induced neuropathic pain.

The changing balance of brainstem–spinal cord modulation of pain processing over the first weeks of rat postnatal life

PubMed Central

Hathway, G J; Koch, S; Low, L; Fitzgerald, M

2009-01-01

Brainstem–spinal cord connections play an essential role in adult pain processing, and the modulation of spinal pain network excitability by brainstem nuclei is known to contribute to hyperalgesia and chronic pain. Less well understood is the role of descending brainstem pathways in young animals when pain networks are more excitable and exposure to injury and stress can lead to permanent modulation of pain processing. Here we show that up to postnatal day 21 (P21) in the rat, the rostroventral medulla of the brainstem (RVM) exclusively facilitates spinal pain transmission but that after this age (P28 to adult), the influence of the RVM shifts to biphasic facilitation and inhibition. Graded electrical microstimulation of the RVM at different postnatal ages revealed a robust shift in the balance of descending control of both spinal nociceptive flexion reflex EMG activity and individual dorsal horn neuron firing properties, from excitation to inhibition, beginning after P21. The shift in polarity of descending control was also observed following excitotoxic lesions of the RVM in adult and P21 rats. In adults, RVM lesions decreased behavioural mechanical sensory reflex thresholds, whereas the same lesion in P21 rats increased thresholds. These data demonstrate, for the first time, the changing postnatal influence of the RVM in spinal nociception and highlight the central role of descending brainstem control in the maturation of pain processing. PMID:19403624

Post-conditioning experience with acute or chronic inflammatory pain reduces contextual fear conditioning in the rat

PubMed Central

Johnston, Ian N.; Maier, Steven F.; Rudy, Jerry W.; Watkins, Linda R.

2017-01-01

There is evidence that pain can impact cognitive function in people. The present study evaluated whether Pavlovian fear conditioning in rats would be reduced if conditioning were followed by persistent inflammatory pain induced by a subcutaneous injection of dilute formalin or complete Freund's adjuvant (CFA) on the dorsal lumbar surface of the back. Formalin-induced pain specifically impaired contextual fear conditioning but not auditory cue conditioning (Experiment 1A). Moreover, formalin pain only impaired contextual fear conditioning if it was initiated within 1 h of conditioning and did not have a significant effect if initiated 2, 8 or 32 h after (Experiments 1A and 1B). Experiment 2 showed that formalin pain initiated after a session of context pre-exposure reduced the ability of that pre-exposure to facilitate contextual fear when the rat was limited to a brief exposure to the context during conditioning. Similar impairments in context- but not CS-fear conditioning were also observed if the rats received an immediate post-conditioning injection with CFA (Experiment 3). Finally, we confirmed that formalin and CFA injected s.c. on the back induced pain-indicative behaviours, hyperalgesia and allodynia with a similar timecourse to intraplantar injections (Experiment 4). These results suggest that persistent pain impairs learning in a hippocampus-dependent task, and may disrupt processes that encode experiences into long-term memory. PMID:21920390

Electrical peripheral nerve stimulation relieves bone cancer pain by inducing Arc protein expression in the spinal cord dorsal horn

PubMed Central

Sun, Ke-fu; Feng, Wan-wen; Liu, Yue-peng; Dong, Yan-bin; Gao, Li; Yang, Hui-lin

2018-01-01

Objective The analgesic effect on chronic pain of peripheral nerve stimulation (PNS) has been proven, but its underlying mechanism remains unknown. Therefore, this study aimed to assess the analgesic effect of PNS on bone cancer pain in a rat model and to explore the underlying mechanism. Materials and methods PNS on sciatic nerves with bipolar electrode was performed in both naïve and bone cancer pain model rats. Then, the protein levels of activity-regulated cytoskeleton-associated protein (Arc), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid–type glutamate receptor 1 (GluA1), and phosphate N-methyl-d-aspartic acid-type glutamate receptor subunit 2B (pGluNR2B) in spinal cord were evaluated by immunohistochemistry and Western blotting. Thermal paw withdraw latency and mechanical paw withdraw threshold were used to estimate the analgesic effect of PNS on bone cancer pain. Intrathecal administration of Arc shRNA was used to inhibit Arc expression in the spinal cord. Results PNS at 60 and 120 Hz for 20 min overtly induced Arc expression in the spinal cord, increased thermal pain thresholds in naïve rats, and relieved bone cancer pain; meanwhile, 10 Hz PNS did not achieve those results. In addition, PNS at 60 and 120 Hz also reduced the expression of GluA1, but not pGluNR2B, in the spinal cord. Finally, the anti-nociceptive effect and GluA1 downregulation induced by PNS were inhibited by intrathecal administration of Arc shRNA. Conclusion PNS (60 Hz, 0.3 mA) can relieve bone-cancer-induced allodynia and hyperalgesia by upregulating Arc protein expression and then by decreasing GluA1 transcription in the spinal cord dorsal horn. PMID:29606887

Evaluation of the novel avocado/soybean unsaponifiable Arthrocen to alter joint pain and inflammation in a rat model of osteoarthritis

PubMed Central

Goudarzi, Ramin; Reid, Allison

2018-01-01

Background Avocado/soybean unsaponifiables such as Arthrocen have been reported to reduce cartilage catabolism and chondrocytic synthesis of inflammatory mediators associated with osteoarthritis (OA). While there is some clinical evidence that avocado/soybean unsaponifiables can reduce OA pain, no preclinical studies have corroborated this observation. The present study determined whether addition of an avocado/soybean unsaponifiable (Arthrocen) to the drinking water of OA rats reduced direct and referred joint pain. Methods OA was induced in male Wistar rats by intra-articular injection of sodium monoiodoacetate (MIA: 0.3mg) and animals were allowed to recover for 14 days. Arthrocen was added to the drinking water which was available to animals ad libitum. On day 30, joint pain was assessed by dynamic incapacitance while referred pain was determined by von Frey hair algesiometry. Results The joint damage induced by MIA injection was severe and was consistent with end-stage OA. Arthrocen consumption (approximately 35 mg/day) attenuated the joint oedema associated with MIA injection. Hindlimb weight bearing also significantly improved in Arthrocen-treated rats (P<0.05); however, von Frey hair mechanosensitivity was unaffected by this treatment. Conclusions These data indicate that Arthrocen has the potential to reduce joint inflammation and pain associated with end-stage OA. PMID:29489828

Effect of the Combined Use of Tramadol and Milnacipran on Pain Threshold in an Animal Model of Fibromyalgia

PubMed Central

Song, Junhwa; Mun, Hyunil; Park, Keon Uk

2009-01-01

Background/Aims Acidic saline injections produce mechanical hyperresponsiveness in male Sprague-Dawley rats. We investigated the effect of milnacipran in conjunction with tramadol on the pain threshold in an acidic saline animal model of pain. Methods The left gastrocnemius muscle of 20 male rats was injected with 100 µL of saline at pH 4.0 under brief isoflurane anesthesia on days 0 and 5. Rats administered acidic saline injections were separated into four study subgroups. After determining the pre-drug pain threshold, rats were injected intraperitoneally with one of the following regimens; saline, milnacipran alone (60 mg/kg), milnacipran (40 mg/kg) plus tramadol (20 mg/kg), or milnacipran (40 mg/kg) plus tramadol (40 mg/kg). Paw withdrawal in response to pressure was measured at 30 min, 120 min, and 5 days after injection. Nociceptive thresholds, expressed in grams, were measured with a Dynamic Plantar Aesthesiometer (Ugo Basile, Italy) by applying increasing pressure to the right or left hind paw until the rat withdrew the paw. Results A potent antihyperalgesic effect was observed when tramadol and milnacipran were used in combination (injected paw, p=0.001; contralateral paw, p=0.012). This finding was observed only at 30 min after the combination treatment. Conclusions We observed potentiation of the antihyperalgesic effect when milnacipran and tramadol were administered in combination in an animal model of fibromyalgia. Further research is required to determine the efficacy of various combination treatments in fibromyalgia in humans. PMID:19543493

The effects of pressure on arthritic knees in a rat model of CFA-induced arthritis.

PubMed

Koo, Sung Tae; Lee, Chang-Hyung; Choi, Hyeunseok; Shin, Yong Il; Ha, Ki Tae; Ye, Hanna; Shim, Hyun Bo

2013-01-01

Pain is influenced by weather changes under certain circumstances, and inflammatory pain in animal models is ameliorated by pressure, but the underlying mechanism of atmospheric pressure has not been clearly elucidated. To examine the effect of pressure on pain in an arthritic animal model. Controlled animal study. Laboratory animal study. Following an injection of complete Freund's adjuvant (CFA) into one side of a knee joint, 32 rats were assigned randomly to 2 groups and either placed under 1 or 2.5 atmospheres absolute (ATA) in a hyperbaric chamber for 5 hours. The pain levels were assessed daily for up to 2 weeks post-injection to determine the changes in weight bearing (WB) of the affected limbs. In addition, the levels of gelatinase, MMP-2, and MMP-9 expression in the synovial fluids of the knees were analyzed. After arthritis induction, the rats in the 1 ATA group showed reduced WB of the affected limbs (< 10% of normal limbs). This reduction in WB peaked at 2 days after the injection and then decreased spontaneously. Nevertheless, the pain behavior lasted for more than 2 weeks. In the 2.5 ATA group, the WB was significantly better during the experiment.  The MMP-9/MMP-2 ratio increased at 7 and 14 days after the CFA injection in the 1 ATA group. However, repetitive exposure to 2.5 ATA significantly reduced this ratio in the 2.5 ATA group. Although a sufficient number of samples were used to support the hypothesis that high atmospheric pressure improves a painful condition in this study, an additional larger-scale study will be needed to confirm these findings. Exposure to elevated pressures appears to relieve arthritic pain for extended periods by reducing the inflammatory process and should be considered as a possible alternative pain-reducing therapy.

Magnesium sulfate reduces formalin-induced orofacial pain in rats with normal magnesium serum levels.

PubMed

Srebro, Dragana P; Vučković, Sonja M; Dožić, Ivan S; Dožić, Branko S; Savić Vujović, Katarina R; Milovanović, Aleksandar P; Karadžić, Branislav V; Prostran, Milica Š

2018-02-01

In humans, orofacial pain has a high prevalence and is often difficult to treat. Magnesium is an essential element in biological a system which controls the activity of many ion channels, neurotransmitters and enzymes. Magnesium produces an antinociceptive effect in neuropathic pain, while in inflammatory pain results are not consistent. We examined the effects of magnesium sulfate using the rat orofacial formalin test, a model of trigeminal pain. Male Wistar rats were injected with 1.5% formalin into the perinasal area, and the total time spent in pain-related behavior (face rubbing) was quantified. We also spectrophotometrically determined the concentration of magnesium and creatine kinase activity in blood serum. Magnesium sulfate administered subcutaneously (0.005-45mg/kg) produced significant antinociception in the second phase of the orofacial formalin test in rats at physiological serum concentration of magnesium. The effect was not dose-dependent. The maximum antinociceptive effect of magnesium sulfate was about 50% and was achieved at doses of 15 and 45mg/kg. Magnesium did not affect increase the levels of serum creatine kinase activity. Preemptive systemic administration of magnesium sulfate as the only drug can be used to prevent inflammatory pain in the orofacial region. Its analgesic effect is not associated with magnesium deficiency. Copyright © 2017 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Cerebrolysin Attenuates Heat Shock Protein (HSP 72 KD) Expression in the Rat Spinal Cord Following Morphine Dependence and Withdrawal: Possible New Therapy for Pain Management

PubMed Central

Sharma, Hari S; Ali, Syed F; Patnaik, Ranjana; Zimmermann-Meinzingen, Sibilla; Sharma, Aruna; Muresanu, Dafin F

2011-01-01

The possibility that pain perception and processing in the CNS results in cellular stress and may influence heat shock protein (HSP) expression was examined in a rat model of morphine dependence and withdrawal. Since activation of pain pathways result in exhaustion of growth factors, we examined the influence of cerebrolysin, a mixture of potent growth factors (BDNF, GDNF, NGF, CNTF etc,) on morphine induced HSP expression. Rats were administered morphine (10 mg/kg, s.c. /day) for 12 days and the spontaneous withdrawal symptoms were developed by cessation of the drug administration on day 13th that were prominent on day 14th and continued up to day 15th (24 to 72 h periods). In a separate group of rats, cerebrolysin was infused intravenously (5 ml/kg) once daily from day one until day 15th. In these animals, morphine dependence and withdrawal along with HSP immunoreactivity was examined using standard protocol. In untreated group mild HSP immunoreaction was observed during morphine tolerance, whereas massive upregulation of HSP was seen in CNS during withdrawal phase that correlated well with the withdrawal symptoms and neuronal damage. Pretreatment with cerebrolysin did not affect morphine tolerance but reduced the HSP expression during this phase. Furthermore, cerebrolysin reduced the withdrawal symptoms on day 14th to 15th. Taken together these observations suggest that cellular stress plays an important role in morphine induced pain pathology and exogenous supplement of growth factors, i.e. cerebrolysin attenuates HSP expression in the CNS and induce neuroprotection. This indicates a new therapeutic role of cerebrolysin in the pathophysiology of drugs of abuse, not reported earlier. PMID:21886595

Morphine-induced antinociception in the rat: supra-additive interactions with imidazoline I₂ receptor ligands.

PubMed

Li, Jun-Xu; Zhang, Yanan; Winter, Jerrold C

2011-11-01

Pain remains a significant clinical challenge and currently available analgesics are not adequate to meet clinical needs. Emerging evidence suggests the role of imidazoline I(2) receptors in pain modulation primarily from studies of the non-selective imidazoline receptor ligand, agmatine. However, little is known of the generality of the effect to selective I(2) receptor ligands. This study examined the antinociceptive effects of two selective I(2) receptor ligands 2-BFI and BU224 (>2000-fold selectivity for I(2) receptors over α(2) adrenoceptors) in a hypertonic (5%) saline-induced writhing test and analyzed their interaction with morphine using a dose-addition analysis. Morphine, 2-BFI and BU224 but not agmatine produced a dose-dependent antinociceptive effect. Both composite additive curve analyses and isobolographical plots revealed a supra-additive interaction between morphine and 2-BFI or BU224, whereas the interaction between 2-BFI and BU224 was additive. The antinociceptive effect of 2-BFI and BU224 was attenuated by the I(2) receptor antagonist/α(2) adrenoceptor antagonist idazoxan but not by the selective α(2) adrenoceptor antagonist yohimbine, suggesting an I(2) receptor-mediated mechanism. Agmatine enhanced the antinociceptive effect of morphine, 2-BFI and BU224 and the enhancement was prevented by yohimbine, suggesting that the effect was mediated by α(2) adrenoceptors. Taken together, these data represent the first report that selective I(2) receptor ligands have substantial antinociceptive activity and produce antinociceptive synergy with opioids in a rat model of acute pain. These data suggest that drugs acting on imidazoline I(2) receptors may be useful either alone or in combination with opioids for the treatment of pain. Copyright © 2011 Elsevier B.V. All rights reserved.

Moxibustion relieves visceral hyperalgesia via inhibition of transient receptor potential vanilloid 1 (TRPV1) and heat shock protein (HSP) 70 expression in rat bone marrow cells.

PubMed

Zou, Weiying; Lin, Hua; Liu, Wenwen; Yang, Bei; Wu, Lei; Duan, Limin; Ling, Ping; Zhu, Lingyan; Dai, Qun; Zhao, Lintong; Zou, Ting; Zhang, Dalei

2016-04-01

To investigate the effects of moxibustion on visceral hyperalgesia (VH) and bone marrow cell transient receptor potential vanilloid type 1 (TRPV1) and heat shock protein (HSP) 70 expression in a rat model of VH. Mechanical colorectal distension was performed to induce VH in neonatal Sprague-Dawley rats. Eight-week-old VH rats were treated with moxibustion at acupuncture point BL25 or an ipsilateral non-acupuncture point. Abdominal withdrawal reflex (AWR) scoring and pain threshold pressure assessment were performed before and after moxibustion treatment for 7 consecutive days. The expression of TRPV1 and HSP70 in bone marrow cells was quantified by real-time quantitative PCR. The expression of TRPV1 and HSP70 in bone marrow cells was increased in rats with VH. Moxibustion at BL25 significantly decreased AWR scores and increased pain threshold pressure in rats with VH. Furthermore, moxibustion at BL25 significantly inhibited the VH-induced increase in the expression of TRPV1 and HSP70 in bone marrow cells. The up-regulation of TRPV1 and HSP70 expression in bone marrow cells may be involved in visceral pain development and the analgesic effect of moxibustion on VH may be mediated through down-regulation of TRPV1 and HSP70 expression in bone marrow cells. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

P2Y12 receptor upregulation in satellite glial cells is involved in neuropathic pain induced by HIV glycoprotein 120 and 2',3'-dideoxycytidine.

PubMed

Yi, Zhihua; Xie, Lihui; Zhou, Congfa; Yuan, Huilong; Ouyang, Shuai; Fang, Zhi; Zhao, Shanhong; Jia, Tianyu; Zou, Lifang; Wang, Shouyu; Xue, Yun; Wu, Bing; Gao, Yun; Li, Guilin; Liu, Shuangmei; Xu, Hong; Xu, Changshui; Zhang, Chunping; Liang, Shangdong

2018-03-01

The direct neurotoxicity of HIV and neurotoxicity of combination antiretroviral therapy medications both contribute to the development of neuropathic pain. Activation of satellite glial cells (SGCs) in the dorsal root ganglia (DRG) plays a crucial role in mechanical and thermal hyperalgesia. The P2Y 12 receptor expressed in SGCs of the DRG is involved in pain transmission. In this study, we explored the role of the P2Y 12 receptor in neuropathic pain induced by HIV envelope glycoprotein 120 (gp120) combined with ddC (2',3'-dideoxycytidine). A rat model of gp120+ddC-induced neuropathic pain was used. Peripheral nerve exposure to HIV-gp120+ddC increased mechanical and thermal hyperalgesia in gp120+ddC-treated model rats. The gp120+ddC treatment increased expression of P2Y 12 receptor mRNA and protein in DRG SGCs. In primary cultured DRG SGCs treated with gp120+ddC, the levels of [Ca 2+ ] i activated by the P2Y 12 receptor agonist 2-(Methylthio) adenosine 5'-diphosphate trisodium salt (2-MeSADP) were significantly increased. P2Y 12 receptor shRNA treatment inhibited 2-MeSADP-induced [Ca 2+ ] i in primary cultured DRG SGCs treated with gp120+ddC. Intrathecal treatment with a shRNA against P2Y 12 receptor in DRG SGCs reduced the release of pro-inflammatory cytokines, decreased phosphorylation of p38 MAPK in the DRG of gp120+ddC-treated rats. Thus, downregulating the P2Y 12 receptor relieved mechanical and thermal hyperalgesia in gp120+ddC-treated rats.

Evidence for spinal N-methyl-d-aspartate receptor involvement in prolonged chemical nociception in the rat.

PubMed

Haley, Jane E; Dickenson, Anthony H

2016-08-15

We used in vivo electrophysiology and a model of more persistent nociceptive inputs to monitor spinal cord neuronal activity in anaesthetised rats to reveal the pharmacology of enhanced pain signalling. The study showed that all responses were blocked by non-selective antagonism of glutamate receptors but a selective and preferential role of the N-methyl-d-aspartate (NMDA) receptor in the prolonged plastic responses was clearly seen. The work lead to many publications, initially preclinical but increasingly from patient studies, showing the importance of the NMDA receptor in central sensitisation within the spinal cord and how this could relate to persistent pain states. This article is part of a Special Issue entitled SI:50th Anniversary Issue. Copyright © 2016 Elsevier B.V. All rights reserved.

Nonlinear Inverted-U Shaped Relationship between Aging and Epidermal Innervation in the Rat Plantar Hind Paw: a Laser Scanning Confocal Microscopy Study.

PubMed

Kaliappan, Sankaranarayanan; Simone, Donald A; Banik, Ratan K

2018-04-13

The under-reporting of pain and atypical manifestations of painful syndromes within the elderly population have been well-documented, however, the specific relationship between pain and aging remains ambiguous. Previous studies have reported degenerative changes in primary afferents with aging. In this study, we questioned whether there is any change in the density of primary afferent endings within the epidermis of aged animals. Rats were categorically assessed in four age groups, each representing a key developmental stage across their life span: juvenile (2 months); adult (7 months); aged (18 months); and senescent (24-26 months). The plantar hind paw skin was removed, post-fixed, cut, and immunostained for protein gene product 9.5 and type IV collagen. Rats in the adult aged groups had significantly increased epidermal nerve densities and total lengths of immunoreactive nerve fibers, compared to both juvenile and senescent rats. However, the paw withdrawal thresholds to punctate mechanical stimulation progressively increased with age, and did not exhibit a clear relationship with epidermal innervation. We conclude a non-linear, inverted-U shaped relationship between rat plantar epidermal nerve density with aging, which does not correlate with mechanically-induced paw withdrawal behaviors. This article presents age-related decreased epidermal innervation in rat hind paw skin, which partly explains mechanisms underlying decreased pain sensitivity in aged subjects. The article may help clinicians to understand that any compromise of pain-sensing pathway can lead to under-reporting of pain, inadequate analgesia, and slower recovery from a painful condition. Copyright © 2018. Published by Elsevier Inc.

Neuropathic pain in experimental autoimmune neuritis is associated with altered electrophysiological properties of nociceptive DRG neurons.

PubMed

Taha, Omneya; Opitz, Thoralf; Mueller, Marcus; Pitsch, Julika; Becker, Albert; Evert, Bernd Oliver; Beck, Heinz; Jeub, Monika

2017-11-01

Guillain-Barré syndrome (GBS) is an acute, immune-mediated polyradiculoneuropathy characterized by rapidly progressive paresis and sensory disturbances. Moderate to severe and often intractable neuropathic pain is a common symptom of GBS, but its underlying mechanisms are unknown. Pathology of GBS is classically attributed to demyelination of large, myelinated peripheral fibers. However, there is increasing evidence that neuropathic pain in GBS is associated with impaired function of small, unmyelinated, nociceptive fibers. We therefore examined the functional properties of small DRG neurons, the somata of nociceptive fibers, in a rat model of GBS (experimental autoimmune neuritis=EAN). EAN rats developed behavioral signs of neuropathic pain. This was accompanied by a significant shortening of action potentials due to a more rapid repolarization and an increase in repetitive firing in a subgroup of capsaicin-responsive DRG neurons. Na + current measurements revealed a significant increase of the fast TTX-sensitive current and a reduction of the persistent TTX-sensitive current component. These changes of Na + currents may account for the significant decrease in AP duration leading to an overall increase in excitability and are therefore possibly directly linked to pathological pain behavior. Thus, like in other animal models of neuropathic and inflammatory pain, Na + channels seem to be crucially involved in the pathology of GBS and may constitute promising targets for pain modulating pharmaceuticals. Copyright © 2017 Elsevier Inc. All rights reserved.

Antinociceptive effects of hydroalcoholic extract from Euterpe oleracea Mart. (Açaí) in a rodent model of acute and neuropathic pain.

PubMed

Sudo, Roberto T; Neto, Miguel L; Monteiro, Carlos E S; Amaral, Rachel V; Resende, Ângela C; Souza, Pergentino J C; Zapata-Sudo, Gisele; Moura, Roberto S

2015-07-02

Plants rich in flavonoids, such as açaí (Euterpe oleraceae Mart.), can induce antinociception in experimental animals. Here, we tested an extract obtained from the stones of açaí fruits (açaí stone extract, ASE), a native plant from the Amazon region of Brazil, in models of acute/inflammatory and chronic pain. Antinociceptive effects of ASE were evaluated in the hot plate, formalin, acetic acid writhing, carrageenan, and neuropathic pain models, as well as in thermal hyperalgesia and mechanical allodynia models induced by spinal nerve ligation. Antinociceptive activities were modulated by the administration of cholinergic, adrenergic, opioid, and L-arginine-NO antagonists. Oral administration of ASE (30, 100, or 300 mg.kg(-1)) dose-dependently reduced nociceptive responses to acute/inflammatory pain in mice, including thermal hyperalgesia, acetic acid-induced writhing, and carrageenan-induced thermal hyperalgesia. Moreover, ASE reduced the neurogenic and inflammatory phases after intraplantar injection of formalin in mice. The antinociceptive effect of ASE (100 mg · kg(-1)) in a hot plate protocol, was inhibited by pre-treatment with naloxone (1 mg · kg(-1)), atropine (2 mg · kg(-1)), yohimbine (5 mg · kg(-1)), or L-NAME (30 mg · kg(-1)). Furthermore, ASE prevented chronic pain in a rat spinal nerve ligation model, including thermal hyperalgesia and mechanical allodynia. ASE showed significant antinociceptive effect via a multifactorial mechanism of action, indicating that the extract may be useful in the development of new analgesic drugs.

Rat experimental model of myocardial ischemia/reperfusion injury: an ethical approach to set up the analgesic management of acute post-surgical pain.

PubMed

Ciuffreda, Maria Chiara; Tolva, Valerio; Casana, Renato; Gnecchi, Massimiliano; Vanoli, Emilio; Spazzolini, Carla; Roughan, John; Calvillo, Laura

2014-01-01

During the past 30 years, myocardial ischemia/reperfusion injury in rodents became one of the most commonly used model in cardiovascular research. Appropriate pain-prevention appears critical since it may influence the outcome and the results obtained with this model. However, there are no proper guidelines for pain management in rats undergoing thoracic surgery. Accordingly, we evaluated three analgesic regimens in cardiac ischemia/reperfusion injury. This study was strongly focused on 3R's ethic principles, in particular the principle of Reduction. Rats undergoing surgery were treated with pre-surgical tramadol (45 mg/kg intra-peritoneal), or carprofen (5 mg/kg sub-cutaneous), or with pre-surgical administration of carprofen followed by 2 post-surgery tramadol injections (multi-modal group). We assessed behavioral signs of pain and made a subjective evaluation of stress and suffering one and two hours after surgery. Multi-modal treatment significantly reduced the number of signs of pain compared to carprofen alone at both the first hour (61±42 vs 123±47; p<0.05) and the second hour (43±21 vs 74±24; p<0.05) post-surgery. Tramadol alone appeared as effective as multi-modal treatment during the first hour, but signs of pain significantly increased one hour later (from 66±72 to 151±86, p<0.05). Carprofen alone was more effective at the second hour post-surgery when signs of pain reduced to 74±24 from 113±40 in the first hour (p<0.05). Stress behaviors during the second hour were observed in only 20% of rats in the multimodal group compared to 75% and 86% in the carprofen and tramadol groups, respectively (p<0.05). Multi-modal treatment with carprofen and tramadol was more effective in preventing pain during the second hour after surgery compared with both tramadol or carprofen. Our results suggest that the combination of carprofen and tramadol represent the best therapy to prevent animal pain after myocardial ischemia/reperfusion. We obtained our results accordingly with the ethical principle of Reduction.

Rat Experimental Model of Myocardial Ischemia/Reperfusion Injury: An Ethical Approach to Set up the Analgesic Management of Acute Post-Surgical Pain

PubMed Central

Ciuffreda, Maria Chiara; Tolva, Valerio; Casana, Renato; Gnecchi, Massimiliano; Vanoli, Emilio; Spazzolini, Carla; Roughan, John; Calvillo, Laura

2014-01-01

Rationale During the past 30 years, myocardial ischemia/reperfusion injury in rodents became one of the most commonly used model in cardiovascular research. Appropriate pain-prevention appears critical since it may influence the outcome and the results obtained with this model. However, there are no proper guidelines for pain management in rats undergoing thoracic surgery. Accordingly, we evaluated three analgesic regimens in cardiac ischemia/reperfusion injury. This study was strongly focused on 3R’s ethic principles, in particular the principle of Reduction. Methods Rats undergoing surgery were treated with pre-surgical tramadol (45 mg/kg intra-peritoneal), or carprofen (5 mg/kg sub-cutaneous), or with pre-surgical administration of carprofen followed by 2 post-surgery tramadol injections (multi-modal group). We assessed behavioral signs of pain and made a subjective evaluation of stress and suffering one and two hours after surgery. Results Multi-modal treatment significantly reduced the number of signs of pain compared to carprofen alone at both the first hour (61±42 vs 123±47; p<0.05) and the second hour (43±21 vs 74±24; p<0.05) post-surgery. Tramadol alone appeared as effective as multi-modal treatment during the first hour, but signs of pain significantly increased one hour later (from 66±72 to 151±86, p<0.05). Carprofen alone was more effective at the second hour post-surgery when signs of pain reduced to 74±24 from 113±40 in the first hour (p<0.05). Stress behaviors during the second hour were observed in only 20% of rats in the multimodal group compared to 75% and 86% in the carprofen and tramadol groups, respectively (p<0.05). Conclusions Multi-modal treatment with carprofen and tramadol was more effective in preventing pain during the second hour after surgery compared with both tramadol or carprofen. Our results suggest that the combination of carprofen and tramadol represent the best therapy to prevent animal pain after myocardial ischemia/reperfusion. We obtained our results accordingly with the ethical principle of Reduction. PMID:24756074

Nav1.7-A1632G Mutation from a Family with Inherited Erythromelalgia: Enhanced Firing of Dorsal Root Ganglia Neurons Evoked by Thermal Stimuli.

PubMed

Yang, Yang; Huang, Jianying; Mis, Malgorzata A; Estacion, Mark; Macala, Lawrence; Shah, Palak; Schulman, Betsy R; Horton, Daniel B; Dib-Hajj, Sulayman D; Waxman, Stephen G

2016-07-13

Voltage-gated sodium channel Nav1.7 is a central player in human pain. Mutations in Nav1.7 produce several pain syndromes, including inherited erythromelalgia (IEM), a disorder in which gain-of-function mutations render dorsal root ganglia (DRG) neurons hyperexcitable. Although patients with IEM suffer from episodes of intense burning pain triggered by warmth, the effects of increased temperature on DRG neurons expressing mutant Nav1.7 channels have not been well documented. Here, using structural modeling, voltage-clamp, current-clamp, and multielectrode array recordings, we have studied a newly identified Nav1.7 mutation, Ala1632Gly, from a multigeneration family with IEM. Structural modeling suggests that Ala1632 is a molecular hinge and that the Ala1632Gly mutation may affect channel gating. Voltage-clamp recordings revealed that the Nav1.7-A1632G mutation hyperpolarizes activation and depolarizes fast-inactivation, both gain-of-function attributes at the channel level. Whole-cell current-clamp recordings demonstrated increased spontaneous firing, lower current threshold, and enhanced evoked firing in rat DRG neurons expressing Nav1.7-A1632G mutant channels. Multielectrode array recordings further revealed that intact rat DRG neurons expressing Nav1.7-A1632G mutant channels are more active than those expressing Nav1.7 WT channels. We also showed that physiologically relevant thermal stimuli markedly increase the mean firing frequencies and the number of active rat DRG neurons expressing Nav1.7-A1632G mutant channels, whereas the same thermal stimuli only increase these parameters slightly in rat DRG neurons expressing Nav1.7 WT channels. The response of DRG neurons expressing Nav1.7-A1632G mutant channels upon increase in temperature suggests a cellular basis for warmth-triggered pain in IEM. Inherited erythromelalgia (IEM), a severe pain syndrome characterized by episodes of intense burning pain triggered by warmth, is caused by mutations in sodium channel Nav1.7, which are preferentially expressed in sensory and sympathetic neurons. More than 20 gain-of-function Nav1.7 mutations have been identified from IEM patients, but the question of how warmth triggers episodes of pain in IEM has not been well addressed. Combining multielectrode array, voltage-clamp, and current-clamp recordings, we assessed a newly identified IEM mutation (Nav1.7-A1632G) from a multigeneration family. Our data demonstrate gain-of-function attributes at the channel level and differential effects of physiologically relevant thermal stimuli on the excitability of DRG neurons expressing mutant and WT Nav1.7 channels, suggesting a cellular mechanism for warmth-triggered pain episodes in IEM patients. Copyright © 2016 the authors 0270-6474/16/367512-12$15.00/0.

Swimming Training Reduces Neuroma Pain by Regulating Neurotrophins

PubMed Central

TIAN, JINGE; YU, TINGTING; XU, YONGMING; PU, SHAOFENG; LV, YINGYING; ZHANG, XIN; DU, DONGPING

2018-01-01

ABSTRACT Introduction Neuroma formation after peripheral nerve transection leads to severe neuropathic pain in amputees. Previous studies suggested that physical exercise could bring beneficial effect on alleviating neuropathic pain. However, the effect of exercise on neuroma pain still remained unclear. In addition, long-term exercise can affect the expression of neurotrophins (NT), such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), which play key roles in nociceptor sensitization and nerve sprouting after nerve injury. Here, we investigated whether long-term swimming exercise could relieve neuroma pain by modulating NT expression. Methods We used a tibial neuroma transposition (TNT) rat model to mimic neuroma pain. After TNT surgery, rats performed swimming exercise for 5 wk. Neuroma pain and tactile sensitivities were detected using von Frey filaments. Immunofluorescence was applied to analyze neuroma formation. NGF and BDNF expressions in peripheral neuroma, dorsal root ganglion, and the spinal cord were measured using enzyme-linked immunosorbent assay and Western blotting. Results TNT led to neuroma formation, induced neuroma pain, and mechanical allodynia in hind paw. Five-week swimming exercise inhibited neuroma formation and relieved mechanical allodynia in the hind paw and neuroma pain in the lateral ankle. The analgesic effect lasted for at least 1 wk, even when the exercise ceased. TNT elevated the expressions of BDNF and NGF in peripheral neuroma, dorsal root ganglion, and the spinal cord to different extents. Swimming also decreased the elevation of NT expression. Conclusions Swimming exercise not only inhibits neuroma formation induced by nerve transection but also relieves pain behavior. These effects might be associated with the modulation of NT. PMID:28846565

Effects of fentanyl on pain and motor behaviors following a collagenase-induced intracerebral hemorrhage in rats

PubMed Central

Saine, Laurence; Hélie, Pierre; Vachon, Pascal

2016-01-01

Purpose Intracerebral hemorrhage (IH) and cephalalgia are common consequences of traumatic brain injury. One of the primary obstacles for patient recovery is the paucity of treatments to support an appropriate analgesic protocol. The present study aimed to assess pain and motor behaviors following different doses of fentanyl on a rat model of IH. Methods Twenty-one male Sprague Dawley rats underwent a stereotaxic surgery to produce a collagenase-induced IH in the right caudoputamen nucleus. The control group (n=6) received saline subcutaneously (SC), and experimental groups received either 5 (n=6), 10 (n=6), or 20 (n=3) µg/kg of fentanyl SC, 2 hours following surgery and on 2 subsequent days. Only 3 animals received 20 µg/kg because this dose caused catalepsy for 15–20 minutes following the injection. The rat grimace scale, a neurological examination, balance beam test, and rotarod test were performed for 5 consecutive days postoperatively to evaluate pain and motor performance. At the end of the experimentation, the brains were evaluated to determine hematoma volume, and the number of reactive astrocytes and necrotic neurons. Results When compared to controls, the grimace scale showed that 5 µg/kg fentanyl significantly alleviated pain on day 2 only (P<0.01) and that 10 µg/kg alleviated pain on days 1 (P<0.01), 2 (P<0.001), and 3 (P<0.01). For the rotarod test, only the 10 µg/kg group showed significant decreases in performance on days 5 (P<0.05) and 6 (P<0.02). The neurological examination was not significantly different between the groups, but only the hopping test showed poor recuperation for the 5 and 10 µg/kg fentanyl group when compared to saline (P<0.01). No differences were found between the groups for the balance beam test, the histopathological results. Conclusion Fentanyl, at a dose of 10 µg/kg SC, provides substantial analgesia following a collagenase-induced IH in rats; however, it can alter motor performance following analgesic treatments. PMID:27895509

The synthetic cannabinoid WIN55,212-2 attenuates hyperalgesia and allodynia in a rat model of neuropathic pain

PubMed Central

Bridges, Daniel; Ahmad, Kamran; Rice, Andrew S C

2001-01-01

The analgesic properties of the synthetic cannabinoid WIN55,212-2 were investigated in a model of neuropathic pain. In male Wistar rats, bilateral hind limb withdrawal thresholds to cold, mechanical and noxious thermal stimuli were measured. Following this, unilateral L5 spinal nerve ligation was performed. Seven days later, sensory thresholds were reassessed and the development of allodynia to cold and mechanical stimuli and hyperalgesia to a noxious thermal stimulus confirmed.The effect of WIN55,212-2 (0.1 – 5.0 mg kg−1, i.p.) on the signs of neuropathy was then determined; there was a dose related reversal of all three signs of painful neuropathy at doses which did not generally alter sensory thresholds in the contralateral unligated limb. This effect was prevented by co-administration of the CB1 receptor antagonist SR141716a, but not by co-administration of the CB2 receptor antagonist SR144528, suggesting this action of WIN55,212-2 is mediated via the CB1 receptor. Administration of SR141716a alone had no affect on the observed allodynia and hyperalgesia, which does not support the concept of an endogenous analgesic tone.These data indicate that cannabinoids may have therapeutic potential in neuropathic pain, and that this effect is mediated through the CB1 receptor. PMID:11399676

Swimming Training Reduces Neuroma Pain by Regulating Neurotrophins.

PubMed

Tian, Jinge; Yu, Tingting; Xu, Yongming; Pu, Shaofeng; Lv, Yingying; Zhang, Xin; DU, Dongping

2018-01-01

Neuroma formation after peripheral nerve transection leads to severe neuropathic pain in amputees. Previous studies suggested that physical exercise could bring beneficial effect on alleviating neuropathic pain. However, the effect of exercise on neuroma pain still remained unclear. In addition, long-term exercise can affect the expression of neurotrophins (NT), such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), which play key roles in nociceptor sensitization and nerve sprouting after nerve injury. Here, we investigated whether long-term swimming exercise could relieve neuroma pain by modulating NT expression. We used a tibial neuroma transposition (TNT) rat model to mimic neuroma pain. After TNT surgery, rats performed swimming exercise for 5 wk. Neuroma pain and tactile sensitivities were detected using von Frey filaments. Immunofluorescence was applied to analyze neuroma formation. NGF and BDNF expressions in peripheral neuroma, dorsal root ganglion, and the spinal cord were measured using enzyme-linked immunosorbent assay and Western blotting. TNT led to neuroma formation, induced neuroma pain, and mechanical allodynia in hind paw. Five-week swimming exercise inhibited neuroma formation and relieved mechanical allodynia in the hind paw and neuroma pain in the lateral ankle. The analgesic effect lasted for at least 1 wk, even when the exercise ceased. TNT elevated the expressions of BDNF and NGF in peripheral neuroma, dorsal root ganglion, and the spinal cord to different extents. Swimming also decreased the elevation of NT expression. Swimming exercise not only inhibits neuroma formation induced by nerve transection but also relieves pain behavior. These effects might be associated with the modulation of NT.

Lentiviral-mediated targeted NF-kappaB blockade in dorsal spinal cord glia attenuates sciatic nerve injury-induced neuropathic pain in the rat.

PubMed

Meunier, Alice; Latrémolière, Alban; Dominguez, Elisa; Mauborgne, Annie; Philippe, Stéphanie; Hamon, Michel; Mallet, Jacques; Benoliel, Jean-Jacques; Pohl, Michel

2007-04-01

Neuropathic pain developing after peripheral nerve injury is associated with altered neuronal and glial cell functions in the spinal cord. Activated glia produces algogenic mediators, exacerbating pain. Among the different intracellular pathways possibly involved in the modified glial function, the nuclear factor kappaB (NF-kappaB) system is of particular interest, as numerous genes encoding inflammation- and pain-related molecules are controlled by this transcription factor. NF-kappaB is a pleiotropic factor also involved in central nervous system homeostasy. To study its role in chronic pain, it is thus essential to inhibit the NF-kappaB pathway selectively in activated spinal glial cells. Here, we show that when restricted to spinal cord and targeted to glial cells, lentiviral vector-mediated delivery of NF-kappaB super- repressor IkappaBalpha resulted in an inhibition of the NF-kappaB pathway activated in the rat spinal cord after sciatic nerve injury (chronic constriction injury, CCI). Concomitantly, IkappaBalpha overproduction prevented the enhanced expression of interleukin-6 and of inducible nitric oxide synthase associated with chronic constriction injury and resulted in prolonged antihyperalgesic and antiallodynic effects. These data show that targeted blockade of NF-kappaB activity in spinal glia efficiently alleviates pain behavior in CCI rats, demonstrating the active participation of the glial NF-kappaB pathway in the development of neuropathic pain after peripheral nerve injury.

The conduction block produced by oxcarbazepine in the isolated rat sciatic nerve: a comparison with lamotrigine.

PubMed

Guven, Mustafa; Kahraman, Ibrahim; Koc, Filiz; Bozdemir, Hacer; Sarica, Yakup; Gunay, Ismail

2011-01-01

Oxcarbazepine is an antiepileptic drug widely used for the treatment of neuropathic pain. In the present study, the effects of oxcarbazepine and lamotrigine on conduction properties in the rat sciatic nerves were examined. The experiments were conducted with in vitro sucrose-gap technique on the isolated wistar rat sciatic nerves. The compound action potentials were obtained by tonic (single) and phasic (10, 40, and 100 Hz) stimulation. Oxcarbazepine produced a significant concentration- and frequency-dependent reduction in the compound action potential amplitude. When the two drugs were applied at concentrations that produced equal levels of tonic (i.e., non-frequency-dependent) conduction block, oxcarbazepine produced the greatest phasic (i.e., frequency-dependent) conduction block, followed by lamotrigine. Oxcarbazepine and lamotrigine reduced the 4-aminopyridine-induced amplitude of delayed depolarization; however, oxcarbazepine had a significantly greater effect than lamotrigine. These results suggest that oxcarbazepine produces more potent frequency-dependent conduction block than lamotrigine, and suppresses the delayed depolarization which contributes to sensory signaling and may play a role in neuropathic pain. The findings provide insight into the mechanisms of action of oxcarbazepine and lamotrigine and may help in the development of novel therapies for neuropathic pain.

The effects of opioid receptor antagonists on electroacupuncture-produced anti-allodynia/hyperalgesia in rats with paclitaxel-evoked peripheral neuropathy.

PubMed

Meng, Xianze; Zhang, Yu; Li, Aihui; Xin, Jiajia; Lao, Lixing; Ren, Ke; Berman, Brian M; Tan, Ming; Zhang, Rui-Xin

2011-09-26

Research supports the effectiveness of acupuncture for conditions such as chronic low back and knee pain. In a five-patient pilot study the modality also improved the symptoms of chemotherapy-induced neuropathic pain. Using an established rat model of paclitaxel-induced peripheral neuropathy, we evaluated the effect of electroacupuncture (EA) on paclitaxel-induced hyperalgesia and allodynia that has not been studied in an animal model. We hypothesize that EA would relieve the paclitaxel-induced mechanical allodynia and hyperalgesia, which was assessed 30 min after EA using von Frey filaments. Beginning on day 13, the response frequency to von Frey filaments (4-15 g) was significantly increased in paclitaxel-injected rats compared to those injected with vehicle. EA at 10 Hz significantly (P<0.05) decreased response frequency at 4-15 g compared to sham EA; EA at 100 Hz only decreased response frequency at 15 g stimulation. Compared to sham EA plus vehicle, EA at 10 Hz plus either a μ, δ, or κ opioid receptor antagonist did not significantly decrease mechanical response frequency, indicating that all three antagonists blocked EA inhibition of allodynia and hyperalgesia. Since we previously demonstrated that μ and δ but not κ opioid receptors affect EA anti-hyperalgesia in an inflammatory pain model, these data show that EA inhibits pain through different opioid receptors under varying conditions. Our data indicate that EA at 10 Hz inhibits mechanical allodynia/hyperalgesia more potently than does EA at 100 Hz. Thus, EA significantly inhibits paclitaxel-induced allodynia/hyperalgesia through spinal opioid receptors, and EA may be a useful complementary treatment for neuropathic pain patients. Copyright © 2011 Elsevier B.V. All rights reserved.

Antinociceptive interaction between spinal clonidine and lidocaine in the rat formalin test: an isobolographic analysis.

PubMed

Hao, S; Takahata, O; Iwasaki, H

2001-03-01

Clinical and basic science studies suggest that spinal alpha-2-adrenergic receptor agonists and local anesthetics produce analgesia, but interaction between alpha-2-adrenergic receptor agonists and local anesthetics in the persistent pain model has not been examined. In the present study, using isobolographic analysis, we investigated the antinociceptive interaction of intrathecal clonidine and lidocaine in the rat formalin test. Sprague-Dawley rats were implanted with chronic lumbar intrathecal catheters, and were tested for paw flinch by formalin injection. Biphasic painful behavior was counted. Intrathecal clonidine (3-12 nmol) was administered 15 min before formalin, and intrathecal lidocaine (375-1850 nmol) was administered 5 min before formalin. To examine the interaction of intrathecal clonidine and lidocaine, an isobolographic design was used. Spinal administration of clonidine produced dose-dependent suppression of the biphasic responses in the formalin test. Spinal lidocaine resulted in dose-dependent transient motor dysfunction and the motor dysfunction recovered to normal at 10-15 min after administration. Spinal lidocaine produced dose-dependent suppression of phase-2 activity in the formalin test. Isobolographic analysis showed that the combination of intrathecal clonidine and lidocaine synergistically reduced Phase-2 activity. We conclude that intrathecal clonidine synergistically interacts with lidocaine in reducing the nociceptive response in the formalin test. Preformalin administration of intrathecal clonidine and lidocaine dose-dependently produced antinociception in the formalin test. The combination of clonidine and lidocaine, synergistically produced suppression of nociceptive response in the persistent pain model.

Effects of XIST/miR-137 axis on neuropathic pain by targeting TNFAIP1 in a rat model.

PubMed

Zhao, Ying; Li, Sen; Xia, Nin; Shi, Yan; Zhao, Chang-Ming

2018-05-01

Non-coding RNAs have been reported to participate in the pathophysiology of neuropathic pain. The objective of our study was to investigate the biological role of XIST in neuropathic pain development. In our study, we identify and validate that lncRNA XIST was markedly increased and miR-137 was significantly decreased in chronic constriction injury (CCI) rats. XIST silencing alleviated pain behaviors including both mechanical and thermal hyperalgesia in the CCI rats. XIST was predicted to interact with miR-137 by bioinformatics technology and dual-luciferase reporter assays confirmed the correlation between XIST and miR-137. miR-137 was negatively modulated by XIST and upregulation of miR-137 greatly reduced neuropathic pain development in CCI rats. Moreover, we observed that tumor necrosis factor alpha-induced protein 1 (TNFAIP1) was enhanced in CCI rats and 3'-untranslated region (UTR) of TNFAIP1 was exhibited to be a target of miR-137 by bioinformatics prediction. TNFAIP1 can act as a crucial inflammation regulator by activating NF-kB activity. Overexpression of miR-137 significantly suppressed TNFAIP1 both in vitro and in vivo. Furthermore, upregulation of XIST reversed the inhibitory role of miR-137 in neuropathic pain development by inhibiting TNFAIP1. In conclusion, our current study indicates that XIST can positively regulate neuropathic pain in rats through regulating the expression of miR-137 and TNFAIP1. Our results imply that XIST/miR-137/TNFAIP1 axis may serve as a novel therapeutic target in neuropathic pain. © 2017 Wiley Periodicals, Inc.

Up-Regulation of the Biosynthesis and Release of Substance P through Wnt/β-Catenin Signaling Pathway in Rat Dorsal Root Ganglion Cells.

PubMed

Li, Yu-Sang; Xi, Yang; Li, Xiao-Jun; Leng, Chang-Long; Jia, Mei-Mei; Zhang, Wei Kevin; Tang, He-Bin

2015-01-01

To examine regulatory effects of β-catenin on the biosynthesis and release of substance P, a rat chronic constriction injury (CCI) model and a rat dorsal root ganglion (DRG) cell culture model were used in the present study. The CCI treatment significantly induced the overall expression of β-catenin (158 ± 6% of sham) in the ipsilateral L5 DRGs in comparison with the sham group (109 ± 4% of sham). The CCI-induced aberrant expression of β-catenin was significantly attenuated by oral administration of diclofenac (119 ± 6% of the sham value; 10 mg/kg). Importantly, aberrant nuclear accumulation of β-catenin in cultured DRG cells resulted in up-regulation of the PPT-A mRNA expression and the substance P release. The up-regulation of both the PPT-A mRNA expression and the substance P release by either a GSK-3β inhibitor TWS119 (10 μM) or a Wnt signaling agonist Wnt-3a (100 ng/ml) were significantly abolished by an inhibitor of cyclooxygenase-2 (COX-2; NS-398, 1 μM). Collectively, these data suggest that nociceptive input-activated β-catenin signaling plays an important role in regulating the biosynthesis and release of substance P, which may contribute to the inflammation responses related to chronic pain.

Anti-nociceptive effect of dexmedetomidine in a rat model of monoarthritis via suppression of the TLR4/NF-κB p65 pathway

PubMed Central

Ji, Dong; Zhou, Yalan; Li, Shuangshuang; Li, Dai; Chen, Hui; Xiong, Yuanchang; Zhang, Yuqiu; Xu, Hua

2017-01-01

As a therapeutic target for neuropathic pain, the anti-nociceptive effects of α 2-adrenoceptors (α2AR) have attracted attention. Dexmedetomidine (DEX), a potent and highly selective α2AR agonist, has exhibited significant analgesic effects in neuropathic pain, but the underlying mechanism has remained elusive. The present study investigated the effect of DEX on Toll-like receptor (TLR)4 and nuclear factor (NF)-κB p65 expression, as well as the production of pro-inflammatory cytokines. The rat monoarthritis (MA) model was induced by intra-articular injection of complete Freund's adjuvant (CFA) at the ankle joint. After induction of MA, the rats were intrathecally treated with normal saline or DEX (2.5 µg) for 3 consecutive days. The concentration of interleukin-1β and −6 as well as tumor necrosis factor-α was examined by ELISA. The expression levels of TLR4 and NF-κB p65 were determined by western blot analysis and immunohistochemistry. The results indicated that the pro-inflammatory cytokines TLR4 and NF-κB p65 were significantly upregulated in MA rats. DEX treatment markedly reduced mechanical and thermal hyperalgesia, suppressed MA-induced elevation of the pro-inflammatory cytokines and inhibited the TLR4/NF-κB p65 pathway, while these effects were blocked by pre-treatment with the selective α2AR antagonist BRL44408 (15 µg) at 30 min prior to CFA injection. These results suggested that DEX has an anti-nociceptive effect via suppressing the TLR4/NF-κB p65 pathway. PMID:29201195

Pulsed magnetic field enhances therapeutic efficiency of mesenchymal stem cells in chronic neuropathic pain model.

PubMed

Mert, Tufan; Kurt, Akif Hakan; Altun, İdiris; Celik, Ahmet; Baran, Furkan; Gunay, Ismail

2017-05-01

Cell-based or magnetic field therapies as alternative approaches to pain management have been tested in several experimental pain models. The aim of this study therefore was to investigate the actions of the cell-based therapy (adipose tissue derived mesenchymal stem cells; ADMSC) or pulsed magnetic field (PMF) therapy and magneto-cell therapy (combination of ADMSC and PMF) in chronic constriction nerve injury model (CCI). The actions of individual ADMSC (route dependent [systemic or local], time-dependent [a day or a week after surgery]), or PMF and their combination (magneto-cell) therapies on hyperalgesia and allodynia were investigated by using thermal plantar test and a dynamic plantar aesthesiometer, respectively. In addition, various cytokine levels (IL-1β, IL-6, and IL-10) of rat sciatic nerve after CCI were analyzed. Following the CCI, both latency and threshold significantly decreased. ADMSC or PMF significantly increased latencies and thresholds. The combination of ADMSC with PMF even more significantly increased latency and threshold when compared with ADMSC alone. However, ADMSC-induced decrease in pro-inflammatory or increase in anti-inflammatory cytokines levels were partially prevented by PMF treatments. Present findings may suggest that both cell-based and magnetic therapies can effectively attenuate chronic neuropathic pain symptoms. Combined magneto-cell therapy may also efficiently reverse neuropathic signs. Bioelectromagnetics. 38:255-264, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Meningeal norepinephrine produces headache behaviors in rats via actions both on dural afferents and fibroblasts.

PubMed

Wei, Xiaomei; Yan, Jin; Tillu, Dipti; Asiedu, Marina; Weinstein, Nicole; Melemedjian, Ohannes; Price, Theodore; Dussor, Gregory

2015-10-01

Stress is commonly reported to contribute to migraine although mechanisms by which this may occur are not fully known. The purpose of these studies was to examine whether norepinephrine (NE), the primary sympathetic efferent transmitter, acts on processes in the meninges that may contribute to the pain of migraine. NE was applied to rat dura using a behavioral model of headache. Primary cultures of rat trigeminal ganglia retrogradely labeled from the dura mater and of rat dural fibroblasts were prepared. Patch-clamp electrophysiology, Western blot, and ELISA were performed to examine the effects of NE. Conditioned media from NE-treated fibroblast cultures was applied to the dura using the behavioral headache model. Dural injection both of NE and media from NE-stimulated fibroblasts caused cutaneous facial and hindpaw allodynia in awake rats. NE application to cultured dural afferents increased action potential firing in response to current injections. Application of NE to dural fibroblasts increased phosphorylation of ERK and caused the release of interleukin-6 (IL-6). These data demonstrate that NE can contribute to pro-nociceptive signaling from the meninges via actions on dural afferents and dural fibroblasts. Together, these actions of NE may contribute to the headache phase of migraine. © International Headache Society 2015.

AMPAkines Target the Nucleus Accumbens to Relieve Postoperative Pain

PubMed Central

Su, Chen; Lin, Hau Yeuh; Yang, Runtao; Xu, Duo; Lee, Michelle; Pawlak, Natalie; Norcini, Monica; Sideris, Alexandra; Recio-Pinto, Esperanza; Huang, Dong; Wang, Jing

2016-01-01

Background AMPAkines augment the function of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in the brain to increase excitatory outputs. These drugs are known to relieve persistent pain. However, their role in acute pain is unknown. Furthermore, a specific molecular and anatomic target for these novel analgesics remains elusive. Methods We studied the analgesic role of an AMPAkine, CX546, in a rat paw incision (PI) model of acute postoperative pain. We measured the effect of AMPAkines on sensory as well as depressive symptoms of pain using mechanical hypersensitivity and forced swim tests. We asked whether AMPA receptors in the nucleus accumbens (NAc), a key node in the brain's reward and pain circuitry, can be a target for AMPAkine analgesia. Results Systemic administration of CX546 (n=13), compared with control (n=13), reduced mechanical hypersensitivity (50% withdrawal threshold of 6.05±1.30g (mean±SEM) vs. 0.62±0.13g), and it reduced depressive features of pain by decreasing immobility on the forced swim test in PI-treated rats (89.0±15.5s vs. 156.7±18.5s). Meanwhile, CX546 delivered locally into the NAc provided pain-relieving effects in both PI (50% withdrawal threshold of 6.81±1.91g vs. 0.50±0.03g; control n=6, CX546 n=8) and persistent postoperative pain (spared nerve injury – SNI) models (50% withdrawal threshold of 3.85±1.23g vs. 0.45±0.00g; control n=7, CX546 n=11). Blocking AMPA receptors in the NAc with 3-dihydroxy-6-nitro-7-sulfamoyl-benzo[f]quinoxaline-2, 3-dione (NBQX) inhibited these pain-relieving effects (50% withdrawal threshold of 7.18±1.52g vs. 1.59±0.66g; n=8 for PI groups; 10.70±3.45g vs. 1.39±0.88g; n=4 for SNI groups). Conclusions AMPAkines relieves postoperative pain by activating AMPA receptors in the NAc. PMID:27627816

The effect of exercise frequency on neuropathic pain and pain-related cellular reactions in the spinal cord and midbrain in a rat sciatic nerve injury model

PubMed Central

Sumizono, Megumi; Otsuka, Shotaro; Terashi, Takuto; Nakanishi, Kazuki; Ueda, Koki; Takada, Seiya; Kikuchi, Kiyoshi

2018-01-01

Background Exercise regimens are established methods that can relieve neuropathic pain. However, the relationship between frequency and intensity of exercise and multiple cellular responses of exercise-induced alleviation of neuropathic pain is still unclear. We examined the influence of exercise frequency on neuropathic pain and the intracellular responses in a sciatic nerve chronic constriction injury (CCI) model. Materials and methods Rats were assigned to four groups as follows: CCI and high-frequency exercise (HFE group), CCI and low-frequency exercise (LFE group), CCI and no exercise (No-Ex group), and naive animals (control group). Rats ran on a treadmill, at a speed of 20 m/min, for 30 min, for 5 (HFE) or 3 (LFE) days a week, for a total of 5 weeks. The 50% withdrawal threshold was evaluated for mechanical sensitivity. The activation of glial cells (microglia and astrocytes), expression of brain-derived neurotrophic factor (BDNF) and μ-opioid receptor in the spinal dorsal horn and endogenous opioid in the midbrain were examined using immunohistochemistry. Opioid receptor antagonists (naloxone) were administered using intraperitoneal injection. Results The development of neuropathic pain was related to the activation of glial cells, increased BDNF expression, and downregulation of the μ-opioid receptor in the ipsilateral spinal dorsal horn. In the No-Ex group, neuropathic pain showed the highest level of mechanical hypersensitivity at 2 weeks, which improved slightly until 5 weeks after CCI. In both exercise groups, the alleviation of neuropathic pain was accelerated through the regulation of glial activation, BDNF expression, and the endogenous opioid system. The expression of BDNF and endogenous opioid in relation to exercise-induced alleviation of neuropathic pain differed in the HFE and LFE groups. The effects of exercise-induced alleviation of mechanical hypersensitivity were reversed by the administration of naloxone. Conclusion The LFE and HFE program reduced neuropathic pain. Our findings indicated that aerobic exercise-induced alleviated neuropathic pain through the regulation of glial cell activation, expression of BDNF in the ipsilateral spinal dorsal horn, and the endogenous opioid system. PMID:29445295

Concurrent validity of different functional and neuroproteomic pain assessment methods in the rat osteoarthritis monosodium iodoacetate (MIA) model.

PubMed

Otis, Colombe; Gervais, Julie; Guillot, Martin; Gervais, Julie-Anne; Gauvin, Dominique; Péthel, Catherine; Authier, Simon; Dansereau, Marc-André; Sarret, Philippe; Martel-Pelletier, Johanne; Pelletier, Jean-Pierre; Beaudry, Francis; Troncy, Eric

2016-06-23

Lack of validity in osteoarthritis pain models and assessment methods is suspected. Our goal was to 1) assess the repeatability and reproducibility of measurement and the influence of environment, and acclimatization, to different pain assessment outcomes in normal rats, and 2) test the concurrent validity of the most reliable methods in relation to the expression of different spinal neuropeptides in a chemical model of osteoarthritic pain. Repeatability and inter-rater reliability of reflexive nociceptive mechanical thresholds, spontaneous static weight-bearing, treadmill, rotarod, and operant place escape/avoidance paradigm (PEAP) were assessed by the intraclass correlation coefficient (ICC). The most reliable acclimatization protocol was determined by comparing coefficients of variation. In a pilot comparative study, the sensitivity and responsiveness to treatment of the most reliable methods were tested in the monosodium iodoacetate (MIA) model over 21 days. Two MIA (2 mg) groups (including one lidocaine treatment group) and one sham group (0.9 % saline) received an intra-articular (50 μL) injection. No effect of environment (observer, inverted circadian cycle, or exercise) was observed; all tested methods except mechanical sensitivity (ICC <0.3), offered good repeatability (ICC ≥0.7). The most reliable acclimatization protocol included five assessments over two weeks. MIA-related osteoarthritic change in pain was demonstrated with static weight-bearing, punctate tactile allodynia evaluation, treadmill exercise and operant PEAP, the latter being the most responsive to analgesic intra-articular lidocaine. Substance P and calcitonin gene-related peptide were higher in MIA groups compared to naive (adjusted P (adj-P) = 0.016) or sham-treated (adj-P = 0.029) rats. Repeated post-MIA lidocaine injection resulted in 34 times lower downregulation for spinal substance P compared to MIA alone (adj-P = 0.029), with a concomitant increase of 17 % in time spent on the PEAP dark side (indicative of increased comfort). This study of normal rats and rats with pain established the most reliable and sensitive pain assessment methods and an optimized acclimatization protocol. Operant PEAP testing was more responsive to lidocaine analgesia than other tests used, while neuropeptide spinal concentration is an objective quantification method attractive to support and validate different centralized pain functional assessment methods.

Role of opioid system in verapamil-induced antinociception in a rat model of orofacial pain

PubMed Central

Tamaddonfard, Esmaeal; Erfanparast, Amir; Taati, Mina; Dabbaghi, Milad

2014-01-01

Calcium, through its various channels involves in local, spinal and supra-spinal transmission of pain. In the present study, we investigated the separate and combined treatment effects of verapamil (a calcium channel blocker), morphine (an opioid agonist) and naloxone (an opioid antagonist) on pain in the orofacial region of rats. Orofacial pain was induced by subcutaneous (SC) injection of formalin (50 µL, 1.5%) into the left upper lip side, and the time durations spent face rubbing with epsilateral forepaw were recorded in three min blocks for a period of 45 min. Formalin induced a biphasic pattern (first phase: 0-3 min; second phase: 15-33 min) of pain. Intraperitoneal (IP) injections of verapamil (2 and 8 mg kg-1) and morphine (2 and 4 mg kg-1) suppressed orofacial pain. Co-administration of sub-analgesic doses of verapamil (0.5 mg kg-1) and morphine (1 mg kg-1) produced second phase analgesia. Both phases of formalin-induced pain were suppressed when an analgesic dose (2 mg kg-1) of verapamil co-administered with a sub-analgesic dose (1 mg kg-1) of morphine. The SC injection of naloxone (2 mg kg-1) alone with no effect on pain intensity, prevented the antinociceptive effects induced by morphine (2 mg kg-1), but not verapamil (2 mg kg-1). The obtained results showed antinociceptive effects for verapamli and morphine on orofacial pain. Co-administrations of verapamil and morphine produced antinociceptive effects. It seems that opioid analgesic system may not have a role in the verapamil-induced antinociception. PMID:25568692

A Novel Compound Analgesic Cream (Ketamine, Pentoxifylline, Clonidine, DMSO) for Complex Regional Pain Syndrome Patients.

PubMed

Russo, Marc A; Santarelli, Danielle M

2016-01-01

Evidence suggests that complex regional pain syndrome (CRPS) is a manifestation of microvascular dysfunction. Topical combinations of α2-adrenergic receptor agonists or nitric oxide donors with phosphodiesterase or phosphatidic acid inhibitors formulated to treat microvascular dysfunction have been shown to reduce allodynia in a rat model of CRPS-I. Driven by these findings, we assessed the outcomes of CRPS patients treated with a compound analgesic cream (CAC) consisting of ketamine 10%, pentoxifylline 6%, clonidine 0.2%, and dimethyl sulfoxide 6% to 10%. An audit was conducted on 13 CRPS patients who trialed the CAC. A detailed report was compiled for each patient which comprised baseline characteristics, including CRPS description, previous treatments, and pain scores (numerical pain rating scale; 0 to 10). Recorded outcomes consisted of pain scores, descriptive outcomes, and concurrent medications/treatments, for which basic analysis was performed to determine the effectiveness of the CAC. Case reports are presented for 3 patients with varying outcomes. Nine patients (69%) reported pain/symptom reduction (4.4 ± 2.1 vs. 6.3 ± 1.9) with use of the CAC. Six patients reported sustained benefits after 2 months of CAC use, and 2 patients reported complete resolution of pain/symptoms: one had early CRPS-I and the other received a partial CRPS diagnosis. An otherwise medication refractory and intolerant patient found partial benefit with the CAC. These results demonstrate promise for this topical combination as a useful treatment in multimodal therapy for patients with CRPS, with the potential to resolve pain/symptoms in early CRPS patients. © 2015 World Institute of Pain.

Spinal activation of alpha7-nicotinic acetylcholine receptor attenuates posttraumatic stress disorder-related chronic pain via suppression of glial activation.

PubMed

Sun, Rao; Zhang, Wei; Bo, Jinhua; Zhang, Zuoxia; Lei, Yishan; Huo, Wenwen; Liu, Yue; Ma, Zhengliang; Gu, Xiaoping

2017-03-06

The high prevalence of chronic pain in posttraumatic stress disorder (PTSD) individuals has been widely reported by clinical studies, which emphasized an urgent need to uncover the underlying mechanisms and identify potential therapeutic targets. Recent studies suggested that targeting activated glia and their pro-inflammatory products may provide a novel and effective therapy for the stress-related pain. In this study, we investigated whether activation of alpha-7 nicotinic acetylcholine receptor (α7 nAChR), a novel anti-inflammatory target, could attenuate PTSD-related chronic pain. The experiments were conducted in a rat model of single prolonged stress (SPS), an established model of PTSD-pain comorbidity. We found that SPS exposure produced persistent mechanical allodynia. Immunohistochemical and enzyme-linked immuno sorbent assay analysis showed that SPS also induced elevated activation of glia cells (including microglia and astrocytes) and accumulation of pro-inflammatory cytokines in spinal cord. In another experiment, we found that intrathecal injection of PHA-543613, a selective α7 nAchR agonist, attenuated the SPS-evoked allodynia in a dose dependent manner. However, this anti-hyperalgesic effect was blocked by pretreatment with methyllycaconitine (MLA), a selective α7 nAchR antagonist. Further analyses showed that PHA-543613 suppressed SPS-induced spinal glial activation and SPS-elevated spinal pro-inflammatory cytokines, and these were abolished by MLA. Taken together, the present study showed that spinal activation of α7 nAChR by PHA-543613 attenuated mechanical allodynia induced by PTSD-like stress, and the suppression of spinal glial activation may underlie this anti-hyperalgesic effect. Our study demonstrated the therapeutic potential of targeting α7 nAChR in the treatment of PTSD-related chronic pain. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

Electrophysiological evidence for voltage-gated calcium channel 2 (Cav2) modulation of mechano- and thermosensitive spinal neuronal responses in a rat model of osteoarthritis.

PubMed

Rahman, W; Patel, R; Dickenson, A H

2015-10-01

Osteoarthritis (OA) remains one of the greatest healthcare burdens in western society, with chronic debilitating pain-dominating clinical presentation yet therapeutic strategies are inadequate in many patients. Development of better analgesics is contingent on improved understanding of the molecular mechanisms mediating OA pain. Voltage-gated calcium channels 2.2 (Cav2.2) play a critical role in spinal nociceptive transmission, therefore blocking Cav2.2 activity represents an attractive opportunity for OA pain treatment, but the only available licensed Cav2.2 antagonist ziconitide (PrilatTM) is of limited use. TROX-1 is an orally available, use dependent and state-selective Cav2 antagonist, exerting its analgesic effect primarily via Cav2.2 blockade, with an improved therapeutic window compared with ziconitide. Using a rat model of monosodium iodoacetate (MIA), 2 mg, induced OA we used in vivo electrophysiology to assess the effects of spinal or systemic administration of TROX-1 on the evoked activity of wide dynamic range spinal dorsal horn neurons in response to electrical, natural mechanical (dynamic brush and von Frey 2, 8, 26 and 6 g) and thermal (40, 45 and 45 °C) stimuli applied to the peripheral receptive field. MIA injection into the knee joint resulted in mechanical hypersensitivity of the ipsilateral hind paw and weight-bearing asymmetry. Spinal administration of TROX-1 (0.1 and 1 μg/50 μl) produced a significant dose-related inhibition of dynamic brush, mechanical (von Frey filament (vF) 8, 26 and 60 g) and noxious thermal-(45 and 48 °C) evoked neuronal responses in MIA rats only. Systemic administration of TROX-1 produced a significant inhibition of the mechanical-(vF 8, 26 and 60 g) evoked neuronal responses in MIA rats. TROX-1 did not produce any significant effect on any neuronal measure in Sham controls. Our in vivo electrophysiological results demonstrate a pathological state-dependent effect of TROX-1, which suggests an increased functional role of Cav2, likely Cav2.2, channels in mediating OA pain. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Silencing of FKBP51 alleviates the mechanical pain threshold, inhibits DRG inflammatory factors and pain mediators through the NF-kappaB signaling pathway.

PubMed

Yu, Hong-Mei; Wang, Qi; Sun, Wen-Bo

2017-09-05

Neuropathic pain is chronic pain caused by lesions or diseases of the somatosensory system, currently available analgesics provide only temporal relief. The precise role of FK506 binding protein 51 (FKBP51) in neuropathic pain induced by chronic constriction injury (CCI) is not clear. The purpose of the present study was to investigate the effects and possible mechanisms of FKBP51 in neuropathic pain in the rat model of CCI. Our results showed that FKBP51 was obviously upregulated in a time-dependent manner in the dorsal root ganglion (DRG) of CCI rats. Additionally, silencing of FKBP51 remarkably attenuated mechanical allodynia and thermal hyperalgesia as reflected by paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) in CCI rats. Moreover, knockdown of FKBP51 reduced the production of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6), nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) expression in the DRG of CCI rats. Furthermore, we revealed that inhibition of FKBP51 greatly suppressed the activation of the NF-kappaB (NF-κB) signaling in the DRG of CCI rats. Interestingly, similar to the FKBP51 siRNA (si-FKBP51), ammonium pyrrolidinedithiocarbamate (PDTC, an inhibitor of NF-κB) also alleviated neuropathic pain and neuro-inflammation, indicating that knockdown of FKBP51 alleviated neuropathic pain development of CCI rats by inhibiting the activation of NF-κB signaling pathway. Taken together, our findings indicate that FKBP51 may serve as a novel therapeutic target for neuropathic pain. Copyright © 2017. Published by Elsevier B.V.

The synergistic effect of treatment with triptolide and MK-801 in the rat neuropathic pain model

PubMed Central

Wang, Jian; Qiao, Yu; Yang, Ri-Sheng; Zhang, Chun-Kui; Wu, Huang-Hui; Lin, Jia-Ji; Zhang, Ting

2017-01-01

Triptolide (T10), an active component of Tripterygium wilfordii Hook F, is reported to have potent anti-inflammatory and analgesic effects. Additionally, MK-801, a noncompetitive N-methyl-D-aspartate receptor antagonist, can reduce glutamate toxicity and has a significant analgesic effect on chronic pain. In this study, we tested the possible synergistic analgesic ability by intrathecal administration of T10 and MK-801 for the treatment of neuropathic pain. Single T10 (3, 10, or 30 µg/kg), MK-801 (10, 30, or 90 µg/kg), or a combination of them were intrathecally administrated in rats with spinal nerve ligation. We found that single administration of T10 caused a slow-acting but long-term analgesic effect, while single administration of MK-801 caused a fast-acting but short-term effect. Administration of their combination showed obviously synergic analgesia and the 1:3 ratio of T10 to MK-801 reached the peak effect. Furthermore, application of T10 and/or MK-801 significantly inhibited the activation of microglia and astrocyte and phosphorylation of STAT3 and NR2B in the spinal dorsal horn induced by chronic neuropathic pain. Our data suggest that the combination of T10 and MK-801 may be a potentially novel strategy for treatment of neuropathic pain. PMID:29166839

Mu-Opioid Receptors in Ganglia, But Not in Muscle, Mediate Peripheral Analgesia in Rat Muscle Pain.

PubMed

Bagues, Ana; Martín, María Isabel; Higuera-Matas, Alejandro; Esteban-Hernández, Jesús; Ambrosio, Emilio; Sánchez-Robles, Eva María

2018-04-01

Previous studies have demonstrated the participation of peripheral μ-opioid receptors (MOR) in the antinociceptive effect of systemically administered morphine and loperamide in an orofacial muscle pain model, induced by hypertonic saline, but not in a spinally innervated one, in rats. In this study, we determine whether this peripheral antinociceptive effect is due to the activation of MOR localized in the muscle, ganglia, or both. To determine the local antinociceptive effect of morphine and loperamide, 2 models of acute muscle pain (trigeminal and spinal) were used. Also, to study the MOR expression, protein quantification was performed in the trigeminal and spinal ganglia, and in the muscles. The behavioral results show that the intramuscular injection of morphine and loperamide did not exert an antinociceptive effect in either muscle (morphine: P = .63, loperamide: P = .9). On the other hand, MOR expression was found in the ganglia but not in the muscles. This expression was on average 44% higher (95% confidence interval, 33.3-53.9) in the trigeminal ganglia than in the spinal one. The peripheral antinociceptive effect of systemically administered opioids may be due to the activation of MOR in ganglia. The greater expression of MOR in trigeminal ganglia could explain the higher antinociceptive effect of opioids in orofacial muscle pain than in spinal muscle pain. Therefore, peripheral opioids could represent a promising approach for the treatment of orofacial pain.

Inflammatory Pain Promotes Increased Opioid Self-Administration: Role of Dysregulated Ventral Tegmental Area μ Opioid Receptors

PubMed Central

Hipólito, Lucia; Wilson-Poe, Adrianne; Campos-Jurado, Yolanda; Zhong, Elaine; Gonzalez-Romero, Jose; Virag, Laszlo; Whittington, Robert; Comer, Sandra D.; Carlton, Susan M.; Walker, Brendan M.; Bruchas, Michael R.

2015-01-01

Pain management in opioid abusers engenders ethical and practical difficulties for clinicians, often resulting in pain mismanagement. Although chronic opioid administration may alter pain states, the presence of pain itself may alter the propensity to self-administer opioids, and previous history of drug abuse comorbid with chronic pain promotes higher rates of opioid misuse. Here, we tested the hypothesis that inflammatory pain leads to increased heroin self-administration resulting from altered mu opioid receptor (MOR) regulation of mesolimbic dopamine (DA) transmission. To this end, the complete Freund's adjuvant (CFA) model of inflammation was used to assess the neurochemical and functional changes induced by inflammatory pain on MOR-mediated mesolimbic DA transmission and on rat intravenous heroin self-administration under fixed ratio (FR) and progressive ratio (PR) schedules of reinforcement. In the presence of inflammatory pain, heroin intake under an FR schedule was increased for high, but attenuated for low, heroin doses with concomitant alterations in mesolimbic MOR function suggested by DA microdialysis. Consistent with the reduction in low dose FR heroin self-administration, inflammatory pain reduced motivation for a low dose of heroin, as measured by responding under a PR schedule of reinforcement, an effect dissociable from high heroin dose PR responding. Together, these results identify a connection between inflammatory pain and loss of MOR function in the mesolimbic dopaminergic pathway that increases intake of high doses of heroin. These findings suggest that pain-induced loss of MOR function in the mesolimbic pathway may promote opioid dose escalation and contribute to opioid abuse-associated phenotypes. SIGNIFICANCE STATEMENT This study provides critical new insights that show that inflammatory pain alters heroin intake through a desensitization of MORs located within the VTA. These findings expand our knowledge of the interactions between inflammatory pain and opioid abuse liability, and should help to facilitate the development of novel and safer opioid-based strategies for treating chronic pain. PMID:26338332

Effects of transcutaneous electrical nerve stimulation on rats with the third lumbar vertebrae transverse process syndrome.

PubMed

Li, Huan; Shang, Xiao-Jun; Dong, Qi-Rong

2015-10-01

To investigate the analgesic and anti-inflammatory effects of transcutaneous electrical nerve stimulation (TENS) at local or distant acupuncture points in a rat model of the third lumbar vertebrae transverse process syndrome. Forty Sprague-Dawley rats were randomly divided into control, model, model plus local acupuncture point stimulation at BL23 (model+LAS) and model plus distant acupuncture point stimulation at ST36 (model+DAS) groups. All rats except controls underwent surgical third lumbar vertebrae transverse process syndrome modelling on day 2. Thereafter, rats in the model+LAS and model+DAS groups were treated daily with TENS for a total of six treatments (2/100 Hz, 30 min/day) from day 16 to day 29. Thermal pain thresholds were measured once a week during treatment and were continued until day 57, when local muscle tissue was sampled for RT-PCR and histopathological examination after haematoxylin and eosin staining. mRNA expression of interleukin-1 β (IL-1β), tumour necrosis factor-α (TNF-α) and inducible nitric oxide synthase (iNOS) was determined. Thermal pain thresholds of all model rats decreased relative to the control group. Both LAS and DAS significantly increased the thermal pain threshold at all but one point during the treatment period. Histopathological assessment revealed that the local muscle tissues around the third lumbar vertebrae transverse process recovered to some degree in both the model+LAS and model+DAS groups; however, LAS appeared to have a greater effect. mRNA expression of IL-1β, TNF-α and iNOS in the local muscle tissues was increased after modelling and attenuated in both model+LAS and model+DAS groups. The beneficial effect was greater after LAS than after DAS. TENS at both local (BL23) and distant (ST36) acupuncture points had a pain-relieving effect in rats with the third lumbar vertebrae transverse process syndrome, and LAS appeared to have greater anti-inflammatory and analgesic effects than DAS. 09073. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Effect of Pulsed Radiofrequency on Rat Sciatic Nerve Chronic Constriction Injury: A Preliminary Study

PubMed Central

Li, Duo-Yi; Meng, Lan; Ji, Nan; Luo, Fang

2015-01-01

Background: Pulsed radiofrequency (PRF) application to the dorsal root ganglia can reduce neuropathic pain (NP) in animal models, but the effect of PRF on damaged peripheral nerves has not been examined. We investigated the effect of PRF to the rat sciatic nerve (SN) on pain-related behavior and SN ultrastructure following chronic constriction injury (CCI). Methods: The analgesic effect was measured by hindpaw mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL). Twenty rats with NP induced by ligating the common SN were then randomly divided into a PRF treatment group and a sham group. The contralateral SN served as a control. The MWT and TWL were determined again 2, 4, 6, 8, 10, 12, and 14 days after the PRF or sham treatment. On day 14, ipsilateral and contralateral common SNs were excised and examined by electron microscopy. Results: Ipsilateral MWT was significantly reduced and TWL significantly shorter compared to the contralateral side 14 days after CCI (both P = 0.000). In the PRF group, MWT was significantly higher and TWL significantly longer 14 days after the PRF treatment compared to before PRF treatment (both P = 0.000), while no such difference was observed in the sham group (P > 0.05). Electron microscopy revealed extensive demyelination and collagen fiber formation in the ipsilateral SN of sham-treated rats but sparse demyelination and some nerve fiber regrowth in the PRF treatment group. Conclusions: Hyperalgesia is relieved, and ultrastructural damage ameliorated after direct PRF treatment to the SN in the CCI rat model of NP. PMID:25673460

Mechanical hypersensitivity, sympathetic sprouting, and glial activation are attenuated by local injection of corticosteroid near the lumbar ganglion in a rat model of neuropathic pain.

PubMed

Li, Jing-Yi; Xie, Wenrui; Strong, Judith A; Guo, Qu-Lian; Zhang, Jun-Ming

2011-01-01

Inflammatory responses in the lumbar dorsal root ganglion (DRG) play a key role in pathologic pain states. Systemic administration of a common anti-inflammatory corticosteroid, triamcinolone acetonide (TA), reduces sympathetic sprouting, mechanical pain behavior, spontaneous bursting activity, and cytokine and nerve growth factor production in the DRG. We hypothesized that systemic TA effects are primarily due to local effects on the DRG. Male Sprague-Dawley rats were divided into 4 groups: SNL (tight ligation and transection of spinal nerves) and normal with and without a single dose of TA injectable suspension slowly injected onto the surface of DRG and surrounding region at the time of SNL or sham surgery. Mechanical threshold was tested on postoperative days 1, 3, 5, and 7. Immunohistochemical staining examined tyrosine hydroxylase and glial fibrillary acidic protein in DRG and CD11B antibody (OX-42) in spinal cord. Local TA treatment attenuated mechanical sensitivity, reduced sympathetic sprouting in the DRG, and decreased satellite glia activation in the DRG and microglia activation in the spinal cord after SNL. A single injection of corticosteroid in the vicinity of the axotomized DRG can mimic many effects of systemic TA, mitigating behavioral and cellular abnormalities induced by spinal nerve ligation. This provides a further rationale for the use of localized steroid injections clinically and provides further support for the idea that localized inflammation at the level of the DRG is an important component of the spinal nerve ligation model, commonly classified as neuropathic pain model.

Expression of the dopaminergic D1 and D2 receptors in the anterior cingulate cortex in a model of neuropathic pain

PubMed Central

2011-01-01

Background The anterior cingulate cortex (ACC) has been related to the affective component of pain. Dopaminergic mesocortical circuits, including the ACC, are able to inhibit neuropathic nociception measured as autotomy behaviour. We determined the changes in dopamine D1 and D2 (D1R and D2R) receptor expression in the ACC (cg1 and cg2) in an animal model of neuropathic pain. The neuropathic group had noxious heat applied in the right hind paw followed 30 min. later by right sciatic denervation. Autotomy score (AS) was recorded for eight days and subsequently classified in low, medium and high AS groups. The control consisted of naïve animals. A semiquantitative RT-PCR procedure was done to determine mRNA levels for D1R and D2R in cg1 and cg2, and protein levels were measured by Western Blot. Results The results of D1R mRNA in cg1 showed a decrease in all groups. D2R mRNA levels in cg1 decreased in low AS and increased in medium and high AS. Regarding D1R in cg2, there was an increase in all groups. D2R expression levels in cg2 decreased in all groups. In cg1, the D2R mRNA correlated positively with autotomy behaviour. Protein levels of D2R in cg1 increased in all groups but to a higher degree in low AS. In cg2 D2R protein only decreased discretely. D1R protein was not found in either ACC region. Conclusions This is the first evidence of an increase of inhibitory dopaminergic receptor (D2R) mRNA and protein in cg1 in correlation with nociceptive behaviour in a neuropathic model of pain in the rat. PMID:22171983

Pharmacokinetics and Pharmacodynamics of (S)-Ketoprofen Co-Administered with Caffeine: A Preclinical Study in Arthritic Rats.

PubMed

Medina-López, Raúl; Vara-Gama, Nancy; Soria-Arteche, Olivia; Moreno-Rocha, Luis A; López-Muñoz, Francisco J

2018-01-26

The purpose of the present study was to determine whether caffeine modifies the pharmacokinetics and pharmacodynamics of ( S )-ketoprofen following oral administration in a gout-type pain model. 3.2 mg/kg of ( S )-ketoprofen alone and combined with 17.8 mg/kg of caffeine were administered to Wistar rats and plasma levels were determined between 0.5 and 24.0 h. Additionally, antinociception was evaluated based on the protocol of the PIFIR (pain-induced functional impairment in the rat) model before blood sampling between 0.5 and 4.0 h. Significant differences in C max , AUC 0-24 , and AUC 0-∞ values were observed with caffeine administration ( p < 0.05). Also, significant differences in E max , T max , and AUC 0-4 values were determined when comparing the treatments with and without caffeine ( p < 0.05). By relating the pharmacokinetic and pharmacodynamic data, a counter-clockwise hysteresis loop was observed regardless of the administration of caffeine. When the relationship between AUCe and AUCp was fitted to the sigmoidal E max model, a satisfactory correlation was found (R² > 0.99) as well as significant differences in E max and EC 50 values ( p < 0.05). With caffeine, E max and EC 50 values changed by 489.5% and 695.4%, respectively. The combination studied represents a convenient alternative for the treatment of pain when considering the advantages offered by using drugs with different mechanisms of action.

Pharmacokinetics and Pharmacodynamics of (S)-Ketoprofen Co-Administered with Caffeine: A Preclinical Study in Arthritic Rats

PubMed Central

Vara-Gama, Nancy; Soria-Arteche, Olivia; Moreno-Rocha, Luis A.; López-Muñoz, Francisco J.

2018-01-01

The purpose of the present study was to determine whether caffeine modifies the pharmacokinetics and pharmacodynamics of (S)-ketoprofen following oral administration in a gout-type pain model. 3.2 mg/kg of (S)-ketoprofen alone and combined with 17.8 mg/kg of caffeine were administered to Wistar rats and plasma levels were determined between 0.5 and 24.0 h. Additionally, antinociception was evaluated based on the protocol of the PIFIR (pain-induced functional impairment in the rat) model before blood sampling between 0.5 and 4.0 h. Significant differences in Cmax, AUC0-24, and AUC0-∞ values were observed with caffeine administration (p < 0.05). Also, significant differences in Emax, Tmax, and AUC0-4 values were determined when comparing the treatments with and without caffeine (p < 0.05). By relating the pharmacokinetic and pharmacodynamic data, a counter-clockwise hysteresis loop was observed regardless of the administration of caffeine. When the relationship between AUCe and AUCp was fitted to the sigmoidal Emax model, a satisfactory correlation was found (R2 > 0.99) as well as significant differences in Emax and EC50 values (p < 0.05). With caffeine, Emax and EC50 values changed by 489.5% and 695.4%, respectively. The combination studied represents a convenient alternative for the treatment of pain when considering the advantages offered by using drugs with different mechanisms of action. PMID:29373537

Anti-inflammatory and Analgesic Activities of Topical Formulations of Pterocarpus Santalinus Powder in Rat Model of Chronic Inflammation

PubMed Central

Gupta, Amit O; Jain, Sourav; Dawane, Jayshree Shriram

2017-01-01

Introduction The incidence of arthritis is quite high and there is a need for the search of natural products to halt the progression of disease or provide symptomatic relief without significant adverse effects. Aim This study aimed at evaluating the anti-inflammatory and analgesic activities of topical Pterocarpus santalinus in an animal model of chronic inflammation. Materials and Methods Albino rats of either sex were divided into five groups of six rats each (Group I – Control, Group II –Gel base, Group III –P. santalinus paste, Group IV –P. santalinus gel, Group V– Diclofenac gel). Chronic inflammation was induced on day 0 by injecting 0.1 ml Complete Freund’s Adjuvant (CFA) in sub-plantar tissue of left hind paw of the rats. Topical treatment was started from day 12 till day 28. Body weight and paw volume (Plethysmometer) were assessed on day 0, 12 and 28. Pain assessment was done using Randall and Selitto paw withdrawal method. Data was analysed using GraphPad Prism version 5. Unpaired students t-test and ANOVA followed by Tukey’s test was used for comparison among groups. Results Only topical P.santalinus gel significantly reduced the body weight (p=0.02) due to reduction in inflammatory oedema of the left limb. P. santalinus gel also showed significant reduction (p=0.03) in paw volume of rats compared to the other groups. There was significant reduction in pain threshold (gm/sec) due to chronic inflammation, with all the study drugs (p<0.05) but with P. santalinus gel, this reduction was less (p<0.001). Conclusion Gel showed significant anti-inflammatory and mild analgesic activity on topical application in rat model of chronic inflammation. PMID:28892928

Effects of microRNA-223 on morphine analgesic tolerance by targeting NLRP3 in a rat model of neuropathic pain

PubMed Central

Xie, Xiao-Juan; Ma, Li-Gang; Xi, Kai; Fan, Dong-Mei; Li, Jian-Guo; Zhang, Quan; Zhang, Wei

2017-01-01

Objective To investigate the effects of microRNA-223 on morphine analgesic tolerance by targeting NLRP3 in a rat model of neuropathic pain. Methods Our study selected 100 clean grade healthy Sprague-Dawley adult male rats weighing 200 to 250 g. After establishment of a rat model of chronic constriction injury, these rats were divided into 10 groups (10 rats in each group): the normal control, sham operation, chronic constriction injury, normal saline, morphine, miR-223, NLRP3, miR-223 + morphine, NLRP3 + morphine, and miR-223 + NLRP3 + morphine groups. The real-time quantitative polymerase chain reaction assay, Western blotting, and enzyme-linked immunosorbent assay were used for detecting the mRNA and protein expressions of NLRP3, apoptosis-associated speck-like protein, Caspase-1, Interleukin (IL)-1β, and IL-18 in sections of lumbar spinal cord. Immunohistochemistry was applied for detecting the positive rates of NLRP3, apoptosis-associated speck-like protein, Caspase-1, IL-1β, and IL-18. Results The paw withdrawal threshold and percentage maximum possible effect (%MPE) were higher in chronic constriction injury group when compared with the normal control and sham operation groups. Behavioral tests showed that compared with the chronic constriction injury and normal saline groups, the morphine and miR-223 + morphine groups showed obvious analgesic effects. Expressions of miR-223 in the miR-223, miR-223 + morphine, and miR-223 + NLRP3 + morphine were significantly higher than those in the chronic constriction injury, normal saline, and morphine groups. Compared with chronic constriction injury, normal saline and morphine groups, the mRNA and protein expressions of NLRP3, apoptosis-associated speck-like protein, Caspase-1, IL-1β, and IL-18 were significantly decreased in the miR-223 and miR-223 + morphine groups, while mRNA and protein expressions of NLRP3, apoptosis-associated speck-like protein, Caspase-1, IL-1β, and IL-18 were significantly increased in the NLRP3 and NLRP3 + morphine group. Conclusion Our study provides strong evidence that miR-223 could suppress the activities of NLRP3 inflammasomes (NLRP3, apoptosis-associated speck-like protein, and Caspase-1) to relieve morphine analgesic tolerance in rats by down-regulating NLRP3. PMID:28580822

Reverse transcription quantitative real-time polymerase chain reaction reference genes in the spared nerve injury model of neuropathic pain: validation and literature search.

PubMed

Piller, Nicolas; Decosterd, Isabelle; Suter, Marc R

2013-07-10

The reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) is a widely used, highly sensitive laboratory technique to rapidly and easily detect, identify and quantify gene expression. Reliable RT-qPCR data necessitates accurate normalization with validated control genes (reference genes) whose expression is constant in all studied conditions. This stability has to be demonstrated.We performed a literature search for studies using quantitative or semi-quantitative PCR in the rat spared nerve injury (SNI) model of neuropathic pain to verify whether any reference genes had previously been validated. We then analyzed the stability over time of 7 commonly used reference genes in the nervous system - specifically in the spinal cord dorsal horn and the dorsal root ganglion (DRG). These were: Actin beta (Actb), Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), ribosomal proteins 18S (18S), L13a (RPL13a) and L29 (RPL29), hypoxanthine phosphoribosyltransferase 1 (HPRT1) and hydroxymethylbilane synthase (HMBS). We compared the candidate genes and established a stability ranking using the geNorm algorithm. Finally, we assessed the number of reference genes necessary for accurate normalization in this neuropathic pain model. We found GAPDH, HMBS, Actb, HPRT1 and 18S cited as reference genes in literature on studies using the SNI model. Only HPRT1 and 18S had been once previously demonstrated as stable in RT-qPCR arrays. All the genes tested in this study, using the geNorm algorithm, presented gene stability values (M-value) acceptable enough for them to qualify as potential reference genes in both DRG and spinal cord. Using the coefficient of variation, 18S failed the 50% cut-off with a value of 61% in the DRG. The two most stable genes in the dorsal horn were RPL29 and RPL13a; in the DRG they were HPRT1 and Actb. Using a 0.15 cut-off for pairwise variations we found that any pair of stable reference gene was sufficient for the normalization process. In the rat SNI model, we validated and ranked Actb, RPL29, RPL13a, HMBS, GAPDH, HPRT1 and 18S as good reference genes in the spinal cord. In the DRG, 18S did not fulfill stability criteria. The combination of any two stable reference genes was sufficient to provide an accurate normalization.

Lentiviral-mediated Targeted NF-κB Blockade in Dorsal Spinal Cord Glia Attenuates Sciatic Nerve Injury-induced Neuropathic Pain in the Rat.

PubMed

Meunier, Alice; Latrémolière, Alban; Dominguez, Elisa; Mauborgne, Annie; Philippe, Stéphanie; Hamon, Michel; Mallet, Jacques; Benoliel, Jean-Jacques; Pohl, Michel

2007-04-01

Neuropathic pain developing after peripheral nerve injury is associated with altered neuronal and glial cell functions in the spinal cord. Activated glia produces algogenic mediators, exacerbating pain. Among the different intracellular pathways possibly involved in the modified glial function, the nuclear factor κB (NF-κB) system is of particular interest, as numerous genes encoding inflammation- and pain-related molecules are controlled by this transcription factor. NF-κB is a pleiotropic factor also involved in central nervous system homeostasy. To study its role in chronic pain, it is thus essential to inhibit the NF-κB pathway selectively in activated spinal glial cells. Here, we show that when restricted to spinal cord and targeted to glial cells, lentiviral vector-mediated delivery of NF-κB super- repressor IκBα resulted in an inhibition of the NF-κB pathway activated in the rat spinal cord after sciatic nerve injury (chronic constriction injury, CCI). Concomitantly, IκBα overproduction prevented the enhanced expression of interleukin-6 and of inducible nitric oxide synthase associated with chronic constriction injury and resulted in prolonged antihyperalgesic and antiallodynic effects. These data show that targeted blockade of NF-κB activity in spinal glia efficiently alleviates pain behavior in CCI rats, demonstrating the active participation of the glial NF-κB pathway in the development of neuropathic pain after peripheral nerve injury. Copyright © 2007 The American Society of Gene Therapy. Published by Elsevier Inc. All rights reserved.

Stress Increases the Negative Effects of Chronic Pain on Hippocampal Neurogenesis.

PubMed

Romero-Grimaldi, Carmen; Berrocoso, Esther; Alba-Delgado, Cristina; Madrigal, Jose Luis M; Perez-Nievas, Beatriz G; Leza, Juan Carlos; Mico, Juan Antonio

2015-10-01

Patients with chronic pain often suffer from affective disorders and cognitive decline, which significantly impairs their quality of life. In addition, many of these patients also experience stress unrelated to their illness, which can aggravate their symptoms. These nociceptive inputs are received by the hippocampus, in which maladaptive neuroplastic changes may occur in the conditions of chronic pain. The hippocampus is a structure involved in emotionality, learning, and memory, and the proliferating cells in the granular layer of the hippocampal dentate gyrus respond to chronic pain by slowing their turnover. However, whether the maturation, survival, and integration of newborn cells in the hippocampus are affected by chronic pain remains unclear. In addition, it is unknown whether an added stress may increase this effect. We have evaluated the proliferation, differentiation, and survival of newborn hippocampal cells in a rat model of neuropathic pain (chronic constriction injury), with or without stress (chronic immobilization), by assessing the incorporation of bromodeoxyuridine into proliferating cells and immunostaining. The data obtained indicated that there was a decrease in the number of proliferating cells 8 days after nerve injury in animals subjected to neuropathic pain, an effect that was exacerbated by stress. Moreover, 4 weeks after nerve injury, neuropathic pain was associated with a loss of neuroblasts and the reduced survival of new mature neurons in the hippocampal granular layer, phenomena that also were increased by stress. By contrast, the rate of differentiation was not affected in this paradigm. Neuropathic pain negatively influences hippocampal neurogenesis (proliferation and survival), and this effect is exacerbated by stress. These neuroplastic changes may account for the affective and cognitive impairment seen in patients with chronic pain.

The inhibition of nitric oxide-activated poly(ADP-ribose) synthetase attenuates transsynaptic alteration of spinal cord dorsal horn neurons and neuropathic pain in the rat.

PubMed

Mao, J; Price, D D; Zhu, J; Lu, J; Mayer, D J

1997-09-01

Transsynaptic alteration of spinal cord dorsal horn neurons characterized by hyperchromatosis of cytoplasm and nucleoplasm (so-called 'dark' neurons) occurs in a rat model of neuropathic pain induced by chronic constriction injury (CCI) of the common sciatic nerve. The incidence of dark neurons in CCI rats has been proposed to be mediated by glutamate-induced neurotoxicity. In the present study, we examined whether the inhibition of the nitric oxide (NO)-activated poly(ADP-ribose) synthetase (PARS), a nuclear enzyme critical to glutamate-induced neurotoxicity, would both reduce the incidence of dark neurons and attenuate behavioral manifestations of neuropathic pain in CCI rats. Dark neurons were observed bilaterally (with ipsilateral predominance) within the spinal cord dorsal horn, particularly in laminae I-II, of rats 8 days after unilateral sciatic nerve ligation as compared to sham operated rats. The number of dark neurons in the dorsal horn was dose-dependently reduced in CCI rats receiving once daily intrathecal (i.t.) treatment with the PARS inhibitor benzamide (200 or 400 nmol, but not 100 nmol benzamide or saline) for 7 days. Consistent with the histological improvement, thermal hyperalgesia, mechanical hyperalgesia, and low threshold mechano-allodynia also were reliably reduced in CCI rats treated with either 200 or 400 nmol benzamide. Neither dark neurons nor neuropathic pain behaviors were reliably affected by i.t. administration of either 800 nmol novobiocin (a mono(ADP-ribose) synthetase) or 800 nmol benzoic acid (the backbone structure of benzamide), indicating a selective effect of benzamide. Intrathecal treatment with an NO synthase inhibitor NG-nitro-L-arginine methyl ester (40 nmol, but not its inactive D-isomer) utilizing the same benzamide treatment regimen resulted in similar reductions of both dark neurons and neuropathic pain behaviors in CCI rats. These results provide, for the first time, in vivo evidence indicating that benzamide is neuroprotective and that the PARS-mediated transsynaptic alteration of spinal cord dorsal horn neurons contributes to behavioral manifestations of neuropathic pain in CCI rats. These observations may have general implications beyond treatment of neuropathic pain in that PARS-mediated neuronal alterations may play a significant role in glutamate-mediated neurotoxicity under many other circumstances.

Anti-inflammatory and Analgesic Activities of Topical Formulations of Pterocarpus Santalinus Powder in Rat Model of Chronic Inflammation.

PubMed

Dhande, Priti Pravin; Gupta, Amit O; Jain, Sourav; Dawane, Jayshree Shriram

2017-07-01

The incidence of arthritis is quite high and there is a need for the search of natural products to halt the progression of disease or provide symptomatic relief without significant adverse effects. This study aimed at evaluating the anti-inflammatory and analgesic activities of topical Pterocarpus santalinus in an animal model of chronic inflammation. Albino rats of either sex were divided into five groups of six rats each (Group I - Control, Group II -Gel base, Group III - P. santalinus paste, Group IV - P. santalinus gel, Group V- Diclofenac gel). Chronic inflammation was induced on day 0 by injecting 0.1 ml Complete Freund's Adjuvant (CFA) in sub-plantar tissue of left hind paw of the rats. Topical treatment was started from day 12 till day 28. Body weight and paw volume (Plethysmometer) were assessed on day 0, 12 and 28. Pain assessment was done using Randall and Selitto paw withdrawal method. Data was analysed using GraphPad Prism version 5. Unpaired students t-test and ANOVA followed by Tukey's test was used for comparison among groups. Only topical P.santalinus gel significantly reduced the body weight (p=0.02) due to reduction in inflammatory oedema of the left limb. P. santalinus gel also showed significant reduction (p=0.03) in paw volume of rats compared to the other groups. There was significant reduction in pain threshold (gm/sec) due to chronic inflammation, with all the study drugs (p<0.05) but with P. santalinus gel, this reduction was less (p<0.001). Gel showed significant anti-inflammatory and mild analgesic activity on topical application in rat model of chronic inflammation.

Development and pharmacological characterization of a model of sleep disruption-induced hypersensitivity in the rat.

PubMed

Wodarski, R; Schuh-Hofer, S; Yurek, D A; Wafford, K A; Gilmour, G; Treede, R-D; Kennedy, J D

2015-04-01

Sleep disturbance is a commonly reported co-morbidity in chronic pain patients, and conversely, disruption of sleep can cause acute and long-lasting hypersensitivity to painful stimuli. The underlying mechanisms of sleep disruption-induced pain hypersensitivity are poorly understood. Confounding factors of previous studies have been the sleep disruption protocols, such as the 'pedestal over water' or 'inverted flower pot' methods, that can cause large stress responses and therefore may significantly affect pain outcome measures. Sleep disruption was induced by placing rats for 8 h in a slowly rotating cylindrical cage causing arousal via the righting reflex. Mechanical (Von Frey filaments) and thermal (Hargreaves) nociceptive thresholds were assessed, and plasma corticosterone levels were measured (mass spectroscopy). Sleep disruption-induced hypersensitivity was pharmacologically characterized with drugs relevant for pain treatment, including gabapentin (30 mg/kg and 50 mg/kg), Ica-6p (Kv7.2/7.3 potassium channel opener; 10 mg/kg), ibuprofen (30 mg/kg and 100 mg/kg) and amitriptyline (10 mg/kg). Eight hours of sleep disruption caused robust mechanical and heat hypersensitivity in the absence of a measurable change in plasma corticosterone levels. Gabapentin had no effect on reduced nociceptive thresholds. Ibuprofen attenuated mechanical thresholds, while Ica-6p and amitriptyline attenuated only reduced thermal nociceptive thresholds. These results show that acute and low-stress sleep disruption causes mechanical and heat hypersensitivity in rats. Mechanical and heat hypersensitivity exhibited differential sensitivity to pharmacological agents, thus suggesting dissociable mechanisms for those two modalities. Ultimately, this model could help identify underlying mechanisms linking sleep disruption and hypersensitivity. © 2014 European Pain Federation - EFIC®

Identifying the integrated neural networks involved in capsaicin-induced pain using fMRI in awake TRPV1 knockout and wild-type rats

PubMed Central

Yee, Jason R.; Kenkel, William; Caccaviello, John C.; Gamber, Kevin; Simmons, Phil; Nedelman, Mark; Kulkarni, Praveen; Ferris, Craig F.

2015-01-01

In the present study, we used functional MRI in awake rats to investigate the pain response that accompanies intradermal injection of capsaicin into the hindpaw. To this end, we used BOLD imaging together with a 3D segmented, annotated rat atlas and computational analysis to identify the integrated neural circuits involved in capsaicin-induced pain. The specificity of the pain response to capsaicin was tested in a transgenic model that contains a biallelic deletion of the gene encoding for the transient receptor potential cation channel subfamily V member 1 (TRPV1). Capsaicin is an exogenous ligand for the TRPV1 receptor, and in wild-type rats, activated the putative pain neural circuit. In addition, capsaicin-treated wild-type rats exhibited activation in brain regions comprising the Papez circuit and habenular system, systems that play important roles in the integration of emotional information, and learning and memory of aversive information, respectively. As expected, capsaicin administration to TRPV1-KO rats failed to elicit the robust BOLD activation pattern observed in wild-type controls. However, the intradermal injection of formalin elicited a significant activation of the putative pain pathway as represented by such areas as the anterior cingulate, somatosensory cortex, parabrachial nucleus, and periaqueductal gray. Notably, comparison of neural responses to capsaicin in wild-type vs. knock-out rats uncovered evidence that capsaicin may function in an antinociceptive capacity independent of TRPV1 signaling. Our data suggest that neuroimaging of pain in awake, conscious animals has the potential to inform the neurobiological basis of full and integrated perceptions of pain. PMID:25745388

A PLGA-PEG-PLGA Thermosensitive Gel Enabling Sustained Delivery of Ropivacaine Hydrochloride for Postoperative Pain Relief.

PubMed

Fu, Xudong; Zeng, Huilin; Guo, Jiaping; Liu, Hong; Shi, Zhen; Chen, Huhai; Li, Dezong; Xie, Xiangyang; Kuang, Changchun

2017-01-01

Postoperative pain is a complex physiological response to disease and tissue injury. Moderate-to-severe pain typically occurs within 48 h after surgery. Amino amide local anesthetics are widely applied to manage postoperative pain, and they have high efficacy, a low risk for addiction and limited side effects. However, these anesthetics also have short half-lives, often necessitating continuous injection to obtain satisfactory pain relief. In the current work, we used a poly(lactic-co-glycolic acid) (PLGA)-polyethylene glycol (PEG)-PLGA (PLGA-PEG-PLGA) temperature-sensitive gel to deliver a local anesthetic, ropivacaine hydrochloride (RP), to prolong its analgesic effect. We investigated the influence of polymer and drug concentration on gelation temperature and the in vitro drug release rate from the temperature-sensitive gel. RP-loaded PLGA-PEG-PLGA solution is a liquid at room temperature and forms a gel at temperatures slightly lower than body temperature. With regard to the gel's drug release rate, 37.5, 51.3 and 72.6% of RP was released at 12, 24 and 48 h, respectively. This in vitro drug release profile conformed to the Higuchi equation. To assess pain control efficacy when using the gel, we evaluated the mechanical paw withdrawal reflex threshold, thermal pain threshold and incision cumulative pain scores in a rat incisional model. The results showed that the anti-pain effect of a single injection of RP-loaded gel at the incision site lasted for 48 h, which is significantly longer than the effect produced by injection of RP solution alone. The use of RP-loaded thermosensitive gels could provide a promising method for managing postoperative pain.

Advances in cancer pain from bone metastasis.

PubMed

Zhu, Xiao-Cui; Zhang, Jia-Li; Ge, Chen-Tao; Yu, Yuan-Yang; Wang, Pan; Yuan, Ti-Fei; Fu, Cai-Yun

2015-01-01

With the technological advances in cancer diagnosis and treatment, the survival rates for patients with cancer are prolonged. The issue of figuring out how to improve the life quality of patients with cancer has become increasingly prominent. Pain, especially bone pain, is the most common symptom in malignancy patients, which seriously affects the life quality of patients with cancer. The research of cancer pain has a breakthrough due to the development of the animal models of cancer pain in recent years, such as the animal models of mouse femur, humerus, calcaneus, and rat tibia. The establishment of several kinds of animal models related to cancer pain provides a new platform in vivo to investigate the molecular mechanisms of cancer pain. In this review, we focus on the advances of cancer pain from bone metastasis, the mechanisms involved in cancer pain, and the drug treatment of cancer pain in the animal models.

Low Intensity Pulsed Ultrasound (LIPUS) for the treatment of intervertebral disc degeneration

NASA Astrophysics Data System (ADS)

Horne, Devante; Jones, Peter; Salgaonkar, Vasant; Adams, Matt; Ozilgen, B. Arda; Zahos, Peter; Tang, Xinyan; Liebenberg, Ellen; Coughlin, Dezba; Lotz, Jeffrey; Diederich, Chris

2017-02-01

Discogenic back pain presents a major public health issue, with current therapeutic interventions limited to short-term symptom relief without providing regenerative remedies for diseased intervertebral discs (IVD). Many of these interventions are invasive and can diminish the biomechanical integrity of the IVDs. Low intensity pulsed ultrasound (LIPUS) is a potential treatment option that is both non-invasive and regenerative. LIPUS has been shown to be a clinically effective method for the enhancement of wound and fracture healing. Recent in vitro studies have shown that LIPUS stimulation induces an upregulation functional matrix proteins and downregulation of inflammatory factors in cultured IVD cells. However, we do not know the effects of LIPUS on an in vivo model for intervertebral disc degeneration. The objective of this study was to show technical feasibility of building a LIPUS system that can target the rat tail IVD and apply this setup to a model for acute IVD degeneration. A LIPUS exposimetry system was built using a 1.0 MHz planar transducer and custom housing. Ex vivo intensity measurements demonstrated LIPUS delivery to the center of the rat tail IVD. Using an established stab-incision model for disc degeneration, LIPUS was applied for 20 minutes daily for five days. For rats that displayed a significant injury response, LIPUS treatment caused significant upregulation of Collagen II and downregulation of Tumor Necrosis Factor - α gene expression. Our preliminary studies indicate technical feasibility of targeted delivery of ultrasound to a rat tail IVD for studies of LIPUS biological effects.

A mass spectrometer for pain-response monitoring in rats

NASA Astrophysics Data System (ADS)

Elizarov, A. Yu.

2017-06-01

A mass spectrometer with a membrane interface has been used for measuring the relative concentration of carbon dioxide (CO2) released from rat skin in response to thermal irritation and pain stimulus during intraperitoneal propofol-lidocaine anesthesia. It is established that the local anesthetic lidocaine directly influences the central nervous system and induces antinociceptive reaction to thermal irritation.

Osthole protects against inflammation in a rat model of chronic kidney failure via suppression of nuclear factor-κB, transforming growth factor-β1 and activation of phosphoinositide 3-kinase/protein kinase B/nuclear factor (erythroid-derived 2)-like 2 signaling.

PubMed

Huang, Tao; Dong, Zhen

2017-10-01

Multiple pharmacological applications of osthole have been previously recognized, including antioxidant, anti-inflammatory, anti‑platelet and estrogenic effects, and resistance to pain. The present study investigated the protective effects of osthole against inflammation in a rat model of chronic kidney failure (CRF) and the underlying mechanisms. Osthole treatment with significantly reversed CRF‑induced changes in serum creatinine, calcium, phosphorus and blood urea nitrogen levels in CRF rats. Male Sprague‑Dawley rats (age, 8 weeks) received 200 mg/kg 2% adenine suspension to induce CRF in the model group. In the osthole‑treated group, rats received 200 mg/kg 2% adenine suspension + osthole (40 mg/kg, intravenously). The results revealed that treatment with osthole significantly inhibited CRF‑induced tumor necrosis factor‑α, interleukin (IL)‑8 and IL‑6 expression, and suppressed nuclear factor‑κB (NF‑κB) protein expression in CRF rats. Osthole treatment significantly attenuated the protein expression of transforming growth factor‑β1 (TGF‑β1), reduced monocyte chemoattractant protein‑1 activity and increased the phosphoinositide 3‑kinase (PI3K)/protein kinase B (Akt) ratio in CRF rats. These results suggested that osthole protects against inflammation in a rat model of CRF via suppression of NF‑κB and TGF‑β1, and activation of PI3K/Akt/nuclear factor (erythroid‑derived 2)‑like 2 signaling. Therefore, osthole may represent a potential therapeutic agent for the treatment of CRF.

Interaction of a Cannabinoid-2 Agonist With Tramadol on Nociceptive Thresholds and Immune Responses in a Rat Model of Incisional Pain.

PubMed

Stachtari, Chrysoula C; Thomareis, Olympia N; Tsaousi, Georgia G; Karakoulas, Konstantinos A; Chatzimanoli, Foteini I; Chatzopoulos, Stavros A; Vasilakos, Dimitrios G

The aim of this study was to elucidate the antinociceptive interaction between cannabinoids and tramadol and their impact on proinflammatory response, in terms of serum intereleukin-6 (IL-6) and interleukin-2 (IL-2) release, in a rat model of incisional pain. Prospective randomized trial assessing the individual or combined application of intraperitoneal tramadol (10 mg/kg) and the selective cannabinoid-2 (CB-2) agonist (R,S)-AM1241 (1 mg/kg) applied postsurgical stress stimulus. Pharmacological specificity was established by antagonizing tramadol with naloxone (0.3 mg/kg) and (R,S)-AM1241 with SR144528 (1 mg/kg). Thermal allodynia was assessed by hot plate test 30 (T30), 60 (T60), and 120 (T120) minutes after incision. Blood samples for plasma IL-6 and IL-2 level determination were obtained 2 hours after incision. Data from 42 rats were included in the final analyses. Significant augmentation of thermal threshold was observed at all time points, after administration of either tramadol or (R,S)-AM1241 compared with the control group (P = 0.004 and P = 0.015, respectively). The combination of (R,S)-AM1241 plus tramadol promoted the induced antinociception in an important manner compared with control (P = 0.002) and (R,S)-AM1241 (P = 0.022) groups. Although the antiallodynic effect produced by tramadol was partially reversed by naloxone 30 and 60 minutes after incision (P = 0.028 and P = 0.016, respectively), SR144528 blocked the effects of (R,S)-AM1241 administration in a significant manner (P = 0.001) at all time points. Similarly, naloxone plus SR144528 also blocked the effects of the combination of (R,S)-AM1241 with tramadol at all time points (P = 0.000). IL-6 level in (R,S)-AM1241 plus tramadol group was significantly attenuated compared with control group (P = 0.000). Nevertheless, IL-2 levels remained unchanged in all experimental groups. It seems that the concomitant administration of a selective CB-2 agonist with tramadol in incisional pain model may improve antinociceptive effects and immune responses of cannabinoids, but this effect does not seem to be superior to that of tramadol alone.

Lumbar Facet Joint Compressive Injury Induces Lasting Changes in Local Structure, Nociceptive Scores, and Inflammatory Mediators in a Novel Rat Model

PubMed Central

Henry, James L.; Yashpal, Kiran; Vernon, Howard; Kim, Jaesung; Im, Hee-Jeong

2012-01-01

Objective. To develop a novel animal model of persisting lumbar facet joint pain. Methods. Sprague Dawley rats were anaesthetized and the right lumbar (L5/L6) facet joint was exposed and compressed to ~1 mm with modified clamps applied for three minutes; sham-operated and naïve animals were used as control groups. After five days, animals were tested for hind-paw sensitivity using von Frey filaments and axial deep tissue sensitivity by algometer on assigned days up to 28 days. Animals were sacrificed at selected times for histological and biochemical analysis. Results. Histological sections revealed site-specific loss of cartilage in model animals only. Tactile hypersensitivity was observed for the ipsi- and contralateral paws lasting 28 days. The threshold at which deep tissue pressure just elicited vocalization was obtained at three lumbar levels; sensitivity at L1 > L3/4 > L6. Biochemical analyses revealed increases in proinflammatory cytokines, especially TNF-α, IL-1α, and IL-1β. Conclusions. These data suggest that compression of a facet joint induces a novel model of local cartilage loss accompanied by increased sensitivity to mechanical stimuli and by increases in inflammatory mediators. This new model may be useful for studies on mechanisms and treatment of lumbar facet joint pain and osteoarthritis. PMID:22966427

Epigenetic suppression of potassium-chloride co-transporter 2 expression in inflammatory pain induced by complete Freund's adjuvant (CFA).

PubMed

Lin, C-R; Cheng, J-K; Wu, C-H; Chen, K-H; Liu, C-K

2017-02-01

Multiple mechanisms contribute to the stimulus-evoked pain hypersensitivity that may be experienced after peripheral inflammation. Persistent pathological stimuli in many pain conditions affect the expression of certain genes through epigenetic alternations. The main purpose of our study was to investigate the role of epigenetic modification on potassium-chloride co-transporter 2 (KCC2) gene expression in the persistence of inflammatory pain. Persistent inflammatory pain was induced through the injection of complete Freund's adjuvant (CFA) in the left hind paw of rats. Acetyl-histone H3 and H4 level was determined by chromatin immunoprecipitation in the spinal dorsal horn. Pain behaviour and inhibitory synaptic function of spinal cord were determined before and after CFA injection. KCC2 expression was determined by real time RT-PCR and Western blot. Intrathecal KCC2 siRNA (2 μg per 10 μL per rat) or HDAC inhibitor (10 μg per 10 μL per rat) was injected once daily for 3 days before CFA injection. Persistent inflammatory pain epigenetically suppressed KCC2 expression through histone deacetylase (HDAC)-mediated histone hypoacetylation, resulting in decreased inhibitory signalling efficacy. KCC2 knock-down caused by intrathecal administration of KCC2 siRNA in naïve rats reduced KCC2 expression in the spinal cord, leading to sensitized pain behaviours and impaired inhibitory synaptic transmission in their spinal cords. Moreover, intrathecal HDAC inhibitor injection in CFA rats increased KCC2 expression, partially restoring the spinal inhibitory synaptic transmission and relieving the sensitized pain behaviour. These findings suggest that the transcription of spinal KCC2 is regulated by histone acetylation epigenetically following CFA. Persistent pain suppresses KCC2 expression through HDAC-mediated histone hypoacetylation and consequently impairs the inhibitory function of inhibitory interneurons. Drugs such as HDAC inhibitors that suppress the influences of persistent pain on the expression of KCC2 may serve as a novel analgesic. © 2016 European Pain Federation - EFIC®.

Rat PPAR delta contains a CGG triplet repeat and is prominently expressed in the thalamic nuclei.

PubMed

Xing, G; Zhang, L; Zhang, L; Heynen, T; Yoshikawa, T; Smith, M; Weiss, S; Detera-Wadleigh, S

1995-12-26

We have isolated a new rat sequence containing motifs of a nuclear hormone receptor from a brain cDNA library. The deduced amino acid sequence encoded by the cDNA clone showed a strong homology to the human NUCI and the mouse peroxisome proliferator activated receptor delta (PPAR delta). We therefore refer to this new clone as rat PPAR delta (rPPAR delta). The new feature of rPPAR delta is a 14 CGG triplet repeat on the 5' untranslated region, not previously reported in either NUCI or mPPAR delta. We found that rPPAR delta was expressed as a 3.5-kb transcript which showed a wide distribution in adult rat tissues. Abundant expression was detected in brain, heart, skeletal muscle, kidney and lung. Weaker expression was noted in the liver, spleen and testis. To determine the specific brain localization of rPPAR delta we performed in situ hybridization analysis. Prominent expression was observed in the thalamus, particularly in the posterior part of the ventral medial nucleus, a site responsive to pain and cold stress. These results raise the possibility that PPAR delta might play a role in modulating response to thermal and pain sensations.

The effects of oxotremorine, epibatidine, atropine, mecamylamine and naloxone in the tail-flick, hot-plate, and formalin tests in the naked mole-rat (Heterocephalus glaber).

PubMed

Dulu, Thomas D; Kanui, Titus I; Towett, Philemon K; Maloiy, Geoffrey M; Abelson, Klas S P

2014-01-01

The naked mole-rat (Heterocephalus glaber) is a promising animal model for the study of pain mechanisms, therefore a thorough characterization of this species is essential. The aim of the present study was to establish the naked mole-rat as a model for studying the cholinergic receptor system in antinociception by investigating the involvement of muscarinic, nicotinic and opioid receptors in nociceptive tests in this species. The effects of systemic administration of the muscarinic receptor agonist oxotremorine and the nicotinic receptor agonist epibatidine were investigated in the tail-flick, the hot-plate, and the formalin tests. The effects of co-administration of the muscarinic receptor antagonist atropine, the nicotinic receptor antagonist mecamylamine, and the opioid receptor antagonist naloxone were also investigated. Oxotremorine and epibatidine induced a significant, dose-dependent antinociceptive effect in the tail-flick, hot-plate, and formalin tests, respectively. The effects of oxotremorine and epibatidine were blocked by atropine and mecamylamine, respectively. In all three nociceptive tests, naloxone in combination with oxotremorine or epibatidine enhanced the antinociceptive effects of the drugs. The present study demonstrated that stimulation of muscarinic and nicotinic receptors produces antinociceptive effects in the naked-mole rat. The reversal effect of atropine and mecamylamine suggests that this effect is mediated by cholinergic receptors. As naloxone increases the antinociceptive effects of cholinergic agonists, it is suggested that the cholinergic antinociception acts via a gateway facilitated by opioid receptor blockage; however, the precise interaction between these receptor systems needs further investigation.

Naringenin regulates production of matrix metalloproteinases in the knee-joint and primary cultured articular chondrocytes and alleviates pain in rat osteoarthritis model.

PubMed

Wang, C C; Guo, L; Tian, F D; An, N; Luo, L; Hao, R H; Wang, B; Zhou, Z H

2017-03-23

Inflammation of cartilage is a primary symptom for knee-joint osteoarthritis. Matrix metalloproteinases (MMPs) are known to play an important role in the articular cartilage destruction related to osteoarthritis. Naringenin is a plant-derived flavonoid known for its anti-inflammatory properties. We studied the effect of naringenin on the transcriptional expression, secretion and enzymatic activity of MMP-3 in vivo in the murine monosodium iodoacetate (MIA) osteoarthritis model. The assessment of pain behavior was also performed in the MIA rats. The destruction of knee-joint tissues was analyzed microscopically. Moreover, the effect of naringenin was also studied in vitro in IL-1β activated articular chondrocytes. The transcriptional expression of MMP-3, MMP-1, MMP-13, thrombospondin motifs (ADAMTS-4) and ADAMTS-5 was also studied in primary cultured chondrocytes of rats. Naringenin caused significant reduction in pain behavior and showed marked improvement in the tissue morphology of MIA rats. Moreover, a significant inhibition of MMP-3 expression in MIA rats was observed upon treatment with naringenin. In the in vitro tests, naringenin caused a significant reduction in the transcriptional expression, secretion and enzymatic activity of the studied degradative enzymes. The NF-κB pathway was also found to be inhibited upon treatment with naringenin in vitro. Overall, the study suggests that naringenin alleviated pain and regulated the production of matrix-metalloproteinases via regulation of NF-κB pathway. Thus, naringenin could be a potent therapeutic option for the treatment of osteoarthritis.

Local Drug Infiltration Analgesia During Knee Surgery to Reduce Postoperative Pain in Rats.

PubMed

Buvanendran, Asokumar; Kroin, Jeffrey S; Della Valle, Craig J; Moric, Mario; Tuman, Kenneth J

2016-01-01

There is increasing interest in local infiltration analgesia (LIA) to reduce postoperative pain with knee surgery. Despite widespread use of LIA, wide variations in drug combinations, infiltration techniques, and the concomitant use of systemic analgesics have made it difficult to determine the optimal drug combination for LIA.Using a previously validated animal knee surgery model, we aimed to determine the optimal combination of medications to reduce postoperative pain, and the best anatomical location and timing for local drug injection during surgery. Knee surgery was performed in an adult rat model under isoflurane anesthesia. During surgery, combinations of bupivacaine, ketorolac, dexamethasone, and morphine were injected around the knee and compared to saline placebo. Similar medications were injected systemically as a comparator group. Postoperative pain was assessed by measuring spontaneous rearing activity. Injections were given after bone drilling and/or just before wound closure. The 3-drug LIA combination of bupivacaine, ketorolac, and dexamethasone increased rearing (decreased pain) at 2 hours (P = 0.0198) and 24 hours (P = 0.0384) postsurgery compared to saline. The same drugs injected systemically had no effect. The ketorolac/dexamethasone combination for LIA was also effective at 2 hours (P = 0.0006) and 24 hours (P = 0.0279), and ketorolac alone reduced pain at 2 hours (P = 0.0045). Bupivacaine alone was less effective, and the addition of morphine had no effect. The 3-drug combination infiltrated just after creating holes in bone was more effective than when given into the wound just before wound closure. Our animal study suggests that clinical trials with LIA combinations of local anesthetic, nonsteroidal anti-inflammatory drug, and corticosteroid might be useful for reducing postoperative pain after knee surgery, with the nonsteroidal anti-inflammatory drug having the greatest effect.Perioperative physicians should consider delivering LIA earlier during the procedure as opposed to solely at the time of wound closure.

Analgesic and anti-arthritic effects of Lingzhi and San Miao San supplementation in a rat model of arthritis induced by Freund's complete adjuvant.

PubMed

Lam, Francis Fu Yuen; Ko, Iris Wai Man; Ng, Ethel Sau Kuen; Tam, Lai Shan; Leung, Ping Chung; Li, Edmund Kwok Ming

2008-10-30

In this study, we have investigated the analgesic and anti-arthritic effects of a traditional Chinese medicine (TCM) combination of Lingzhi and San Miao San (SMS) in a rat model of arthritis induced by Freund's complete adjuvant (FCA). Sprague-Dawley rats were induced with monoarthritis by single unilateral injection of FCA into the knee joint. The TCM combination was administered to the rats daily by intraperitoneal injection (50mg/(kgday)) or via oral administration (500mg/(kgday)) for 7 days before induction of arthritis and 7 days after. Extension angle that provoked struggling behavior, and size and blood flow of the rat knees were measured to give indexes of allodynia, edema, and hyperemia, respectively. The extent of cell infiltration, tissue proliferation, and erosions of joint cartilage provided additional indexes of the arthritis condition. FCA injection produced significant allodynia, edema, hyperemia, immune cell infiltration, synovial tissue proliferation, and erosions of joint cartilage in the ipsilateral knees compared with the contralateral saline-injected knees. Intraperitoneal injection of the TCM combination (50mg/(kgday)) suppressed allodynia, edema, and hyperemia in the inflamed knees, and oral administration (500mg/(kgday)) suppressed edema and hyperemia. Histological examination showed that the TCM administered by either route reduced immune cell infiltration and erosion of joint cartilage. These findings suggest the Lingzhi and SMS formulation has analgesic and anti-inflammatory effects in arthritic rat knees, and concur to previous clinical studies that showed the TCM combination reduced pain in rheumatoid arthritis patients, and extends its possible benefit to suppression of inflammatory symptoms in these patients.

The cumulative analgesic effect of repeated electroacupuncture involves synaptic remodeling in the hippocampal CA3 region☆

PubMed Central

Xu, Qiuling; Liu, Tao; Chen, Shuping; Gao, Yonghui; Wang, Junying; Qiao, Lina; Liu, Junling

2012-01-01

In the present study, we examined the analgesic effect of repeated electroacupuncture at bilateral Zusanli (ST36) and Yanglingquan (GB34) once a day for 14 consecutive days in a rat model of chronic sciatic nerve constriction injury-induced neuropathic pain. In addition, concomitant changes in calcium/calmodulin-dependent protein kinase II expression and synaptic ultrastructure of neurons in the hippocampal CA3 region were examined. The thermal pain threshold (paw withdrawal latency) was increased significantly in both groups at 2 weeks after electroacupuncture intervention compared with 2 days of electroacupuncture. In ovariectomized rats with chronic constriction injury, the analgesic effect was significantly reduced. Electroacupuncture for 2 weeks significantly diminished the injury-induced increase in synaptic cleft width and thinning of the postsynaptic density, and it significantly suppressed the down-regulation of intracellular calcium/calmodulin-dependent protein kinase II expression in the hippocampal CA3 region. Repeated electroacupuncture intervention had a cumulative analgesic effect on injury-induced neuropathic pain reactions, and it led to synaptic remodeling of hippocampal neurons and upregulated calcium/calmodulin-dependent protein kinase II expression in the hippocampal CA3 region. PMID:25657670

Analgesic effect of Minocycline in rat model of inflammation-induced visceral pain

PubMed Central

Kannampalli, Pradeep; Pochiraju, Soumya; Bruckert, Mitchell; Shaker, Reza; Banerjee, Banani; Sengupta, Jyoti N.

2014-01-01

The present study investigates the analgesic effect of minocycline, a semi-synthetic tetracycline antibiotic, in a rat model of inflammation-induced visceral pain. Inflammation was induced in male rats by intracolonic administration of tri-nitrobenzenesulphonic acid (TNBS). Visceral hyperalgesia was assessed by comparing the viscero-motor response (VMR) to graded colorectal distension (CRD) prior and post 7 days after TNBS treatment. Electrophysiology recordings from CRD-sensitive pelvic nerve afferents (PNA) and lumbo-sacral (LS) spinal neurons were performed in naïve and inflamed rats. Colonic inflammation produced visceral hyperalgesia characterized by increase in the VMRs to CRD accompanied with simultaneous activation of microglia in the spinal cord and satellite glial cells (SGCs) in the dorsal root ganglions (DRGs). Selectively inhibiting the glial activation following inflammation by araC (Arabinofuranosyl Cytidine) prevented the development of visceral hyperalgesia. Intrathecal minocycline significantly attenuated the VMR to CRD in inflamed rats, whereas systemic minocycline produced a delayed effect. In electrophysiology experiments, minocycline significantly attenuated the mechanotransduction of CRD-sensitive PNAs and the responses of CRD-sensitive LS spinal neurons in TNBS-treated rats. While the spinal effect of minocycline was observed within 5 min of administration, systemic injection of the drug produced a delayed effect (60 min) in inflamed rats. Interestingly, minocycline did not exhibit analgesic effect in naïve, non-inflamed rats. The results demonstrate that intrathecal injection of minocycline can effectively attenuate inflammation-induced visceral hyperalgesia. Minocycline might as well act on neuronal targets in the spinal cord of inflamed rats, in addition to the widely reported glial inhibitory action to produce analgesia. PMID:24485889

Paradoxical effects of the cannabinoid CB2 receptor agonist GW405833 on rat osteoarthritic knee joint pain.

PubMed

Schuelert, N; Zhang, C; Mogg, A J; Broad, L M; Hepburn, D L; Nisenbaum, E S; Johnson, M P; McDougall, J J

2010-11-01

The present study examined whether local administration of the cannabinoid-2 (CB(2)) receptor agonist GW405833 could modulate joint nociception in control rat knee joints and in an animal model of osteoarthritis (OA). OA was induced in male Wistar rats by intra-articular injection of sodium monoiodo-acetate with a recovery period of 14 days. Immunohistochemistry was used to evaluate the expression of CB(2) and transient receptor potential vanilloid channel-1 (TRPV1) receptors in the dorsal root ganglion (DRG) and synovial membrane of sham- and sodium mono-iodoacetate (MIA)-treated animals. Electrophysiological recordings were made from knee joint primary afferents in response to rotation of the joint both before and following close intra-arterial injection of different doses of GW405833. The effect of intra-articular GW405833 on joint pain perception was determined by hindlimb incapacitance. An in vitro neuronal release assay was used to see if GW405833 caused release of an inflammatory neuropeptide (calcitonin gene-related peptide - CGRP). CB(2) and TRPV1 receptors were co-localized in DRG neurons and synoviocytes in both sham- and MIA-treated animals. Local application of the GW405833 significantly reduced joint afferent firing rate by up to 31% in control knees. In OA knee joints, however, GW405833 had a pronounced sensitising effect on joint mechanoreceptors. Co-administration of GW405833 with the CB(2) receptor antagonist AM630 or pre-administration of the TRPV1 ion channel antagonist SB366791 attenuated the sensitising effect of GW405833. In the pain studies, intra-articular injection of GW405833 into OA knees augmented hindlimb incapacitance, but had no effect on pain behaviour in saline-injected control joints. GW405833 evoked increased CGRP release via a TRPV1 channel-dependent mechanism. These data indicate that GW405833 reduces the mechanosensitivity of afferent nerve fibres in control joints but causes nociceptive responses in OA joints. The observed pro-nociceptive effect of GW405833 appears to involve TRPV1 receptors. Copyright © 2010 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Up-Regulation of the Biosynthesis and Release of Substance P through Wnt/β-Catenin Signaling Pathway in Rat Dorsal Root Ganglion Cells

PubMed Central

Li, Yu-Sang; Xi, Yang; Li, Xiao-Jun; Leng, Chang-Long; Jia, Mei-Mei; Zhang, Wei Kevin; Tang, He-Bin

2015-01-01

To examine regulatory effects of β-catenin on the biosynthesis and release of substance P, a rat chronic constriction injury (CCI) model and a rat dorsal root ganglion (DRG) cell culture model were used in the present study. The CCI treatment significantly induced the overall expression of β-catenin (158 ± 6% of sham) in the ipsilateral L5 DRGs in comparison with the sham group (109 ± 4% of sham). The CCI-induced aberrant expression of β-catenin was significantly attenuated by oral administration of diclofenac (119 ± 6% of the sham value; 10 mg/kg). Importantly, aberrant nuclear accumulation of β-catenin in cultured DRG cells resulted in up-regulation of the PPT-A mRNA expression and the substance P release. The up-regulation of both the PPT-A mRNA expression and the substance P release by either a GSK-3β inhibitor TWS119 (10 μM) or a Wnt signaling agonist Wnt-3a (100 ng/ml) were significantly abolished by an inhibitor of cyclooxygenase-2 (COX-2; NS-398, 1 μM). Collectively, these data suggest that nociceptive input-activated β-catenin signaling plays an important role in regulating the biosynthesis and release of substance P, which may contribute to the inflammation responses related to chronic pain. PMID:26054011

MicroRNA cluster miR-17-92 regulates multiple functionally related voltage-gated potassium channels in chronic neuropathic pain

PubMed Central

Sakai, Atsushi; Saitow, Fumihito; Maruyama, Motoyo; Miyake, Noriko; Miyake, Koichi; Shimada, Takashi; Okada, Takashi; Suzuki, Hidenori

2017-01-01

miR-17-92 is a microRNA cluster with six distinct members. Here, we show that the miR-17-92 cluster and its individual members modulate chronic neuropathic pain. All cluster members are persistently upregulated in primary sensory neurons after nerve injury. Overexpression of miR-18a, miR-19a, miR-19b and miR-92a cluster members elicits mechanical allodynia in rats, while their blockade alleviates mechanical allodynia in a rat model of neuropathic pain. Plausible targets for the miR-17-92 cluster include genes encoding numerous voltage-gated potassium channels and their modulatory subunits. Single-cell analysis reveals extensive co-expression of miR-17-92 cluster and its predicted targets in primary sensory neurons. miR-17-92 downregulates the expression of potassium channels, and reduced outward potassium currents, in particular A-type currents. Combined application of potassium channel modulators synergistically alleviates mechanical allodynia induced by nerve injury or miR-17-92 overexpression. miR-17-92 cluster appears to cooperatively regulate the function of multiple voltage-gated potassium channel subunits, perpetuating mechanical allodynia. PMID:28677679

D1- and D2-like dopamine receptors within the nucleus accumbens contribute to stress-induced analgesia in formalin-related pain behaviours in rats.

PubMed

Faramarzi, G; Zendehdel, M; Haghparast, A

2016-10-01

Stressful experiences can produce analgesia, termed stress-induced analgesia (SIA). Meanwhile, it has been widely established that the mesolimbic dopamine pathway and nucleus accumbens (NAc) have a profound role in pain modulation. In this study, we examined the role of accumbal dopamine receptors in antinociception caused by forced swim stress (FSS) in order to understand more about the function of these receptors within the NAc in FSS-induced analgesia. Stereotaxic surgery was unilaterally performed on adult male Wistar rats weighing 230-250 g (some on the left and some on the right side of the midline). Two supergroups were microinjected into the NAc with a D1-like dopamine receptor antagonist, SCH-23390, at doses of 0.25, 1 and 4 μg/0.5 μl saline per rat or Sulpiride as a D2-like dopamine receptor antagonist at the same doses [0.25, 1 and 4 μg/0.5 μl dimethyl sulfoxide (DMSO) per rat]; while their controls just received intra-accumbal saline or DMSO at 0.5 μl, respectively. The formalin test was performed after rats were subjected to FSS (6 min, 25 ± 1 °C) to assess pain-related behaviours. The results demonstrated that intra-accumbal infusions of SCH-23390 and Sulpiride dose-dependently reduced FSS-induced antinociception in both phases of the formalin test. However, the percentage decrease in area under the curve (AUC) values calculated for treatment groups compared to formalin-control group was more significant in the late phase than the early phase. Our findings suggest that D1- and D2-like dopamine receptors in the NAc are involved in stress-induced antinociceptive behaviours in the formalin test as an animal model of persistent inflammatory pain. Forced swim stress (FSS) induces the antinociception in both phases of formalin test. Blockade of accumbal dopamine receptors attenuate the antinociception induced by FSS. Stress-induced analgesia is dose-dependently reduced by dopamine receptor antagonists in both phases, although it is more prominent during the late phase. © 2016 European Pain Federation - EFIC®

Antinociceptive and anti-inflammatory effects of the methanolic stem bark extract of Antrocaryon klaineanum Pierre (Anacardiaceae) in mice and rat.

PubMed

Fongang, Annie Laure Magne; Laure Nguemfo, Edwige; Djouatsa Nangue, Yolande; Bogning Zangueu, Calvin; Fouokeng, Yannick; Azebaze, Anatole Guy Blaise; José Llorent-Martínez, Eulogio; Córdova, Maria Luisa Fernández-de; Bertrand Dongmo, Alain; Vierling, Wolfgang

2017-05-05

Antrocaryon klaineanum is used by traditional healers to treat many disorders including pain and inflammatory diseases. This study aimed to evaluate the analgesic and antiinflammatory activities of methanol extract of A. klaineanum in mice and rats. Reverse phase high-performance liquid chromatography (RP-HPLC) was performed to establish the chromatographic fingerprint and to identify various chemical components of the plant extract. The anti-nociceptive activity of methanol extract of A. klaineanum was assessed using the acetic acid-induced abdominal constriction model, formalin test, capsaicin and cinnamaldehyde induced-neurogenic pain and hot plate test. Anti-inflammatory activity was assessed on carrageenan-induced inflammation. Extract was administrated orally at 200, 400 and 600mg/kg. Phytochemical analysis indicated the presence of proanthocyanidins, phenolic acids and flavonoids. The results of anti-nociceptive and anti-inflammatory activities showed that methanol extract significantly (p<0.01) reduced the pain induced by acetic acid with an inhibition percentage of 45.49% (600mg/kg). In the formalin test, the extract also significantly (p<0.01) reduced linking time in both phase (neurogenic and inflammatory) of the test with inhibition percentage of 56.28% and 60.73% respectively at the dose of 600mg/kg. The methanol extract of A. klaineanum significantly (P<0.001) reduced neurogenic pain linking time induced by capsaicin and cinnamaldehyde by 82.54% and 75.94% at the highest dose (600mg/kg) respectively. More over the extract significantly increase the reaction time in hot plate test. In the inflammatory test, the plant extract significantly reduced the carrageen induced rat paw oedema from 30min to 6h with a maximum percentage inhibition of 89.88% (6h) at the dose of 600mg/kg. These results demonstrate that the methanol extract of A. klaineanum may possess analgesic and anti-inflammatory effects and provide support of the traditional use of this plant in the treatment of different pain and inflammatory conditions. Further investigation could reveal metabolites of the extract responsible for the observed effects. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

High-frequency transcutaneous electrical nerve stimulation attenuates postsurgical pain and inhibits excess substance P in rat dorsal root ganglion.

PubMed

Chen, Yu-Wen; Tzeng, Jann-Inn; Lin, Min-Fei; Hung, Ching-Hsia; Hsieh, Pei-Ling; Wang, Jhi-Joung

2014-01-01

Transcutaneous electrical nerve stimulation (TENS) is a common therapeutic modality for pain management, but its effectiveness in skin/muscle incision and retraction (SMIR)-evoked pain is unknown. We aimed to examine the effects of TENS on postoperative pain and the levels of substance P (SP), N-methyl-D-aspartate receptor 1 (NR1), and interleukin 1β (IL-1β) in rat dorsal root ganglion (DRG). High-frequency (100 Hz) TENS was administered daily beginning on postoperative day 1 (POD1) and continued until animal subjects were killed for tissues. Mechanical sensitivity to von Frey stimuli (6g and 15g) and the levels of NR1, SP, and IL-1β in DRG were assessed in the sham-operated, SMIR-operated, TENS after SMIR surgery, and placebo-TENS after SMIR surgery groups. Skin/muscle incision and retraction rats exhibited a significant hypersensitivity to von Frey stimuli on POD3. In contrast with SMIR rats, SMIR-operated rats receiving TENS therapy demonstrated a rapid recovery of mechanical hypersensitivity. The SMIR-operated rats showed an up-regulation of NR1, SP, and IL-1β in DRG on PODs 14 and 28, whereas the SMIR-operated rats after TENS administration reversed this up-regulation. By contrast, the placebo-TENS after SMIR operation did not alter postsurgical pain nor the levels of NR1, SP, and IL-1β. Our data demonstrated that TENS intervention reduced persistent postoperative pain caused by SMIR operation. Up-regulation of NR1, SP, and IL-1β in DRG, activated after SMIR surgery, is important in the development of prolonged postincisional pain. The TENS pain relief may be related to the suppression of NR1, SP, and IL-1β in DRG of SMIR rats.

Monosodium iodoacetate-induced joint pain is associated with increased phosphorylation of mitogen activated protein kinases in the rat spinal cord.

PubMed

Lee, Younglim; Pai, Madhavi; Brederson, Jill-Desiree; Wilcox, Denise; Hsieh, Gin; Jarvis, Michael F; Bitner, Robert S

2011-05-20

Intra-articular injection of monosodium iodoacetate (MIA) in the knee joint of rats disrupts chondrocyte metabolism resulting in cartilage degeneration and subsequent nociceptive behavior that has been described as a model of osteoarthritis (OA) pain. Central sensitization through activation of mitogen activated protein kinases (MAPKs) is recognized as a pathogenic mechanism in chronic pain. In the present studies, induction of central sensitization as indicated by spinal dorsal horn MAPK activation, specifically ERK and p38 phosphorylation, was assessed in the MIA-OA model. Behaviorally, MIA-injected rats displayed reduced hind limb grip force 1, 2, and 3 weeks post-MIA treatment. In the same animals, activation of phospho ERK1/2 was gradually increased, reaching a significant level at post injection week 3. Conversely, phosphorylation of p38 MAPK was enhanced maximally at post injection week 1 and decreased, but remained elevated, thereafter. Double labeling from 3-wk MIA rats demonstrated spinal pERK1/2 expression in neurons, but not glia. In contrast, p-p38 was expressed by microglia and a subpopulation of neurons, but not astrocytes. Additionally, there was increased ipsilateral expression of microglia, but not astrocytes, in 3-wk MIA-OA rats. Consistent with increased MAPK immunoreactivity in the contralateral dorsal horn, mechanical allodynia to the contralateral hind-limb was observed 3-wk following MIA. Finally, intrathecal injection of the MEK1 inhibitor PD98059 blocked both reduced hind-limb grip force and pERK1/2 induction in MIA-OA rats. Results of these studies support the role of MAPK activation in the progression and maintenance of central sensitization in the MIA-OA experimental pain model.

The thalidomide analgesic effect is associated with differential TNF-α receptor expression in the dorsal horn of the spinal cord as studied in a rat model of neuropathic pain.

PubMed

Andrade, Pablo; Visser-Vandewalle, Veerle; Del Rosario, John S; Daemen, Marc A; Buurman, Wim A; Steinbusch, Harry W; Hoogland, Govert

2012-04-23

The proinflammatory cytokine tumor necrosis factor-α (TNF-α) is well recognized as a key player in nociceptive signaling. Yet, therapeutic capitalization of this knowledge requires a better understanding of how TNF receptors (TNFR) contribute to pain. To address this question, we studied TNFR expression in the chronic sciatic nerve constriction (CCI) model of neuropathic pain. CCI and sham operated rats received two subcutaneous injections (one immediately after surgery, the other on postoperative day 5) containing either saline, GABA-reuptake inhibitor (NO-711), insulin-like growth factor-1 (IGF-1), ZVAD or thalidomide. Mechanical (using von Frey filaments) and thermal hypersensitivity (Hargreaves test) were assessed preoperatively and weekly during the first four postoperative weeks. Spinal cord dorsal horn samples were collected from animals that were sacrificed at 2 weeks and 4 weeks after surgery, and analyzed for TNFR1 and TNFR2 mRNA levels by qPCR and protein levels by Western blot. Compared to saline, all applied drug treatments resulted in a faster recovery from mechanical and thermal hypersensitivity, yet in a potency order of thalidomide>ZVAD=IGF-1>NO-711. CCI resulted in increased TNFR1 and TNFR2 mRNA and protein levels in the ipsilateral dorsal horn. Thalidomide was the only treatment that attenuated these increases. Finally, animals that showed a poor behavioral recovery were characterized by a significantly higher TNFR1/TNFR2 mRNA ratio. These data show that differential expression of TNFR in the dorsal horn is associated with recovery from pain in this model and suggest that the analgesic effects of thalidomide may act via this mechanism. Copyright © 2012 Elsevier B.V. All rights reserved.

Pharmacologic Profile of Naloxegol, a Peripherally Acting µ-Opioid Receptor Antagonist, for the Treatment of Opioid-Induced Constipation

PubMed Central

Floettmann, Eike; Sostek, Mark; Payza, Kemal; Eldon, Michael

2017-01-01

Opioid-induced constipation (OIC) is a common side effect of opioid pharmacotherapy for the management of pain because opioid agonists bind to µ-opioid receptors in the enteric nervous system (ENS). Naloxegol, a polyethylene glycol derivative of naloxol, which is a derivative of naloxone and a peripherally acting µ-opioid receptor antagonist, targets the physiologic mechanisms that cause OIC. Pharmacologic measures of opioid activity and pharmacokinetic measures of central nervous system (CNS) penetration were employed to characterize the mechanism of action of naloxegol. At the human µ-opioid receptor in vitro, naloxegol was a potent inhibitor of binding (Ki = 7.42 nM) and a neutral competitive antagonist (pA2 - 7.95); agonist effects were <10% up to 30 μM and identical to those of naloxone. The oral doses achieving 50% of the maximal effect in the rat for antagonism of morphine-induced inhibition of gastrointestinal transit and morphine-induced antinociception in the hot plate assay were 23.1 and 55.4 mg/kg for naloxegol and 0.69 and 1.14 mg/kg by for naloxone, respectively. In the human colon adenocarcinoma cell transport assay, naloxegol was a substrate for the P-glycoprotein transporter, with low apparent permeability in the apical to basolateral direction, and penetrated the CNS 15-fold slower than naloxone in a rat brain perfusion model. Naloxegol-derived radioactivity was poorly distributed throughout the rat CNS and was eliminated from most tissues within 24 hours. These findings corroborate phase 3 clinical studies demonstrating that naloxegol relieves OIC-associated symptoms in patients with chronic noncancer pain by antagonizing the µ-opioid receptor in the ENS while preserving CNS-mediated analgesia. PMID:28336575

Endogenous opioids released during non-nociceptive environmental stress induce latent pain sensitization Via a NMDA-dependent process.

PubMed

Le Roy, Chloé; Laboureyras, Emilie; Gavello-Baudy, Stéphanie; Chateauraynaud, Jérémy; Laulin, Jean-Paul; Simonnet, Guy

2011-10-01

Although stress induces analgesia, there is evidence that stressful events may exacerbate pain syndromes. Here, we studied the effects of 1 to 3 prestressful events (days 0, 2, and 7), such as non-nociceptive environmental stress, on inflammatory hyperalgesia induced by a carrageenan injection (day 14) in 1 rat hind paw. Changes in nociceptive threshold were evaluated by the paw pressure vocalization test. The higher the number of stress sessions presented to the rats, the greater was the inflammatory hyperalgesia. Blockade of opioid receptors by naltrexone before each stress inhibited stress-induced analgesia and suppressed the exaggerated inflammatory hyperalgesia. Stressed versus nonstressed animals could be discriminated by their response to a fentanyl ultra-low dose (fULD), that produced hyperalgesia or analgesia, respectively. This pharmacological test permitted the prediction of the pain vulnerability level of prestressed rats because fULD analgesic or hyperalgesic indices were positively correlated with inflammatory hyperalgesic indices (r(2) = .84). In prestressed rats, fULD-induced hyperalgesia and the exaggerated inflammatory hyperalgesia were prevented NMDA receptor antagonists. This study provides some preclinical evidence that pain intensity is not only the result of nociceptive input level but is also dependent on the individual history, especially prior life stress events associated with endogenous opioid release. Based on these preclinical data, it would be of clinical interest to evaluate whether prior stressful events may also affect further pain sensation in humans. Moreover, this preclinical model could be a good tool for evaluating new therapeutic strategies for relieving pain hypersensitivity. Copyright © 2011 American Pain Society. Published by Elsevier Inc. All rights reserved.

Evaluating the Toxicity of the Analgesic Glutaminase Inhibitor 6-Diazo-5-Oxo-L-Norleucine in vitro and on Rat Dermal Skin Fibroblasts

PubMed Central

Crosby, Heith A; Ihnat, Michael; Miller, Kenneth E

2018-01-01

6-diazo-5-oxo-l-norleucine (DON) is a glutamine antagonist produced naturally by Streptomyces. It inhibits several glutamine-dependent enzyme pathways. Of particular note is its inhibitory effect on the mitochondrial enzyme, glutaminase (GLS), the primary producer of neuronal glutamate. Glutamate is an excitatory neurotransmitter released by primary sensory peripheral nerve terminals and spinal synaptic terminals during pain signaling. Previous work using the tail incision and inflammatory models of pain has demonstrated that a single application of the glutaminase inhibitor, DON, into a surgical incision or the paw of arthritic animals results in pain relief. Even though this compound shows promise as a therapeutic agent, limited data exist regarding its dermal toxicity. As a first approach, we evaluated the effect of several concentrations of DON, on the viability, mitochondrial oxidative capacity and proliferation of rat skin fibroblasts, and then examined the effect of DON after incubation with human liver microsomes on proliferation. Finally, we evaluated DON treated rat skin (tail and hind paw) for cellular necrosis, inflammation and mitotic bodies. No significant effects (p > 0.05) of DON were noted on apoptosis, necrosis, and mitochondrial activity in experiments with cultured rat skin fibroblasts. Flow cytometry revealed the absence of apoptosis in cells treated at the IC50 of 232.5 μM. Enhanced toxicity post-exposure to human microsomes was not observed when compared to DON alone. The H&E staining of the rat skin revealed no obvious pathology in the DON treatment group (10 mM). DON has no/minimal cellular toxicity in vitro on dermal fibroblasts at concentrations that effectively provide analgesia. The local application of concentrations greater than the in vitro IC50 for DON revealed no in vivo skin toxicity. These data provide results indicating zero-to-minimal cellular toxicity with DON and support the further investigation of DON as an analgesic. PMID:29750203

Peripheral Nerve Injury Leads to Working Memory Deficits and Dysfunction of the Hippocampus by Upregulation of TNF-α in Rodents

PubMed Central

Ren, Wen-Jie; Liu, Yong; Zhou, Li-Jun; Li, Wei; Zhong, Yi; Pang, Rui-Ping; Xin, Wen-Jun; Wei, Xu-Hong; Wang, Jun; Zhu, He-Quan; Wu, Chang-You; Qin, Zhi-Hai; Liu, Guosong; Liu, Xian-Guo

2011-01-01

Patients with chronic pain usually suffer from working memory deficits, which may decrease their intellectual ability significantly. Despite intensive clinical studies, the mechanism underlying this form of memory impairment remains elusive. In this study, we investigated this issue in the spared nerve injury (SNI) model of neuropathic pain, a most common form of chronic pain. We found that SNI impaired working memory and short-term memory in rats and mice. To explore the potential mechanisms, we studied synaptic transmission/plasticity in hippocampus, a brain region critically involved in memory function. We found that frequency facilitation, a presynaptic form of short-term plasticity, and long-term potentiation at CA3–CA1 synapses were impaired after SNI. Structurally, density of presynaptic boutons in hippocampal CA1 synapses was reduced significantly. At the molecular level, we found that tumor necrosis factor-α (TNF-α) increased in cerebrospinal fluid, in hippocampal tissue and in plasma after SNI. Intracerebroventricular or intrahippocampal injection of recombinant rat TNF mimicked the effects of SNI in naive rats, whereas inhibition of TNF-α or genetic deletion of TNF receptor 1 prevented both memory deficits and synaptic dysfunction induced by SNI. As TNF-α is critical for development of neuropathic pain, we suggested that the over-production of TNF-α following peripheral nerve injury might lead to neuropathic pain and memory deficits, simultaneously. PMID:21289602

Pharmacologic Profile of Naloxegol, a Peripherally Acting µ-Opioid Receptor Antagonist, for the Treatment of Opioid-Induced Constipation.

PubMed

Floettmann, Eike; Bui, Khanh; Sostek, Mark; Payza, Kemal; Eldon, Michael

2017-05-01

Opioid-induced constipation (OIC) is a common side effect of opioid pharmacotherapy for the management of pain because opioid agonists bind to µ -opioid receptors in the enteric nervous system (ENS). Naloxegol, a polyethylene glycol derivative of naloxol, which is a derivative of naloxone and a peripherally acting µ -opioid receptor antagonist, targets the physiologic mechanisms that cause OIC. Pharmacologic measures of opioid activity and pharmacokinetic measures of central nervous system (CNS) penetration were employed to characterize the mechanism of action of naloxegol. At the human µ -opioid receptor in vitro, naloxegol was a potent inhibitor of binding ( K i = 7.42 nM) and a neutral competitive antagonist (p A 2 - 7.95); agonist effects were <10% up to 30 μ M and identical to those of naloxone. The oral doses achieving 50% of the maximal effect in the rat for antagonism of morphine-induced inhibition of gastrointestinal transit and morphine-induced antinociception in the hot plate assay were 23.1 and 55.4 mg/kg for naloxegol and 0.69 and 1.14 mg/kg by for naloxone, respectively. In the human colon adenocarcinoma cell transport assay, naloxegol was a substrate for the P-glycoprotein transporter, with low apparent permeability in the apical to basolateral direction, and penetrated the CNS 15-fold slower than naloxone in a rat brain perfusion model. Naloxegol-derived radioactivity was poorly distributed throughout the rat CNS and was eliminated from most tissues within 24 hours. These findings corroborate phase 3 clinical studies demonstrating that naloxegol relieves OIC-associated symptoms in patients with chronic noncancer pain by antagonizing the µ -opioid receptor in the ENS while preserving CNS-mediated analgesia. Copyright © 2017 The Author(s).

Synergistic interactions between paracetamol and oxcarbazepine in somatic and visceral pain models in rodents.

PubMed

Tomić, Maja A; Vucković, Sonja M; Stepanović-Petrović, Radica M; Ugresić, Nenad D; Prostran, Milica S; Bosković, Bogdan

2010-04-01

Combination therapy is a valid approach in pain treatment, in which a reduction of doses could reduce side effects and still achieve optimal analgesia. We examined the effects of coadministered paracetamol, a widely used non-opioid analgesic, and oxcarbazepine, a relatively novel anticonvulsant with analgesic properties, in a rat model of paw inflammatory hyperalgesia and in a mice model of visceral pain and determined the type of interaction between components. The effects of paracetamol, oxcarbazepine, and their combinations were examined in carrageenan-induced (0.1 mL, 1%) paw inflammatory hyperalgesia in rats and in an acetic acid-induced (10 mg/kg, 0.75%) writhing test in mice. In both models, drugs were coadministered in fixed-dose fractions of the 50% effective dose (ED(50)), and type of interaction was determined by isobolographic analysis. Paracetamol (50-200 mg/kg peroral), oxcarbazepine (40-160 mg/kg peroral), and their combination (1/8, 1/4, 1/3, and 1/2 of a single drug ED(50)) produced a significant, dose-dependent antihyperalgesia in carrageenan-injected rats. In the writhing test in mice, paracetamol (60-180 mg/kg peroral), oxcarbazepine (20-80 mg/kg peroral), and their combination (1/16, 1/8, 1/4, and 1/2 of a single drug ED(50)) significantly and dose dependently reduced the number of writhes. In both models, isobolographic analysis revealed a significant synergistic interaction between paracetamol and oxcarbazepine, with a >4-fold reduction of doses of both drugs in combination, compared with single drugs ED(50). The synergistic interaction between paracetamol and oxcarbazepine provides new information about combination pain treatment and should be explored further in patients, especially with somatic and/or visceral pain.

Alcohol and high fat induced chronic pancreatitis: TRPV4 antagonist reduces hypersensitivity.

PubMed

Zhang, L P; Kline, R H; Deevska, G; Ma, F; Nikolova-Karakashian, M; Westlund, K N

2015-12-17

The pathogenesis of pain in chronic pancreatitis is poorly understood, and its treatment can be a major clinical challenge. Surgical and other invasive methods have variable outcomes that can be unsatisfactory. Therefore, there is a great need for further discovery of the pathogenesis of pancreatitis pain and new therapeutic targets. Human and animal studies indicate a critical role for oxidative stress and activation of transient receptor potential (TRP) cation channel subfamily members TRPV1 and TRPA1 on pancreatic nociceptors in sensitization mechanisms that result in pain. However, the in vivo role of transient receptor potential cation channel subfamily V member 4 (TRPV4) in chronic pancreatitis needs further evaluation. The present study characterized a rat alcohol/high fat diet (AHF)-induced chronic pancreatitis model with hypersensitivity, fibrotic pathology, and fat vacuolization consistent with the clinical syndrome. The rats with AHF-induced pancreatitis develop referred visceral pain-like behaviors, i.e. decreased hindpaw mechanical thresholds and shortened abdominal and hindpaw withdrawal latency to heat. In this study, oxidative stress was characterized as well as the role of TRPV4 in chronic visceral hypersensitivity. Lipid peroxidase and oxidative stress were indicated by increased plasma thiobarbituric acid reactive substances (TBARS) and diminished pancreatic manganese superoxide dismutase (MnSOD). The secondary sensitization associated with AHF-induced pancreatitis was effectively alleviated by the TRPV4 antagonist, HC 067047. Similarity of the results to those with the peripherally restricted μ-opiate receptor agonist, loperamide, suggested TRPV4 channel activated peripheral sensitization. This study using a reliable model that provides pre-clinical correlates of human chronic pancreatitis provides further evidence that TRPV4 channel is a potential therapeutic target for treatment of pancreatitis pain. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

Effect of dexmedetomidine and cold stress in a rat model of neuropathic pain: Role of interleukin-6 and tumor necrosis factor-α.

PubMed

Farghaly, Hanan Sayed M; Mahmoud, Ahmed Mostafa; Abdel-Sater, Khaled A

2016-04-05

Dexmedetomidine (Dex) is a novel Alpha 2-adrenoceptor agonist. It decreases sympathetic tone and attenuates the stress responses to anesthesia and surgery. People exposed to cold suffer unpleasant thermal pain, which is experienced as stress and causes the release of noradrenaline from the sympathetic terminals. The present study investigated the effects of cold stress and dexmedetomidine on chronic constriction injury (CCI) model of the sciatic nerve in rats. Sixty four male Wistar rats were divided into seven groups of eight rats each: repeated cold stress (RCS) group, sham RCS group, CCI group, sham CCI group, Dex-treated group received a single dose of Dex (5 μg/kg), CCI+Dex group, CCI+RCS group. Interleukin-6 (IL-6) and tumor necrosis factor- alpha (TNF-α) levels in the serum were measured by enzyme-linked immunosorbent assay. The mean body weight of CCI, RCS, CCI+RCS, CCI+Dex and RCS+Dex groups decreased significantly compared with pre-values. Dexmedetomidine and CCI caused significant changes of the systolic, diastolic and mean blood pressure. Both RCS and CCI groups showed significant decreased of reaction time in the hot plate test. The RCS and CCI groups demonstrated a significant mechanical hyperalgesia, while pain threshold was increased in the RCS+Dex group. A significant decrease of serum IL-6 and TNF-α was demonstrated in CCI+RCS and CCI+Dex groups. The therapeutic effectiveness of dexmedetomidine in neuropathic pain may be through inhibition of proinflammatory cytokines, primarily IL-6 and TNF-α. Moreover, cold stress may result in increased resistance to neuropathic pain. Copyright © 2016 Elsevier B.V. All rights reserved.

Platelet-Rich Plasma Injection in Burn Scar Areas Alleviates Neuropathic Scar Pain

PubMed Central

Huang, Shu-Hung; Wu, Sheng-Hua; Lee, Su-Shin; Lin, Yun-Nan; Chai, Chee-Yin; Lai, Chung-Sheng; Wang, Hui-Min David

2018-01-01

Objective: No effective treatments have yet been developed for burn-induced neuropathic pain. Platelet-rich plasma (PRP) has been reported to ameliorate various types of inflammation pain. However, the effect of PRP on burn-induced neuropathic pain is unclear. Methods: Burn-induced neuropathic pain Sprague-Dawley rat model was confirmed using a mechanical response test 4 weeks after the burn injuries were sustained, following which PRP was injected in the scar area. The rats were divided into four groups (n = 6) as following: Group A, Sham; Group B, Sham + PRP; Group C, Burn; and Group D, Burn + PRP. Four weeks after the PRP injection, the animals were subjected to behavior tests and then sacrificed; specimens were collected for inflammation tests, Masson's trichrome stain and chromosome 10 (PTEN) in the injured skin; and PTEN, phosphorylated mammalian target of rapamycin (p-mTOR), p38, nuclear factor κB (NFκB), chemokine (CC motif) ligand 2 (CCL2), and CCL2 cognate receptor (CCR2) in spinal cord dorsal horns through immunohistochemistry and immunofluorescence staining. Results: PRP significantly alleviated allodynia in burn-induced neuropathic pain 4 weeks after treatment, and PTEN expression in the skin and spinal cord were significantly increased in group D compared with the group C. p-PTEN, p-mTOR, and CCL2 expression in neuron cells; p-p38 and p-NFκB expression in microglia; and p-JNK and p-NFκB activation in spinal astrocytes decreased significantly in the group D compared with the group C. Conclusions: PRP is effective in treating burn-induced neuropathic pain and may be used in clinical practice. PMID:29483815

MF498 [N-{[4-(5,9-Diethoxy-6-oxo-6,8-dihydro-7H-pyrrolo[3,4-g]quinolin-7-yl)-3-methylbenzyl]sulfonyl}-2-(2-methoxyphenyl)acetamide], a selective E prostanoid receptor 4 antagonist, relieves joint inflammation and pain in rodent models of rheumatoid and osteoarthritis.

PubMed

Clark, Patsy; Rowland, Steven E; Denis, Danielle; Mathieu, Marie-Claude; Stocco, Rino; Poirier, Hugo; Burch, Jason; Han, Yongxin; Audoly, Laurent; Therien, Alex G; Xu, Daigen

2008-05-01

Previous evidence has implicated E prostanoid receptor 4 (EP4) in mechanical hyperalgesia induced by subplantar inflammation. However, its role in chronic arthritis remains to be further defined because previous attempts have generated two conflicting lines of evidence, with one showing a marked reduction of arthritis induced by a collagen antibody in mice lacking EP4, but not EP1-EP3, and the other showing no impact of EP4 antagonism on arthritis induced by collagen. Here, we assessed the effect of a novel and selective EP4 antagonist MF498 [N-{[4-(5,9-diethoxy-6-oxo-6,8-dihydro-7H-pyrrolo[3,4-g]quinolin-7-yl)-3-methylbenzyl]sulfonyl}-2-(2-methoxyphenyl)acetamide] on inflammation in adjuvant-induced arthritis (AIA), a rat model for rheumatoid arthritis (RA), and joint pain in a guinea pig model of iodoacetate-induced osteoarthritis (OA). In the AIA model, MF498, but not the antagonist for EP1, MF266-1 [1-(5-{3-[2-(benzyloxy)-5-chlorophenyl]-2-thienyl}pyridin-3-yl)-2,2,2-trifluoroethane-1,1-diol] or EP3 MF266-3 [(2E)-N-[(5-bromo-2-methoxyphenyl)sulfonyl]-3-[5-chloro-2-(2-naphthylmethyl)phenyl]acrylamide], inhibited inflammation, with a similar efficacy as a selective cyclooxygenase 2 (COX-2) inhibitor MF-tricyclic. In addition, MF498 was as effective as an nonsteroidal anti-inflammatory drug, diclofenac, or a selective microsomal prostaglandin E synthase-1 inhibitor, MF63 [2-(6-chloro-1H-phenanthro[9,10-d]imidazol-2-yl)isophthalonitrile], in relieving OA-like pain in guinea pigs. When tested in rat models of gastrointestinal toxicity, the EP4 antagonist was well tolerated, causing no mucosal leakage or erosions. Lastly, we evaluated the renal effect of MF498 in a furosemide-induced diuresis model and demonstrated that the compound displayed a similar renal effect as MF-tricyclic [3-(3,4-difluorophenyl)-4-(4-(methylsulfonyl)phenyl)-2-(5H)-furanone], reducing furosemide-induced natriuresis by approximately 50%. These results not only suggest that EP4 is the major EP receptor in both RA and OA but also provide a proof of principle to the concept that antagonism of EP4 may be useful for treatment of arthritis.

Efficacy of Common Analgesics for Postsurgical Pain in Rats

PubMed Central

Waite, Megan E; Tomkovich, Ashleigh; Quinn, Tammie L; Schumann, Alan P; Dewberry, L Savannah; Totsch, Stacie K; Sorge, Robert E

2015-01-01

Each year, millions of rats undergo surgery for research purposes and receive analgesics to alleviate pain. We sought to evaluate the efficacy of common analgesics in tests of hot-plate nociception and postsurgical pain by using the Rat Grimace Scale. Rats received a single dose of one of several drug–dose combinations and were tested by using the hot-plate test (acute pain) or after laparotomy (with either prophylactic or intraoperative analgesic). The efficacy of analgesics for hot-plate pain was generally not predictive of efficacy for surgical pain. Carprofen and ketoprofen were rarely effective in any of the conditions tested. With the exception of the opioid buprenorphine, several of the drugs we tested required higher-than-recommended doses to alleviate pain. Taken together, our data suggest that current analgesic use frequently is insufficient, and many rats may experience significant postsurgical pain even when analgesics are used in commonly recommended doses. PMID:26224443

Sensory Innervation of the Nonspecialized Connective Tissues in the Low Back of the Rat

PubMed Central

Corey, Sarah M.; Vizzard, Margaret A.; Badger, Gary J.; Langevin, Helene M.

2011-01-01

Chronic musculoskeletal pain, including low back pain, is a worldwide debilitating condition; however, the mechanisms that underlie its development remain poorly understood. Pathological neuroplastic changes in the sensory innervation of connective tissue may contribute to the development of nonspecific chronic low back pain. Progress in understanding such potentially important abnormalities is hampered by limited knowledge of connective tissue's normal sensory innervation. The goal of this study was to evaluate and quantify the sensory nerve fibers terminating within the nonspecialized connective tissues in the low back of the rat. With 3-dimensional reconstructions of thick (30–80 μm) tissue sections we have for the first time conclusively identified sensory nerve fiber terminations within the collagen matrix of connective tissue in the low back. Using dye labeling techniques with Fast Blue, presumptive dorsal root ganglia cells that innervate the low back were identified. Of the Fast Blue-labeled cells, 60–88% also expressed calcitonin gene-related peptide (CGRP) immunoreactivity. Based on the immunolabeling with CGRP and the approximate size of these nerve fibers (≤2 μm) we hypothesize that they are Aδ or C fibers and thus may play a role in the development of chronic pain. PMID:21411968

Acute and chronic nociceptive phases observed in a rat hind paw ischemia/reperfusion model depend on different mechanisms.

PubMed

Klafke, J Z; da Silva, M A; Rossato, M F; de Prá, S Dal Toé; Rigo, F K; Walker, C I B; Bochi, G V; Moresco, R N; Ferreira, J; Trevisan, G

2016-02-01

Complex regional pain syndrome type 1 (CRPS1) may be evoked by ischemia/reperfusion, eliciting acute and chronic pain that is difficult to treat. Despite this, the underlying mechanism of CRPS1 has not been fully elucidated. Therefore, the goal of this study is to evaluate the involvement of inflammation, oxidative stress, and the transient receptor potential ankyrin 1 (TRPA1) channel, a chemosensor of inflammation and oxidative substances, in an animal model of chronic post-ischemia pain (CPIP). Male Wistar rats were subjected to 3 h hind paw ischemia/reperfusion (CPIP model). Different parameters of nociception, inflammation, ischemia, and oxidative stress were evaluated at 1 (acute) and 14 (chronic) days after CPIP. The effect of a TRPA1 antagonist and the TRPA1 immunoreactivity were also observed after CPIP. In the CPIP acute phase, we observed mechanical and cold allodynia; increased levels of tumor necrosis factor-α (hind paw), ischemia-modified albumin (IMA) (serum), protein carbonyl (hind paw and spinal cord), lactate (serum), and 4-hydroxy-2-nonenal (4-HNE, hind paw and spinal cord); and higher myeloperoxidase (MPO) and N-acetyl-β-D-glucosaminidase (NAGase) activities (hind paw). In the CPIP chronic phase, we detected mechanical and cold allodynia and increased levels of IMA (serum), protein carbonyl (hind paw and spinal cord), and 4-HNE (hind paw and spinal cord). TRPA1 antagonism reduced mechanical and cold allodynia 1 and 14 days after CPIP, but no change in TRPA1 immunoreactivity was observed. Different mechanisms underlie acute (inflammation and oxidative stress) and chronic (oxidative stress) phases of CPIP. TRPA1 activation may be relevant for CRPS1/CPIP-induced acute and chronic pain.

High-frequency electroacupuncture versus carprofen in an incisional pain model in rats

PubMed Central

Teixeira, F.M.; Castro, L.L.; Ferreira, R.T.; Pires, P.A.; Vanderlinde, F.A.; Medeiros, M.A.

2012-01-01

The objective of the present study was to compare the effect of electroacupuncture (EA) and carprofen (CP) on postoperative incisional pain using the plantar incision (PI) model in rats. A 1-cm longitudinal incision was made through skin, fascia and muscles of a hind paw of male Wistar rats and the development of mechanical and thermal hypersensitivity was determined over 4 days using the von Frey and Hargreaves methods, respectively. Based on the experimental treatments received on the third postoperative day, the animals were divided into the following groups: PI+CP (CP, 2 mg/kg, po); PI+EAST36 (100-Hz EA applied bilaterally at the Zusanli point (ST36)); PI+EANP (EA applied to a non-acupoint region); PI+IMMO (immobilization only); PI (vehicle). In the von Frey test, the PI+EAST36 group had higher withdrawal force thresholds in response to mechanical stimuli than the PI, PI+IMMO and PI+EANP groups at several times studied. Furthermore, the PI+EAST36 group showed paw withdrawal thresholds in response to mechanical stimuli that were similar to those of the PI+CP group. In the Hargreaves test, all groups had latencies higher than those observed with PI. The PI+EAST36 group was similar to the PI+IMMO, PI+EANP and PI+CP groups. We conclude that 100-Hz EA at the ST36 point, but not at non-acupoints, can reduce mechanical nociception in the rat model of incisional pain, and its effectiveness is comparable to that of carprofen. PMID:22911345

Controlled release of celecoxib inhibits inflammation, bone cysts and osteophyte formation in a preclinical model of osteoarthritis.

PubMed

Tellegen, A R; Rudnik-Jansen, I; Pouran, B; de Visser, H M; Weinans, H H; Thomas, R E; Kik, M J L; Grinwis, G C M; Thies, J C; Woike, N; Mihov, G; Emans, P J; Meij, B P; Creemers, L B; Tryfonidou, M A

2018-11-01

Major hallmarks of osteoarthritis (OA) are cartilage degeneration, inflammation and osteophyte formation. COX-2 inhibitors counteract inflammation-related pain, but their prolonged oral use entails the risk for side effects. Local and prolonged administration in biocompatible and degradable drug delivery biomaterials could offer an efficient and safe treatment for the long-term management of OA symptoms. Therefore, we evaluated the disease-modifying effects and the optimal dose of polyesteramide microspheres delivering the COX-2 inhibitor celecoxib in a rat OA model. Four weeks after OA induction by anterior cruciate ligament transection and partial medial meniscectomy, 8-week-old female rats (n = 6/group) were injected intra-articular with celecoxib-loaded microspheres at three dosages (0.03, 0.23 or 0.39 mg). Unloaded microspheres served as control. During the 16-week follow-up, static weight bearing and plasma celecoxib concentrations were monitored. Post-mortem, micro-computed tomography and knee joint histology determined progression of synovitis, osteophyte formation, subchondral bone changes, and cartilage integrity. Systemic celecoxib levels were below the detection limit 6 days upon delivery. Systemic and local adverse effects were absent. Local delivery of celecoxib reduced the formation of osteophytes, subchondral sclerosis, bone cysts and calcified loose bodies, and reduced synovial inflammation, while cartilage histology was unaffected. Even though the effects on pain could not be evualated directly in the current model, our results suggest the application of celecoxib-loaded microspheres holds promise as novel, safe and effective treatment for inflammation and pain in OA.

High-frequency electroacupuncture versus carprofen in an incisional pain model in rats.

PubMed

Teixeira, F M; Castro, L L; Ferreira, R T; Pires, P A; Vanderlinde, F A; Medeiros, M A

2012-12-01

The objective of the present study was to compare the effect of electroacupuncture (EA) and carprofen (CP) on postoperative incisional pain using the plantar incision (PI) model in rats. A 1-cm longitudinal incision was made through skin, fascia and muscles of a hind paw of male Wistar rats and the development of mechanical and thermal hypersensitivity was determined over 4 days using the von Frey and Hargreaves methods, respectively. Based on the experimental treatments received on the third postoperative day, the animals were divided into the following groups: PI+CP (CP, 2 mg/kg, po); PI+EAST36 (100-Hz EA applied bilaterally at the Zusanli point (ST36)); PI+EANP (EA applied to a non-acupoint region); PI+IMMO (immobilization only); PI (vehicle). In the von Frey test, the PI+EAST36 group had higher withdrawal force thresholds in response to mechanical stimuli than the PI, PI+IMMO and PI+EANP groups at several times studied. Furthermore, the PI+EAST36 group showed paw withdrawal thresholds in response to mechanical stimuli that were similar to those of the PI+CP group. In the Hargreaves test, all groups had latencies higher than those observed with PI. The PI+EAST36 group was similar to the PI+IMMO, PI+EANP and PI+CP groups. We conclude that 100-Hz EA at the ST36 point, but not at non-acupoints, can reduce mechanical nociception in the rat model of incisional pain, and its effectiveness is comparable to that of carprofen.

Manipulating the extracellular matrix: an animal model of the bladder pain syndrome.

PubMed

Offiah, Ifeoma; Didangelos, Athanasios; OʼReilly, Barry A; McMahon, Stephen B

2017-01-01

Bladder pain syndrome (BPS) is associated with breakdown of the protective uroepithelial barrier of the urinary bladder allowing urinary constituents access to bladder sensory neurons. Although there are several animal models of cystitis, none specifically relates to BPS. Here, we aimed to create such a model using enzymatic digestion of the barrier proteoglycans (PGs) in the rat. Twenty female Wistar rats were anaesthetized and transurethrally catheterized. Ten animals were treated with 0.25IU of intravesical chondroitinase ABC and heparanase III to digest chondroitin sulphate and heparin sulphate PGs, respectively. Ten animals received saline. Following PG deglycosylation, bladders showed irregular loss of the apical uroplakin and a significant increase in neutrophils, not evident in the control group. Spinal cord sections were also collected for c-fos analysis. A large and significant increase in fos immunoreactivity in the L6/S1 segments in the treatment vs control bladders was observed. Cystometry was performed on 5 treatment and 5 control animals. Analysis revealed a significant increase in micturition reflex excitability postdeglycosylation. On a further group of 10 animals, von Frey mechanical withdrawal thresholds were tested on abdominal skin before and after PG digestions. There was a significant decrease in abdominal mechanical withdrawal threshold postdeglycosylation compared with controls. The results of this animal study suggest that many of the clinical features of BPS are seen after PG digestion from the bladder lumen. This model can be used to further understand mechanisms of pain in patients with BPS and to test new therapeutic strategies.

Role of Sigma-1 Receptor/p38 MAPK Inhibition in Acupoint Catgut Embedding-Mediated Analgesic Effects in Complete Freund's Adjuvant-Induced Inflammatory Pain.

PubMed

Du, Kairong; Wang, Xue; Chi, Laiting; Li, Wenzhi

2017-08-01

The endoplasmic reticulum chaperone protein Sigma-1 receptor (Sig-1 R) and mitogen-activated protein kinases (MAPKs) are involved in the mechanism of pain. Acupoint stimulation exerts an exact antihyperalgesic effect in inflammatory pain. However, whether Sig-1 R and MAPKs are associated with the acupoint stimulation-induced analgesic effects is not clear. This study investigated the analgesic effect of acupoint catgut embedding (ACE) and the inhibition of Sig-1 R and MAPKs in ACE analgesia. Rats were prepared with intrathecal catheter implantation. ACE was applied to bilateral "Kunlun" (BL60), "Zusanli" (ST36), and "Sanyinjiao" (SP6) acupoints in the rat model of inflammatory pain (complete Freund's adjuvant [CFA] intraplantar injection). Then, Sig-1R agonist PRE084 or saline was intrathecally given daily. The paw withdrawal thresholds and paw edema were measured before CFA injection and at 1, 3, and 5 day after CFA injection. Western bolt was used to evaluate the protein expression of spinal Sig-1R, p38MAPK, and extracellular signal-regulated kinase (ERK), and immunohistochemistry of Sig-1R was detected at 1, 3, and 5 days after CFA injection. ACE exhibited specific analgesic effects. ACE increased paw withdrawal thresholds and markedly decreased CFA-induced paw edema at 1, 3, and 5 days. ACE downregulated the protein expression of Sig-1R, which was increased significantly at 1, 3, and 5 days after CFA injection. ACE decreased the expression of p38 MAPK and ERK at 1 and 3 days but not at 5 days. However, an injection of Sig-1R agonist PRE084 markedly reversed these alterations, except ERK expression. The present study demonstrated that ACE exhibited antihyperalgesic effects via the inhibition of the Sig-1R that modulated p38 MAPK, but not ERK, expression in the CFA-induced inflammatory pain model in rats.

Adrenergic signaling mediates mechanical hyperalgesia through activation of P2X3 receptors in primary sensory neurons of rats with chronic pancreatitis.

PubMed

Wang, Shusheng; Zhu, Hong-Yan; Jin, Yi; Zhou, Youlang; Hu, Shufen; Liu, Tong; Jiang, Xinghong; Xu, Guang-Yin

2015-04-15

The mechanism of pain in chronic pancreatitis (CP) is poorly understood. The aim of this study was designed to investigate roles of norepinephrine (NE) and P2X receptor (P2XR) signaling pathway in the pathogenesis of hyperalgesia in a rat model of CP. CP was induced in male adult rats by intraductal injection of trinitrobenzene sulfonic acid (TNBS). Mechanical hyperalgesia was assessed by referred somatic behaviors to mechanical stimulation of rat abdomen. P2XR-mediated responses of pancreatic dorsal root ganglion (DRG) neurons were measured utilizing calcium imaging and whole cell patch-clamp-recording techniques. Western blot analysis and immunofluorescence were performed to examine protein expression. TNBS injection produced a significant upregulation of P2X3R expression and an increase in ATP-evoked responses of pancreatic DRG neurons. The sensitization of P2X3Rs was reversed by administration of β-adrenergic receptor antagonist propranolol. Incubation of DRG neurons with NE significantly enhanced ATP-induced intracellular calcium signals, which were abolished by propranolol, and partially blocked by protein kinase A inhibitor H-89. Interestingly, TNBS injection led to a significant elevation of NE concentration in DRGs and the pancreas, an upregulation of β2-adrenergic receptor expression in DRGs, and amplification of the NE-induced potentiation of ATP responses. Importantly, pancreatic hyperalgesia was markedly attenuated by administration of purinergic receptor antagonist suramin or A317491 or β2-adrenergic receptor antagonist butoxamine. Sensitization of P2X3Rs, which was likely mediated by adrenergic signaling in primary sensory neurons, contributes to pancreatic pain, thus identifying a potential target for treating pancreatic pain caused by inflammation. Copyright © 2015 the American Physiological Society.

Prostanoid-dependent spontaneous pain and PAR2-dependent mechanical allodynia following oral mucosal trauma

PubMed Central

Ito, Misa; Hitomi, Suzuro; Nodai, Tomotaka; Sago, Teppei; Yamaguchi, Kiichiro; Harano, Nozomu; Gunjigake, Kaori; Hosokawa, Ryuji; Kawamoto, Tatsuo; Inenaga, Kiyotoshi

2017-01-01

During dental treatments, intraoral appliances frequently induce traumatic ulcers in the oral mucosa. Such mucosal injury-induced mucositis leads to severe pain, resulting in poor quality of life and decreased cooperation in the therapy. To elucidate mucosal pain mechanisms, we developed a new rat model of intraoral wire-induced mucositis and investigated pain mechanisms using our proprietary assay system for conscious rats. A thick metal wire was installed in the rats between the inferior incisors for one day. In the mucosa of the mandibular labial fornix region, which was touched with a free end of the wire, traumatic ulcer and submucosal abscess were induced on day 1. The ulcer was quickly cured until next day and abscess formation was gradually disappeared until five days. Spontaneous nociceptive behavior was induced on day 1 only, and mechanical allodynia persisted over day 3. Antibiotic pretreatment did not affect pain induction. Spontaneous nociceptive behavior was sensitive to indomethacin (cyclooxygenase inhibitor), ONO-8711 (prostanoid receptor EP1 antagonist), SB-366791, and HC-030031 (TRPV1 and TRPA1 antagonists, respectively). Prostaglandin E2 and 15-deoxyΔ12,14-prostaglandin J2 were upregulated only on day 1. In contrast, mechanical allodynia was sensitive to FSLLRY-NH2 (protease-activated receptor PAR2 antagonist) and RN-1734 (TRPV4 antagonist). Neutrophil elastase, which is known as a biased agonist for PAR2, was upregulated on days 1 to 2. These results suggest that prostanoids and PAR2 activation elicit TRPV1- and TRPA1-mediated spontaneous pain and TRPV4-mediated mechanical allodynia, respectively, independently of bacterial infection, following oral mucosal trauma. The pathophysiological pain mechanism suggests effective analgesic approaches for dental patients suffering from mucosal trauma-induced pain. PMID:28381109

Electrical stimulation of the insular cortex as a novel target for the relief of refractory pain: An experimental approach in rodents.

PubMed

Dimov, Luiz Fabio; Toniolo, Elaine Flamia; Alonso-Matielo, Heloísa; de Andrade, Daniel Ciampi; Garcia-Larrea, Luis; Ballester, Gerson; Teixeira, Manoel Jacobsen; Dale, Camila Squarzoni

2018-07-02

Cortical electrical stimulation (CES) has shown to be an effective therapeutic alternative for neuropathic pain refractory to pharmacological treatment. The primary motor cortex(M1) was the main cortical target used in the vast majority of both invasive and non-invasive studies. Despite positive results M1-based approaches still fail to relieve pain in a significant proportion of individuals. It has been advocated that the direct stimulation of cortical areas directly implicated in the central integration of pain could increase the efficacy of analgesic brain stimulation. Here, we evaluated the behavioral effects of electrical stimulation of the insular cortex (ESI) on pain sensitivity in an experimental rat model of peripheral neuropathy, and have described the pathways involved. Animals underwent chronic constriction of the sciatic nerve in the right hind limb and had concentric electrodes implanted in the posterior dysranular insular cortex. Mechanical nociception responses were evaluated before and at the end of a 15-min session of ESI (60Hz, 210μs, 1V). ESI reversed mechanical hypersensitivity in the paw contralateral to the brain hemisphere stimulated, without inducing motor impairment in the open-field test. Pharmacological blockade of μ-opioid (MOR) or type 1-cannabinoid receptors (CB1R) abolished ESI-induced antinociceptive effects. Evaluation of CB1R and MOR spatial expression demonstrated differential modulation of CB1R and MOR in the periaqueductal gray matter (PAG) of ESI-treated rats in sub-areas involved in pain processing/modulation. These results indicate that ESI induces antinociception by functionally modulating opioid and cannabinoid systems in the PAG pain circuitry in rats with experimentally induced neuropathic pain. Copyright © 2017 Elsevier B.V. All rights reserved.

Expression of background potassium channels in rat DRG is cell-specific and down-regulated in a neuropathic pain model.

PubMed

Pollema-Mays, Sarah L; Centeno, Maria Virginia; Ashford, Crystle J; Apkarian, A Vania; Martina, Marco

2013-11-01

Neuropathic pain is associated with hyperexcitability of DRG neurons. Despite the importance of leakage potassium channels for neuronal excitability, little is known about their cell-specific expression in DRGs and possible modulation in neuropathic pain. Multiple leakage channels are expressed in DRG neurons, including TASK1, TASK3, TRESK, TRAAK, TWIK1, TREK1 and TREK2 but little is known about their distribution among different cell types. Our immunohistochemical studies show robust TWIK1 expression in large and medium size neurons, without overlap with TRPV1 or IB4 staining. TASK1 and TASK3, on the contrary, are selectively expressed in small cells; TASK1 expression closely overlaps TRPV1-positive cells, while TASK3 is expressed in TRPV1- and IB4-negative cells. We also studied mRNA expression of these channels in L4-L5 DRGs in control conditions and up to 4 weeks after spared nerve injury lesion. We found that TWIK1 expression is much higher than TASK1 and TASK3 and is strongly decreased 1, 2 and 4 weeks after neuropathic injury. TASK3 expression, on the other hand, decreases 1 week after surgery but reverts to baseline by 2weeks; TASK1 shows no significant change at any time point. These data suggest an involvement of TWIK1 in the maintenance of the pain condition. © 2013.

Spinal SIRPα1-SHP2 interaction regulates spinal nerve ligation-induced neuropathic pain via PSD-95-dependent NR2B activation in rats.

PubMed

Peng, Hsien-Yu; Chen, Gin-Den; Lai, Cheng-Yuang; Hsieh, Ming-Chun; Lin, Tzer-Bin

2012-05-01

The fact that neuropathic pain mechanisms are not well understood is a major impediment in the development of effective clinical treatments. We examined whether the interaction between signal regulatory protein alpha 1 (SIRPα1) and Src homology-2 domain-containing protein tyrosine phosphatase 2 (SHP2), and the downstream spinal SHP2/postsynaptic density 95 (PSD-95)/N-methyl-d-aspartate receptor NR2B subunit signaling cascade play a role in neuropathic pain. Following spinal nerve ligation (L5), we assessed tactile allodynia using the von Frey filament test and analyzed dorsal horn samples (L4-5) by Western blotting, reverse transcription polymerase chain reaction, coimmunoprecipitation, and immunofluorescence. Nerve ligation induced allodynia, SIRPα1, SHP2, phosphorylated SHP2 (pSHP2), and phosphorylated NR2B (pNR2B) expression, and SHP2-PSD-95, pSHP2-PSD-95, PSD-95-NR2B, and PSD-95-pNR2B coimmunoprecipitation in the ipsilateral dorsal horn. In allodynic rats, injury-induced SHP2 immunoreactivity was localized in the ipsilateral dorsal horn neurons and coincident with PSD-95 and NR2B immunoreactivity. SIRPα1 silencing using small interfering RNA (siRNA; 1, 3, or 5μg/rat for 7days) prevented injury-induced allodynia and the associated changes in protein expression, phosphorylation, and coimmunoprecipitation. Intrathecal administration of NSC-87877 (an SHP2 antagonist; 1, 10, or 100μM/rat) and SIRPα1-neutralizing antibodies (1, 10, or 30μg/rat) suppressed spinal nerve ligation-induced allodynia, spinal SHP2 and NR2B phosphorylation, and SHP2/phosphorylated SHP2-PSD-95 and PSD-95-NR2B/phosphorylated NR2B coprecipitation. SHP2 siRNA led to similar effects as the NSC-87877 and SIRPα1 antibody treatments, except it prevented the allodynia-associated spinal SHP2 expression. In conclusion, our results suggest that a spinal SIRPα1-SHP2 interaction exists that subsequently triggers SHP2/PSD-95/NR2B signaling, thereby playing a role in neuropathic pain development. Copyright © 2012 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.

Minocycline attenuates the development of diabetic neuropathy by inhibiting spinal cord Notch signaling in rat.

PubMed

Yang, Cheng; Gao, Jie; Wu, Banglin; Yan, Nuo; Li, Hui; Ren, Yiqing; Kan, Yufei; Liang, Jiamin; Jiao, Yang; Yu, Yonghao

2017-10-01

We studied the effects of minocycline (an inhibitor of microglial activation) on the expression and activity of Notch-1 receptor, and explored the therapeutic efficacy of minocycline combined with Notch inhibitor DAPT in the treatment of diabetic neuropathic pain (DNP). Diabetic rat model was established by intraperitoneal injection (ip) of Streptozotocin (STZ). Expression and activity of Notch-1 and expression of macrophage/microglia marker Iba-1 were detected by WB. Diabetes induction significantly attenuated sciatic nerve conduction velocity, and dramatically augmented the expression and the activity of Notch-1 in the lumbar enlargement of the spinal cord. Minocycline treatment, however, accelerated the decreased conduction velocity of sciatic nerve and suppressed Notch-1expression and activity in diabetic rats. Similar to DAPT treatment, minocycline administration also prolonged thermal withdrawal latency (TWL) and increase mechanical withdrawal threshold (MWT) in diabetic rats in response to heat or mechanical stimulation via inhibition the expression and the activity of Notch-1 in spinal cord. Combination of DAPT and minocycline further inhibited Notch-1 receptor signaling and reduce neuropathic pain exhibited as improved TWL and MWT. Our study revealed a novel mechanism of Notch-1 receptor inhibition in spinal cord induced by minocycline administration, and suggested that the combination of minocycline and DAPT has the potential to treat DNP. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

AMPAkines Target the Nucleus Accumbens to Relieve Postoperative Pain.

PubMed

Su, Chen; Lin, Hau Yeuh; Yang, Runtao; Xu, Duo; Lee, Michelle; Pawlak, Natalie; Norcini, Monica; Sideris, Alexandra; Recio-Pinto, Esperanza; Huang, Dong; Wang, Jing

2016-11-01

AMPAkines augment the function of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors in the brain to increase excitatory outputs. These drugs are known to relieve persistent pain. However, their role in acute pain is unknown. Furthermore, a specific molecular and anatomic target for these novel analgesics remains elusive. The authors studied the analgesic role of an AMPAkine, CX546, in a rat paw incision (PI) model of acute postoperative pain. The authors measured the effect of AMPAkines on sensory and depressive symptoms of pain using mechanical hypersensitivity and forced swim tests. The authors asked whether AMPA receptors in the nucleus accumbens (NAc), a key node in the brain's reward and pain circuitry, can be a target for AMPAkine analgesia. Systemic administration of CX546 (n = 13), compared with control (n = 13), reduced mechanical hypersensitivity (50% withdrawal threshold of 6.05 ± 1.30 g [mean ± SEM] vs. 0.62 ± 0.13 g), and it reduced depressive features of pain by decreasing immobility on the forced swim test in PI-treated rats (89.0 ± 15.5 vs. 156.7 ± 18.5 s). Meanwhile, CX546 delivered locally into the NAc provided pain-relieving effects in both PI (50% withdrawal threshold of 6.81 ± 1.91 vs. 0.50 ± 0.03 g; control, n = 6; CX546, n = 8) and persistent postoperative pain (spared nerve injury) models (50% withdrawal threshold of 3.85 ± 1.23 vs. 0.45 ± 0.00 g; control, n = 7; CX546, n = 11). Blocking AMPA receptors in the NAc with 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo[f]quinoxaline-2,3-dione inhibited these pain-relieving effects (50% withdrawal threshold of 7.18 ± 1.52 vs. 1.59 ± 0.66 g; n = 8 for PI groups; 10.70 ± 3.45 vs. 1.39 ± 0.88 g; n = 4 for spared nerve injury groups). AMPAkines relieve postoperative pain by acting through AMPA receptors in the NAc.

Calcium Channel α2δ1 Proteins Mediate Trigeminal Neuropathic Pain States Associated with Aberrant Excitatory Synaptogenesis*

PubMed Central

Li, Kang-Wu; Yu, Yanhui Peter; Zhou, Chunyi; Kim, Doo-Sik; Lin, Bin; Sharp, Kelli; Steward, Oswald; Luo, Z. David

2014-01-01

To investigate a potential mechanism underlying trigeminal nerve injury-induced orofacial hypersensitivity, we used a rat model of chronic constriction injury to the infraorbital nerve (CCI-ION) to study whether CCI-ION caused calcium channel α2δ1 (Cavα2δ1) protein dysregulation in trigeminal ganglia and associated spinal subnucleus caudalis and C1/C2 cervical dorsal spinal cord (Vc/C2). Furthermore, we studied whether this neuroplasticity contributed to spinal neuron sensitization and neuropathic pain states. CCI-ION caused orofacial hypersensitivity that correlated with Cavα2δ1 up-regulation in trigeminal ganglion neurons and Vc/C2. Blocking Cavα2δ1 with gabapentin, a ligand for the Cavα2δ1 proteins, or Cavα2δ1 antisense oligodeoxynucleotides led to a reversal of orofacial hypersensitivity, supporting an important role of Cavα2δ1 in orofacial pain processing. Importantly, increased Cavα2δ1 in Vc/C2 superficial dorsal horn was associated with increased excitatory synaptogenesis and increased frequency, but not the amplitude, of miniature excitatory postsynaptic currents in dorsal horn neurons that could be blocked by gabapentin. Thus, CCI-ION-induced Cavα2δ1 up-regulation may contribute to orofacial neuropathic pain states through abnormal excitatory synapse formation and enhanced presynaptic excitatory neurotransmitter release in Vc/C2. PMID:24459143

AMPK activation by peri-sciatic nerve administration of ozone attenuates CCI-induced neuropathic pain in rats.

PubMed

Lu, Lijuan; Pan, Cailong; Chen, Lu; Hu, Liang; Wang, Chaoyu; Han, Yuan; Yang, Yanjing; Cheng, Zhixiang; Liu, Wen-Tao

2017-04-01

Neuropathic pain is a debilitating clinical condition with few efficacious treatments, warranting development of novel therapeutics. Ozone is widely used as an alternative therapy for many different pain conditions, with exact mechanisms still elusive. In this study, we found that a single peri-sciatic nerve injection of ozone decreased mechanical allodynia and thermal hyperalgesia, and normalized the phosphorylation of protein kinase C γ, N-methyl-D-aspartate receptor, and extracellular signal-regulated kinase in a chronic constriction injury (CCI) model in rat sciatic nerve. Meanwhile, ozone significantly suppressed CCI-induced activation of spinal microglia. More importantly, the anti-nociceptive effect of ozone depended on the activation of 5'-adenosine monophosphate (AMP)-activated protein kinase (AMPK), which was proved by the fact that the phosphorylated AMPK level increased during the ozone therapy and AMPK antagonist abolished the effect of ozone in vivo and in vitro. In addition, direct injection of AMPK agonist could replicate the anti-nociceptive effect of ozone in CCI rats. In conclusion, our observations indicate that peri-sciatic nerve injection of ozone activates AMPK to attenuate CCI-induced neuropathic pain. © The Author (2016). Published by Oxford University Press on behalf of Journal of Molecular Cell Biology, IBCB, SIBS, CAS. All rights reserved.

Local infiltration of the surgical wounds with levobupivacaine, dexibuprofen, and norepinephrine to reduce postoperative pain: A randomized, vehicle-controlled, and preclinical study.

PubMed

Gao, Zongwen; Cui, Feng; Cao, Xuemei; Wang, Dejun; Li, Xiao; Li, Tianzuo

2017-08-01

Postoperative pain may lead to poor wound healing, insomnia, and increased postoperative hospitalization. The objective of the study was to explore the effect of local infiltration of the surgical wound with levobupivacaine, dexibuprofen, and norepinephrine in postoperative pain. A randomized, parallel experimental design was applied in 40, 9-11-week-old Wister albino rats. A laparotomy was performed in all groups of 10 rats each. During surgery, the sutured muscle was infiltrated with 40μL of a normal saline (vehicle group), a normal saline containing 0.25% v/v levobupivacaine, 0.2mg/mL dexibuprofen, and 0.1mg/mL norepinephrine (treatment group) before skin closure. The same combination (negative control group) and a 10-fold higher dose (positive control group) were administered systematically. Rat Grimace Scale scores, based on facial expression, 24h after suturing of the tissues, histopathology and tensile strength of the surgical wound, two weeks after suturing of the tissues were measured. The one-way ANOVA and the two-tailed paired t-test/the Dunnett multiple comparisons test were used to compare the Rat Grimace Scale scores for pain within the group and between groups. The Kruskal-Wallis test and the one-way ANOVA/the Dunnett multiple comparisons test were used to compare the histopathology study and the tensile strength. The difference for statistical analysis was considered significant at the 95% of confidence level. The mean Rat Grimace Scale score at 24h for the treatment, negative control, and positive control groups was 1.945 (p=0.0025; q=3.257), 1.1 (p=0.1), and 1.95 (p=0.0021 q=3.547) respectively. The reduction in postoperative pain started within 1h after the suturing of the tissues in the treatment group. There were significant difference for epidermal and dermal regeneration (p=0.043), granulation tissue thickness (p=0.025), and angiogenesis (p=0.002) between treatment group and vehicle group. Tensile strength for the treatment group was 0.82±0.013N/cm 2 (p=0.003; q=5.231). The rapid infiltration of surgical wounds with a low-dose levobupivacaine, dexibuprofen, and norepinephrine may reduce postoperative pain and increase the wound regeneration process. Copyright © 2017. Published by Elsevier Masson SAS.

The peripheral antinociceptive effects of endomorphin-1 and kynurenic acid in the rat inflamed joint model.

PubMed

Mecs, Laszlo; Tuboly, Gabor; Nagy, Endre; Benedek, Gyorgy; Horvath, Gyongyi

2009-10-01

Several data suggest that both opioid and N-methyl-d-aspartate (NMDA) receptors are localized at the peripheral level, and drugs acting on these receptors may produce antinociception after topical administration; however, the antinociceptive effect of endogenous ligands at these receptors is poorly clarified. Our goal in this study was to determine the antinociceptive potency of the endogenous opioid peptide, endomorphin-1 (EM1), and the endogenous NMDA receptor antagonist, kynurenic acid (KYNA), and their interaction at the peripheral level in the rat inflamed joint model. Mechanical hypersensitivity was produced by injection of carrageenan (300 microg/20 microL) into the tibiotarsal joint of the right hind leg. The mechanical pain threshold was assessed by von Frey filaments (0.064-110 g). EM1 (30, 100, and 200 microg), KYNA (30, 100, 200, and 400 microg), and their combinations in a fixed-dose ratio (1:1) were injected into the inflamed joint, and the pain threshold was determined repeatedly for 75 min after the drug administrations. Neither EM1 nor KYNA administered to the inflamed joint influenced the pain threshold at the noninflamed side. Both ligands produced dose-dependent antihyperalgesia, and the highest doses caused a prolonged effect. EM1 had higher potency (30% effective dose [ED(30)] and 50% effective dose [ED(50)] values were 112 microg [confidence interval {CI}: 80-146] and 167 microg [CI: 135-220], respectively) compared with KYNA (ED(30) and ED(50) values were 204 microg [CI: 160-251] and 330 microg [CI: 280-407], respectively). The antinociceptive effect of EM1 was prevented by subcutaneous naltrexone pretreatment. The coadministration of EM1 with KYNA caused an enhanced and/or prolonged antinociceptive effect. The ED(30) and ED(50) values of the combination were 141 microg [CI: 83-182] and 231 microg [CI: 190-293], respectively, which did not differ significantly from the theoretically additive values (ED(30) and ED(50) values were 145 microg [CI: 68-237] and 220 microg [CI: 144-230], respectively), thus the interaction between these ligands is additive. None of the treatments caused any sign of side effects. Peripherally administered endogenous opioid agonist and NMDA receptor antagonist ligands might be beneficial in inflammatory pain. Because both drugs barely cross the blood-brain barrier, their local administration causes no central side effects.

Cross-centre replication of suppressed burrowing behaviour as an ethologically relevant pain outcome measure in the rat: a prospective multicentre study.

PubMed

Wodarski, Rachel; Delaney, Ada; Ultenius, Camilla; Morland, Rosie; Andrews, Nick; Baastrup, Catherine; Bryden, Luke A; Caspani, Ombretta; Christoph, Thomas; Gardiner, Natalie J; Huang, Wenlong; Kennedy, Jeffrey D; Koyama, Suguru; Li, Dominic; Ligocki, Marcin; Lindsten, Annika; Machin, Ian; Pekcec, Anton; Robens, Angela; Rotariu, Sanziana M; VoB, Sabrina; Segerdahl, Marta; Stenfors, Carina; Svensson, Camilla I; Treede, Rolf-Detlef; Uto, Katsuhiro; Yamamoto, Kazumi; Rutten, Kris; Rice, Andrew S C

2016-10-01

Burrowing, an ethologically relevant rodent behaviour, has been proposed as a novel outcome measure to assess the global impact of pain in rats. In a prospective multicentre study using male rats (Wistar, Sprague-Dawley), replication of suppressed burrowing behaviour in the complete Freund adjuvant (CFA)-induced model of inflammatory pain (unilateral, 1 mg/mL in 100 µL) was evaluated in 11 studies across 8 centres. Following a standard protocol, data from participating centres were collected centrally and analysed with a restricted maximum likelihood-based mixed model for repeated measures. The total population (TP-all animals allocated to treatment; n = 249) and a selected population (SP-TP animals burrowing over 500 g at baseline; n = 200) were analysed separately, assessing the effect of excluding "poor" burrowers. Mean baseline burrowing across studies was 1113 g (95% confidence interval: 1041-1185 g) for TP and 1329 g (1271-1387 g) for SP. Burrowing was significantly suppressed in the majority of studies 24 hours (7 studies/population) and 48 hours (7 TP, 6 SP) after CFA injections. Across all centres, significantly suppressed burrowing peaked 24 hours after CFA injections, with a burrowing deficit of -374 g (-479 to -269 g) for TP and -498 g (-609 to -386 g) for SP. This unique multicentre approach first provided high-quality evidence evaluating suppressed burrowing as robust and reproducible, supporting its use as tool to infer the global effect of pain on rodents. Second, our approach provided important informative value for the use of multicentre studies in the future.

Voltage-gated sodium channel expression in mouse DRG after SNI leads to re-evaluation of projections of injured fibers

PubMed Central

2014-01-01

Background Dysregulation of voltage-gated sodium channels (Navs) is believed to play a major role in nerve fiber hyperexcitability associated with neuropathic pain. A complete transcriptional characterization of the different isoforms of Navs under normal and pathological conditions had never been performed on mice, despite their widespread use in pain research. Navs mRNA levels in mouse dorsal root ganglia (DRG) were studied in the spared nerve injury (SNI) and spinal nerve ligation (SNL) models of neuropathic pain. In the SNI model, injured and non-injured neurons were intermingled in lumbar DRG, which were pooled to increase the tissue available for experiments. Results A strong downregulation was observed for every Navs isoform expressed except for Nav1.2; even Nav1.3, known to be upregulated in rat neuropathic pain models, was lower in the SNI mouse model. This suggests differences between these two species. In the SNL model, where the cell bodies of injured and non-injured fibers are anatomically separated between different DRG, most Navs were observed to be downregulated in the L5 DRG receiving axotomized fibers. Transcription was then investigated independently in the L3, L4 and L5 DRG in the SNI model, and an important downregulation of many Navs isoforms was observed in the L3 DRG, suggesting the presence of numerous injured neurons there after SNI. Consequently, the proportion of axotomized neurons in the L3, L4 and L5 DRG after SNI was characterized by studying the expression of activating transcription factor 3 (ATF3). Using this marker of nerve injury confirmed that most injured fibers find their cell bodies in the L3 and L4 DRG after SNI in C57BL/6 J mice; this contrasts with their L4 and L5 DRG localization in rats. The spared sural nerve, through which pain hypersensitivity is measured in behavioral studies, mostly projects into the L4 and L5 DRG. Conclusions The complex regulation of Navs, together with the anatomical rostral shift of the DRG harboring injured fibers in C57BL/6 J mice, emphasize that caution is necessary and preliminary anatomical experiments should be carried out for gene and protein expression studies after SNI in mouse strains. PMID:24618114

Human Mas-Related G Protein-Coupled Receptors-X1 Induce Chemokine Receptor 2 Expression in Rat Dorsal Root Ganglia Neurons and Release of Chemokine Ligand 2 from the Human LAD-2 Mast Cell Line

PubMed Central

Solinski, Hans Jürgen; Petermann, Franziska; Rothe, Kathrin; Boekhoff, Ingrid; Gudermann, Thomas; Breit, Andreas

2013-01-01

Primate-specific Mas-related G protein-coupled receptors-X1 (MRGPR-X1) are highly enriched in dorsal root ganglia (DRG) neurons and induce acute pain. Herein, we analyzed effects of MRGPR-X1 on serum response factors (SRF) or nuclear factors of activated T cells (NFAT), which control expression of various markers of chronic pain. Using HEK293, DRG neuron-derived F11 cells and cultured rat DRG neurons recombinantly expressing human MRGPR-X1, we found activation of a SRF reporter gene construct and induction of the early growth response protein-1 via extracellular signal-regulated kinases-1/2 known to play a significant role in the development of inflammatory pain. Furthermore, we observed MRGPR-X1-induced up-regulation of the chemokine receptor 2 (CCR2) via NFAT, which is considered as a key event in the onset of neuropathic pain and, so far, has not yet been described for any endogenous neuropeptide. Up-regulation of CCR2 is often associated with increased release of its endogenous agonist chemokine ligand 2 (CCL2). We also found MRGPR-X1-promoted release of CCL2 in a human connective tissue mast cell line endogenously expressing MRGPR-X1. Thus, we provide first evidence to suggest that MRGPR-X1 induce expression of chronic pain markers in DRG neurons and propose a so far unidentified signaling circuit that enhances chemokine signaling by acting on two distinct yet functionally co-operating cell types. Given the important role of chemokine signaling in pain chronification, we propose that interruption of this signaling circuit might be a promising new strategy to alleviate chemokine-promoted pain. PMID:23505557

A systems approach for discovering linoleic acid derivatives that potentially mediate pain and itch

PubMed Central

Ramsden, Christopher E.; Domenichiello, Anthony F.; Yuan, Zhi-Xin; Sapio, Matthew R.; Keyes, Gregory S.; Mishra, Santosh K.; Gross, Jacklyn R.; Majchrzak-Hong, Sharon; Zamora, Daisy; Horowitz, Mark S.; Davis, John M.; Sorokin, Alexander V.; Dey, Amit; LaPaglia, Danielle M.; Wheeler, Joshua J.; Vasko, Michael R.; Mehta, Nehal N.; Mannes, Andrew J.; Iadarola, Michael J.

2018-01-01

Chronic pain and itch are common hypersensitivity syndromes that are affected by endogenous mediators. We applied a systems-based, translational approach to predict, discover, and characterize mediators of pain and itch that are regulated by diet and inflammation. Profiling of tissue-specific precursor abundance and biosynthetic gene expression predicted that inflamed skin would be abundant in four previously unknown 11-hydroxy-epoxy-or 11-keto-epoxy-octadecenoate linoleic acid derivatives and four previously identified 9- or 13-hydroxy-epoxy- or 9- or 13-keto-epoxy-octadecenoate linoleic acid derivatives. All of these mediators were confirmed to be abundant in rat and human skin by mass spectrometry. However, only the two 11-hydroxy-epoxy-octadecenoates sensitized rat dorsal root ganglion neurons to release more calcitonin gene–related peptide (CGRP), which is involved in pain transmission, in response to low pH (which mimics an inflammatory state) or capsaicin (which activates ion channels involved in nociception). The two 11-hydroxy-epoxy-octadecenoates share a 3-hydroxy-Z-pentenyl-E-epoxide moiety, thus suggesting that this substructure could mediate nociceptor sensitization. In rats, intradermal hind paw injection of 11-hydroxy-12,13-trans-epoxy-(9Z)-octadecenoate elicited C-fiber–mediated sensitivity to thermal pain. In a randomized trial testing adjunctive strategies to manage refractory chronic headaches, reducing the dietary intake of linoleic acid was associated with decreases in plasma 11-hydroxy-12,13-trans-epoxy-(9Z)-octadecenoate, which correlated with clinical pain reduction. Human psoriatic skin had 30-fold higher 9-keto-12,13-trans-epoxy-(10E)-octadecenoate compared to control skin, and intradermal injection of this compound induced itch-related scratching behavior in mice. Collectively, these findings define a family of endogenous mediators with potential roles in pain and itch. PMID:28831021

A Judgement Bias Test to Assess Affective State and Potential Therapeutics in a Rat Model of Chemotherapy-Induced Mucositis.

PubMed

George, Rebecca P; Barker, Timothy H; Lymn, Kerry A; Bigatton, Dylan A; Howarth, Gordon S; Whittaker, Alexandra L

2018-05-29

Chemotherapy-induced mucositis is an extremely painful condition that occurs in 40-60% of patients undergoing chemotherapy. As mucositis currently has no effective treatment, and due to the self-limiting nature of the condition, the major treatment aims are to manage symptoms and limit pain with significance placed on improving patient quality of life. Rodent models are frequently used in mucositis research. These investigations typically assess pathological outcomes, yet fail to include a measure of affective state; the key therapeutic goal. Assessment of cognitive biases is a novel approach to determining the affective state of animals. Consequently, this study aimed to validate a cognitive bias test through a judgement bias paradigm to measure affective state in a rat model of chemotherapy-induced intestinal mucositis. Rats with intestinal mucositis demonstrated a negative affective state, which was partially ameliorated by analgesic administration, whilst healthy rats showed an optimistic response. This study concluded that the judgement bias test was able to evaluate the emotional state of rats with chemotherapy-induced mucositis. These findings provide a foundation for future refinement to the experimental design associated with the animal model that will expedite successful transitioning of novel therapeutics to clinical practice, and also improve humane endpoint implementation.

Morphine amplifies mechanical allodynia via TLR4 in a rat model of spinal cord injury

PubMed Central

Ellis, Amanda; Grace, Peter M.; Wieseler, Julie; Favret, Jacob; Springer, Kendra; Skarda, Bryce; Hutchinson, Mark R.; Falci, Scott; Rice, Kenner C.; Maier, Steven F.; Watkins, Linda R.

2016-01-01

Central neuropathic pain (CNP) is a pervasive, debilitating problem that impacts thousands of people living with central nervous system disorders, including spinal cord injury (SCI). Current therapies for treating this type of pain are ineffective and often have dose-limiting side effects. Although opioids are one of the most commonly used CNP treatments, recent animal literature has indicated that administering opioids shortly after a traumatic injury can actually have deleterious effects on long-term health and recovery. In order to study the deleterious effects of administering morphine shortly after trauma, we employed our low thoracic (T13) dorsal root avulsion model (Spinal Neuropathic Avulsion Pain, SNAP). Administering a weeklong course of 10 mg/kg/day morphine beginning 24 hr after SNAP resulted in amplified mechanical allodynia. Co-administering the non-opioid toll-like receptor 4 (TLR4) antagonist (+)-naltrexone throughout the morphine regimen prevented morphine-induced amplification of SNAP. Exploration of changes induced by early post-trauma morphine revealed that this elevated gene expression of TLR4, TNF, IL-1β, and NLRP3, as well as IL-1β protein at the site of spinal cord injury. These data suggest that a short course of morphine administered early after spinal trauma can exacerbate CNP in the long term. TLR4 initiates this phenomenon and, as such, may be potential therapeutic targets for preventing the deleterious effects of administering opioids after traumatic injury. PMID:27519154

Crocin improved locomotor function and mechanical behavior in the rat model of contused spinal cord injury through decreasing calcitonin gene related peptide (CGRP).

PubMed

Karami, Masoume; Bathaie, S Zahra; Tiraihi, Taqi; Habibi-Rezaei, Mehran; Arabkheradmand, Jalil; Faghihzadeh, Soghrat

2013-12-15

Various approaches have been offered to alleviate chronic pain resulting from spinal cord injuries (SCIs). Application of herbs and natural products, with potentially lower adverse effects, to cure diseases has been recommended in both traditional and modern medicines. Here, the effect of crocin on chronic pain induced by spinal cord contusion was investigated in an animal model. Female Wistar rats were randomly divided into five groups (5 rats in each); three groups were contused at the L1 level. One group was treated with crocin (150mg/kg) two weeks after spinal cord injury; the second group, control, was treated with vehicle only; and the third group was treated with ketoprofen. Two normal groups were also considered with or without crocin treatment. The mechanical behavioral test, the locomotor recovery test and the thermal behavioral test were applied weekly to evaluate the injury and recovery of rats. Significant improvements (p<0.05) in mechanical behavioral and locomotor recovery tests were seen in the rats treated with crocin. Thermal behavioral test did not show any significant changes due to crocin treatment. Plasma concentration of calcitonin-gene related peptide (CGRP) changed from 780.2±2.3 to 1140.3±4.5pg/ml due to SCI and reached 789.1±2.7pg/ml after crocin treatment. These changes were significant at the level of p<0.05. The present study shows the beneficial effects of crocin treatment on chronic pain induced by SCI, through decreasing CGRP as an important mediator of inflammation and pain. Copyright © 2013 Elsevier GmbH. All rights reserved.

A back translation of pregabalin and carbamazepine against evoked and non-evoked endpoints in the rat spared nerve injury model of neuropathic pain.

PubMed

Lau, W; Dykstra, C; Thevarkunnel, S; Silenieks, L B; de Lannoy, I A M; Lee, D K H; Higgins, G A

2013-10-01

The purpose of the present study was twofold. First to characterize endpoints distinct to the reflexive responses to sensory stimuli typically used in neuropathic pain models. A second aim was to evaluate two clinically approved drugs carbamazepine (Tegretol) and pregabalin (Lyrica) against these endpoints with the purpose to backtranslate from the clinical to preclinical setting. The selected neuropathic pain model was the spared nerve injury (SNI) model and the endpoints were burrowing and measures of paw posture in Sprague Dawley rats. As previously described, SNI surgery produced a robust heightened sensitivity to tactile and thermal (cold) stimuli. SNI surgery also produced robust decreases in burrowing and affected multiple measures of paw position. There was no correlation between magnitude of change in burrowing and sensory allodynia within SNI operated rats. Pregabalin (10-30 mg/kg IP) produced a reliable reversal of both tactile and cold allodynia and also the burrowing deficit, with minimal effect on neurological function evaluated using rotorod, beam walking and open field activity. Pregabalin did not affect any measure of paw position. Pharmacokinetic studies conducted in satellite animals identified plasma levels of pregabalin at the 10 mg/kg IP dose to be equivalent to clinically efficacious levels recorded in neuropathic patients (3-6 μg/ml). In contrast carbamazepine (10-60 mg/kg IP) had only a very modest effect against a reflexive (tactile) measure, and no effect against the burrowing deficit. Carbamazepine also affected various measures of neurological function, complicating interpretation of the reflexive measure. Measurement of burrowing appears to detect a behavioural deficit associated with the SNI model, that may be attenuated by pregabalin but not carbamazepine. Overall the present findings support an advantage of pregabalin over carbamazepine in terms of both efficacy and tolerability which is consistent with clinical experience. The inclusion of additional endpoints beyond traditional reflexive behaviours further supports the value of rodent neuropathic pain models, such as the SNI, as behavioural assays to detect new chemical entities to treat this pain condition. Copyright © 2013 Elsevier Ltd. All rights reserved.

Suppression of Pax2 attenuates allodynia and hyperalgesia through ET-1-ETAR-NFAT5 signaling in a rat model of neuropathic pain.

PubMed

Tai, Lydia Wai; Pan, Zhiqiang; Sun, Liting; Li, Haobo; Gu, Pan; Wong, Stanley Sau Ching; Chung, Sookja K; Cheung, Chi Wai

2018-05-27

Endothelin-1 (ET-1) and its receptors (ETAR/ETBR) emerge to be a key signaling axis in neuropathic pain processing and are recognized as new therapeutic targets. Yet, little is known on the functional regulation of ET-1 axis during neuropathic pain. Bioinformatics analysis indicated that paired box gene 2 (Pax2) or nuclear factor of activated T-cells 5 (NFAT5), two transcription factors involved in the modulation of neurotransmission, may regulate ET-1. Therefore, we hypothesized that ET-1 axis may be regulated by Pax2 or NFAT5 in the development of neuropathic pain. After partial sciatic nerve ligation (pSNL), rats displayed allodynia and hyperalgesia, which was associated with increased mRNA and protein expressions of spinal Pax2, NFAT5, and mRNA levels of ET-1 and ETAR, but not ETBR. Knockdown of Pax2 or NFAT5 with siRNA, or inhibition of ETAR with BQ-123 attenuated pSNL-induced pain-like behaviors. At molecular level, Pax2 siRNA, but not NFAT5 siRNA, downregulated ET-1 and ETAR, while ETAR inhibitor reduced NFAT5, indicating Pax2 in the upstream of ET-1 axis with NFAT5 in the downstream. Further, suppression of Pax2 (inhibiting ET-1) or impairment of ET-1 signaling (inhibition of ETAR and/or decrease of NFAT5) deactivated mitogen-activated protein kinases (MAPK) and nuclear factor-kappa B (NF-κB) signaling pathways, supporting the significance of functional regulation of ET-1 axis in neuropathic pain signaling. These findings demonstrate that Pax2 targeting ET-1-ETAR-NFAT5 is a novel regulatory mechanism underlying neuropathic pain. Copyright © 2018 IBRO. Published by Elsevier Ltd. All rights reserved.

Vasculitic peripheral neuropathy induced by ischemia-reperfusion in the rat femoral artery involves activation of proinflammatory signaling pathway in the sciatic nerve.

PubMed

Chung, Chih-Yang; Chang, Yi-Wei; Huang, Chun-Jen; Wang, Po-Kai; Wan, Hung-Chieh; Lin, Yi-Ying; Kao, Ming-Chang

2017-08-24

Ischemia-reperfusion (IR) in the rat femoral artery has been proposed as an experimental model of vasculitic peripheral neuropathy (VPN) which presents neuropathic pain and peripheral nerve injury patterns observed clinically. This study investigates the involvement of the proinflammatory signaling pathway underlying the peripheral mechanisms of VPN. Male Sprague-Dawley rats were allocated to receive either a sham operation or IR. IR was induced by occluding the right femoral artery for 4h followed by reperfusion periods from 0 to 72h. The behavioral parameters were assessed at baseline as well as at days 1, 2 and 3 after reperfusion. The time-course analyses of proinflammatory mediators in the sciatic nerves were also performed on rats of the sham group or IR groups with reperfusion periods of 0, 2, 4, 24 and 72h, respectively. The behavioral data confirmed that this VPN model induced hindpaw mechano-allodynia and heat hyperalgesia as well as impaired hindpaw grip strength. The molecular data revealed that IR in the femoral artery activated the expression of nuclear factor-κB (NF-κB) in the sciatic nerve indicating a neuroinflammatory response. Moreover, IR in the femoral artery increased the expression of proinflammatory cytokines TNF-α and IL-1β in the sciatic nerve. This study elucidated the novel time-course expression profiles of NF-κB and proinflammatory cytokines in VPN induced by IR which may be involved in the development of neuropathic pain. Since NF-κB is a key element during neuroinflammation, strategies targeting the NF-κB signaling pathway may provide therapeutic potential against VPN induced by IR. Copyright © 2017 Elsevier B.V. All rights reserved.

Magnesium attenuates chronic hypersensitivity and spinal cord NMDA receptor phosphorylation in a rat model of diabetic neuropathic pain

PubMed Central

Rondón, L J; Privat, A M; Daulhac, L; Davin, N; Mazur, A; Fialip, J; Eschalier, A; Courteix, C

2010-01-01

Neuropathic pain is a common diabetic complication affecting 8–16% of diabetic patients. It is characterized by aberrant symptoms of spontaneous and stimulus-evoked pain including hyperalgesia and allodynia. Magnesium (Mg) deficiency has been proposed as a factor in the pathogenesis of diabetes-related complications, including neuropathy. In the central nervous system, Mg is also a voltage-dependant blocker of the N-methyl-d-aspartate receptor channels involved in abnormal processing of sensory information. We hypothesized that Mg deficiency might contribute to the development of neuropathic pain and the worsening of clinical and biological signs of diabetes and consequently, that Mg administration could prevent or improve its complications. We examined the effects of oral Mg supplementation (296 mg l−1 in drinking water for 3 weeks) on the development of neuropathic pain and on biological and clinical parameters of diabetes in streptozocin (STZ)-induced diabetic rats. STZ administration induced typical symptoms of type 1 diabetes. The diabetic rats also displayed mechanical hypersensitivity and tactile and thermal allodynia. The level of phosphorylated NMDA receptor NR1 subunit (pNR1) was higher in the spinal dorsal horn of diabetic hyperalgesic/allodynic rats. Magnesium supplementation failed to reduce hyperglycaemia, polyphagia and hypermagnesiuria, or to restore intracellular Mg levels and body growth, but increased insulinaemia and reduced polydipsia. Moreover, it abolished thermal and tactile allodynia, delayed the development of mechanical hypersensitivity, and prevented the increase in spinal cord dorsal horn pNR1. Thus, neuropathic pain symptoms can be attenuated by targeting the Mg-mediated blockade of NMDA receptors, offering new therapeutic opportunities for the management of chronic neuropathic pain. PMID:20837644

Antihyperalgesic Activity of Rhodiola rosea in a Diabetic Rat Model.

PubMed

Déciga-Campos, Myrna; González-Trujano, Maria Eva; Ventura-Martínez, Rosa; Montiel-Ruiz, Rosa Mariana; Ángeles-López, Guadalupe Esther; Brindis, Fernando

2016-02-01

Preclinical Research Rhodiola rosea L. (Crassulaceae) is used for enhancing physical and mental performance. Recent studies demonstrated that R. rosea had anti-inflammatory activity in animal models, for example, carrageenan- and nystatin-induced edema in rats, possibly by inhibiting phospholipase A2 and cyclooxygenases-1 and -2. In addition, R. rosea had antinociceptive activity in thermal and chemical pain tests as well as mechanical hyperalgesia. The purpose of the present study was to assess the antihyperalgesic effect of an ethanol extract of Rhodiola rosea (R. rosea) in a diabetic rat model. Rats were administered a single dose of streptozotocin (STZ; 50 mg/kg, i.p.) and hyperalgesia was evaluated four weeks later. Formalin-evoked (0.5%) flinching was increased in diabetic rats compared with nondiabetic controls Systemic (1-100 mg/kg, i.p.) and local (0.1-10 mg/paw into the dorsal surface of the right hind paw) administration of R. rosea ethanol extract dose-dependently reduced formalin-induced hyperalgesia in diabetic rats. The antihyperalgesic effect of R. rosea was compared with gabapentin. These results suggest that R. rosea ethanol extract may have potential as a treatment for diabetic hyperalgesia. © 2016 Wiley Periodicals, Inc.

Macroscopic and pathological assessment of methylene blue and normal saline on postoperative adhesion formation in a rat cecum model.

PubMed

Panahi, Farzad; Sadraie, Seyed Homayoon; Khoshmohabat, Hadi; Shahram, Elias; Kaka, Gholamreza; Hosseinalipour, Mohammad

2012-01-01

Adhesion formation after abdominal surgery is a major cause of postoperative bowel obstruction, infertility, and chronic abdominal pain. In this study, we evaluated the effect of normal saline and methylene blue (MB) on postoperative adhesion formation in a rat cecum model. A total of 30 Wistar female rats in 2 treatment and 1 control groups underwent midline laparotomy and standardized abrasion of the visceral peritoneum. Normal saline and methylene blue were administrated intraperitoneally at the end of the surgical procedure in 2 treatment groups. Fourteen days after surgery, a re-laparotomy was performed for macroscopic and pathological assessment. The adhesion grade and extent of the normal saline group was lower than control and MB groups in macroscopic assessment (P<0.05 for both). A comparison of adhesion stages in pathological assessment showed increment in abdominal adhesion by usage methylene blue 1% and demonstrated significant difference between MB and 2 other groups (P<0.05). Administrated normal saline individually reduce the adhesion grade near cecum. Conversely, usage of methylene blue 1% may unpredictably increase risk of adhesion formation. Copyright © 2012 Surgical Associates Ltd. Published by Elsevier Ltd. All rights reserved.

Chronic Nerve Compression Accelerates the Progression of Diabetic Peripheral Neuropathy in a Rat Model: A Study of Gene Expression Profiling.

PubMed

Tu, Yiji; Chen, Zenggan; Hu, Junda; Ding, Zuoyou; Lineaweaver, William C; Dellon, A Lee; Zhang, Feng

2018-04-25

 This article investigates the role of chronic nerve compression in the progression of diabetic peripheral neuropathy (DPN) by gene expression profiling.  Chronic nerve compression was created in streptozotocin (STZ)-induced diabetic rats by wrapping a silicone tube around the sciatic nerve (SCN). Neurological deficits were evaluated using pain threshold test, motor nerve conduction velocity (MNCV), and histopathologic examination. Differentially expressed genes (DGEs) and metabolic processes associated with chronic nerve compression were analyzed.  Significant changes in withdrawal threshold and MNCV were observed in diabetic rats 6 weeks after diabetes induction, and in DPN rats 4 weeks after diabetes induction. Histopathologic examination of the SCN in DPN rats presented typical changes of myelin degeneration in DPN. Function analyses of DEGs demonstrated that biological processes related to inflammatory response, extracellular matrix component, and synaptic transmission were upregulated after diabetes induction, and chronic nerve compression further enhanced those changes. While processes related to lipid and glucose metabolism, response to insulin, and apoptosis regulation were inhibited after diabetes induction, chronic nerve compression further enhanced these inhibitions.  Our study suggests that additional silicone tube wrapping on the SCN of rat with diabetes closely mimics the course and pathologic findings of human DPN. Further studies are needed to verify the effectiveness of this rat model of DPN and elucidate the roles of the individual genes in the progression of DPN. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Effects of orally administered OP-1206 alpha-CD with loxoprofen-Na on walking dysfunction in the rat neuropathic intermittent claudication model.

PubMed

Nakai, Katsuhiko; Takenobu, Yoshifumi; Takimizu, Hideyuki; Akimaru, Shinji; Ito, Hidenori; Maegawa, Hitoshi; Marsala, Martin; Katsube, Nobuo

2003-10-01

An orally active prostaglandin E1 analogue, OP-1206 alpha-CD improves walking dysfunction in the rat spinal stenosis model. Loxoprofen-Na, a non-steroidal anti-inflammatory drug, is used to relieve chronic pain in patients with lumbar spinal canal stenosis. To determine whether the OP-1206 alpha-CD in combination with loxoprofen-Na could induce a greater therapeutical effect on walking dysfunction and spinal cord blood flow (SCBF) than OP-1206 alpha-CD treatment alone after chronic spinal stenosis in the rat. Spinal stenosis was induced by placing two pieces of silicon rubber strips in the lumbar (L4 and L6) epidural space of rats. After surgery, walking function was measured using a treadmill apparatus and SCBF was measured using a laser-Doppler flow meter. Drugs were administered orally twice a day for 11 days from the day 3 post-surgery. OP-1206 alpha-CD elicited a significant improvement of walking dysfunction on days 7 and 14 post-surgery and significantly increased spinal cord blood flow on day 15, whereas walking dysfunction and SCBF of rats treated with loxoprofen-Na alone remained unchanged. Combined treatment of OP-1206 alpha-CD with loxoprofen-Na did not provide additive therapeutical effect. These results suggest that a significant improvement seen after OP-1206 alpha-CD treatment is primarily mediated by improvement of the local spinal cord blood flow. This effect is not ameliorated or potentiated by a combined treatment with loxoprofen-Na.

Influence of manual therapy on functional mobility after joint injury in a rat model.

PubMed

Ruhlen, Rachel L; Snider, Eric J; Sargentini, Neil J; Worthington, Bart D; Singh, Vineet K; Pazdernik, Vanessa K; Johnson, Jane C; Degenhardt, Brian F

2013-10-01

Animal models can be used to investigate manual therapy mechanisms, but testing manipulation in animal models is problematic because animals cannot directly report their pain. To develop a rat model of inflammatory joint injury to test the efficacy of manual therapy in reducing nociception and restoring function. The authors induced acute inflammatory joint injury in rats by injecting carrageenan into the ankle and then measured voluntary running wheel activity in treated and untreated rats. Treatments included manual therapy applied to the ankle and knee of the injured limb and several analgesic medications (eg, morphine, ketorolac, prednisone). Intra-articular injection of carrageenan to the ankle produced significant swelling (diameter of the ankle increased by 64% after injection; P=.004) and a robust reduction in voluntary running wheel activity (running distance reduced by 91% compared with controls; P<.001). Injured rats gradually returned to running levels equal to controls over 10 days. Neither manual therapy nor analgesic medications increased running wheel activity relative to untreated rats. Voluntary running wheel activity appears to be an appropriate functional measure to evaluate the impact of an acute inflammatory joint injury. However, efforts to treat the injury did not restore running relative to untreated rats.

Analgesic effects of tramadol, carprofen or multimodal analgesia in rats undergoing ventral laparotomy.

PubMed

Zegre Cannon, Coralie; Kissling, Grace E; Goulding, David R; King-Herbert, Angela P; Blankenship-Paris, Terry

2011-03-01

In this study, the authors evaluated the analgesic efficacy of tramadol (an opioid-like analgesic), carprofen (a nonsteroidal anti-inflammatory drug) and a combination of both drugs (multimodal therapy) in a rat laparotomy model. The authors randomly assigned rats to undergo either surgery (abdominal laparotomy with visceral manipulation and anesthesia) or anesthesia only. Rats in each group were treated with tramadol (12.5 mg per kg body weight), carprofen (5 mg per kg body weight), a combination of tramadol and carprofen (12.5 mg per kg body weight and 5 mg per kg body weight, respectively) or saline (anesthesia control group only; 5 mg per kg body weight). The authors administered analgesia 10 min before anesthesia, 4 h after surgery or (for the rats that received anesthesia only) anesthesia and 24 h after surgery or anesthesia. They measured locomotor activity, running wheel activity, feed and water consumption, body weight and fecal corticosterone concentration of each animal before and after surgery. Clinical observations were made after surgery or anesthesia to evaluate signs of pain and distress. The authors found that carprofen, tramadol and a combination of carprofen and tramadol were all acceptable analgesia regimens for a rat laparotomy model.

Effect of caffeine coadministration and of nitric oxide synthesis inhibition on the antinociceptive action of ketorolac.

PubMed

López-Muñoz, F J; Castañeda-Hernández, G; Flores-Murrieta, F J; Granados-Soto, V

1996-07-25

The effects of caffeine and nitric oxide synthesis inhibition on the antinociceptive action of ketorolac were assessed using the pain-induced functional impairment model in the rat. Nociception was induced by the intra-articular injection of uric acid. Ketorolac, but not caffeine, produced an antinociceptive effect which was reduced by NG nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthesis. Caffeine coadministration potentiated the ketorolac effect. L-NAME induced a dose-dependent reduction of this potentiation. The results suggest the participation of the L-arginine-nitric oxide-cyclic GMP pathway in the caffeine potentiation of ketorolac-induced antinociception.

Selectively targeting pain in the trigeminal system

PubMed Central

Kim, Hyun Yeong; Kim, Kihwan; Li, Hai Ying; Chung, Gehoon; Park, Chul-Kyu; Kim, Joong Soo; Jung, Sung Jun; Lee, Min Kyung; Ahn, Dong Kuk; Hwang, Se Jin; Kang, Youngnam; Binshtok, Alexander M.; Bean, Bruce P.; Woolf, Clifford J.; Oh, Seog Bae

2015-01-01

We tested whether it is possible to selectively block pain signals in the orofacial area by delivering the permanently charged lidocaine derivative QX-314 into nociceptors via TPRV1 channels. We examined the effects of co-applied QX-314 and capsaicin on nociceptive, proprioceptive, and motor function in the rat trigeminal system. QX-314 alone failed to block voltage-gated sodium channel currents (INa) and action potentials (APs) in trigeminal ganglion (TG) neurons. However, co-application of QX-314 and capsaicin blocked INa and APs in TRPV1-positive TG and dental nociceptive neurons, but not in TRPV1-negative TG neurons or in small neurons from TRPV1 knock-out mice. Immunohistochemistry revealed that TRPV1 is not expressed by trigeminal motor and trigeminal mesencephalic neurons. Capsaicin had no effect on rat trigeminal motor and proprioceptive mesencephalic neurons and therefore should not allow QX-314 to enter these cells. Co-application of QX-314 and capsaicin inhibited the jaw-opening reflex evoked by noxious electrical stimulation of the tooth pulp when applied to a sensory but not a motor nerve, and produced long-lasting analgesia in the orofacial area. These data show that selective block of pain signals can be achieved by co-application of QX-314 with TRPV1 agonists. This approach has potential utility in the trigeminal system for treating dental and facial pain. PMID:20236764

Opioidergic mechanisms are not involved in the antihyperalgesic effects of carbamazepine and oxcarbazepine.

PubMed

Stepanovic-Petrovic, Radica M; Tomic, M A; Vuckovic, S M; Ugresic, N D; Prostran, M S; Boskovic, B

2007-04-01

The mechanisms of the analgesic action of carbamazepine and oxcarbazepine, in particular the role of opioid receptors, have not been established precisely. The systemic effects of naloxone, an opioid receptor antagonist, on the antihyperalgesic effects of carbamazepine and oxcarbazepine were examined in the model of inflammatory hyperalgesia induced by the intraplantar (i.pl.) administration of concanavaline A (Con A, 0.8 mg/paw) into the rat hind paw. Naloxone (3 mg/kg; i.p.) did not alter the antihyperalgesic effects of either carbamazepine or oxcarbazepine. These results indicate that the opioid system of pain modulation does not play a significant role in the antihyperalgesic effects of carbamazepine and oxcarbazepine.

Evaluation of heat hyperalgesia and anxiety like-behaviors in a rat model of orofacial cancer.

PubMed

Gambeta, Eder; Kopruszinski, Caroline Machado; Dos Reis, Renata Cristiane; Zanoveli, Janaina Menezes; Chichorro, Juliana Geremias

2016-04-21

Pain and anxiety are commonly experienced by cancer patients and both significantly impair their quality of life. Some authors claim that there is a relationship between pain and anxiety, while others suggest that there is not a direct association. In any case, there is indeed a consensus that anxiety impairs the pain condition beyond be under diagnosed and undertreated in cancer pain patients. Herein we investigated if rats presenting heat hyperalgesia induced by orofacial cancer cell inoculation would display anxiety-like behaviors. In addition, we evaluated if pain blockade would result in alleviation of anxiety behaviors, as well as, if blockade of anxiety would result in pain relief. Orofacial cancer was induced in male Wistar rats by inoculation of Walker-256 cells into the right vibrissal pad. Heat facial hyperalgesia was assessed on day 6 after the inoculation, and on this time point rats were submitted to the elevated plus maze and the light-dark transition tests. The influence of lidocaine and midazolam on heat hyperalgesia and anxiety-like behaviors was assessed. The peak of facial heat hyperalgesia was detected 6 days after cancer cells inoculation, and at this time point, rats exhibited increased anxiety-like behaviors. Local treatment with lidocaine (2%/50μL) caused a marked reduction of heat hyperalgesia, but failed to affect the anxiety-like behaviors, while midazolam (0.5mg/kg, i.p.) treatment failed to change the heat threshold, but induced an anxiolytic-like effect. Altogether, our data demonstrated that rats with orofacial cancer present pain- and anxiety-like behaviors, but brief heat hyperalgesia relief does not affect the anxiety-like behaviors, and vice-versa, in our experimental conditions. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Sensitization of TRPV1 by protein kinase C in rats with mono-iodoacetate-induced joint pain.

PubMed

Koda, K; Hyakkoku, K; Ogawa, K; Takasu, K; Imai, S; Sakurai, Y; Fujita, M; Ono, H; Yamamoto, M; Fukuda, I; Yamane, S; Morita, A; Asaki, T; Kanemasa, T; Sakaguchi, G; Morioka, Y

2016-07-01

To assess the functional changes of Transient receptor potential vanilloid 1 (TRPV1) receptor and to clarify its mechanism in a rat mono-iodoacetate (MIA)-induced joint pain model (MIA rats), which has joint degeneration with cartilage loss similar to osteoarthritis. Sensitization of TRPV1 in MIA rats was assessed by transient spontaneous pain behavior induced by capsaicin injection in knee joints and electrophysiological changes of dorsal root ganglion (DRG) neurons innervating knee joints in response to capsaicin. Mechanisms of TRPV1 sensitization were analyzed by a newly developed sandwich enzyme-linked immunosorbent assay that detects phosphorylated TRPV1, followed by functional and expression analyses of protein kinase C (PKC) in vivo and in vitro, which involves TRPV1 phosphorylation. Pain-related behavior induced by intra-articular injection of capsaicin was significantly increased in MIA rats compared with sham rats. In addition, capsaicin sensitivity, evaluated by capsaicin-induced inward currents, was significantly increased in DRG neurons of MIA rats. Protein levels of TRPV1 remained unchanged, but phosphorylated TRPV1 at Ser800 increased in DRG neurons of MIA rats. Phosphorylated-PKCɛ (p-PKCɛ) increased and co-localized with TRPV1 in DRG neurons of MIA rats. Capsaicin-induced pain-related behavior in MIA rats was inhibited by intra-articular pretreatment of the PKC inhibitor bisindolylmaleimide I. In addition, intra-articular injection of the PKC activator phorbol 12-myristate 13-acetate increased capsaicin-induced pain-related behavior in normal rats. TRPV1 was sensitized at the knee joint and at DRG neurons of MIA rats through PKC activation. Thus, TRPV1 sensitization might be involved in chronic pain caused by osteoarthritis. Copyright © 2016 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

Randomized Clinical Trial of the Innovative Bilayered Wound Dressing Made of Silk and Gelatin: Safety and Efficacy Tests Using a Split-Thickness Skin Graft Model

PubMed Central

Hasatsri, Sukhontha; Angspatt, Apichai

2015-01-01

We developed the novel silk fibroin-based bilayered wound dressing for the treatment of partial thickness wounds. And it showed relevant characteristics and accelerated the healing of full-thickness wounds in a rat model. This study is the clinical evaluation of the bilayered wound dressing to confirm its safety and efficacy for the treatment of split-thickness skin donor sites. The safety test was performed using a patch model and no evidence of marked and severe cutaneous reactions was found. The efficacy test of the bilayered wound dressing was conducted on 23 patients with 30 split-thickness skin graft donor sites to evaluate healing time, pain score, skin barrier function, and systemic reaction in comparison to Bactigras. We found that the healing time of donor site wounds treated with the bilayered wound dressing (11 ± 6 days) was significantly faster than those treated with Bactigras (14 ± 6 days) (p = 10−6). The wound sites treated with the bilayered wound dressing showed significantly less pain and more rapid skin functional barrier recovery than those treated with Bactigras (p = 10−5). Therefore, these results confirmed the clinical safety and efficacy of the bilayered wound dressing for the treatment of split-thickness skin graft donor sites. PMID:26221170

Antinociceptive Effect of Racemic Flurbiprofen and Caffeine Co-Administration in an Arthritic Gout-Type Pain in Rats.

PubMed

Liévano-Reyes, Ricardo; Pérez-Méndez, Hermínia Ines; Solís-Oba, Aida; Jaramillo-Morales, Osmar Antonio; Espinosa-Juárez, Josué Vidal; López-Muñoz, Francisco Javier

2016-06-01

Preclinical Research Drug combinations are routinely used in the treatment of pain. In drug associations, adjuvants such as caffeine, are employed with different non-steroidal anti-inflammatories drugs (NSAIDs), however, at present does not exist studies showing the effect of the combination of racemic flurbiprofen (rac-Flur) in association with caffeine. The objective of this work was to evaluate the combination of rac-Flur + caffeine oral in arthritic gout-type pain in rats. The antinociceptive effects of the rac-Flur alone and in combination with caffeine were analyzed on a pain-induced functional impairment model in rat. rac-Flur induced a dose-dependent antinociceptive effect and caffeine did not present any effect. The combination of rac-Flur and caffeine achieve a higher percentage of antinociceptive effect compared with the individual administration of rac-Flur. The dose-response curve (DRCs) shows that the combination of rac-Flur (31.6 mg/kg) + caffeine (17.8 mg/kg) exhibited the maximal antinociceptive efficacy (294.0 ± 21.2 area units), while rac-Flur alone (31.6 mg/kg) showed 207.2 ± 35.2 au, thus indicating an increase in efficacy (potentiation). Furthermore, the DRCs of the combinations presented a displacement to the left, indicating a change in the potency. Caffeine is able to increase the effect of rac-Flur in the arthritic gout-type pain in rats. Drug Dev Res 77 : 192-198, 2016.   © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Houttuynia cordata Thunb reverses oxaliplatin-induced neuropathic pain in rat by regulating Th17/Treg balance.

PubMed

Wan, Cheng-Fu; Zheng, Li-Li; Liu, Yan; Yu, Xue

2016-01-01

Oxaliplatin is a widely used anti-advanced colorectal cancer drug, while it could induce neuropathy. Houttuynia cordata Thunb (HCT) has a wide range of biological activities, such as anti-inflammation, anti-cancer, and immune regulation. In the present study, we investigated the effect of HCT on oxaliplatin-induced neuropathy in rat models. HCT (1000 mg/kg/day) significantly decreased the number of withdrawal responses and the withdrawal latency in oxaliplatin-treated rats. HCT could down-regulated the serum levels of Interleukin-6 (IL-6) and macrophage inflammatory protein1-α (MIP-1α) in oxaliplatin-treated rats. Th17/Treg balance was reversed by HCT in oxaliplatin-treated rats by regulating PI3K/Akt/mTOR signaling pathway. The present results suggest that HCT is useful as a therapeutic drug for oxaliplatin-induced neuropathic pain.

Houttuynia cordata Thunb reverses oxaliplatin-induced neuropathic pain in rat by regulating Th17/Treg balance

PubMed Central

Wan, Cheng-Fu; Zheng, Li-Li; Liu, Yan; Yu, Xue

2016-01-01

Oxaliplatin is a widely used anti-advanced colorectal cancer drug, while it could induce neuropathy. Houttuynia cordata Thunb (HCT) has a wide range of biological activities, such as anti-inflammation, anti-cancer, and immune regulation. In the present study, we investigated the effect of HCT on oxaliplatin-induced neuropathy in rat models. HCT (1000 mg/kg/day) significantly decreased the number of withdrawal responses and the withdrawal latency in oxaliplatin-treated rats. HCT could down-regulated the serum levels of Interleukin-6 (IL-6) and macrophage inflammatory protein1-α (MIP-1α) in oxaliplatin-treated rats. Th17/Treg balance was reversed by HCT in oxaliplatin-treated rats by regulating PI3K/Akt/mTOR signaling pathway. The present results suggest that HCT is useful as a therapeutic drug for oxaliplatin-induced neuropathic pain. PMID:27186286

WenTong HuoXue Cream Can Inhibit the Reduction of the Pain-Related Molecule PLC-β3 in the Dorsal Root Ganglion of a Rat Model of Diabetic Peripheral Neuropathy.

PubMed

Feng, Chengcheng; Xu, Lijuan; Guo, Shiyun; Chen, Qian; Shen, Yuguo; Zang, Deng; Ma, Li

2018-01-01

WenTong HuoXue Cream (WTHX-Cream) has been shown to effectively alleviate clinical symptoms of diabetic peripheral neuropathy (DPN). This study investigated the gene and protein expression of the pain-related molecule PLC- β 3 in the dorsal root ganglion (DRG) of DPN rats. 88 specific pathogen-free male Wistar rats were randomly divided into placebo (10 rats) and DPN model (78 rats) groups, and the 78 model rats were used to establish the DPN model by intraperitoneal injection of streptozotocin and were then fed a high-fat diet for 8 weeks. These rats were randomly divided into the model group, the high-, medium-, and low-dose WTHX-Cream + metformin groups, the metformin group, the capsaicin cream group, and the capsaicin cream + metformin group. After 4 weeks of continuous drug administration, the blood glucose, body weight, behavioral indexes, and sciatic nerve conduction velocity were measured. The pathological structure of the DRG and the sciatic nerve were observed. PLC- β 3 mRNA and protein levels in the DRG of rats were measured. Compared with the model group, the high-dose WTHX-Cream group showed increased sciatic nerve conduction velocity, improved sciatic nerve morphological changes, and increased expression of PLC- β 3 mRNA and protein in the DRG. This study showed that WTHX-Cream improves hyperalgesia symptoms of DPN by inhibiting the reduction of PLC- β 3 mRNA and protein expression in the diabetic DRG of DPN rats.

Notch3 is necessary for neuronal differentiation and maturation in the adult spinal cord

PubMed Central

Rusanescu, Gabriel; Mao, Jianren

2014-01-01

Notch receptors are key regulators of nervous system development and promoters of neural stem cells renewal and proliferation. Defects in the expression of Notch genes result in severe, often lethal developmental abnormalities. Notch3 is generally thought to have a similar proliferative, anti-differentiation and gliogenic role to Notch1. However, in some cases, Notch3 has an opposite, pro-differentiation effect. Here, we show that Notch3 segregates from Notch1 and is transiently expressed in adult rat and mouse spinal cord neuron precursors and immature neurons. This suggests that during the differentiation of adult neural progenitor cells, Notch signalling may follow a modified version of the classical lateral inhibition model, involving the segregation of individual Notch receptors. Notch3 knockout mice, otherwise neurologically normal, are characterized by a reduced number of mature inhibitory interneurons and an increased number of highly excitable immature neurons in spinal cord laminae I–II. As a result, these mice have permanently lower nociceptive thresholds, similar to chronic pain. These results suggest that defective neuronal differentiation, for example as a result of reduced Notch3 expression or activation, may underlie human cases of intractable chronic pain, such as fibromyalgia and neuropathic pain. PMID:25164209

Role of NFkappaB in an animal model of complex regional pain syndrome-type I (CRPS-I).

PubMed

de Mos, Marissa; Laferrière, André; Millecamps, Magali; Pilkington, Mercedes; Sturkenboom, Miriam C J M; Huygen, Frank J P M; Coderre, Terence J

2009-11-01

NFkappaB is involved in several pathogenic mechanisms that are believed to underlie the complex regional pain syndrome (CRPS), including ischemia, inflammation and sensitization. Chronic postischemia pain (CPIP) has been developed as an animal model that mimics the symptoms of CRPS-I. The possible involvement of NFkappaB in CRPS-I was studied using CPIP rats. Under sodium pentobarbital anesthesia, a tourniquet was placed around the rat left ankle joint, producing 3 hours of ischemia, followed by rapid reperfusion (IR injury). NFkappaB was measured in nuclear extracts of muscle and spinal cord tissue using ELISA. Moreover, the anti-allodynic (mechanical and cold) effect was tested for systemic, intrathecal, or intraplantar treatment with the NFkappaB inhibitor pyrrolidine dithiocarbamate (PDTC). At 2 and 48 hours after IR injury, NFkappaB was elevated in muscle and spinal cord of CPIP rats compared to shams. At 7 days, NFkappaB levels were normalized in muscle, but still elevated in spinal cord tissue. Systemic PDTC treatment relieved mechanical and cold allodynia in a dose-dependent manner, lasting for at least 3 hours. Intrathecal-but not intraplantar-administration also relieved mechanical allodynia. The results suggest that muscle and spinal NFkappaB plays a role in the pathogenesis of CPIP and potentially of human CRPS. Using the CPIP model, we demonstrate that NFkappaB is involved in the development of allodynia after a physical injury (ischemia and reperfusion) without direct nerve trauma. Since CPIP animals exhibit many features of human CRPS-I, this observation indicates a potential role for NFkappaB in human CRPS.

The antinociceptive effect of intrathecal administration of epibatidine with clonidine or neostigmine in the formalin test in rats.

PubMed

Hama, A T; Lloyd, G K; Menzaghi, F

2001-03-01

The analgesic effect of intrathecal injection of epibatidine, clonidine and neostigmine, compounds that elevate ACh, was examined in the formalin test, a model of post-injury central sensitization in the rat. The compounds were injected alone and in combination. Intrathecal injection of epibatidine alone did not alter pain behaviors, compared to vehicle-treated rats. Intrathecal injection of clonidine dose-dependently reduced tonic pain behaviors (ED(50)+/-95% confidence limits=6.7+/-4.8 microg). The combination of clonidine and epibatidine (C:E), in the ratio of 26:1, dose-dependently reduced tonic pain behaviors; and the ED(50) of C:E was 1.1+/-0.98 microg a significant 6-fold leftward shift of the dose response curve, compared with clonidine alone. The antinociceptive effect of C:E (26:1) was attenuated by pre-treatment with the nAChR antagonist mecamylamine. Neostigmine dose-dependently reduced tonic pain behaviors (ED(50)=1.5+/-1.3 microg). The combination of neostigmine and epibatidine, in a ratio of 8:1, significantly shifted the dose response curve 4-fold to the left (ED(50)=0.4+/-0.3 microg). The effect is mediated in part by the activation of the nAChR and possibly by the enhanced release of ACh. These data demonstrate significant enhancement of the antinociceptive effects of spinally delivered analgesics by a nAChR agonist, suggesting that this class of compounds may have utility as adjuvants when combined with conventional therapeutics.

Colorectal distension-induced pseudoaffective changes as indices of nociception in the anesthetized female rat: morphine and strain effects on visceral sensitivity.

PubMed

Sivarao, Digavalli V; Langdon, Shaun; Bernard, Christopher; Lodge, Nicholas

2007-01-01

Colorectal distension of a sufficient intensity evokes several characteristic postural, visceromotor and cardiovascular reflexes in conscious rats that have been extensively utilized for testing putative visceral analgesics. The neural circuitry for these reflexes is encompassed within the spinobulbar region and continues to be robust even after decerebration. Yet, these are not consistently replicated in anesthetized animals, presumably due to medullary depression. In the following studies, we tested the hypothesis that a carefully chosen anesthetic regimen can replicate the pattern of pseudoaffective responses seen in awake animals. Female rats were anesthetized with methohexital sodium and equipped with arterial and venous catheters, a colorectal balloon and abdominal wire electrodes. Subsequent anesthesia was maintained with urethane. Colorectal distension produced clear changes in visceromotor and cardiovascular indices that not only mimicked responses to distension seen in conscious rats, but also importantly, showed a comparable stimulus sensitivity and stability. Morphine (ED(50), 0.17 mg/kg, iv) was highly efficacious in attenuating response in a dose-dependent and naloxone-selective manner. Using this model, we compared three commonly used rat strains (Wistar, Wistar-Kyoto and Sprague-Dawley) for distension-mediated responses. Whereas Wistar-Kyoto rats were significantly hyper-responsive to distension, the sensory threshold for distension was nearly identical across strains. Thus, we report an anesthetized female rat model that replicates characteristic responses associated with visceral pain in conscious rats and its modulation by known factors like analgesia and strain. These findings provide a simple insensate model for testing novel visceral analgesics while eliminating postoperative recovery and motion-related artifact typically associated with colorectal distension studies in conscious rats. Thus, a viable and humane alternative to visceral nociception studies in conscious animals is offered.

Co-administration of MK-801 and morphine attenuates neuropathic pain in rat.

PubMed

Hamidi, Gholam Ali; Manaheji, Homa; Janahmadi, Mahyar; Noorbakhsh, Sayed Mohammad; Salami, Mahmoud

2006-07-30

Partial peripheral nerve injury often leads to chronic pain states, including allodynia and hyperalgesia. The purpose of this study was to investigate the involvement of the N-methyl-D-aspartate and opioid receptors in the behavioural responses following chronic constriction nerve injury (CCI). The animals were injected a combination of MK-801 (0.3 mg/kg, 20 min before, and 6 h after the operation) and morphine (8 mg/kg, 30 min prior to the operation) and were tested for allodynia and hyperalgesia reactions at 0, 3, 7, 14, 21 and 28 days after CCI. Compound action potentials were also recorded from the injured nerve 2 weeks post-operation to indicate nerve injury state electrophysiologically. Our results indicate that the CCI model importantly influences the behavioural responses to both the thermal and mechanical stimulations. Also, the pre-emptive co-administration of MK-801 and morphine has suppressive effects on the cold allodynia but a slight alleviation on the mechano-allodynia and heat hyperalgesia.

Gene Transfer of Glutamic Acid Decarboxylase 67 by Herpes Simplex Virus Vectors Suppresses Neuropathic Pain Induced by Human Immunodeficiency Virus gp120 Combined with ddC in Rats.

PubMed

Kanao, Megumi; Kanda, Hirotsugu; Huang, Wan; Liu, Shue; Yi, Hyun; Candiotti, Keith A; Lubarsky, David A; Levitt, Roy C; Hao, Shuanglin

2015-06-01

Human immunodeficiency virus (HIV)-related painful sensory neuropathies primarily consist of the HIV infection-related distal sensory polyneuropathy and antiretroviral toxic neuropathies. Pharmacotherapy provides only partial relief of pain in patients with HIV/acquired immune deficiency syndrome because little is known about the exact neuropathological mechanisms for HIV-associated neuropathic pain (NP). Hypofunction of γ-aminobutyric acid (GABA) GABAergic inhibitory mechanisms has been reported after peripheral nerve injury. In this study, we tested the hypothesis that HIV gp120 combined with antiretroviral therapy reduces spinal GABAergic inhibitory tone and that restoration of GABAergic inhibitory tone will reduce HIV-related NP in a rat model. The application of recombinant HIV-1 envelope protein gp120 into the sciatic nerve plus systemic ddC (one antiretroviral drug) induced mechanical allodynia. The hind paws of rats were inoculated with replication-defective herpes simplex virus (HSV) vectors genetically encoding gad1 gene to express glutamic acid decarboxylase 67 (GAD67), an enzyme that catalyzes the decarboxylation of glutamate to GABA. Mechanical threshold was tested using von Frey filaments before and after treatments with the vectors. The expression of GAD67 in both the lumbar spinal cord and the L4-5 dorsal root ganglia was examined using western blots. The expression of mitochondrial superoxide in the spinal dorsal horn was examined using MitoSox imaging. The immunoreactivity of spinal GABA, pCREB, and pC/EBPβ was tested using immunohistochemistry. In the gp120 with ddC-induced neuropathic pain model, GAD67 expression mediated by the HSV vector caused an elevation of mechanical threshold that was apparent on day 3 after vector inoculation. The antiallodynic effect of the single HSV vector inoculation expressing GAD67 lasted >28 days. The area under the time-effect curves in the HSV vector expressing GAD67 was increased compared with that in the control vectors (P = 0.0005). Intrathecal GABA-A/B agonists elevated mechanical threshold in the pain model. The HSV vectors expressing GAD67 reversed the lowered GABA immunoreactivity in the spinal dorsal horn in the neuropathic rats. HSV vectors expressing GAD67 in the neuropathic rats reversed the increased signals of mitochondrial superoxide in the spinal dorsal horn. The vectors expressing GAD67 reversed the upregulated immunoreactivity expression of pCREB and pC/EBPβ in the spinal dorsal horn in rats exhibiting NP. Based on our results, we suggest that GAD67 mediated by HSV vectors acting through the suppression of mitochondrial reactive oxygen species and transcriptional factors in the spinal cord decreases pain in the HIV-related neuropathic pain model, providing preclinical evidence for gene therapy applications in patients with HIV-related pain states.

Electroacupuncture reduces the evoked responses of the spinal dorsal horn neurons in ankle-sprained rats

PubMed Central

Kim, Jae Hyo; Kim, Hee Young; Chung, Kyungsoon

2011-01-01

Acupuncture is shown to be effective in producing analgesia in ankle sprain pain in humans and animals. To examine the underlying mechanisms of the acupuncture-induced analgesia, the effects of electroacupuncture (EA) on weight-bearing forces (WBR) of the affected foot and dorsal horn neuron activities were examined in a rat model of ankle sprain. Ankle sprain was induced manually by overextending ligaments of the left ankle in the rat. Dorsal horn neuron responses to ankle movements or compression were recorded from the lumbar spinal cord using an in vivo extracellular single unit recording setup 1 day after ankle sprain. EA was applied to the SI-6 acupoint on the right forelimb (contralateral to the sprained ankle) by trains of electrical pulses (10 Hz, 1-ms pulse width, 2-mA intensity) for 30 min. After EA, WBR of the sprained foot significantly recovered and dorsal horn neuron activities were significantly suppressed in ankle-sprained rats. However, EA produced no effect in normal rats. The inhibitory effect of EA on hyperactivities of dorsal horn neurons of ankle-sprained rats was blocked by the α-adrenoceptor antagonist phentolamine (5 mg/kg ip) but not by the opioid receptor antagonist naltrexone (10 mg/kg ip). These data suggest that EA-induced analgesia in ankle sprain pain is mediated mainly by suppressing dorsal horn neuron activities through α-adrenergic descending inhibitory systems at the spinal level. PMID:21389301

Endometriosis Is Associated With a Shift in MU Opioid and NMDA Receptor Expression in the Brain Periaqueductal Gray

PubMed Central

Torres-Reverón, Annelyn; Palermo, Karylane; Hernández-López, Anixa; Hernández, Siomara; Cruz, Myrella L.; Thompson, Kenira J.; Flores, Idhaliz; Appleyard, Caroline B.

2016-01-01

Studies have examined how endometriosis interacts with the nervous system, but little attention has been paid to opioidergic systems, which are relevant to pain signaling. We used the autotransplantation rat model of endometriosis and allowed to progress for 60 days. The brain was collected and examined for changes in endogenous opioid peptides, mu opioid receptors (MORs), and the N-methyl-d-aspartate subunit receptor (NR1) in the periaqueductal gray (PAG), since both of these receptors can regulate PAG activity. No changes in endogenous opioid peptides in met- and leu-enkephalin or β-endorphin levels were observed within the PAG. However, MOR immunoreactivity was significantly decreased in the ventral PAG in the endometriosis group. Endometriosis reduced by 20% the number of neuronal profiles expressing MOR and reduced by 40% the NR1 profiles. Our results suggest that endometriosis is associated with subtle variations in opioidergic and glutamatergic activity within the PAG, which may have implications for pain processing. PMID:27089914

Spinal Actions of Lipoxin A4 and 17(R)-Resolvin D1 Attenuate Inflammation-Induced Mechanical Hypersensitivity and Spinal TNF Release

PubMed Central

Abdelmoaty, Sally; Wigerblad, Gustaf; Bas, Duygu B.; Codeluppi, Simone; Fernandez-Zafra, Teresa; El-Awady, El-Sayed; Moustafa, Yasser; Abdelhamid, Alaa El-din S.; Brodin, Ernst; Svensson, Camilla I.

2013-01-01

Lipoxins and resolvins have anti-inflammatory and pro-resolving actions and accumulating evidence indicates that these lipid mediators also attenuate pain-like behavior in a number of experimental models of inflammation and tissue injury-induced pain. The present study was undertaken to assess if spinal administration of lipoxin A4 (LXA4) or 17 (R)-resolvin D1 (17(R)-RvD1) attenuates mechanical hypersensitivity in the carrageenan model of peripheral inflammation in the rat. Given the emerging role of spinal cytokines in the generation and maintenance of inflammatory pain we measured cytokine levels in the cerebrospinal fluid (CSF) after LXA4 or 17(R)-RvD1 administration, and the ability of these lipid metabolites to prevent stimuli-induced release of cytokines from cultured primary spinal astrocytes. We found that intrathecal bolus injection of LXA4 and17(R)-RvD1 attenuated inflammation-induced mechanical hypersensitivity without reducing the local inflammation. Furthermore, both LXA4 and 17(R)-RvD1 reduced carrageenan-induced tumor necrosis factor (TNF) release in the CSF, while only 17(R)-RvD1attenuated LPS and IFN-γ-induced TNF release in astrocyte cell culture. In conclusion, this study demonstrates that lipoxins and resolvins potently suppress inflammation-induced mechanical hypersensitivity, possibly by attenuating cytokine release from spinal astrocytes. The inhibitory effect of lipoxins and resolvins on spinal nociceptive processing puts them in an intriguing position in the search for novel pain therapeutics. PMID:24086560

Potent analgesic effects of anticonvulsants on peripheral thermal nociception in rats

PubMed Central

Todorovic, Slobodan M; Rastogi, A J; Jevtovic-Todorovic, Vesna

2003-01-01

Anticonvulsant agents are commonly used to treat neuropathic pain conditions because of their effects on voltage- and ligand-gated channels in central pain pathways. However, their interaction with ion channels in peripheral pain pathways is poorly understood. Therefore, we studied the potential analgesic effects of commonly used anticonvulsant agents in peripheral nociception. We injected anticonvulsants intradermally into peripheral receptive fields of sensory neurons in the hindpaws of adult rats, and studied pain perception using the model of acute thermal nociception. Commonly used anticonvulsants such as voltage-gated Na+ channel blockers, phenytoin and carbamazepine, and voltage-gated Ca2+ channel blockers, gabapentin and ethosuximide, induced dose-dependent analgesia in the injected paw, with ED50 values of 0.30, 0.32 and 8, 410 μg per 100 μl, respectively. Thermal nociceptive responses were not affected in the contralateral, noninjected paws, indicating a lack of systemic effects with doses of anticonvulsants that elicited local analgesia. Hill slope coefficients for the tested anticonvulsants indicate that the dose–response curve was less steep for gabapentin than for phenytoin, carbamazepine and ethosuximide. Our data strongly suggest that cellular targets like voltage-gated Na+ and Ca2+ channels, similar to those that mediate the effects of anticonvulsant agents in the CNS, may exist in the peripheral nerve endings of rat sensory neurons. Thus, peripherally applied anticonvulsants that block voltage-gated Na+ and Ca2+ channels may be useful analgesics. PMID:12970103

Rostral Ventral Medulla Cholinergic Mechanism in Pain-Induced Analgesia

PubMed Central

Gear, Robert W.; Levine, Jon D.

2009-01-01

The ascending nociceptive control (ANC), a novel spinostriatal pain modulation pathway, mediates a form of pain-induced analgesia referred to as noxious stimulus-induced antinociception (NSIA). ANC includes specific spinal cord mechanisms as well as circuitry in nucleus accumbens, a major component of the ventral striatum. Here, using the trigeminal jaw-opening reflex (JOR) in the rat as a nociceptive assay, we show that microinjection of the nicotinic acetylcholine receptor (nAChR) antagonist mecamylamine into the rostral ventral medulla (RVM) blocks NSIA, implicating RVM as a potentially important link between ANC and the PAG – RVM – spinal descending pain modulation system. A circuit connecting nucleus accumbens to the RVM is proposed as a novel striato-RVM pathway. PMID:19699268

Suppression of MyD88-dependent signaling alleviates neuropathic pain induced by peripheral nerve injury in the rat.

PubMed

Liu, Fan; Wang, Zhiyao; Qiu, Yue; Wei, Min; Li, Chunyan; Xie, Yikuan; Shen, Le; Huang, Yuguang; Ma, Chao

2017-03-31

MyD88 is the adaptor protein of MyD88-dependent signaling pathway of TLRs and IL-1 receptor and regulates innate immune response. However, it was not clear whether and how MyD88 and related signaling pathways in the dorsal root ganglion (DRG) and spinal dorsal horn (SDH) are involved in neuropathic pain. Chronic constriction injury (CCI) was used to induce neuropathic pain in the rat. The expression of MyD88, TRIF, IBA1, and GFAP was detected with immunofluorescent staining and Western blot. The expression of interleukin-1 beta (IL-1β), high mobility group box 1 (HMGB1), NF-κB-p65, phosphorylated NF-κB-p65, ERK, phosphorylated ERK, and tumor necrosis factor-alpha (TNF-α) was detected with Western blot. Pain-related behavioral effects of MyD88 homodimerization inhibitory peptide (MIP) were accessed up to 3 weeks after intrathecal administration. Peripheral nerve injury significantly increased the protein level of MyD88 in the DRG and SDH, but had no effect on TRIF. MyD88 was found partly distributed in the nociceptive neurons in the DRGs and the astrocytes and microglia in the SDH. HMGB1 and IL-1β were also found upregulated in nociceptive pathways of CCI rats. Intrathecal application of MIP significantly alleviated mechanical and thermal hyperalgesia in the CCI rats and also reversed CCI-induced upregulation of MyD88 in both DRG and SDH. Further investigation revealed that suppression of MyD88 protein reduced the release of TNF-α and glial activation in the SDH in the CCI rats. MyD88-dependent TIR pathway in the DRG and SDH may play a role in CCI-induced neuropathic pain. MyD88 might serve as a potential therapeutic target for neuropathic pain.

Effects of the Methanolic Extract of Vitellaria paradoxa Stem Bark Against Scopolamine-Induced Cognitive Dysfunction and Oxidative Stress in the Rat Hippocampus.

PubMed

Foyet, Harquin Simplice; Asongalem, Acha Emmanuel; Oben, Eyong Kenneth; Cioanca, Oana; Hancianu, Monica; Hritcu, Lucian

2016-10-01

Vitellaria paradoxa C.F. Gaertn (Sapotaceae) is a perennial three which naturally grows in the northern part of Cameroon. It has been traditionally used in the Cameroonian folk medicine for treating inflammation and pain. In the present study, we evaluate the possible anti-amnesic and antioxidative effects of the methanolic extract of V. paradoxa stem bark in an Alzheimer's disease (AD) rat model of scopolamine. Rats received a single injection of scopolamine (1.5 mg/kg) before behavioral testing and were treated with the methanolic extract (25 and 50 mg/kg), daily, for eight continuous days. Also, the antioxidant activity in the hippocampus was assessed using the total content of reduced glutathione and malondialdehyde levels. The scopolamine-treated rats exhibited the following: decrease of exploratory time and discrimination index within the novel object recognition test, decrease of spontaneous alternations percentage within Y-maze task, and increase of working memory errors, reference memory errors, and time taken to consume all five baits within radial arm-maze task. Administration of the methanolic extract significantly improved these parameters, suggesting positive effects on memory formation processes and antioxidant potential. Our results suggest that the methanolic extract ameliorates scopolamine-induced memory impairment by attenuation of the oxidative stress in the rat hippocampus.

Cross-centre replication of suppressed burrowing behaviour as an ethologically relevant pain outcome measure in the rat: a prospective multicentre study

PubMed Central

Wodarski, Rachel; Delaney, Ada; Ultenius, Camilla; Morland, Rosie; Andrews, Nick; Baastrup, Catherine; Bryden, Luke A.; Caspani, Ombretta; Christoph, Thomas; Gardiner, Natalie J.; Huang, Wenlong; Kennedy, Jeffrey D.; Koyama, Suguru; Li, Dominic; Ligocki, Marcin; Lindsten, Annika; Machin, Ian; Pekcec, Anton; Robens, Angela; Rotariu, Sanziana M.; Voß, Sabrina; Segerdahl, Marta; Stenfors, Carina; Svensson, Camilla I.; Treede, Rolf-Detlef; Uto, Katsuhiro; Yamamoto, Kazumi; Rutten, Kris; Rice, Andrew S.C.

2016-01-01

Abstract Burrowing, an ethologically relevant rodent behaviour, has been proposed as a novel outcome measure to assess the global impact of pain in rats. In a prospective multicentre study using male rats (Wistar, Sprague-Dawley), replication of suppressed burrowing behaviour in the complete Freund adjuvant (CFA)-induced model of inflammatory pain (unilateral, 1 mg/mL in 100 µL) was evaluated in 11 studies across 8 centres. Following a standard protocol, data from participating centres were collected centrally and analysed with a restricted maximum likelihood-based mixed model for repeated measures. The total population (TP—all animals allocated to treatment; n = 249) and a selected population (SP—TP animals burrowing over 500 g at baseline; n = 200) were analysed separately, assessing the effect of excluding “poor” burrowers. Mean baseline burrowing across studies was 1113 g (95% confidence interval: 1041-1185 g) for TP and 1329 g (1271-1387 g) for SP. Burrowing was significantly suppressed in the majority of studies 24 hours (7 studies/population) and 48 hours (7 TP, 6 SP) after CFA injections. Across all centres, significantly suppressed burrowing peaked 24 hours after CFA injections, with a burrowing deficit of −374 g (−479 to −269 g) for TP and −498 g (−609 to −386 g) for SP. This unique multicentre approach first provided high-quality evidence evaluating suppressed burrowing as robust and reproducible, supporting its use as tool to infer the global effect of pain on rodents. Second, our approach provided important informative value for the use of multicentre studies in the future. PMID:27643836

Rat Models and Identification of Candidate Early Serum Biomarkers of Battlefield Traumatic Brain Injury

DTIC Science & Technology

2007-07-31

brain injury) All surgeries were performed using aseptic technique. Animals were checked for pain /distress immediately prior to anesthesia/surgery... Pain /distress checks were performed at 3, 6, 12, 24, 36, 48, 60, and 72 hours post-injury. Fluid Percussion Injury (FPI) For animals in the...NIH), and Neurobehavioral Scale (NBS). The criteria used to obtain the scores are detailed in Tables 2 and 3. As an additional endpoint, we also

Neonatal Handling Produces Sex Hormone-Dependent Resilience to Stress-Induced Muscle Hyperalgesia in Rats.

PubMed

Alvarez, Pedro; Green, Paul G; Levine, Jon D

2018-06-01

Neonatal handling (NH) of male rat pups strongly attenuates stress response and stress-induced persistent muscle hyperalgesia in adults. Because female sex is a well established risk factor for stress-induced chronic muscle pain, we explored whether NH provides resilience to stress-induced hyperalgesia in adult female rats. Rat pups underwent NH, or standard (control) care. Muscle mechanical nociceptive threshold was assessed before and after water avoidance (WA) stress, when they were adults. In contrast to male rats, NH produced only a modest protection against WA stress-induced muscle hyperalgesia in female rats. Gonadectomy completely abolished NH-induced resilience in male rats but produced only a small increase in this protective effect in female rats. The administration of the antiestrogen drug fulvestrant, in addition to gonadectomy, did not enhance the protective effect of NH in female rats. Finally, knockdown of the androgen receptor by intrathecal antisense treatment attenuated the protective effect of NH in intact male rats. Together, these data indicate that androgens play a key role in NH-induced resilience to WA stress-induced muscle hyperalgesia. NH induces androgen-dependent resilience to stress-induced muscle pain. Therefore, androgens may contribute to sex differences observed in chronic musculoskeletal pain and its enhancement by stress. Copyright © 2018 The American Pain Society. Published by Elsevier Inc. All rights reserved.

Pregnancy suppresses neuropathic pain induced by chronic constriction injury in rats through the inhibition of TNF-α

PubMed Central

Onodera, Yoshiko; Kanao-Kanda, Megumi; Kanda, Hirotsugu; Sasakawa, Tomoki; Iwasaki, Hiroshi; Kunisawa, Takayuki

2017-01-01

Purpose Pregnancy-induced analgesia develops during late pregnancy, but it is unclear whether this analgesia is effective against neuropathic pain. The detailed molecular mechanisms underlying pregnancy-induced analgesia have not been investigated. We examined the antinociceptive effect of pregnancy-induced analgesia in a neuropathic pain model and the expression of tumor necrosis factor (TNF)-α, glial fibrillary acidic protein (GFAP), Iba-1, and c-Fos in the spinal dorsal horn just before parturition. Materials and methods Female Sprague Dawley rats (200–250 g) were randomly assigned to one of four groups (pregnant + chronic constriction injury [CCI]; pregnant + sham injury; not pregnant + CCI; and not pregnant + sham injury). Separate groups were used for the behavioral and tissue analyses. CCI of the left sciatic nerve was surgically induced 3 days after confirming pregnancy in the pregnancy group or on day 3 in the not pregnant group. The spinal cord was extracted 18 days after CCI. TNF-α, GFAP, Iba-1, and c-Fos expression levels in the spinal dorsal horn were measured by Western blot analysis. Mechanical threshold was tested using von Frey filaments. Results The lowered mechanical threshold induced by CCI was significantly attenuated within 1 day before parturition and decreased after delivery. TNF-α expression in CCI rats was decreased within 1 day before parturition. Further, GFAP, Iba-1, and c-Fos expression in the spinal dorsal horn was reduced in the pregnant rats. Serum TNF-α in all groups was below measurable limits. Conclusion Our findings indicate that pregnancy-induced analgesia suppresses neuropathic pain through reducing spinal levels of TNF-α, GFAP, Iba-1, and c-Fos in a rat model of CCI. PMID:28331359

Possible mechanism of protective effect of thalidomide in STZ-induced-neuropathic pain behavior in rats.

PubMed

Taliyan, Rajeev; Sharma, Pyare Lal

2012-04-01

Diabetes-induced neuropathic pain is recognized as one of the most difficult type of pain to treat and conventional analgesics are well known to be partially effective or associated with potential toxicity. Recently, it has been demonstrated that thalidomide, besides its teratogenic potential, reduced chronic pain in an SNL experimental pain model. The present study was designed to investigate the effect of thalidomide on streptozotocin (STZ)-induced neuropathic pain in rats. Streptozotocin (20 mg/kg, i.p, daily × 4 days) was administered to induce diabetes in the rats. Nociceptive latency was measured using tail-flick and paw-withdrawal test. Thermal hyperalgesia and mechanical allodynia were measured using planter test and dynamic aesthesiometer (Ugo-Basile, Italy), respectively. Urinary and serum nitrite concentration was estimated using Greiss reagent method. Spleen homogenate supernatant was prepared from spleen of 28th day diabetic rats and administered to normal rats (400 ul, i.v) daily for 28 days. Pain threshold progressively decreased in STZ-treated rats, as compared with control rats. 3 weeks after induction of diabetes, the rat exhibited thermal hyperalgesia and mechanical allodynia. The analgesic effect of morphine (8 mg/kg, s.c.) was significantly decreased in both diabetic and in SHS-treated non-diabetic rats. Administration of thalidomide (25 and 50 mg/kg, i.p), a TNF-α inhibitor, significantly prevented hyperglycemia-induced thermal hyperalgesia and mechanical allodynia and also attenuated the increase in serum and urinary nitrite concentration, as compared with untreated diabetic rats. Also, thalidomide (25 and 50 mg/kg, i.p) 1 h before or concurrently with morphine significantly restored the analgesic effect of morphine in diabetic rats. It may be concluded that thalidomide has a beneficial effect in neuropathic pain by decreasing cytokines (TNF-α) and nitric oxide level and may provide a novel promising therapeutic approach for managing painful diabetic neuropathy.

Different Role of CA1 5HT3 Serotonin Receptors on Memory Acquisition Deficit Induced by Total (TSD) and REM Sleep Deprivation (RSD).

PubMed

Eydipour, Zainab; Vaezi, Gholamhassan; Nasehi, Mohammad; Haeri-Rouhani, Seyed-Ali; Zarrindast, Mohammad-Reza

2017-09-01

Serotonin receptors such as 5-HT3 plays critical role in regulation of sleep, wake cycle and cognitive process. Thus, we investigated the role of CA1 5HT3 serotonin receptors in memory acquisition deficit induced by total sleep deprivation (TSD; for 24 hour) and REM sleep deprivation (RSD; for 24 hour). Pain perception and locomotor activity were also assessed as factors that may affect the memory process. Modified water box and multi-platform apparatus were used to induce TSD or RSD, respectively. Passive avoidance, hot plate and open field devices were used for assessment of memory acquisition, pain and locomotor activity, respectively. Totally, 152 male Wistar rats were used in the study. Pre-training, intra-CA1 injection of 5-HT3 receptor agonist Chlorophenylbiguanide (Mchl; 0.01 and 0.001 µg/rat; P < 0.001) and antagonist Y-25130 (0.1 µg/rat; P < 0.001) reduced memory acquisition and did not alter pain response, while higher dose of both drugs increased locomotor activity in normal rats. Both TSD and RSD reduced memory acquisition (P < 0.001) and did not alter locomotor activity, while TSD (P < 0.001) but not RSD induced analgesia effect. The amnesia induced by TSD was restored by subthreshold dose of Y25130 (0.001 µg/rat; P < 0.001) but not Mchl (0.0001 µg/rat), while both drugs reversed TSD-induced analgesia effect (P < 0.01 for Mchl and P < 0.05 for Y25130), and Y25130 increased locomotor activity in TSD rats (P < 0.05). In RSD rats, subthreshold dose of both drugs did not alter memory acquisition deficit and increased locomotor activity (P < 0.001 for Mchl and P < 0.01 for Y25130), while the Y25130 (P < 0.001), but not Mchl induced analgesia in the RSD rats. Based on the above data, CA1 5HT3 receptors seem to play a critical role in cognitive and non-cognitive behaviors induced by TSD and RSD.

Discovery of Ecopladib, an indole inhibitor of cytosolic phospholipase A2alpha.

PubMed

Lee, Katherine L; Foley, Megan A; Chen, Lihren; Behnke, Mark L; Lovering, Frank E; Kirincich, Steven J; Wang, Weiheng; Shim, Jaechul; Tam, Steve; Shen, Marina W H; Khor, Soopeang; Xu, Xin; Goodwin, Debra G; Ramarao, Manjunath K; Nickerson-Nutter, Cheryl; Donahue, Frances; Ku, M Sherry; Clark, James D; McKew, John C

2007-03-22

The synthesis and structure-activity relationship of a series of indole inhibitors of cytosolic phospholipase A2alpha (cPLA2alpha, type IVA phospholipase) are described. Inhibitors of cPLA2alpha are predicted to be efficacious in treating asthma as well as the signs and symptoms of osteoarthritis, rheumatoid arthritis, and pain. The introduction of a benzyl sulfonamide substituent at C2 was found to impart improved potency of these inhibitors, and the SAR of these sulfonamide analogues is disclosed. Compound 123 (Ecopladib) is a sub-micromolar inhibitor of cPLA2alpha in the GLU micelle and rat whole blood assays. Compound 123 displayed oral efficacy in the rat carrageenan air pouch and rat carrageenan-induced paw edema models.

Participation of pro- and anti-nociceptive interleukins in botulinum toxin A-induced analgesia in a rat model of neuropathic pain.

PubMed

Zychowska, Magdalena; Rojewska, Ewelina; Makuch, Wioletta; Luvisetto, Siro; Pavone, Flaminia; Marinelli, Sara; Przewlocka, Barbara; Mika, Joanna

2016-11-15

Botulinum neurotoxin serotype A (BoNT/A) shows antinociceptive properties, and its clinical applications in pain therapy are continuously increasing. BoNT/A specifically cleaves SNAP-25, which results in the formation of a non-functional SNARE complex, thereby potently inhibiting the release of neurotransmitters and neuropeptides, including those involved in nociception. The aim of the present study was to determine the effects of BoNT/A (300pg/paw) on pain-related behavior and the levels of glial markers and interleukins in the spinal cord and dorsal root ganglia (DRG) after chronic constriction injury (CCI) to the sciatic nerve in rats. Glial activity was also examined after repeated intraperitoneal injection of minocycline combined with a single BoNT/A injection. Our results show that a single intraplantar BoNT/A injection did not influence motor function but strongly diminished pain-related behaviors in naïve and CCI-exposed rats. Additionally, microglial inhibition using minocycline enhanced the analgesic effects of BoNT/A. Western blotting results suggested that CCI induces the upregulation of the pronociceptive proteins IL-18, IL-6 and IL-1β in the ipsilateral lumbar spinal cord and DRG, but no changes in the levels of the antinociceptive proteins IL-18BP, IL-1RA and IL-10 were observed. Interestingly, BoNT/A injection suppressed the CCI-induced upregulation of IL-18 and IL-1β in the spinal cord and/or DRG and increased the levels of IL-10 and IL-1RA in the DRG. In summary, our results suggest that BoNT/A significantly attenuates pain-related behavior and microglial activation and restores the neuroimmune balance in a CCI model by decreasing the levels of pronociceptive factors (IL-1β and IL-18) and increasing the levels of antinociceptive factors (IL-10 and IL-1RA) in the spinal cord and DRG. Copyright © 2016 Elsevier B.V. All rights reserved.

Chronic stress and peripheral pain: Evidence for distinct, region-specific changes in visceral and somatosensory pain regulatory pathways.

PubMed

Zheng, Gen; Hong, Shuangsong; Hayes, John M; Wiley, John W

2015-11-01

Chronic stress alters the hypothalamic-pituitary-adrenal (HPA) axis and enhances visceral and somatosensory pain perception. It is unresolved whether chronic stress has distinct effects on visceral and somatosensory pain regulatory pathways. Previous studies reported that stress-induced visceral hyperalgesia is associated with reciprocal alterations of endovanilloid and endocannabinoid pain pathways in DRG neurons innervating the pelvic viscera. In this study, we compared somatosensory and visceral hyperalgesia with respect to differential responses of peripheral pain regulatory pathways in a rat model of chronic, intermittent stress. We found that chronic stress induced reciprocal changes in the endocannabinoid 2-AG (increased) and endocannabinoid degradation enzymes COX-2 and FAAH (decreased), associated with down-regulation of CB1 and up-regulation of TRPV1 receptors in L6-S2 DRG but not L4-L5 DRG neurons. In contrast, sodium channels Nav1.7 and Nav1.8 were up-regulated in L4-L5 but not L6-S2 DRGs in stressed rats, which was reproduced in control DRGs treated with corticosterone in vitro. The reciprocal changes of CB1, TRPV1 and sodium channels were cell-specific and observed in the sub-population of nociceptive neurons. Behavioral assessment showed that visceral hyperalgesia persisted, whereas somatosensory hyperalgesia and enhanced expression of Nav1.7 and Nav1.8 sodium channels in L4-L5 DRGs normalized 3 days after completion of the stress phase. These data indicate that chronic stress induces visceral and somatosensory hyperalgesia that involves differential changes in endovanilloid and endocannabinoid pathways, and sodium channels in DRGs innervating the pelvic viscera and lower extremities. These results suggest that chronic stress-induced visceral and lower extremity somatosensory hyperalgesia can be treated selectively at different levels of the spinal cord. Copyright © 2015 Elsevier Inc. All rights reserved.

Peripheral hyperpolarization-activated cyclic nucleotide-gated channels contribute to inflammation-induced hypersensitivity of the rat temporomandibular joint.

PubMed

Hatch, R J; Jennings, E A; Ivanusic, J J

2013-08-01

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels conduct an inward cation current (Ih ) that contributes to the maintenance of neuronal membrane potential and have been implicated in a number of animal models of neuropathic and inflammatory pain. In the current study, we investigated HCN channel involvement in inflammatory pain of the temporomandibular joint (TMJ). The contribution of HCN channels to inflammation (complete Freund's adjuvant; CFA)-induced mechanical hypersensitivity of the rat TMJ was tested with injections of the HCN channel blocker ZD7288. Retrograde labelling and immunohistochemistry was used to explore HCN channel expression in sensory neurons that innervate the TMJ. Injection of CFA into the TMJ (n = 7) resulted in a significantly increased mechanical sensitivity relative to vehicle injection (n = 7) (p < 0.05). The mechanical hypersensitivity generated by CFA injection was blocked by co-injection of ZD7288 with the CFA (n = 7). Retrograde labelling and immunohistochemistry experiments revealed expression predominantly of HCN1 and HCN2 channel subunits in trigeminal ganglion neurons that innervate the TMJ (n = 3). No change in the proportion or intensity of HCN channel expression was found in inflamed (n = 6) versus control (n = 5) animals at the time point tested. Our findings suggest a role for peripheral HCN channels in inflammation-induced pain of the TMJ. Peripheral application of a HCN channel blocker could provide therapeutic benefit for inflammatory TMJ pain and avoid side effects associated with activation of HCN channels in the central nervous system. © 2012 European Federation of International Association for the Study of Pain Chapters.

Sialorphin, a natural inhibitor of rat membrane-bound neutral endopeptidase that displays analgesic activity.

PubMed

Rougeot, Catherine; Messaoudi, Michaël; Hermitte, Véronique; Rigault, Anne Gaëlle; Blisnick, Thierry; Dugave, Christophe; Desor, Didier; Rougeon, François

2003-07-08

Sialorphin is an exocrine and endocrine signaling mediator, which has been identified by a genomic approach. It is synthesized predominantly in the submandibular gland and prostate of adult rats in response to androgen steroids and is released locally and systemically in response to stress. We now demonstrate that the cell surface molecule to which sialorphin binds in vivo in the rat kidney is the membrane-anchored neutral endopeptidase (neprilysin; NEP, EC 3.4.24.11). NEP plays an important role in nervous and peripheral tissues, as it turns off several peptide-signaling events at the cell surface. We show that sialorphin prevents spinal and renal NEP from breaking down its two physiologically relevant substrates, substance P and Met-enkephalin in vitro. Sialorphin inhibited the breakdown of substance P with an IC50 of 0.4-1 microM and behaved as a competitive inhibitor. In vivo, i.v. sialorphin elicited potent antinociceptive responses in two behavioral rat models of injury-induced acute and tonic pain, the pin-pain test and formalin test. The analgesia induced by 100-200 mcicrog/kg doses of sialorphin required the activation of mu- and delta-opioid receptors, consistent with the involvement of endogenous opioid receptors in enkephalinergic transmission. We conclude that sialorphin protects endogenous enkephalins released after nociceptive stimuli by inhibiting NEP in vivo. Sialorphin is a natural systemically active regulator of NEP activity. Furthermore, our study provides evidence that it is a physiological modulator of pain perception after injury and might be the progenitor of a new class of therapeutic molecules.

Thermal nociception is decreased by hypocretin-1 and an adenosine A1 receptor agonist microinjected into the pontine reticular formation of Sprague Dawley rat.

PubMed

Watson, Sarah L; Watson, Christopher J; Baghdoyan, Helen A; Lydic, Ralph

2010-06-01

Clinical and preclinical data concur that sleep disruption causes hyperalgesia, but the brain mechanisms through which sleep and pain interact remain poorly understood. Evidence that pontine components of the ascending reticular activating system modulate sleep and nociception encouraged the present study testing the hypothesis that hypocretin-1 (orexin-A) and an adenosine receptor agonist administered into the pontine reticular nucleus, oral part (PnO) each alter thermal nociception. Adult male rats (n = 23) were implanted with microinjection guide tubes aimed for the PnO. The PnO was microinjected with saline (control), hypocretin-1, the adenosine A(1) receptor agonist N(6)-p-sulfophenyladenosine (SPA), the hypocretin receptor-1 antagonist N-(2-Methyl-6-benzoxazolyl)-N''-1,5-naphthyridin-4-yl-urea (SB-334867), and hypocretin-1 plus SB-334867. As an index of antinociceptive behavior, the latency (in seconds) to paw withdrawal away from a thermal stimulus was measured following each microinjection. Compared to control, antinociception was significantly increased by hypocretin-1 and by SPA. SB-334867 increased nociceptive responsiveness, and administration of hypocretin-1 plus SB-334867 blocked the antinociception caused by hypocretin-1. These results suggest for the first time that hypocretin receptors in rat PnO modulate nociception. Widely distributed and overlapping neural networks regulate states of sleep and pain. Specifying the brain regions and neurotransmitters through which pain and sleep interact is an essential step for developing adjunctive therapies that diminish pain without disrupting states of sleep and wakefulness. Copyright (c) 2010 American Pain Society. Published by Elsevier Inc. All rights reserved.

An adenosine kinase inhibitor attenuates tactile allodynia in a rat model of diabetic neuropathic pain.

PubMed

Lynch, J J; Jarvis, M F; Kowaluk, E A

1999-01-08

The present study was conducted to characterize the development of tactile allodynia in the streptozotocin-induced rat model of diabetes, and to evaluate the antinociceptive effects of systemically administered morphine and the adenosine kinase inhibitor, 5'-deoxy-5-iodotubercidin (5'd-5IT) in this model. Rats were injected with 75 mg/kg streptozotocin (i.p.), and blood glucose levels were determined 3-4 weeks later. Diabetic (blood glucose levels > or = 250 mg/dl) and vehicle-injected rats were examined weekly for the development of tactile allodynia by measuring the threshold for hind paw withdrawal using von Frey hairs. Withdrawal thresholds were reduced to 6.8+/-0.6 g (mean+/-S.E.M.) in approximately one-third of streptozotocin-treated rats 7 weeks after streptozotocin treatment as compared to control thresholds (13.2+/-0.1 g), and this allodynia persisted for at least an additional 7 weeks. In additional experiments, morphine sulfate (5-21 micromol/kg, i.p.) produced dose-dependent antinociceptive effects on tactile allodynia for up to 2 h post-dosing. The adenosine kinase inhibitor, 5'd-5IT (2.5 and 5 micromol/kg, i.p.) also dose-dependently attenuated tactile allodynia. Pretreatment with the opioid receptor antagonist, naloxone (27 micromol/kg, i.p.) or the non-selective adenosine receptor antagonist, theophylline (111 micromol/kg, i.p.) significantly diminished the anti-allodynic effects of morphine and 5'd-5IT, respectively. The present study demonstrates that the potent and selective adenosine kinase inhibitor, 5'd-5IT, is equally effective as morphine in blocking tactile allodynia in this model.

Sialorphin, a natural inhibitor of rat membrane-bound neutral endopeptidase that displays analgesic activity

PubMed Central

Rougeot, Catherine; Messaoudi, Michaël; Hermitte, Véronique; Rigault, Anne Gaëlle; Blisnick, Thierry; Dugave, Christophe; Desor, Didier; Rougeon, François

2003-01-01

Sialorphin is an exocrine and endocrine signaling mediator, which has been identified by a genomic approach. It is synthesized predominantly in the submandibular gland and prostate of adult rats in response to androgen steroids and is released locally and systemically in response to stress. We now demonstrate that the cell surface molecule to which sialorphin binds in vivo in the rat kidney is the membrane-anchored neutral endopeptidase (neprilysin; NEP, EC 3.4.24.11). NEP plays an important role in nervous and peripheral tissues, as it turns off several peptide-signaling events at the cell surface. We show that sialorphin prevents spinal and renal NEP from breaking down its two physiologically relevant substrates, substance P and Met-enkephalin in vitro. Sialorphin inhibited the breakdown of substance P with an IC50 of 0.4–1 μM and behaved as a competitive inhibitor. In vivo, i.v. sialorphin elicited potent antinociceptive responses in two behavioral rat models of injury-induced acute and tonic pain, the pin-pain test and formalin test. The analgesia induced by 100–200 μg/kg doses of sialorphin required the activation of μ- and δ-opioid receptors, consistent with the involvement of endogenous opioid receptors in enkephalinergic transmission. We conclude that sialorphin protects endogenous enkephalins released after nociceptive stimuli by inhibiting NEP in vivo. Sialorphin is a natural systemically active regulator of NEP activity. Furthermore, our study provides evidence that it is a physiological modulator of pain perception after injury and might be the progenitor of a new class of therapeutic molecules. PMID:12835417

Corneal Sensitivity Following Lacrimal Gland Excision in the Rat

PubMed Central

Meng, Ian D.; Barton, Stephen T.; Mecum, Neal E.; Kurose, Masayuki

2015-01-01

Purpose. Dry eye disease (DED) produces ocular pain and irritation, yet a detailed characterization of ocular sensitivity in a preclinical model of DED is lacking. The aim of the present study was to assess nociceptive behaviors in an aqueous tear deficiency model of DED in the rat. Methods. Spontaneous blinking, corneal mechanical thresholds, and eye wipe behaviors elicited by hypertonic saline (5.0 M) were examined over a period of 8 weeks following the unilateral excision of either the exorbital lacrimal gland or of the exorbital and infraorbital lacrimal glands, and in sham surgery controls. The effect of topical proparacaine on spontaneous blinking and of systemic morphine (0.5–3.0 mg/kg, subcutaneous [SC]) on spontaneous blinking and eye wipe responses were also examined. Results. Lacrimal gland excision resulted in mechanical hypersensitivity and an increase in spontaneous blinking in the ipsilateral eye over an 8-week period that was more pronounced after infra- and exorbital gland excision. The time spent eye wiping was also enhanced in response to hypertonic saline (5.0 M) at both 1- and 8-week time-points, but only in infra- and exorbital gland excised animals. Morphine attenuated spontaneous blinking, and the response to hypertonic saline in dry eye animals and topical proparacaine application reduced spontaneous blinking down to control levels. Conclusions. These results indicate that aqueous tear deficiency produces hypersensitivity in the rat cornea. In addition, the increase in spontaneous blinks and their reduction by morphine and topical anesthesia indicate the presence of persistent irritation elicited by the activation of corneal nociceptors. PMID:26024120

Role of muscarinic receptor subtypes in central antinociception.

PubMed Central

Bartolini, A.; Ghelardini, C.; Fantetti, L.; Malcangio, M.; Malmberg-Aiello, P.; Giotti, A.

1992-01-01

1. The ability to modify the pain threshold by the two M1-muscarinic agonists: McN-A-343 and AF-102B and by the specific M2-agonist arecaidine was examined in mice and rats by using three different noxious stimuli: chemical (writhing test), thermic (hot-plate test) and mechanical (paw pressure test). 2. In the mouse hot-plate test McN-A-343 (20-50 micrograms per mouse i.c.v.) and AF-102B (1-10 mg kg-1 i.p.) produced significant antinociception which was prevented by atropine (1 microgram per mouse i.c.v.) and by the two selective M1 antagonists: pirenzepine (0.01 micrograms per mouse i.c.v.) and dicyclomine (0.08 micrograms per mouse i.c.v. or 10 mg kg-1 i.p.) but not by the specific M2-antagonist AFDX-116 (0.1 micrograms per mouse i.c.v.), naloxone (1 mg kg-1 i.p.) or by the acetylcholine (ACh) depletor hemicholinium-3 (HC-3) (1 micrograms per mouse i.c.v.). McN-A-343 and AF-102B were able to increase the pain threshold also in the mouse acetic acid writhing test and in rat paw pressure test. These antinociceptive effects were completely prevented by dicyclomine (0.08 micrograms per mouse i.c.v. or 10 mg kg-1 i.p.) but not by AFDX-116 (0.1 microgram per mouse or rat i.c.v.). 3. In contrast with the M1-agonists, the M2-agonist arecaidine (0.1-2 micrograms per mouse or rat i.c.v.) did not induce antinociception in all three analgesic tests. However, arecaidine, at the same i.c.v. doses, was able to reduce the pain threshold in the hot-plate and paw pressure tests.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1375858

Voltage-gated sodium channel expression in mouse DRG after SNI leads to re-evaluation of projections of injured fibers.

PubMed

Laedermann, Cédric J; Pertin, Marie; Suter, Marc R; Decosterd, Isabelle

2014-03-11

Dysregulation of voltage-gated sodium channels (Na(v)s) is believed to play a major role in nerve fiber hyperexcitability associated with neuropathic pain. A complete transcriptional characterization of the different isoforms of Na(v)s under normal and pathological conditions had never been performed on mice, despite their widespread use in pain research. Na(v)s mRNA levels in mouse dorsal root ganglia (DRG) were studied in the spared nerve injury (SNI) and spinal nerve ligation (SNL) models of neuropathic pain. In the SNI model, injured and non-injured neurons were intermingled in lumbar DRG, which were pooled to increase the tissue available for experiments. A strong downregulation was observed for every Na(v)s isoform expressed except for Na(v)1.2; even Na(v)1.3, known to be upregulated in rat neuropathic pain models, was lower in the SNI mouse model. This suggests differences between these two species. In the SNL model, where the cell bodies of injured and non-injured fibers are anatomically separated between different DRG, most Na(v)s were observed to be downregulated in the L5 DRG receiving axotomized fibers. Transcription was then investigated independently in the L3, L4 and L5 DRG in the SNI model, and an important downregulation of many Na(v)s isoforms was observed in the L3 DRG, suggesting the presence of numerous injured neurons there after SNI. Consequently, the proportion of axotomized neurons in the L3, L4 and L5 DRG after SNI was characterized by studying the expression of activating transcription factor 3 (ATF3). Using this marker of nerve injury confirmed that most injured fibers find their cell bodies in the L3 and L4 DRG after SNI in C57BL/6 J mice; this contrasts with their L4 and L5 DRG localization in rats. The spared sural nerve, through which pain hypersensitivity is measured in behavioral studies, mostly projects into the L4 and L5 DRG. The complex regulation of Na(v)s, together with the anatomical rostral shift of the DRG harboring injured fibers in C57BL/6 J mice, emphasize that caution is necessary and preliminary anatomical experiments should be carried out for gene and protein expression studies after SNI in mouse strains.

Modelling affective pain in mice: Effects of inflammatory hypersensitivity on place escape/avoidance behaviour, anxiety and hedonic state.

PubMed

Refsgaard, L K; Hoffmann-Petersen, J; Sahlholt, M; Pickering, D S; Andreasen, J T

2016-03-15

The place escape/avoidance paradigm (PEAP) has been used to assess the affective component of pain in rats. Using the Complete Freund's Adjuvant (CFA) model of inflammatory pain, the current study aimed at developing a mouse version of PEAP and investigating the relation between PEAP and other behavioural responses, namely anxiety-like behaviour, locomotor activity, and hedonic state. A novel paradigm assessing the affective component of pain in mice was developed by modifying the setup known from rat studies: Animals were forced to stay 2 × 5 min in the light and the dark area of a box while being stimulated with a suprathreshold filament on the untreated or treated paw, respectively. This was followed by a 30-min test with unrestricted movement. Anxiety-like behaviour, locomotor activity, and hedonic state were assessed with the elevated zero maze (EZM), an open field setup, and a saccharin preference test, respectively, and correlated with the PEAP behaviour to examine potentially confounding parameters of the novel paradigm. In the PEAP, CFA-treated animals spent more time in the light area. CFA also increased anxiety-like behaviour significantly, whereas locomotor activity was unaffected. A significant, albeit modest, reduction in saccharin preference was observed. PEAP responses showed no significant correlations with any other behavioural measure. The PEAP results suggest that this paradigm might be successfully applied in mice to study affective pain. CFA treatment was associated with increased anxiety-like behaviour and anhedonia; however, this appeared unrelated to the PEAP responses. Copyright © 2016 Elsevier B.V. All rights reserved.

WenTong HuoXue Cream Can Inhibit the Reduction of the Pain-Related Molecule PLC-β3 in the Dorsal Root Ganglion of a Rat Model of Diabetic Peripheral Neuropathy

PubMed Central

Feng, Chengcheng; Xu, Lijuan; Guo, Shiyun; Chen, Qian; Shen, Yuguo; Zang, Deng

2018-01-01

WenTong HuoXue Cream (WTHX-Cream) has been shown to effectively alleviate clinical symptoms of diabetic peripheral neuropathy (DPN). This study investigated the gene and protein expression of the pain-related molecule PLC-β3 in the dorsal root ganglion (DRG) of DPN rats. 88 specific pathogen-free male Wistar rats were randomly divided into placebo (10 rats) and DPN model (78 rats) groups, and the 78 model rats were used to establish the DPN model by intraperitoneal injection of streptozotocin and were then fed a high-fat diet for 8 weeks. These rats were randomly divided into the model group, the high-, medium-, and low-dose WTHX-Cream + metformin groups, the metformin group, the capsaicin cream group, and the capsaicin cream + metformin group. After 4 weeks of continuous drug administration, the blood glucose, body weight, behavioral indexes, and sciatic nerve conduction velocity were measured. The pathological structure of the DRG and the sciatic nerve were observed. PLC-β3 mRNA and protein levels in the DRG of rats were measured. Compared with the model group, the high-dose WTHX-Cream group showed increased sciatic nerve conduction velocity, improved sciatic nerve morphological changes, and increased expression of PLC-β3 mRNA and protein in the DRG. This study showed that WTHX-Cream improves hyperalgesia symptoms of DPN by inhibiting the reduction of PLC-β3 mRNA and protein expression in the diabetic DRG of DPN rats. PMID:29599806

A long noncoding RNA contributes to neuropathic pain by silencing Kcna2 in primary afferent neurons

PubMed Central

Zhao, Xiuli; Tang, Zongxiang; Zhang, Hongkang; Atianjoh, Fidelis E.; Zhao, Jian-Yuan; Liang, Lingli; Wang, Wei; Guan, Xiaowei; Kao, Sheng-Chin; Tiwari, Vinod; Gao, Yong-Jing; Hoffman, Paul N.; Cui, Hengmi; Li, Min; Dong, Xinzhong; Tao, Yuan-Xiang

2013-01-01

Neuropathic pain is a refractory disease characterized by maladaptive changes in gene transcription and translation within the sensory pathway. Long noncoding RNAs (lncRNAs) are emerging as new players in gene regulation, but how lncRNAs operate in the development of neuropathic pain is unclear. Here we identify a conserved lncRNA for Kcna2 (named Kcna2 antisense RNA) in first-order sensory neurons of rat dorsal root ganglion (DRG). Peripheral nerve injury increases Kcna2 antisense RNA expression in injured DRG through activation of myeloid zinc finger protein 1, a transcription factor that binds to Kcna2 antisense RNA gene promoter. Mimicking this increase downregulates Kcna2, reduces total Kv current, increases excitability in DRG neurons, and produces neuropathic pain symptoms. Blocking this increase reverses nerve injury-induced downregulation of DRG Kcna2 and attenuates development and maintenance of neuropathic pain. These findings suggest native Kcna2 antisense RNA as a new therapeutic target for the treatment of neuropathic pain. PMID:23792947

Alterations in intervertebral disc composition, matrix homeostasis and biomechanical behavior in the UCD-T2DM rat model of type 2 diabetes

PubMed Central

Fields, Aaron J.; Berg-Johansen, Britta; Metz, Lionel N.; Miller, Stephanie; La, Brandan; Liebenberg, Ellen C.; Coughlin, Dezba G.; Graham, James L.; Stanhope, Kimber L.; Havel, Peter J.; Lotz, Jeffrey C.

2015-01-01

Type 2 diabetes (T2D) adversely affects many tissues, and the greater incidence of discogenic low back pain among diabetic patients suggests that the intervertebral disc is affected too. Using a rat model of polygenic obese T2D, we demonstrate that diabetes compromises several aspects of disc composition, matrix homeostasis and biomechanical behavior. Coccygeal motion segments were harvested from 6-month-old lean Sprague-Dawley rats, obese Sprague-Dawley rats, and diabetic obese UCD-T2DM rats (diabetic for 69 ± 7 days). Findings indicated that diabetes but not obesity reduced disc glycosaminoglycan and water contents, and these degenerative changes correlated with increased vertebral endplate thickness and decreased endplate porosity, and with higher levels of the advanced glycation end-product (AGE) pentosidine. Consistent with their diminished glycosaminoglycan and water contents and their higher AGE levels, discs from diabetic rats were stiffer and exhibited less creep when compressed. At the matrix level, elevated expression of hypoxia-inducible genes and catabolic markers in the discs from diabetic rats coincided with increased oxidative stress and greater interactions between AGEs and one of their receptors (RAGE). Taken together, these findings indicate that endplate sclerosis, increased oxidative stress and AGE/RAGE-mediated interactions could be important factors for explaining the greater incidence of disc pathology in T2D. PMID:25641259

Neural tissue engineering scaffold with sustained RAPA release relieves neuropathic pain in rats.

PubMed

Ding, Tan; Zhu, Chao; Kou, Zhen-Zhen; Yin, Jun-Bin; Zhang, Ting; Lu, Ya-Cheng; Wang, Li-Ying; Luo, Zhuo-Jing; Li, Yun-Qing

2014-09-01

To investigate the effect of locally slow-released rapamycin (RAPA) from bionic peripheral nerve stent to reduce the incidence of neuropathic pain or mitigate the degree of pain after nerve injury. We constructed a neural tissue engineering scaffold with sustained release of RAPA to repair 20mm defects in rat sciatic nerves. Four presurgical and postsurgical time windows were selected to monitor the changes in the expression of pain-related dorsal root ganglion (DRG) voltage-gated sodium channels 1.3 (Nav1.3), 1.7 (Nav1.7), and 1.8 (Nav1.8) through immunohistochemistry (IHC) and Western Blot, along with the observation of postsurgical pathological pain in rats by pain-related behavior approaches. Relatively small upregulation of DRG sodium channels was observed in the experimental group (RAPA+poly(lactic-co-glycolic acid) (PLGA)+stent) after surgery, along with low degrees of neuropathic pain and anxiety, which were similar to those in the Autologous nerve graft group. Autoimmune inflammatory response plays a leading role in the occurrence of post-traumatic neuropathic pain, and that RAPA significantly inhibits the abnormal upregulation of sodium channels to reduce pain by alleviating inflammatory response. Copyright © 2014 Elsevier Inc. All rights reserved.

A-1048400 is a novel, orally active, state-dependent neuronal calcium channel blocker that produces dose-dependent antinociception without altering hemodynamic function in rats.

PubMed

Scott, Victoria E; Vortherms, Timothy A; Niforatos, Wende; Swensen, Andrew M; Neelands, Torben; Milicic, Ivan; Banfor, Patricia N; King, Andrew; Zhong, Chengmin; Simler, Gricelda; Zhan, Cenchen; Bratcher, Natalie; Boyce-Rustay, Janel M; Zhu, Chang Z; Bhatia, Pramila; Doherty, George; Mack, Helmut; Stewart, Andrew O; Jarvis, Michael F

2012-02-01

Blockade of voltage-gated Ca²⁺ channels on sensory nerves attenuates neurotransmitter release and membrane hyperexcitability associated with chronic pain states. Identification of small molecule Ca²⁺ channel blockers that produce significant antinociception in the absence of deleterious hemodynamic effects has been challenging. In this report, two novel structurally related compounds, A-686085 and A-1048400, were identified that potently block N-type (IC₅₀=0.8 μM and 1.4 μM, respectively) and T-type (IC₅₀=4.6 μM and 1.2 μM, respectively) Ca²⁺ channels in FLIPR based Ca²⁺ flux assays. A-686085 also potently blocked L-type Ca²⁺ channels (EC₅₀=0.6 μM), however, A-1048400 was much less active in blocking this channel (EC₅₀=28 μM). Both compounds dose-dependently reversed tactile allodynia in a model of capsaicin-induced secondary hypersensitivity with similar potencies (EC₅₀=300-365 ng/ml). However, A-686085 produced dose-related decreases in mean arterial pressure at antinociceptive plasma concentrations in the rat, while A-1048400 did not significantly alter hemodynamic function at supra-efficacious plasma concentrations. Electrophysiological studies demonstrated that A-1048400 blocks native N- and T-type Ca²⁺ currents in rat dorsal root ganglion neurons (IC₅₀=3.0 μM and 1.6 μM, respectively) in a voltage-dependent fashion. In other experimental pain models, A-1048400 dose-dependently attenuated nociceptive, neuropathic and inflammatory pain at doses that did not alter psychomotor or hemodynamic function. The identification of A-1048400 provides further evidence that voltage-dependent inhibition of neuronal Ca²⁺ channels coupled with pharmacological selectivity vs. L-type Ca²⁺ channels can provide robust antinociception in the absence of deleterious effects on hemodynamic or psychomotor function. Copyright © 2011 Elsevier Inc. All rights reserved.

Activation of cutaneous immune responses in complex regional pain syndrome

PubMed Central

Birklein, Frank; Drummond, Peter D.; Li, Wenwu; Schlereth, Tanja; Albrecht, Nahid; Finch, Philip M.; Dawson, Linda F.; Clark, J. David; Kingery, Wade S.

2014-01-01

The pathogenesis of complex regional pain syndrome (CRPS) is unresolved, but TNF-α and IL-6 are elevated in experimental skin blister fluid from CRPS affected limbs, as is tryptase, a marker for mast cells. In the rat fracture model of CRPS exaggerated sensory and sympathetic neural signaling stimulate keratinocyte and mast cell proliferation, causing the local production of high levels of inflammatory cytokines leading to pain behavior. The current investigation used CRPS patient skin biopsies to determine whether keratinocyte and mast cell proliferation occur in CRPS skin and to identify the cellular source of the up-regulated TNF-α, IL-6, and tryptase observed in CRPS experimental skin blister fluid. Skin biopsies were collected from the affected skin and the contralateral mirror site in 55 CRPS patients and the biopsy sections were immunostained for keratinocyte, cell proliferation, mast cell markers, TNF-α, and IL-6. In early CRPS keratinocytes were activated in the affected skin, resulting in proliferation, epidermal thickening, and up-regulated TNF-α and IL-6 expression. In chronic CRPS there was reduced keratinocyte proliferation with epidermal thinning in the affected skin. Acute CRPS patients also had increased mast cell accumulation in the affected skin, but there was no increase in mast cell numbers in chronic CRPS. PMID:24462502

Use of paper for treatment of a peripheral nerve trauma in the rat.

PubMed

Kauppila, T; Jyväsjärvi, E; Murtomäki, S; Mansikka, H; Pertovaara, A; Virtanen, I; Liesi, P

1997-09-29

Reinnervation of the muscles and skin in the rat hindpaw was studied after transection and attempted repair of the sciatic nerve. Reconnecting the transected nerve with lens cleaning paper was at least as effective in rejoining the transected nerves as traditional microsurgical neurorraphy. Paper induced a slightly bigger fibrous scar around the site of transection than neurorraphy, but this scar did not cause impairment of functional recovery or excessive signs of neuropathic pain. We conclude that a paper graft can be used in restorative surgery of severed peripheral nerves.

Notch3 is necessary for neuronal differentiation and maturation in the adult spinal cord.

PubMed

Rusanescu, Gabriel; Mao, Jianren

2014-10-01

Notch receptors are key regulators of nervous system development and promoters of neural stem cells renewal and proliferation. Defects in the expression of Notch genes result in severe, often lethal developmental abnormalities. Notch3 is generally thought to have a similar proliferative, anti-differentiation and gliogenic role to Notch1. However, in some cases, Notch3 has an opposite, pro-differentiation effect. Here, we show that Notch3 segregates from Notch1 and is transiently expressed in adult rat and mouse spinal cord neuron precursors and immature neurons. This suggests that during the differentiation of adult neural progenitor cells, Notch signalling may follow a modified version of the classical lateral inhibition model, involving the segregation of individual Notch receptors. Notch3 knockout mice, otherwise neurologically normal, are characterized by a reduced number of mature inhibitory interneurons and an increased number of highly excitable immature neurons in spinal cord laminae I-II. As a result, these mice have permanently lower nociceptive thresholds, similar to chronic pain. These results suggest that defective neuronal differentiation, for example as a result of reduced Notch3 expression or activation, may underlie human cases of intractable chronic pain, such as fibromyalgia and neuropathic pain. © 2014 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

[Analgesic effects of ionotropic glutamate receptor antagonists MK-801 and NBQX on collagen-induced arthritis rats].

PubMed

Zhu, H; Zhu, R; Deng, Z D; Feng, Y C; Shen, H L

2016-12-18

The ionotropic glutamate receptorantagonists include two types: MK-801, antagonist of N-methyl-D-asparticacid (NMDA) receptor, and NBQX, antagonist of non-NMDA receptor.The above-mentioned ionotropic antagonists can block the glutamate and its corresponding receptor binding to produce analgesic effect. The objective of this research was to study two antagonists in analgesic effect on rat behavior,as well as to investigate the down-regulation and up-regulation of cyclooxygenase-2 (COX-2) and Janus-activated kinase (Jak3) in collagen-induced arthritis (CIA) rat serum and tissue fluid after the application of these antagonists, that is, the effect on molecular biology. This study used the ionotropic glutamate receptors as the target and established CIA rat model. Vivo studies were used to observe changes in behavior and molecular biology of the CIA rat.Behavioral assessment includedmechanical allodynia and joint swelling in the CIA rat,where themechanical allodynia was measured using the paw-withdrawal threshold (PWT) with VonFrey filaments according to the "Up-Down" method,and the drainage volume was used to assess joint swelling. Then the blood samples taken from the heart of the rat and the tissue homogenate were collected to detect the down-regulation and up-regulation of COX-2 and Jak3 in the serum and tissue fluid after the antagonists wereused. Using MK-801, NBQX alone or using the combination of these two antagonists,these three methods all could alleviate pain(P<0.01).The analgesic effect lasted more than 24 h.Both antagonists reached the peak of analgesia at the end of 4 hours post-injection. NBQX had stronger analgesic effect than MK-801 (P<0.05).Whether alone or combined use of these two antagonists,could not change the CIA rats' swelling of the joint (P>0.05). MK-801 could decrease the expression of COX-2 (P<0.01).At the same time, NBQX did not have this effect (P>0.05). Using MK-801, NBQX alone or combination of these two antagonists could not affect the increased expression of Jak3 caused by the CIA (P>0.05). MK-801 and NBQX could both alleviate pain, NBQX was much better than MK-801. Neither MK-801 nor NBQX had the effect on the swelling of the joint. NMDA receptor and COX-2 inflammatory pathways had certain interactions. For Jak3, it could not be found to have cross-function with ionotropic glutamate signaling pathways by this experiment.

Ketorolac administration does not delay early fracture healing in a juvenile rat model: a pilot study.

PubMed

Cappello, Teresa; Nuelle, Julia A V; Katsantonis, Nicolas; Nauer, Rachel K; Lauing, Kristen L; Jagodzinski, Jason E; Callaci, John J

2013-06-01

Nonsteroidal anti-inflammatory drugs (NSAIDs) are effective at controlling pain in children, especially in the treatment of fractures. Adult animal and adult clinical studies demonstrate conflicting evidence for the inhibitory relationship between NSAIDs and fracture healing. Published pediatric orthopaedic clinical studies do not demonstrate an inhibitory effect of ketorolac on bone healing. Little is known about the effects of any NSAID on bone formation in juvenile animals. This study investigates the effects of the NSAID ketorolac on fracture healing in a juvenile rat model. Unilateral surgically induced and stabilized tibial shaft fractures were created in 45 juvenile (3 to 4 wk old) male Sprague-Dawley rats. Either ketorolac (5 mg/kg; n=24) or saline (0.9% normal saline; n=21) was then administered to the rats 6 d/wk by intraperitoneal injections. Animals were then randomly assigned into time groups and euthanized at 7 days (n=8 ketorolac, n=7 saline), 14 days (n=8 ketorolac, n=7 saline), or 21 days (n=8 ketorolac, n=7 saline) postfracture. Biomechanical analysis was performed using a custom-designed 4-point bending loading apparatus. Statistics for tibial stiffness and strength data were performed using software package Systat 11. Specimens were also evaluated histologically using hematoxylin and eosin staining. Strength and stiffness of all fractured tibiae increased over time from day 7 to day 21 regardless of treatment type. No statistical difference was found between the fractured tibiae strength or stiffness in the ketorolac or control-treated specimens at the same time point. In addition, the quality of the fracture callus was similar in both groups at each of the time points. In this study of a juvenile rat model with a stabilized tibia fracture, fracture callus strength, stiffness, and histologic characteristics were not affected by the administration of ketorolac during the first 21 days of fracture healing. The absence of inhibitory effects of ketorolac on early juvenile rat fracture healing supports the clinical practice of utilizing NSAIDs for analgesia in children with long bone fractures.

The role of P2X7R/ERK signaling in dorsal root ganglia satellite glial cells in the development of chronic postsurgical pain induced by skin/muscle incision and retraction (SMIR).

PubMed

Song, Jingnian; Ying, Yanlu; Wang, Wei; Liu, Xianguo; Xu, Xuebing; Wei, Xuhong; Ruan, Xiangcai

2018-03-01

The mechanisms of chronic postsurgical pain remain to be elucidated. We reported here that skin/muscle incision and retraction (SMIR), a rat model of postsurgical pain, phosphorylated the extracellular regulated protein kinases (ERK) signaling components c-Raf, MEK (ERK kinase) and ERK1/2 in lumbar 3 dorsal root ganglion (L3 DRG) in rats. Intrathecal injection of ERK specific inhibitor SCH772984 suppressed the mechanical allodynia induced by SMIR. Furthermore, SMIR upregulated tumor necrosis factor alpha (TNFα) in L3 DRG, which could be inhibited by SCH772984. Intrathecal injection of TNF antagonist Etanercept could also inhibit the mechanical allodynia and the increased ERK phosphorylation in L3 DRG induced by SMIR. In addition, immunofluorescent data showed that P2X7R was located exclusively in GFAP labeled satellite glial cells and was highly colocalized with p-ERK1/2 following SMIR. Pretreatment with P2X7R antagonist Brilliant Blue G (BBG) could also block the mechanical allodynia, inhibited the phosphorylation of c-Raf, MEK, ERK1/2, and decrease the expression of TNF-α. Finally, intrathecal injection of BzATP produced mechanical allodynia and induced ERK phosphorylation in satellite glial cells in L3 DRG. Thus, P2X7R activation in satellite glial cells in L3 DRG, leading to a positive feedback between ERK pathway activation and TNF-α production, is suggested to be involved in the induction of chronic postsurgical pain following SMIR. Copyright © 2017 Elsevier Inc. All rights reserved.

Systemic ketamine inhibits hypersensitivity after surgery via descending inhibitory pathways in rats.

PubMed

Koizuka, Shiro; Obata, Hideaki; Sasaki, Masayuki; Saito, Shigeru; Goto, Fumio

2005-05-01

Systemic ketamine suppresses several types of chronic pain. Although ketamine is used as a general anesthetic agent, the analgesic effect of systemic ketamine for early-stage postoperative pain is not clear. We investigated the efficacy and mechanism of systemic ketamine in a rat model of postoperative pain. An incision was made in the plantar aspect of the left hind paw in male Wistar rats. Mechanical hypersensitivity was measured using calibrated von Frey filaments. The anti-hypersensitivity effect of systemic or intrathecal administration of ketamine was determined every hour after making the incision. We examined the effects of intrathecal pretreatment with yohimbine, an alpha2-adrenoceptor antagonist, and methysergide, a serotonergic receptor antagonist, on the anti-hypersensitivity effect of ketamine. We also examined the effect of systemic ketamine on the c-fos immunoreactivity in the spinal cord. Systemic administration of ketamine at doses from 3 to 30 mg.kg(-1) produced anti-hypersensitivity effects in a dose-dependent manner. Intrathecal administration of ketamine had no effect. There was no significant difference between effects of pre- and post-incisional administration. Intrathecal pretreatment with yohimbine (10 microg) or methysergide (15 microg) completely reversed the anti-hypersensitivity effects of systemic ketamine. Systemic ketamine reduced fos expression in laminae I-II in the dorsal horn of the lumbar spinal cord ipsilateral to the paw incision. The results suggest that systemic administration of ketamine perioperatively suppresses early-stage postoperative pain via monoaminergic descending inhibitory pathways.

Descending serotonergic facilitation mediated by spinal 5-HT3 receptors engages spinal rapamycin-sensitive pathways in the rat

PubMed Central

Asante, Curtis O.; Dickenson, Anthony H.

2010-01-01

We have recently reported the importance of spinal rapamycin-sensitive pathways in maintaining persistent pain-like states. A descending facilitatory drive mediated through spinal 5-HT3 receptors (5-HT3Rs) originating from superficial dorsal horn NK1-expressing neurons and that relays through the parabrachial nucleus and the rostroventral medial medulla to act on deep dorsal horn neurons is known be important in maintaining these pain-like states. To determine if spinal rapamycin-sensitive pathways are activated by a descending serotonergic drive, we investigated the effects of spinally administered rapamycin on responses of deep dorsal horn neurons that had been pre-treated with the selective 5-HT3R antagonist ondansetron. We also investigated the effects of spinally administered cell cycle inhibitor (CCI)-779 (a rapamycin ester analogue) on deep dorsal horn neurons from rats with carrageenan-induced inflammation of the hind paw. Unlike some other models of persistent pain, this model does not involve an altered 5-HT3R-mediated descending serotonergic drive. We found that the inhibitory effects of rapamycin were significantly reduced for neuronal responses to mechanical and thermal stimuli when the spinal cord was pre-treated with ondansetron. Furthermore, CCI-779 was found to be ineffective in attenuating spinal neuronal responses to peripheral stimuli in carrageenan-treated rats. Therefore, we conclude that 5-HT3R-mediated descending facilitation is one requirement for activation of rapamycin-sensitive pathways that contribute to persistent pain-like states. PMID:20709148

Ketorolac Administration Does Not Delay Early Fracture Healing in a Juvenile Rat Model

PubMed Central

Cappello, Teresa; Nuelle, Julia A.V.; Katsantonis, Nicolas; Nauer, Rachel K.; Lauing, Kristen L.; Jagodzinski, Jason E.; Callaci, John J.

2014-01-01

Background Nonsteroidal anti-inflammatory drugs (NSAIDs) are effective at controlling pain in children, especially in the treatment of fractures. Adult animal and adult clinical studies demonstrate conflicting evidence for the inhibitory relationship between NSAIDs and fracture healing. Published pediatric orthopaedic clinical studies do not demonstrate an inhibitory effect of ketorolac on bone healing. Little is known about the effects of any NSAID on bone formation in juvenile animals. This study investigates the effects of the NSAID ketorolac on fracture healing in a juvenile rat model. Methods Unilateral surgically induced and stabilized tibial shaft fractures were created in 45 juvenile (3 to 4wk old) male Sprague-Dawley rats. Either ketorolac (5 mg/kg; n=24) or saline (0.9% normal saline; n=21) was then administered to the rats 6 d/wk by intraperitoneal injections. Animals were then randomly assigned into time groups and euthanized at 7 days (n=8 ketorolac, n=7 saline), 14 days (n=8 ketorolac, n=7 saline), or 21 days (n=8 ketorolac, n=7 saline) postfracture. Biomechanical analysis was performed using a custom-designed 4-point bending loading apparatus. Statistics for tibial stiffness and strength data were performed using software package Systat 11. Specimens were also evaluated histologically using hematoxylin and eosin staining. Results Strength and stiffness of all fractured tibiae increased over time from day 7 to day 21 regardless of treatment type. No statistical difference was found between the fractured tibiae strength or stiffness in the ketorolac or control-treated specimens at the same time point. In addition, the quality of the fracture callus was similar in both groups at each of the time points. Conclusions In this study of a juvenile rat model with a stabilized tibia fracture, fracture callus strength, stiffness, and histologic characteristics were not affected by the administration of ketorolac during the first 21 days of fracture healing. Clinical Relevance The absence of inhibitory effects of ketorolac on early juvenile rat fracture healing supports the clinical practice of utilizing NSAIDs for analgesia in children with long bone fractures. PMID:23653032

The Locus Coeruleus–Norepinephrine System Mediates Empathy for Pain through Selective Up-Regulation of P2X3 Receptor in Dorsal Root Ganglia in Rats

PubMed Central

Lü, Yun-Fei; Yang, Yan; Li, Chun-Li; Wang, Yan; Li, Zhen; Chen, Jun

2017-01-01

Empathy for pain (vicariously felt pain), an ability to feel, recognize, understand and share the painful emotions of others, has been gradually accepted to be a common identity in both humans and rodents, however, the underlying neural and molecular mechanisms are largely unknown. Recently, we have developed a rat model of empathy for pain in which pain can be transferred from a cagemate demonstrator (CD) in pain to a naïve cagemate observer (CO) after 30 min dyadic priming social interaction. The naïve CO rats display both mechanical pain hypersensitivity (hyperalgesia) and enhanced spinal nociception. Chemical lesions of bilateral medial prefrontal cortex (mPFC) abolish the empathic pain response completely, suggesting existence of a top-down facilitation system in production of empathy for pain. However, the social transfer of pain was not observed in non-cagemate observer (NCO) after dyadic social interaction with a non-cagemate demonstrator (NCD) in pain. Here we showed that dyadic social interaction with a painful CD resulted in elevation of circulating norepinephrine (NE) and increased neuronal activity in the locus coeruleus (LC) in the CO rats. Meanwhile, CO rats also had over-expression of P2X3, but not TRPV1, in the dorsal root ganglia (DRG). Chemical lesion of the LC-NE neurons by systemic DSP-4 and pharmacological inhibition of central synaptic release of NE by clonidine completely abolished increase in circulating NE and P2X3 receptor expression, as well as the sympathetically-maintained development of empathic mechanical hyperalgesia. However, in the NCO rats, neither the LC-NE neuronal activity nor the P2X3 receptor expression was altered after dyadic social interaction with a painful NCD although the circulating corticosterone and NE were elevated. Finally, in the periphery, both P2X3 receptor and α1 adrenergic receptor were found to be involved in the development of empathic mechanical hyperalgesia. Taken together with our previous results, empathy for pain observed in the CO rats is likely to be mediated by activation of the top-down mPFC-LC/NE-sympathoadrenomedullary (SAM) system that further up-regulates P2X3 receptors in the periphery, however, social stress observed in the NCO rats is mediated by activation of both hypothalamic-pituitary-adrenocortical axis and SAM axis. PMID:28979194

Metastatic human breast cancer to the spine produces mechanical hyperalgesia and gait deficits in rodents.

PubMed

Sarabia-Estrada, Rachel; Ruiz-Valls, Alejandro; Guerrero-Cazares, Hugo; Ampuero, Ana M; Jimenez-Estrada, Ismael; De Silva, Samantha; Bernhardt, Lydia J; Goodwin, Courtney Rory; Ahmed, Ali Karim; Li, Yuxin; Phillips, Neil A; Gokaslan, Ziya L; Quiñones-Hinojosa, Alfredo; Sciubba, Daniel M

2017-09-01

Metastases to the spine are a common source of severe pain in cancer patients. The secondary effects of spinal metastases include pain, bone fractures, hypercalcemia, and neurological deficits. As the disease progresses, pain severity can increase until it becomes refractory to medical treatments and leads to a decreased quality of life for patients. A key obstacle in the study of pain-induced spinal cancer is the lack of reliable and reproducible spine cancer animal models. In the present study, we developed a reproducible and reliable rat model of spinal cancer using human-derived tumor tissue to evaluate neurological decline using imaging and behavioral techniques. The present study outlines the development and characterization of an orthotopic model of human breast cancer to the spine in immunocompromised rats. This is a basic science study. Female immunocompromised rats were randomized into three groups: tumor (n=8), RBC3 mammary adenocarcinoma tissue engrafted in the L5 vertebra body; sham (n=6), surgery performed but not tumor engrafted; and control (n=6), naive rats, no surgery performed. To evaluate the neurological impairment due to tumor invasion, functional assessment was done in all rodents at day 40 after tumor engraftment using locomotion gait analysis and pain response to a mechanical stimulus (Randall-Selitto test). Bioluminescence (BLI) was used to evaluate tumor growth in vivo and cone beam computed tomography (CBCT) was performed to evaluate bone changes due to tumor invasion. The animals were euthanized at day 45 and their spines were harvested and processed for hematoxylin and eosin (H&E) staining. Tumor growth in the spine was confirmed by BLI imaging and corroborated by histological analysis. Cone beam computed tomography images were characterized by a decrease in the bone intensity in the lumbar spine consistent with tumor location on BLI. On H&E staining of tumor-engrafted animals, there was a near-complete ablation of the ventral and posterior elements of the L5 vertebra with severe tumor invasion in the bony components displacing the spinal cord. Locomotion gait analysis of tumor-engrafted rats showed a disruption in the normal gait pattern with asignificant reduction in length (p=.02), duration (p=.002), and velocity (p=.002) of right leg strides and only in duration (p=.0006) and velocity (p=.001) of left leg strides, as compared with control and sham rats. Tumor-engrafted animals were hypersensitive to pain stimulus shown as a significantly reduced response in time (p=.02) and pressure (p=.01) applied when compared with control groups. We developed a system for the quantitative analysis of pain and locomotion in an animal model of metastatic human breast cancer of the spine. Tumor-engrafted animals showed locomotor and sensory deficits that are in accordance with clinical manifestation in patients with spine metastasis. Pain response and locomotion gait analysis were performed during follow-up. The Randall-Selitto test was a sensitive method to evaluate pain in the rat's spine. We present a model for the study of bone-associated cancer pain secondary to cancer metastasis to the spine, as well as for the study of new therapies and treatments to lessen pain from metastatic cancer to the neuroaxis. Copyright © 2017 Elsevier Inc. All rights reserved.

Bidirectional modulation of windup by NMDA receptors in the rat spinal trigeminal nucleus.

PubMed

Woda, Alain; Blanc, Olivier; Voisin, Daniel L; Coste, Jérôme; Molat, Jean-Louis; Luccarini, Philippe

2004-04-01

Activation of afferent nociceptive pathways is subject to activity-dependent plasticity, which may manifest as windup, a progressive increase in the response of dorsal horn nociceptive neurons to repeated stimuli. At the cellular level, N-methyl-d-aspartate (NMDA) receptor activation by glutamate released from nociceptive C-afferent terminals is currently thought to generate windup. Most of the wide dynamic range nociceptive neurons that display windup, however, do not receive direct C-fibre input. It is thus unknown where the NMDA mechanisms for windup operate. Here, using the Sprague-Dawley rat trigeminal system as a model, we anatomically identify a subpopulation of interneurons that relay nociceptive information from the superficial dorsal horn where C-fibres terminate, to downstream wide dynamic range nociceptive neurons. Using in vivo electrophysiological recordings, we show that at the end of this pathway, windup was reduced (24 +/- 6%, n = 7) by the NMDA receptor antagonist AP-5 (2.0 fmol) and enhanced (62 +/- 19%, n = 12) by NMDA (1 nmol). In contrast, microinjections of AP-5 (1.0 fmol) within the superficial laminae increased windup (83 +/- 44%, n = 9), whereas NMDA dose dependently decreased windup (n = 19). These results indicate that NMDA receptor function at the segmental level depends on their precise location in nociceptive neural networks. While some NMDA receptors actually amplify pain information, the new evidence for NMDA dependent inhibition of windup we show here indicates that, simultaneously, others act in the opposite direction. Working together, the two mechanisms may provide a fine tuning of gain in pain.

lncRNA NONRATT021972 siRNA Decreases Diabetic Neuropathic Pain Mediated by the P2X3 Receptor in Dorsal Root Ganglia.

PubMed

Peng, Haiying; Zou, Lifang; Xie, Jinyan; Wu, Hong; Wu, Bing; Zhu, Gaochun; Lv, Qiulan; Zhang, Xi; Liu, Shuangmei; Li, Guilin; Xu, Hong; Gao, Yun; Xu, Changshui; Zhang, Chunping; Wang, Shouyu; Xue, Yun; Liang, Shangdong

2017-01-01

Long noncoding RNAs (lncRNAs) participate in physiological and pathophysiological processes. Type 2 diabetes mellitus (T2DM) accounts for more than 90 % of all cases of diabetes mellitus (DM). Diabetic neuropathic pain (DNP) is a common complication of T2DM. The aim of this study was to investigate the effects of lncRNA NONRATT021972 small interference RNA (siRNA) on DNP mediated by the P2X 3 receptor in dorsal root ganglia (DRG). These experiments showed that the expression levels of NONRATT021972 in DRG were increased in the T2DM rat model (intraperitoneal injection of STZ with 30 mg/kg). The concentration of NONRATT021972 in T2DM patient serum was higher compared to control healthy subjects. The mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) in T2DM rats were lower compared to control rats. MWT and TWL in T2DM rats treated with NONRATT021972 siRNA were higher compared with those in T2DM rats. The expression levels of the P2X 3 protein and messenger RNA (mRNA) of T2DM rat DRG were higher compared to the control, while those in T2DM rats treated with NONRATT021972 siRNA were significantly lower compared to T2DM rats. The level of tumor necrosis factor-α (TNF-α) in the serum of T2DM rats treated with NONRATT021972 siRNA was significantly decreased compared with T2DM rats. NONRATT021972 siRNA inhibited the phosphorylation and activation of ERK1/2 in T2DM DRG. Thus, NONRATT021972 siRNA treatment may suppress the upregulated expression and activation of the P2X 3 receptor and reduce the hyperalgesia potentiated by the pro-inflammatory cytokine TNF-α in T2DM rats.

Occurrence of urea-based soluble epoxide hydrolase inhibitors from the plants in the order Brassicales

PubMed Central

Kitamura, Seiya; Morisseau, Christophe; Harris, Todd R.; Inceoglu, Bora

2017-01-01

Recently, dibenzylurea-based potent soluble epoxide hydrolase (sEH) inhibitors were identified in Pentadiplandra brazzeana, a plant in the order Brassicales. In an effort to generalize the concept, we hypothesized that plants that produce benzyl glucosinolates and corresponding isothiocyanates also produce these dibenzylurea derivatives. Our overall aim here was to examine the occurrence of urea derivatives in Brassicales, hoping to find biologically active urea derivatives from plants. First, plants in the order Brassicales were analyzed for the presence of 1, 3-dibenzylurea (compound 1), showing that three additional plants in the order Brassicales produce the urea derivatives. Based on the hypothesis, three dibenzylurea derivatives with sEH inhibitory activity were isolated from maca (Lepidium meyenii) roots. Topical application of one of the identified compounds (compound 3, human sEH IC50 = 222 nM) effectively reduced pain in rat inflammatory pain model, and this compound was bioavailable after oral administration in mice. The biosynthetic pathway of these urea derivatives was investigated using papaya (Carica papaya) seed as a model system. Finally, a small collection of plants from the Brassicales order was grown, collected, extracted and screened for sEH inhibitory activity. Results show that several plants of the Brassicales order could be potential sources of urea-based sEH inhibitors. PMID:28472063

Astragali radix: could it be an adjuvant for oxaliplatin-induced neuropathy?

PubMed Central

Di Cesare Mannelli, Lorenzo; Pacini, Alessandra; Micheli, Laura; Femia, Angelo Pietro; Maresca, Mario; Zanardelli, Matteo; Vannacci, Alfredo; Gallo, Eugenia; Bilia, Anna Rita; Caderni, Giovanna; Firenzuoli, Fabio; Mugelli, Alessandro; Ghelardini, Carla

2017-01-01

Neurotoxicity is a major side effect of platinum derivatives both during and after treatment. In the absence of effective pharmacological compounds, the opportunity to identify safe adjuvant treatments among medicinal plants seems appropriate. Astragali radix is an adaptogenic herbal product recently analyzed in platinum-treated cancer patients. With the aim of evaluating the anti-neuropathic profile of Astragali radix, a previously characterized aqueous (Aqu) and two hydroalcoholic (20%HA and 50%HA) extracts were tested in a rat model of oxaliplatin-induced neuropathy. Repeated administrations significantly reduced oxaliplatin-dependent hypersensitivity with 50%HA, the most effective, fully preventing mechanical and thermal hypersensitivity. Ex vivo, 50%HA reduced morphometric and molecular alterations induced by oxaliplatin in peripheral nerve and dorsal-root-ganglia. In the spinal cord and in brain areas, 50%HA significantly decreased activation of microglia and astrocytes. Furthermore, 50%HA prevented the nephro- and hepato-toxicity induced by the anticancer drug. The protective effect of 50%HA did not alter oxaliplatin-induced apoptosis in colon tumors of Pirc rats, an Apc-driven model of colon carcinogenesis. The hydroalcoholic extract (50%HA) of Astragali radix relieves pain and promotes the rescue mechanisms that protect nervous tissue from the damages triggering chronic pain. A safe profile strongly suggests the usefulness of this natural product in oxaliplatin-induced neuropathy. PMID:28186109

Development of Intra-knee Joint Sustained-Release Gel Formulation and Evaluation of Its Pharmacological Efficiency in Rats.

PubMed

Noda, Takehiro; Okuda, Tomoyuki; Ban, Kousuke; Mizuno, Ryota; Tagami, Tatsuaki; Ozeki, Tetsuya; Okamoto, Hirokazu

2017-06-01

In the development of a drug for intra-articular administration, a sustained-release formulation is desirable since it is difficult to sustain the effects of conventional injections due to fast drug leakage from the joint cavity. In this study, we prepared sustained release gel formulations for intra-articular administration containing indocyanine green (ICG) as a model drug to follow its fate after intra-articular administration in rats with in-vivo imaging system (IVIS). ICG administered as an aqueous solution leaked from the joint cavity in a short time and was excreted out of the body within a day. On the other hand, ICG in the sustained-release formulations was retained and released in the joint cavity for a week. Next, we prepared a sustained-release formulation with hyaluronic acid (HA) as the gel base containing a pain-relief drug (Drug A). We had administered it and other formulations into the rat knee where we injected bradykinin to evaluate their walking distance after 1 and 3 d. The effect of an aqueous solution of Drug A disappeared on day 3. The HA gel formulation without Drug A was more effective than the aqueous solution. The HA gel formulation with Drug A was the most effective; the walking distance was about 85% of the baseline on day 3. This study showed that the gel formulations were effective to sustain the release of a drug in the knee joint, and that the combination of a pain-relief drug with HA gel was effective to improve the mobility of the acute pain model rats.

Identification of 2,3-diaryl-pyrazolo[1,5-b]pyridazines as potent and selective cyclooxygenase-2 inhibitors.

PubMed

Beswick, Paul; Bingham, Sharon; Bountra, Chas; Brown, Terry; Browning, Kerry; Campbell, Ian; Chessell, Iain; Clayton, Nick; Collins, Sue; Corfield, John; Guntrip, Stephen; Haslam, Claudine; Lambeth, Paul; Lucas, Fiona; Mathews, Neil; Murkit, Graham; Naylor, Alan; Pegg, Neil; Pickup, Elizabeth; Player, Hazel; Price, Helen; Stevens, Alexander; Stratton, Sharon; Wiseman, Joanne

2004-11-01

GW406381 (8), currently undergoing clinical evaluation for the treatment of inflammatory pain is a member of a novel series of 2,3-diaryl-pyrazolo[1,5-b]pyridazine based cyclooxygenase-2 (COX-2) inhibitors, which have been shown to be highly potent and selective. Several examples of the series, in addition to possessing favourable pharmacokinetic profiles and analgesic activity in vivo, have also demonstrated relatively high brain penetration in the rat compared with the clinically available compounds, which may ultimately prove beneficial in the treatment of pain.

Low-Level Blast Exposure Increases Transient Receptor Potential Vanilloid 1 (TRPV1) Expression in the Rat Cornea

PubMed Central

Por, Elaine D.; Choi, Jae-Hyek; Lund, Brian J.

2016-01-01

ABSTRACT Background: Blast-related ocular injuries sustained by military personnel have led to rigorous efforts to elucidate the effects of blast exposure on neurosensory function. Recent studies have provided some insight into cognitive and visual deficits sustained following blast exposure; however, limited data are available on the effects of blast on pain and inflammatory processes. Investigation of these secondary effects of blast exposure is necessary to fully comprehend the complex pathophysiology of blast-related injuries. The overall purpose of this study is to determine the effects of single and repeated blast exposure on pain and inflammatory mediators in ocular tissues. Methods: A compressed air shock tube was used to deliver a single or repeated blast (68.0 ± 2.7 kPa) to anesthetized rats daily for 5 days. Immunohistochemistry was performed on ocular tissues to determine the expression of the transient receptor potential vanilloid 1 (TRPV1) channel, calcitonin gene-related peptide (CGRP), substance P (SP), and endothelin-1 (ET-1) following single and repeated blast exposure. Neutrophil infiltration and myeloperoxidase (MPO) expression were also assessed in blast tissues via immunohistochemistry and enzyme-linked immunosorbent assay (ELISA) analysis, respectively. Results: TRPV1 expression was increased in rat corneas exposed to both single and repeated blast. Increased secretion of CGRP, SP, and ET-1 was also detected in rat corneas as compared to control. Moreover, repeated blast exposure resulted in neutrophil infiltration in the cornea and stromal layer as compared to control animals. Conclusion: Single and repeated blast exposure resulted in increased expression of TRPV1, CGRP, SP, and ET-1 as well as neutrophil infiltration. Collectively, these findings provide novel insight into the activation of pain and inflammation signaling mediators following blast exposure. PMID:27049881

Morphological changes in hind limb muscles elicited by adjuvant-induced arthritis of the rat knee.

PubMed

Ozawa, J; Kurose, T; Kawamata, S; Yamaoka, K

2010-02-01

We investigated qualitative and quantitative changes in rat hind limb muscles caused by complete Freund's adjuvant (CFA)-induced knee joint pain. One week after CFA injection, muscle atrophy was induced only on the CFA-injected side. Wet weight of the rectus femoris (RF) and soleus (SOL) muscles were significantly decreased by 20% and 19%, respectively. The reduction in cross-sectional areas by CFA was similar for fast and slow muscle fibers in the RF (10% vs 15%, respectively) and SOL muscles (16% vs 16%, respectively). At the light microscopic level, pathological changes were not found in the RF muscles on both sides, although the infiltration of mononuclear cells and muscle regeneration were found in the SOL muscles on CFA-injected and contralateral control sides. On the other hand, electron microscopy revealed degenerative changes in the RF and SOL muscles on the CFA-injected side. Interestingly, sarcomere hypercontraction, indicating overexercise, was observed to a limited extent in the SOL muscles on the control side. In conclusions, knee joint pain can trigger the rapid development of muscle atrophy with degenerative changes not only in thigh but also calf muscles. This indicates that early interventions to inhibit joint pain or inflammation may prevent muscle atrophy.

The potential of treating Gulf War Illness with curcumin.

PubMed

Leibowitz, Jeffrey A; Ormerod, Brandi K

2018-05-01

A large proportion of Gulf War Veterans suffer from Gulf War Illness (GWI) - a devastating chronic disorder characterized by heterogeneous fatigue, pain and neuropsychological symptoms. In their recent Brain, Behavior and Immunity publication entitled "Curcumin Treatment Leads to Better Cognitive and Mood Function in a Model of Gulf War Illness with Enhanced Neurogenesis, and Alleviation of Inflammation and Mitochondrial Dysfunction in the Hippocampus", Kodali and colleagues (2018) report that the polyphenol curcumin improves cognition and mood in a rat model of GWI, potentially by increasing the expression of antioxidant genes and by reversing the effects of chronic combined acetylcholinesterase inhibitor exposure on neuroinflammation, mitochondrial respiration and hippocampal neurogenesis. This preclinical work is encouraging for our veterans who suffer chronically from GWI as well as for developing strategies to protect our troops during future deployments in similar environments. Copyright © 2018 Elsevier Inc. All rights reserved.

Internal-Specific Morphological Analysis of Sciatic Nerve Fibers in a Radiofrequency-Induced Animal Neuropathic Pain Model

PubMed Central

Choi, Samjin; Choi, Hyuk Jai; Cheong, Youjin; Lim, Young-Jin; Park, Hun-Kuk

2013-01-01

This study investigated the reversible effects of pulsed radiofrequency (PRF) treatment at 42°C on the ultrastructural and biological changes in nerve and collagen fibers in the progression of neuropathic pain after rat sciatic nerve injury. Assessments of morphological changes in the extracellular matrices by atomic force microscopy and hematoxylin-eosin, Masson’s trichrome and picrosirius-red staining as well as the expressions of two fibril-forming collagens, types-I and -III, and two inflammatory cytokines, TNF-α and IL-6, were evaluated on day 30 after RF exposure. There were four groups for different RF thermal treatments: no treatment, no current, PRF, and continuous RF (CRF). An RF procedure similar to that used in human clinical trials was used in this study. The CRF treatment at 82°C led to neural and collagen damage by the permanent blockage of sensory nociceptors. The PRF treatment led to excellent performance and high expandability compared to CRF, with effects including slight damage and swelling of myelinated axons, a slightly decreased amount of collagen fibers, swelling of collagen fibril diameters, decreased immunoreactivity of collagen types-I and -III, presence of newly synthesized collagen, and recovery of inflammatory protein immunoreactivity. These evidence-based findings suggest that PRF-based pain relief is responsible for the temporary blockage of nerve signals as well as the preferential destruction of pain-related principal sensory fibers like the Aδ and C fibers. This suggestion can be supported by the interaction between the PRF-induced electromagnetic field and cell membranes; therefore, PRF treatment provides pain relief while allowing retention of some tactile sensation. PMID:24066083

Voltage-gated Na+ currents in human dorsal root ganglion neurons

PubMed Central

Zhang, Xiulin; Priest, Birgit T; Belfer, Inna; Gold, Michael S

2017-01-01

Available evidence indicates voltage-gated Na+ channels (VGSCs) in peripheral sensory neurons are essential for the pain and hypersensitivity associated with tissue injury. However, our understanding of the biophysical and pharmacological properties of the channels in sensory neurons is largely based on the study of heterologous systems or rodent tissue, despite evidence that both expression systems and species differences influence these properties. Therefore, we sought to determine the extent to which the biophysical and pharmacological properties of VGSCs were comparable in rat and human sensory neurons. Whole cell patch clamp techniques were used to study Na+ currents in acutely dissociated neurons from human and rat. Our results indicate that while the two major current types, generally referred to as tetrodotoxin (TTX)-sensitive and TTX-resistant were qualitatively similar in neurons from rats and humans, there were several differences that have important implications for drug development as well as our understanding of pain mechanisms. DOI: http://dx.doi.org/10.7554/eLife.23235.001 PMID:28508747

Inhibition of G protein-coupled P2Y2 receptor induced analgesia in a rat model of trigeminal neuropathic pain.

PubMed

Li, Na; Lu, Zhan-ying; Yu, Li-hua; Burnstock, Geoffrey; Deng, Xiao-ming; Ma, Bei

2014-03-18

ATP and P2X receptors play important roles in the modulation of trigeminal neuropathic pain, while the role of G protein-coupled P2Y₂ receptors and the underlying mechanisms are less clear. The threshold and frequency of action potentials, fast inactivating transient K+ channels (IA) are important regulators of membrane excitability in sensory neurons because of its vital role in the control of the spike onset. In this study, pain behavior tests, QT-RT-PCR, immunohistochemical staining, and patch-clamp recording, were used to investigate the role of P2Y₂ receptors in pain behaviour. In control rats: 1) UTP, an agonist of P2Y₂/P2Y₄ receptors, caused a significant decrease in the mean threshold intensities for evoking action potentials and a striking increase in the mean number of spikes evoked by TG neurons. 2) UTP significantly inhibited IA and the expression of Kv1.4, Kv3.4 and Kv4.2 subunits in TG neurons, which could be reversed by the P2 receptor antagonist suramin and the ERK antagonist U0126. In ION-CCI (chronic constriction injury of infraorbital nerve) rats: 1) mRNA levels of Kv1.4, Kv3.4 and Kv4.2 subunits were significantly decreased, while the protein level of phosphorylated ERK was significantly increased. 2) When blocking P2Y₂ receptors by suramin or injection of P2Y2R antisense oligodeoxynucleotides both led to a time- and dose-dependent reverse of allodynia in ION-CCI rats. 3) Injection of P2Y₂ receptor antisense oligodeoxynucleotides induced a pronounced decrease in phosphorylated ERK expression and a significant increase in Kv1.4, Kv3.4 and Kv4.2 subunit expression in trigeminal ganglia. Our data suggest that inhibition of P2Y₂ receptors leads to down-regulation of ERK-mediated phosphorylation and increase of the expression of I(A)-related Kv channels in trigeminal ganglion neurons, which might contribute to the clinical treatment of trigeminal neuropathic pain.

Nociceptive Response to L-DOPA-Induced Dyskinesia in Hemiparkinsonian Rats.

PubMed

Nascimento, G C; Bariotto-Dos-Santos, K; Leite-Panissi, C R A; Del-Bel, E A; Bortolanza, M

2018-04-02

Non-motor symptoms are increasingly identified to present clinical and diagnostic importance for Parkinson's disease (PD). The multifactorial origin of pain in PD makes this symptom of great complexity. The dopamine precursor, L-DOPA (L-3,4-dihydroxyphenylalanine), the classic therapy for PD, seems to be effective in pain threshold; however, there are no studies correlating L-DOPA-induced dyskinesia (LID) and nociception development in experimental Parkinsonism. Here, we first investigated nociceptive responses in a 6-hydroxydopamine (6-OHDA)-lesioned rat model of Parkinson's disease to a hind paw-induced persistent inflammation. Further, the effect of L-DOPA on nociception behavior at different times of treatment was investigated. Pain threshold was determined using von Frey and Hot Plate/Tail Flick tests. Dyskinesia was measured by abnormal involuntary movements (AIMs) induced by L-DOPA administration. This data is consistent to show that 6-OHDA-lesioned rats had reduced nociceptive thresholds compared to non-lesioned rats. Additionally, when these rats were exposed to a persistent inflammatory challenge, we observed increased hypernociceptive responses, namely hyperalgesia. L-DOPA treatment alleviated pain responses on days 1 and 7 of treatment, but not on day 15. During that period, we observed an inverse relationship between LID and nociception threshold in these rats, with a high LID rate corresponding to a reduced nociception threshold. Interestingly, pain responses resulting from CFA-induced inflammation were significantly enhanced during established dyskinesia. These data suggest a pro-algesic effect of L-DOPA-induced dyskinesia, which is confirmed by the correlation founded here between AIMs and nociceptive indexes. In conclusion, our results are consistent with the notion that central dopaminergic mechanism is directly involved in nociceptive responses in Parkinsonism condition.

Protective effect of Panax ginseng in cisplatin-induced cachexia in rats.

PubMed

Lobina, Carla; Carai, Mauro A M; Loi, Barbara; Gessa, Gian Luigi; Riva, Antonella; Cabri, Walter; Petrangolini, Giovanna; Morazzoni, Paolo; Colombo, Giancarlo

2014-05-01

This study investigated the protective effect of a standardized extract of Panax ginseng on multiple cisplatin-induced 'sickness behaviors' (model of cancer-induced cachexia) in rats. Cisplatin was administered twice weekly (1-2 mg/kg, intraperitoneal) for 5 consecutive weeks. Panax ginseng extract (0, 25 and 50 mg/kg, intragastric) was administered daily over the 5-week period of cisplatin exposure. Malaise, bodyweight and temperature, pain sensitivity, and endurance running were recorded at baseline and at 5 weekly intervals. Treatment with cisplatin produced severe signs of malaise, marked loss of bodyweight, hypothermia, hyperalgesia and reduction in running time. Treatment with Panax ginseng extract completely prevented all cisplatin-induced alterations. These data indicate that treatment with Panax ginseng extract exerted a protective effect in a rat model of cachexia and suggest that Panax ginseng extract may be a therapeutic promising tool for supportive care in oncology.

A novel antagonist of the prostaglandin E(2) EP(4) receptor inhibits Th1 differentiation and Th17 expansion and is orally active in arthritis models.

PubMed

Chen, Q; Muramoto, K; Masaaki, N; Ding, Y; Yang, H; Mackey, M; Li, W; Inoue, Y; Ackermann, K; Shirota, H; Matsumoto, I; Spyvee, M; Schiller, S; Sumida, T; Gusovsky, F; Lamphier, M

2010-05-01

Rheumatoid arthritis (RA) is an autoimmune disorder involving subsets of activated T cells, in particular T helper (Th) 1 and Th17 cells, which infiltrate and damage tissues and induce inflammation. Prostaglandin E(2) (PGE(2)) enhances the Th17 response, exacerbates collagen-induced arthritis (CIA) and promotes inflammatory pain. The current study investigated whether selective antagonism of the PGE(2) EP(4) receptor would suppress Th1/Th17 cell development and inflammatory arthritis in animal models of RA. Effects of PGE(2) and a novel EP(4) receptor antagonist ER-819762 on Th1 differentiation, interleukin-23 (IL-23) production by dendritic cells (DCs), and Th17 development were assessed in vitro. The effect of ER-819762 was evaluated in CIA and glucose-6-phosphate isomerase (GPI)-induced arthritis models. In addition, the effects of ER-819762 on pain were evaluated in a model of chronic inflammatory pain induced by complete Freund's adjuvant (CFA) in the rat. Stimulation of the EP(4) receptor enhanced Th1 differentiation via phosphatidylinositol 3 kinase signalling, selectively promoted Th17 cell expansion, and induced IL-23 secretion by activated DCs, effects suppressed by ER-819762 or anti-PGE(2) antibody. Oral administration of ER-19762 suppressed Th1 and Th17 cytokine production, suppressed disease in collagen- and GPI-induced arthritis in mice, and suppressed CFA-induced inflammatory pain in rats. PGE(2) stimulates EP(4) receptors to promote Th1 differentiation and Th17 expansion and is critically involved in development of arthritis in two animal models. Selective suppression of EP(4) receptor signalling may have therapeutic value in RA both by modifying inflammatory arthritis and by relieving pain.

Down-regulation of A-type potassium channel in gastric-specific DRG neurons in a rat model of functional dyspepsia.

PubMed

Li, S; Chen, J D Z

2014-07-01

Although without evidence of organic structural abnormalities, pain or discomfort is a prominent symptom of functional dyspepsia and considered to reflect visceral hypersensitivity whose underlying mechanism is poorly understood. Here, we studied electrophysiological properties and expression of voltage-gated potassium channels in dorsal root ganglion (DRG) neurons in a rat model of functional dyspepsia induced by neonatal gastric irritation. Male Sprague-Dawley rat pups at 10-day old received 0.1% iodoacetamide (IA) or vehicle by oral gavage for 6 days and studied at adulthood. Retrograde tracer-labeled gastric-specific T8 -T12 DRG neurons were harvested for the patch-clamp study in voltage and current-clamp modes and protein expression of K(+) channel in T8 -T12 DRGs was examined by western blotting. (1) Gastric specific but not non-gastric DRG neurons showed an enhanced excitability in neonatal IA-treated rats compared to the control: depolarized resting membrane potentials, a lower current threshold for action potential (AP) activation, and an increase in the number of APs in response to current stimulation. (2) The current density of tetraethylammonium insensitive (transiently inactivating A-type current), but not the tetraethylammonium sensitive (slow-inactivating delayed rectifier K(+) currents), was significantly smaller in IA-treated rats (65.4 ± 6.9 pA/pF), compared to that of control (93.1 ± 8.3 pA/pF). (3) Protein expression of KV 4.3 was down-regulated in IA-treated rats. A-type potassium channels are significantly down-regulated in the gastric-specific DRG neurons in adult rats with mild neonatal gastric irritation, which in part contribute to the enhanced DRG neuron excitabilities that leads to the development of gastric hypersensitivity. © 2014 John Wiley & Sons Ltd.

5-HT2C Receptor Knockdown in the Amygdala Inhibits Neuropathic-Pain-Related Plasticity and Behaviors.

PubMed

Ji, Guangchen; Zhang, Wei; Mahimainathan, Lenin; Narasimhan, Madhusudhanan; Kiritoshi, Takaki; Fan, Xiuzhen; Wang, Jigong; Green, Thomas A; Neugebauer, Volker

2017-02-08

Neuroplasticity in the amygdala drives pain-related behaviors. The central nucleus (CeA) serves major amygdala output functions and can generate emotional-affective behaviors and modulate nocifensive responses. The CeA receives excitatory and inhibitory inputs from the basolateral nucleus (BLA) and serotonin receptor subtype 5-HT 2C R in the BLA, but not CeA, has been implicated anxiogenic behaviors and anxiety disorders. Here, we tested the hypothesis that 5-HT 2C R in the BLA plays a critical role in CeA plasticity and neuropathic pain behaviors in the rat spinal nerve ligation (SNL) model. Local 5-HT 2C R knockdown in the BLA with stereotaxic injection of 5-HT 2C R shRNA AAV vector decreased vocalizations and anxiety- and depression-like behaviors and increased sensory thresholds of SNL rats, but had no effect in sham controls. Extracellular single-unit recordings of CeA neurons in anesthetized rats showed that 5-HT 2C R knockdown blocked the increase in neuronal activity (increased responsiveness, irregular spike firing, and increased burst activity) in SNL rats. At the synaptic level, 5-HT 2C R knockdown blocked the increase in excitatory transmission from BLA to CeA recorded in brain slices from SNL rats using whole-cell patch-clamp conditions. Inhibitory transmission was decreased by 5-HT 2C R knockdown in control and SNL conditions to a similar degree. The findings can be explained by immunohistochemical data showing increased expression of 5-HT 2C R in non-GABAergic BLA cells in SNL rats. The results suggest that increased 5-HT 2C R in the BLA contributes to neuropathic-pain-related amygdala plasticity by driving synaptic excitation of CeA neurons. As a rescue strategy, 5-HT 2C R knockdown in the BLA inhibits neuropathic-pain-related behaviors. SIGNIFICANCE STATEMENT Neuroplasticity in the amygdala has emerged as an important pain mechanism. This study identifies a novel target and rescue strategy to control abnormally enhanced amygdala activity in an animal model of neuropathic pain. Specifically, an integrative approach of gene transfer, systems and brain slice electrophysiology, behavior, and immunohistochemistry was used to advance the novel concept that serotonin receptor subtype 5-HT 2C contributes critically to the imbalance between excitatory and inhibitory drive of amygdala output neurons. Local viral vector-mediated 5-HT 2C R knockdown in the amygdala normalizes the imbalance, decreases neuronal activity, and inhibits neuropathic-pain-related behaviors. The study provides valuable insight into serotonin receptor (dys)function in a limbic brain area. Copyright © 2017 the authors 0270-6474/17/371378-16$15.00/0.

Through the central V2, not V1 receptors influencing the endogenous opiate peptide system, arginine vasopressin, not oxytocin in the hypothalamic paraventricular nucleus involves in the antinociception in the rat.

PubMed

Yang, Jun; Chen, Jian-min; Song, Cao-You; Liu, Wen-Yan; Wang, Gen; Wang, Cheng-hai; Lin, Bao-Chen

2006-01-19

Our previous study has proven that hypothalamic paraventricular nucleus (PVN) played a role in the antinociception. The central bioactive substances involving in the PVN regulating antinociception were investigated in the rat. The results showed that electrical stimulation of the PVN increased the pain threshold, and L-glutamate sodium injection into the PVN elevated the pain threshold, but the PVN cauterization decreased the pain threshold; pain stimulation raised the arginine vasopressin (AVP), not oxytocin (OXT), leucine-enkephalin (L-Ek), beta-endorphin (beta-Ep) and DynorphinA1-13 (DynA1-13) concentrations in the PVN tissue using micropunch method, heightened AVP, L-Ek, beta-Ep and DynA1-13, not OXT concentrations in the PVN perfuse liquid, and reduced the number of AVP-, not OXT, L-Ek, beta-Ep and DynA1-13-immunoreactive neurons in the PVN especially in the posterior magnocellular part of the PVN using immunocytochemistry. There was a negative relationship between the PVN AVP concentration and the pain threshold; pain stimulation enhanced the AVP, not OXT mRNA expression in the PVN using in situ hybridization and RT-PCR; intraventricular injection of anti-AVP serum completely reversed L-glutamate sodium injection into the PVN-induced antinociception, and administration of naloxone - the opiate peptide antagonist, partly blocked this L-glutamate sodium effect, but anti-OXT serum pretreatment did not influence this L-glutamate sodium effect; L-glutamate sodium injection into the PVN-induced analgesia was inhibited by V2 receptor antagonist - d(CH2)5[D-Ile2, Ile4, Ala-NH2(9)]AVP, not V1 receptor antagonist - d(CH2)5Tyr(Me)AVP. The data suggested that the PVN was limited to the central AVP, not OXT, which was through V2, not V1 receptors influencing the endogenous opiate peptide system, to regulate antinociception.

Molecular mechanisms underlying the effects of acupuncture on neuropathic pain

PubMed Central

Ju, Ziyong; Cui, Huashun; Guo, Xiaohui; Yang, Huayuan; He, Jinsen; Wang, Ke

2013-01-01

Acupuncture has been used to treat neuropathic pain for a long time, but its mechanisms of action remain unknown. In this study, we observed the effects of electroacupuncture and manual acu-puncture on neuropathic pain and on ephrin-B/EphB signaling in rats models of chronic constriction injury-induced neuropathic pain. The results showed that manual acupuncture and elec-puncture significantly reduced mechanical hypersensitivity following chronic constriction injury, es-pecially electroacupuncture treatment. Real-time PCR results revealed that ephrin-B1/B3 and EphB1/B2 mRNA expression levels were significantly increased in the spinal dorsal horns of chronic constriction injury rats. Electroacupuncture and manual acupuncture suppressed the high sion of ephrin-B1 mRNA, and elevated EphB3/B4 mRNA expression. Electroacupuncture signifi-cantly enhanced the mRNA expression of ephrin-B3 and EphB3/B6 in the dorsal horns of neuro-pathic pain rats. Western blot results revealed that electroacupuncture in particular, and manual acupuncture, significantly up-regulated ephrin-B3 protein levels in rat spinal dorsal horns. The re-sults of this study suggest that acupuncture could activate ephrin-B/EphB signaling in neuropathic pain rats and improve neurological function. PMID:25206545

Beneficial effect of daidzin in dry eye rat model through the suppression of inflammation and oxidative stress in the cornea.

PubMed

Xiao, Fan; Cui, Hua; Zhong, Xiao

2018-05-01

Present investigation evaluates the effect of daidzin in dry eye rat model through the suppression of inflammation and oxidative stress in the cornea. Briefly, electron spine resonance was used for the estimation of radical scavenging activity of daidzin and COX Fluorescent Activity Assay Kit was used for the estimation of PGS activity. Dry eye rat model was developed by removing the lacrimal gland and effect of daidzin was evaluated in dry eye rat model by estimating the fluorescein score, tear volume and expressions of heme oxigenase (HO-1), TNF α, Interlukin 6 (IL-6), matrix metallopeptidase 9 (MMP-9) and PGS-2. Result of the present study suggested that daidzin possess tyrosyl radical scavenging activity and thereby decreases the oxidative stress. Activity of PGS significantly increases in dry eye which was inhibited by daidzin treatment due to competitive inhibition of PGS. It also recovers the tear volume in dry eye rat model in which lacrimal gland was removed. Thus corneal erosion was improved by daidzin in dry eye rat model. Thus present study concludes that treatment with daidzin protects the cornea in dry eye rat model by suppression inflammation and oxidative stress.

Gravity stress elevates the nociceptive threshold level with immunohistochemical changes in the rat brain

NASA Astrophysics Data System (ADS)

Kumei, Yasuhiro; Shimokawa, Reiko; Kimoto, Mari; Kawauchi, Yasuko; Shimokawa, Hitoyata; Makita, Koshi; Ohya, Keiichi; Toda, Kazuo

2001-08-01

Young Wistar male rats were exposed to 2G hypergravity by continuous centrifugation for 15 minutes. The nociceptive threshold was measured by using the von Frey type filament on the rat skin surfaces after hypergravity exposure. Following the hypergravity exposure, rats were sacrificed with anesthesia, then perfused and fixed for immunohistochemical examination. The 2G hypergravity elevated the nociceptive threshold up to 2-fold and induced analgesic effects on rats that remained for 2 hours after termination of centrifugation. Expression of Fos-immunoreactive proteins was prominently induced by 2G hypergravity in the arcuate nucleas and the paraventricular nucleus of the hypothalamus. The 15-minute flash exposure to 2G hypergravity induced pain suppression in rats, which might be attributed to change of neuronal activity in rat hypothalamus.

A Biopsychosocial-Spiritual Model of Chronic Pain in Adults with Sickle Cell Disease

PubMed Central

Taylor, Lou Ella V.; Stotts, Nancy A.; Humphreys, Janice; Treadwell, Marsha J.; Miaskowski, Christine

2011-01-01

Chronic pain in adults with sickle cell disease (SCD) is a complex multidimensional experience that includes biological, psychological, sociological, and spiritual factors. To date, three models of pain associated with SCD (i.e., biomedical model; biopsychosocial model for SCD pain; Health Belief Model) are published. The biopsychosocial (BPS) multidimensional approach to chronic pain developed by Turk and Gatchel is a widely used model of chronic pain. However, this model has not been applied to chronic pain associated with SCD. In addition, a spiritual/religious dimension is not included in this model. Because spirituality/religion is central to persons affected by SCD, this dimension needs to be added to any model of chronic pain in adults with SCD. In fact, data from one study suggest that spirituality/religiosity is associated with decreased pain intensity in adults with chronic pain from SCD. A BPS-Spiritual model is proposed for adults with chronic pain from SCD since it embraces the whole person. This model includes the biological, psychological, sociological, and spiritual factors relevant to adults with SCD based on past and current research. The purpose of this paper is to describe an adaptation of Turk and Gatchel’s model of chronic pain for adults with SCD and to summarize research findings that support each component of the revised model (i.e., biological, psychological, sociological, spiritual). The paper concludes with a discussion of implications for the use of this model in research. PMID:24315252

Chronic constriction injury-induced microRNA-146a-5p alleviates neuropathic pain through suppression of IRAK1/TRAF6 signaling pathway.

PubMed

Wang, Zhiyao; Liu, Fan; Wei, Min; Qiu, Yue; Ma, Chao; Shen, Le; Huang, Yuguang

2018-06-09

microRNA-146a-5p (miRNA-146a-5p) is a key molecule in the negative regulation pathway of TLRs and IL-1 receptor (TIR) signaling. Our recent study demonstrated that MyD88-dependent signaling pathway of TIR in the dorsal root ganglion (DRG) and spinal dorsal horn (SDH) plays a role in peripheral nerve injury-induced neuropathic pain. However, it was not clear whether and how miRNA-146a-5p regulates the TIR pathway of DRG and SDH in the development of neuropathic pain. The sciatic nerve chronic constriction injury (CCI) model of rat was used to induce chronic neuropathic pain. The levels and cellular distribution of miRNA-146a-5p were detected with quantitative real-time PCR (qPCR) and fluorescent in situ hybridization (FISH). The RNA level, protein level, and cellular distribution of IRAK1 and TRAF6 that is targeted by miRNA-146a-5p were detected with qPCR, western blot, and immunofluorescent. The pain-related behavioral effect of miRNA-146a-5p was accessed after intrathecal administration. Mechanical stimuli and radiant heat were used to evaluate mechanical allodynia and thermal hyperalgesia. We found that the level of miRNA-146a-5p significantly increased in L4-L6 DRGs and SDH after CCI surgery; meanwhile, the protein level of IRAK1 and TRAF6 in DRGs was significantly increased after CCI. Intrathecal injection of miR146a-5p agomir or miRNA-146a-5p antagomir regulates miRNA-146a-5p level of L4-L6 DRGs and SDH. We found that intrathecal injection of miR146a-5p agomir can alleviate mechanical and thermal hyperalgesia in CCI rats and reverse the upregulation of IRAK1 and TRAF6 of L4-L6 DRGs and SDH induced by CCI. We furthermore found that intrathecal injection of miRNA-146a-5p antagomir can exacerbate the mechanical and thermal pain-related behavior of CCI rats and meanwhile increase IRAK1 and TRAF6 of L4-L6 DRGs and SDH expression even further. miRNA-146a-5p of DRG and SDH can modulate the development of CCI-induced neuropathic pain through inhibition of IRAK1 and TRAF6 in the TIR signaling pathway. Hence, miRNA-146a-5p may serve as a potential therapeutic target for neuropathic pain.

Physiologically-Based Pharmacokinetic (PBPK) Model for the Thyroid Hormones in the Pregnant Rat and Fetus.

EPA Science Inventory

A developmental PBPK model is constructed to quantitatively describe the tissue economy of the thyroid hormones (THs), thyroxine (T4) and triiodothyronine (T3), in the rat. The model is also used to link maternal (THs) to rat fetal tissues via placental transfer. THs are importan...

A BBDR-HPT Axis Model for the Lactating Rat and Nursing Pup: Evaluation of Iodide Deficiency

EPA Science Inventory

A biologically based dose response (BBDR) model for the lactating rat and pup hypothalamic-pituitary-thyroid (HPT) axis is being developed to advance understanding of thyroid hormone disruptions and developmental neurotoxicity (DNT). The model for the lactating rat and pup quanti...

Delayed onset of changes in soma action potential genesis in nociceptive A-beta DRG neurons in vivo in a rat model of osteoarthritis

PubMed Central

Wu, Qi; Henry, James L

2009-01-01

Background Clinical data on osteoarthritis (OA) suggest widespread changes in sensory function that vary during the progression of OA. In previous studies on a surgically-induced animal model of OA we have observed that changes in structure and gene expression follow a variable trajectory over the initial days and weeks. To investigate mechanisms underlying changes in sensory function in this model, the present electrophysiological study compared properties of primary sensory nociceptive neurons at one and two months after model induction with properties in naïve control animals. Pilot data indicated no difference in C- or Aδ-fiber associated neurons and therefore the focus is on Aβ-fiber nociceptive neurons. Results At one month after unilateral derangement of the knee by cutting the anterior cruciate ligament and removing the medial meniscus, the only changes observed in Aβ-fiber dorsal root ganglion (DRG) neurons were in nociceptor-like unresponsive neurons bearing a hump on the repolarization phase; these changes consisted of longer half width, reflecting slowed dynamics of AP genesis, a depolarized Vm and an increased AP amplitude. At two months, changes observed were in Aβ-fiber high threshold mechanoreceptors, which exhibited shorter AP duration at base and half width, shorter rise time and fall time, and faster maximum rising rate/maximum falling rate, reflecting accelerated dynamics of AP genesis. Conclusion These data indicate that Aβ nociceptive neurons undergo significant changes that vary in time and occur later than changes in structure and in nociceptive scores in this surgically induced OA model. Thus, if changes in Aβ-fiber nociceptive neurons in this model reflect a role in OA pain, they may relate to mechanisms underlying pain associated with advanced OA. PMID:19785765

Molecular mechanisms underlying the effects of acupuncture on neuropathic pain.

PubMed

Ju, Ziyong; Cui, Huashun; Guo, Xiaohui; Yang, Huayuan; He, Jinsen; Wang, Ke

2013-09-05

Acupuncture has been used to treat neuropathic pain for a long time, but its mechanisms of action remain unknown. In this study, we observed the effects of electroacupuncture and manual acu-puncture on neuropathic pain and on ephrin-B/EphB signaling in rats models of chronic constriction injury-induced neuropathic pain. The results showed that manual acupuncture and elec-puncture significantly reduced mechanical hypersensitivity following chronic constriction injury, es-pecially electroacupuncture treatment. Real-time PCR results revealed that ephrin-B1/B3 and EphB1/B2 mRNA expression levels were significantly increased in the spinal dorsal horns of chronic constriction injury rats. Electroacupuncture and manual acupuncture suppressed the high sion of ephrin-B1 mRNA, and elevated EphB3/B4 mRNA expression. Electroacupuncture signifi-cantly enhanced the mRNA expression of ephrin-B3 and EphB3/B6 in the dorsal horns of neuro-pathic pain rats. Western blot results revealed that electroacupuncture in particular, and manual acupuncture, significantly up-regulated ephrin-B3 protein levels in rat spinal dorsal horns. The re-sults of this study suggest that acupuncture could activate ephrin-B/EphB signaling in neuropathic pain rats and improve neurological function.

A BBDR-HPT Axis Model for the Pregnant Rat and Fetus: Evaluation of Iodide Deficiency

EPA Science Inventory

A biologically based dose response (BBDR) model for the hypothalamic-pituitarythyroid (HPT) axis for the pregnant rat and fetus is being developed to advance understanding of thyroid hormone disruptions and developmental neurotoxicity (DNT). The model for the pregnant rat and fet...

[Effects of intrathecal injection PI3K antagonist on inflammatory cytokines in spinal cord of bone cancer pain model in rats].

PubMed

Xu, Shijie; Yao, Ming; Xu, Longsheng; Wang, Hanqi; Li, Hongbo; Huang, Bing; Zhou, Xuyan

2016-01-26

To investigate the roles of PI3K in bone cancer pain, the present study was performed to demonstrate the changes of pain-related behavior and the production of IL-1β, IL-6 and TNF-α after intrathecal injection of wortmannin (antagonist of PI3K receptors) in rat model. A total of 44 SD rats were randomly divided into 4 groups, sham group (group S), sham + wormannin group (group SW), cancer group (group A), cancer + wortmannin group (group AW). Group S and group W were injected with 10 μl Hank's solution into left tibial medullary cavity; group A and group AW received injections of Walker 256 mammary cancer cells(10 μl, 2×10 cells/ml) into the same place to establish the model of bone cancer pain. In the meantime intratheacal catheterization was performed between L3 and L4 vertrbra on the rats of every group. Nine days after the operation, group S and group A received a single intratheacal injection of saline (0.9%, 10 μl), group SW and group AW received intratheacal wortmannin 0.5 μg/10 μl. Mechanical withdrawal thresholds were measured on the left hind paw before and every 10 min after intrathecal injection. Then the L4-L6 sections of spinal cord 30 min after injection were collected to determine the expression of IL-1β, IL-6 and TNF-α. At 30 min post-injection, mechanical withdrawal thresholds of groups S, SW, A and AW were (30.1±4.3), (31.7±1.3), (17.2±2.0), (24.8±2.3) g respectively at Day 9 postinoculation (F=22.403, P<0.01), the mechanical withdrawal thresholds in group AW increased obviously versus group A. The expressions of TNF-α in groups S, SW, A and AW were (84.5±6.3), (78.7±12.5), (110.5±7.3), (57.8±4.6) pg/ml. Compared with groups S and W, the expression of TNF-α in group A showed a significant upregulation (F=28.119, P<0.01). An intrathecal injection of wortmannin may alleviate hyperalgesia, and inhibit the up-regulated expression of spinal cord inflammatory cytokines TNF-α in rats with bone cancer. PI3K may be involved in the development of bone cancer pain by regulating the expressions of TNF-α.

Effect of DA-9701 on colorectal distension-induced visceral hypersensitivity in a rat model.

PubMed

Kim, Eun Ran; Min, Byung-Hoon; Lee, Tae Ho; Son, Miwon; Rhee, Poong-Lyul

2014-07-01

DA-9701 is a newly developed drug made from the vegetal extracts of Pharbitidis semen and Co-rydalis tuber. The aim of this study was to evaluate the effect of DA-9701 on colorectal distension (CRD)-induced visceral hypersensitivity in a rat model. Male Sprague-Dawley rats were subjected to neonatal colon irritation (CI) using CRD at 1 week after birth (CI group). At 6 weeks after birth, CRD was applied to these rats with a pressure of 20 to 90 mm Hg, and changes in the mean arterial pressure (MAP) were measured at baseline (i.e., without any drug administration) and after the administration of different doses of DA-9701. In the absence of DA-9701, the MAP changes after CRD were significantly higher in the CI group than in the control group at all applied pressures. In the control group, MAP changes after CRD were not significantly affected by the administration of DA-9701. In the CI group, however, the administration of DA-9701 resulted in a significant decrease in MAP changes after CRD. The administration of DA-9701 at a dose of 1.0 mg/kg produced a more significant decrease in MAP changes than the 0.3 mg/kg dose. The administration of DA-9701 resulted in a significant increase in pain threshold in rats with CRD-induced visceral hypersensitivity.

Running Exercise Alleviates Pain and Promotes Cell Proliferation in a Rat Model of Intervertebral Disc Degeneration

PubMed Central

Luan, Shuo; Wan, Qing; Luo, Haijie; Li, Xiao; Ke, Songjian; Lin, Caina; Wu, Yuanyuan; Wu, Shaoling; Ma, Chao

2015-01-01

Chronic low back pain accompanied by intervertebral disk degeneration is a common musculoskeletal disorder. Physical exercise, which is clinically recommended by international guidelines, has proven to be effective for degenerative disc disease (DDD) patients. However, the mechanism underlying the analgesic effects of physical exercise on DDD remains largely unclear. The results of the present study showed that mechanical withdrawal thresholds of bilateral hindpaw were significantly decreased beginning on day three after intradiscal complete Freund’s adjuvant (CFA) injection and daily running exercise remarkably reduced allodynia in the CFA exercise group beginning at day 28 compared to the spontaneous recovery group (controls). The hindpaw withdrawal thresholds of the exercise group returned nearly to baseline at the end of experiment, but severe pain persisted in the control group. Histological examinations performed on day 70 revealed that running exercise restored the degenerative discs and increased the cell densities of the annulus fibrosus (AF) and nucleus pulposus (NP). Furthermore, immunofluorescence labeling revealed significantly higher numbers of 5-bromo-2-deoxyuridine (BrdU)-positive cells in the exercise group on days 28, 42, 56 and 70, which indicated more rapid proliferation compared to the control at the corresponding time points. Taken together, these results suggest that running exercise might alleviate the mechanical allodynia induced by intradiscal CFA injection via disc repair and cell proliferation, which provides new evidence for future clinical use. PMID:25607736

Effect of DA-9701 on Colorectal Distension-Induced Visceral Hypersensitivity in a Rat Model

PubMed Central

Kim, Eun Ran; Min, Byung-Hoon; Lee, Tae Ho; Son, Miwon; Rhee, Poong-Lyul

2014-01-01

Background/Aims DA-9701 is a newly developed drug made from the vegetal extracts of Pharbitidis semen and Co-rydalis tuber. The aim of this study was to evaluate the effect of DA-9701 on colorectal distension (CRD)-induced visceral hypersensitivity in a rat model. Methods Male Sprague-Dawley rats were subjected to neonatal colon irritation (CI) using CRD at 1 week after birth (CI group). At 6 weeks after birth, CRD was applied to these rats with a pressure of 20 to 90 mm Hg, and changes in the mean arterial pressure (MAP) were measured at baseline (i.e., without any drug administration) and after the administration of different doses of DA-9701. Results In the absence of DA-9701, the MAP changes after CRD were significantly higher in the CI group than in the control group at all applied pressures. In the control group, MAP changes after CRD were not significantly affected by the administration of DA-9701. In the CI group, however, the administration of DA-9701 resulted in a significant decrease in MAP changes after CRD. The administration of DA-9701 at a dose of 1.0 mg/kg produced a more significant decrease in MAP changes than the 0.3 mg/kg dose. Conclusions The administration of DA-9701 resulted in a significant increase in pain threshold in rats with CRD-induced visceral hypersensitivity. PMID:25071903

Development of microparticles for oral administration of the non-conventional radical scavenger IAC and testing in an inflammatory rat model.

PubMed

Passerini, Nadia; Albertini, Beatrice; Sabatino, Marcello Di; Corace, Giuseppe; Luppi, Barbara; Canistro, Donatella; Vivarelli, Fabio; Cirillo, Silvia; Soleti, Antonio; Merizzi, Giulia; Paolini, Moreno

2016-10-15

The bis (1-hydroxy-2,2,6,6-tetramethyl-4-piperidinyl)-decandioate (IAC), is an innovative non- radical scavenger used with success in numerous disease models such as inflammation, neurological disorders, hepatitis and diabetes. The pharmacological treatments have been performed by the intraperitoneal route of administration, representing to date, the main limit for the drug use. The aim of this study was to develop a delivery system that allows the oral administration of IAC while maintaining its therapeutic efficacy. Solid Lipid Microparticles (SLMs) containing a theoretical 18% (w/w) of IAC have been produced by the spray congealing technology; three formulations have been tested (A, B and C) using different low melting point carriers (stearic acid, Compritol(®) HD5ATO and carnauba wax) alone or in combination. All IAC loaded SLMs exhibited a spherical shape, encapsulation efficiency higher than 94% and particle size suitable for the oral route. Administered per os at different dosages in an inflammation rat model, all SLMs demonstrated their efficacy in reducing oedema and alleviating pain, compared to the gold standards Indomethacin and Paracetamol. These results suggested that the SLMs are an efficacious delivery system for the oral administration of IAC, potentially useful for the treatment of others diseases related to an over production of free radicals. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of human umbilical cord mesenchymal stem cells transplantation on nerve fibers of a rat model of endometriosis.

PubMed

Chen, Yan; Li, Dong; Zhang, Zhe; Takushige, Natsuko; Kong, Bei-Hua; Wang, Guo-Yun

2015-01-01

Endometriosis is a common, benign, oestrogen-dependent, chronic gynaecological disorder associated with pelvic pain and infertility. Some researchers have identified nerve fibers in endometriotic lesions in women with endometriosis. Mesenchymal stem cells (MSCs) have attracted interest for their possible use for both cell and gene therapies because of their capacity for self-renewal and multipotentiality of differentiation. We investigated how human umbilical cord-MSCs (hUC-MSCs) could affect nerve fibers density in endometriosis. In this experimental study, hUC-MSCs were isolated from fresh human umbilical cord, characterized by flow cytometry, and then transplanted into surgically induced endometriosis in a rat model. Ectopic endometrial implants were collected four weeks later. The specimens were sectioned and stained immunohistochemically with antibodies against neurofilament (NF), nerve growth factor (NGF), NGF receptor p75 (NGFRp75), tyrosine kinase receptor-A (Trk-A), calcitonin gene-related peptide (CGRP) and substance P (SP) to compare the presence of different types of nerve fibers between the treatment group with the transplantation of hUC-MSCs and the control group without the transplantation of hUC-MSCs. There were significantly less nerve fibers stained with specific markers we used in the treatment group than in the control group (p<0.05). MSC from human umbilical cord reduced nerve fiber density in the treatment group with the transplantation of hUC-MSCs.

Posttraumatic stress symptoms and the diathesis-stress model of chronic pain and disability in patients undergoing major surgery.

PubMed

Martin, Andrea L; Halket, Eileen; Asmundson, Gordon J G; Flora, David B; Katz, Joel

2010-01-01

To (1) use structural equation modeling (SEM) to examine relationships proposed in Turk's diathesis-stress model of chronic pain and disability as well as (2) investigate what role, if any, posttraumatic stress symptoms (PTSS) play in predicting pain disability, relative to some of the other factors in the model. The study sample consisted of 208 patients scheduled for general surgery, 21 to 60 years of age (mean age=47.18 y, SD=9.72 y), who reported experiencing persistent pain for an average of 5.56 years (SD=7.90 y). At their preadmission hospital visit, patients completed the Anxiety Sensitivity Index, Pain Catastrophizing Scale, Pain Anxiety Symptoms Scale-20, Pain Disability Index, posttraumatic stress disorder Checklist, and rated the average intensity of their pain (0 to 10 numeric rating scale). SEM was used to test a model of chronic pain disability and to explore potential relationships between PTSS and factors in the diathesis-stress model. SEM results provided support for a model in which anxiety sensitivity predicted fear of pain and catastrophizing, fear of pain predicted escape/avoidance, and escape/avoidance predicted pain disability. Results also provided support for a feedback loop between disability and fear of pain. SEM analyses provided preliminary support for the inclusion of PTSS in the diathesis-stress model, with PTSS accounting for a significant proportion of the variance in pain disability. Results provide empirical support for aspects of Turk's diathesis-stress model in a sample of patients with persistent pain. Findings also offer preliminary support for the role of PTSS in fear-avoidance models of chronic pain.

Spinal translocator protein (TSPO) modulates pain behavior in rats with CFA-induced monoarthritis.

PubMed

Hernstadt, Hayley; Wang, Shuxing; Lim, Grewo; Mao, Jianren

2009-08-25

Translocator protein 18 kDa (TSPO), previously known as the peripheral benzodiazepine receptor (PBR), is predominantly located in the mitochondrial outer membrane and plays an important role in steroidogenesis, immunomodulation, cell survival and proliferation. Previous studies have shown an increased expression of TSPO centrally in neuropathology, as well as in injured nerves. TSPO has also been implicated in modulation of nociception. In the present study, we examined the hypothesis that TSPO is involved in the initiation and maintenance of inflammatory pain using a rat model of Complete Freund's Adjuvant (CFA)-induced monoarthritis of the tibio-tarsal joint. Immunohistochemistry was performed using Iba-1 (microglia), NeuN (neurons), anti-Glial Fibrillary Acidic Protein, GFAP (astrocytes) and anti-PBR (TSPO) on Days 1, 7 and 14 after CFA-induced arthritis. Rats with CFA-induced monoarthritis showed mechanical allodynia and thermal hyperalgesia on the ipsilateral hindpaw, which correlated with the increased TSPO expression in ipsilateral laminae I-II on all experimental days. Iba-1 expression in the ipsilateral dorsal horn was also increased on Days 7 and 14. Moreover, TSPO was colocalized with Iba-1, GFAP and NeuN within the spinal cord dorsal horn. The TSPO agonist Ro5-4864, given intrathecally, dose-dependently retarded or prevented the development of mechanical allodynia and thermal hyperalgesia in rats with CFA-induced monoarthritis. These findings provide evidence that spinal TSPO is involved in the development and maintenance of inflammatory pain behaviors in rats. Thus, spinal TSPO may present a central target as a complementary therapy to reduce inflammatory pain.

SPINAL TRANSLOCATOR PROTEIN (TSPO) MODULATES PAIN BEHAVIOR IN RATS WITH CFA-INDUCED MONOARTHRITIS

PubMed Central

Hernstadt, Hayley; Wang, Shuxing; Lim, Grewo; Mao, Jianren

2009-01-01

Translocator protein 18kDa (TSPO), previously known as the peripheral benzodiazepine receptor (PBR), is predominantly located in the mitochondrial outer membrane and plays an important role in steroidogenesis, immunomodulation, cell survival and proliferation. Previous studies have shown an increased expression of TSPO centrally in neuropathology, as well as in injured nerves. TSPO has also been implicated in modulation of nociception. In the present study, we examined the hypothesis that TSPO is involved in the initiation and maintenance of inflammatory pain using a rat model of Complete Freund’s Adjuvant (CFA)-induced monoarthritis of the tibio-tarsal joint. Immunohistochemistry was performed using Iba-1 (microglia), NeuN (neurons), anti-Glial Fibrillary Acidic Protein, GFAP (astrocytes) and anti-PBR (TSPO) on day 1, 7 and 14 after CFA-induced arthritis. Rats with CFA-induced monoarthritis showed mechanical allodynia and thermal hyperalgesia on the ipsilateral hindpaw, which correlated with the increased TSPO expression in ipsilateral lamina I-II on all experimental days. Iba-1 expression in the ipsilateral dorsal horn was also increased on Day 7 and 14. Moreover, TSPO was co-localized with Iba-1, GFAP and NeuN within the spinal cord dorsal horn. The TSPO agonist Ro5-4864, given intrathecally, dose-dependently retarded or prevented the development of mechanical allodynia and thermal hyperalgesia in rats with CFA-induced monoarthritis. These findings provide evidence that spinal TSPO is involved in the development and maintenance of inflammatory pain behaviors in rats. Thus, spinal TSPO may present a central target as a complementary therapy to reduce inflammatory pain. PMID:19555675

Inhibition of acid-sensing ion channels by levo-tetrahydropalmatine in rat dorsal root ganglion neurons.

PubMed

Liu, Ting-Ting; Qu, Zu-Wei; Qiu, Chun-Yu; Qiu, Fang; Ren, Cuixia; Gan, Xiong; Peng, Fang; Hu, Wang-Ping

2015-02-01

Levo-tetrahydropalmatine (l-THP), a main bioactive Chinese herbal constituent from the genera Stephania and Corydalis, has been in use in clinical practice for years in China as a traditional analgesic agent. However, the mechanism underlying the analgesic action of l-THP is poorly understood. This study shows that l-THP can exert an inhibitory effect on the functional activity of native acid-sensing ion channels (ASICs), which are believed to mediate pain caused by extracellular acidification. l-THP dose dependently decreased the amplitude of proton-gated currents mediated by ASICs in rat dorsal root ganglion (DRG) neurons. l-THP shifted the proton concentration-response curve downward, with a decrease of 40.93% ± 8.45% in the maximum current response to protons, with no significant change in the pH0.5 value. Moreover, l-THP can alter the membrane excitability of rat DRG neurons to acid stimuli. It significantly decreased the number of action potentials and the amplitude of the depolarization induced by an extracellular pH drop. Finally, peripherally administered l-THP inhibited the nociceptive response to intraplantar injection of acetic acid in rats. These results indicate that l-THP can inhibit the functional activity of ASICs in dissociated primary sensory neurons and relieve acidosis-evoked pain in vivo, which for the first time provides a novel peripheral mechanism underlying the analgesic action of l-THP. © 2014 Wiley Periodicals, Inc.

Distinct Expression of Phenotypic Markers in Placodes- and Neural Crest-Derived Afferent Neurons Innervating the Rat Stomach.

PubMed

Trancikova, Alzbeta; Kovacova, Eva; Ru, Fei; Varga, Kristian; Brozmanova, Mariana; Tatar, Milos; Kollarik, Marian

2018-02-01

Visceral pain is initiated by activation of primary afferent neurons among which the capsaicin-sensitive (TRPV1-positive) neurons play an important role. The stomach is a common source of visceral pain. Similar to other organs, the stomach receives dual spinal and vagal afferent innervation. Developmentally, spinal dorsal root ganglia (DRG) and vagal jugular neurons originate from embryonic neural crest and vagal nodose neurons originate from placodes. In thoracic organs the neural crest- and placodes-derived TRPV1-positive neurons have distinct phenotypes differing in activation profile, neurotrophic regulation and reflex responses. It is unknown to whether such distinction exists in the stomach. We hypothesized that gastric neural crest- and placodes-derived TRPV1-positive neurons express phenotypic markers indicative of placodes and neural crest phenotypes. Gastric DRG and vagal neurons were retrogradely traced by DiI injected into the rat stomach wall. Single-cell RT-PCR was performed on traced gastric neurons. Retrograde tracing demonstrated that vagal gastric neurons locate exclusively into the nodose portion of the rat jugular/petrosal/nodose complex. Gastric DRG TRPV1-positive neurons preferentially expressed markers PPT-A, TrkA and GFRα 3 typical for neural crest-derived TRPV1-positive visceral neurons. In contrast, gastric nodose TRPV1-positive neurons preferentially expressed markers P2X 2 and TrkB typical for placodes-derived TRPV1-positive visceral neurons. Differential expression of neural crest and placodes markers was less pronounced in TRPV1-negative DRG and nodose populations. There are phenotypic distinctions between the neural crest-derived DRG and placodes-derived vagal nodose TRPV1-positive neurons innervating the rat stomach that are similar to those described in thoracic organs.

Catechol-O-methlytransferase inhibition alters pain and anxiety-related volitional behaviors through activation of β-adrenergic receptors in the rat

PubMed Central

Kline, R. H.; Exposto, F. G.; O’Buckley, S. C.; Westlund, K. N.; Nackley, A. G.

2015-01-01

Reduced catechol-O-methyltransferase (COMT) activity resulting from genetic variation or pharmacological depletion results in enhanced pain perception in humans and nociceptive behaviors in animals. Using phasic mechanical and thermal reflex tests (e.g. von Frey, Hargreaves), recent studies show that acute COMT-dependent pain in rats is mediated by β-adrenergic receptors (βARs). In order to more closely mimic the characteristics of human chronic pain conditions associated with prolonged reductions in COMT, the present study sought to determine volitional pain-related and anxiety-like behavioral responses following sustained as well as acute COMT inhibition using an operant 10–45°C thermal place preference task and a light/dark preference test. In addition, we sought to evaluate the effects of sustained COMT inhibition on generalized body pain by measuring tactile sensory thresholds of the abdominal region. Results demonstrated that acute and sustained administration of the COMT inhibitor OR486 increased pain behavior in response to thermal heat. Further, sustained administration of OR486 increased anxiety behavior in response to bright light, as well as abdominal mechanosensation. Finally, all pain-related behaviors were blocked by the non-selective βAR antagonist propranolol. Collectively, these findings provide the first evidence that stimulation of ARs following acute or chronic COMT inhibition drives cognitive-affective behaviors associated with heightened pain that affects multiple body sites. PMID:25659347

Quercetin attenuates mitochondrial dysfunction and biogenesis via upregulated AMPK/SIRT1 signaling pathway in OA rats.

PubMed

Qiu, Linan; Luo, Yuju; Chen, Xiaojuan

2018-07-01

Despite the severity of osteoarthritis (OA), current medical therapy strategies for OA aim at symptom control and pain reduction, as there is no ideal drug for effective OA treatment. OA rat model was used to explore the therapeutic function of quercetin on remission of OA, by determining the reactive oxygen species (ROS) levels, mitochondrial function and extracellular matrix integrity. Quercetin could attenuate ROS generation and augment the glutathione (GSH) and glutathione peroxidase (GPx) expression levels in OA rat. Quercetin not only enhanced mitochondrial membrane potential, oxygen consumption, adenosine triphosphate (ATP) levels in mitochondria, but also increased the mitochondrial copy number. Furthermore, the interlukin (IL)-1β-induced accumulation of nitric oxide (NO), matrixmetalloproteinase (MMP)-3) and MMP-13 could be suppressed by quercetin. Finally, we confirmed that the therapeutic properties of quercetin on OA might function through the adenosine monophosphate-activated protein kinase/sirtuin 1 (AMPK/SIRT1) signaling pathway. In summary, quercetin could alleviate OA through attenuating the ROS levels, reversing the mitochondrial dysfunction and keeping the integrality of extracellular matrix of joint cartilage. The underlying mechanism might involve the regulation of AMPK/SIRT1 signaling pathway. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Different patterns of morphological changes in the hippocampus and dentate gyrus accompany the differential expression of disability following nerve injury.

PubMed

Kalman, Eszter; Keay, Kevin A

2014-12-01

Physical and psychological trauma which results in mood disorders and the disruption of complex behaviours is associated with reductions in hippocampal volume. Clinical evaluation of neuropathic pain reveals mood and behavioural change in a significant number of patients. A rat model of neuropathic injury results in complex behavioural changes in a subpopulation (~30%) of injured rats; these changes are co-morbid with a range of other 'disabilities'. The specific objective of this study was to determine in rats the morphology of the hippocampus and dentate gyrus in individuals with and without complex behavioural disruptions following a constriction injury of the sciatic nerve, and to determine whether rats that develop disabilities following nerve injury have a reduced hippocampal volume compared with injured rats with no disabilities. The social behaviours of nerve-injured rats were evaluated before and after nerve injury. The morphology of the hippocampus of rats with and without behavioural disruptions was compared in serial histological sections. Single-housing and repeated social-interaction testing had no effect on the morphology of either the hippocampus or the dentate gyrus. Rats with transient or ongoing disability identified by behavioural disruption following sciatic nerve injury, show bilateral reductions in hippocampal volume, and lateralised reduction in the dentate gyrus (left side). Disabled rats display a combination of behavioural and physiological changes, which resemble many of the criteria used clinically to diagnose mood disorders. They also show reductions in the volume of the hippocampus similar to people with clinically diagnosed mood disorders. The sciatic nerve injury model reveals a similarity to the human neuropathic pain presentation presenting an anatomically specific focus for the investigation of the neural mechanisms underpinning the co-morbidity of chronic pain and mood disorder. © 2014 Anatomical Society.

In vitro characterization and in vivo analgesic and anti-allodynic activity of PLGA-bupivacaine nanoparticles

NASA Astrophysics Data System (ADS)

Garcia, Xavier; Escribano, Elvira; Domenech, Josep; Queralt, Josep; Freixes, Joan

2011-05-01

An injectable controlled release system containing local anesthetics able to provide long-lasting analgesia in nociceptive and neuropathic pain could have a marked impact in pain management. In order to address this issue, bupivacaine, a widely used local anesthetic, has been nanoencapsulated using poly(lactic-co-glycolic acid) from an oil-in-water emulsion by the solvent evaporation technique. Nanoparticles were evaluated in vitro studying their drug release mechanism by fitting different model equations, and in vivo by testing its analgesic and anti-allodynic activity in front of heat-induced nociceptive pain and sciatic nerve chronic constriction injury in rats, respectively. The particle size of the PLGA nanoparticles obtained was of 453 ± 29 nm, the encapsulation efficiency, drug loading, and burst effect at 30 min were 82.10 ± 0.001, 45.06 ± 0.001, and 4.6 ± 0.6%, respectively. A prolonged release of the drug in comparison to bupivacaine solution was seen. The mean dissolution time (MDT) obtained for nanoparticles was relatively long (9.44 ± 0.56 h) proving the sustained release process, while the dissolution efficiency (DE) (84.10 ± 1.01%) was similar to the maximum percentage of drug released. Korsmeyer-Peppas was the best model that fitted our release data. A non-Fickian mechanism was concluded to be involved in the release of bupivacaine from the nanoparticles, taking into account the value of the diffusional exponent obtained ( n = 0.95). After local infiltration in the rat, the antinociceptive and anti-allodynic activity of the nanoencapsulated bupivacaine was longer lasting than that of bupivacaine solution. An increase in the values of the area under the curve (AUC) of the antinociceptive and anti-allodynic effect versus time of 67 and 36%, respectively, was observed when the drug was encapsulated.

[Effect of electroacupuncture on phosphorylation of NR2B at Tyr 1742 site in the spinal dorsal horn of CFA rats].

PubMed

Liang, Yi; Fang, Jian-Qiao; Fang, Jun-Fan; Du, Jun-Ying; Qiu, Yu-Jie; Liu, Jin

2013-10-01

To observe the effect of electroacupuncture (EA) on phosphorylation of spinal NR2B at Tyr 1742 site in complete Freund's adjuvant (CFA) induced inflammatory pain rats. METHods Forty male Sprague Dawley rats were randomly divided into normal group (N group, n = 10), the model group (CFA group, n = 15), and the EA group (n = 15). The inflammatory pain model was established by subcutaneous injecting CFA (0.1 mL per rat) into the right hind paw. Paw withdrawal thresholds (PWTs) were measured before CFA injection (as the base), as well as at 24 h, 25 h, 3rd day, and 7th day after CFA injection. Phosphorylation of NR2B at Tyr 1742 site in the ispilateral spinal dorsal horn at the 3rd day post-injection were detected using immunohistochemical assay. PWTs in the CFA group were significantly lower than those of the N group at every detective time point post-injection (P < 0.01). PWTs were obviously lower in the EA group than in the N group at 24 h post-injection (P < 0.01). It showed increasing tendency, markedly higher than those of the CFA group at 25 h and 3rd day post-injection (P < 0.01). Compared with the N group, the ratio of p-NR2B positive cells in the ispilateral spinal dorsal horn of rats in the CFA group was up-regulated. Compared with the CFA group, the ratio of p-NR2B positive cells in the ispilateral spinal dorsal horn of rats showed a decreasing tendency in the EA group. EA might effectively inhibit CFA-induced inflammatory pain possibly associated with down-regulating phosphorylation of NR2B at Tyr 1742 site in the ispilateral spinal dorsal horn.

Chimeric Agents Derived from the Functionalized Amino Acid, Lacosamide, and the α-Aminoamide, Safinamide: Evaluation of Their Inhibitory Actions on Voltage-Gated Sodium Channels, and Antiseizure and Antinociception Activities and Comparison with Lacosamide and Safinamide

PubMed Central

2015-01-01

The functionalized amino acid, lacosamide ((R)-2), and the α-aminoamide, safinamide ((S)-3), are neurological agents that have been extensively investigated and have displayed potent anticonvulsant activities in seizure models. Both compounds have been reported to modulate voltage-gated sodium channel activity. We have prepared a series of chimeric compounds, (R)-7–(R)-10, by merging key structural units in these two clinical agents, and then compared their activities with (R)-2 and (S)-3. Compounds were assessed for their ability to alter sodium channel kinetics for inactivation, frequency (use)-dependence, and steady-state activation and fast inactivation. We report that chimeric compounds (R)-7–(R)-10 in catecholamine A-differentiated (CAD) cells and embryonic rat cortical neurons robustly enhanced sodium channel inactivation at concentrations far lower than those required for (R)-2 and (S)-3, and that (R)-9 and (R)-10, unlike (R)-2 and (S)-3, produce sodium channel frequency (use)-dependence at low micromolar concentrations. We further show that (R)-7–(R)-10 displayed excellent anticonvulsant activities and pain-attenuating properties in the animal formalin model. Of these compounds, only (R)-7 reversed mechanical hypersensitivity in the tibial-nerve injury model for neuropathic pain in rats. PMID:25418676

Hyperexcitable neurons and altered non-neuronal cells in the compressed spinal ganglion

PubMed Central

LaMotte, Robert H.; Chao, MA

2009-01-01

The cell body or soma in the dosal root ganglion (DRG) is normally excitable and this excitability can increase and persist after an injury of peripheral sensory neurons. In a rat model of radicular pain, an intraforaminal implantation of a rod that chronically compressed the lumbar DRG (“CCD” model) resulted in neuronal somal hyperexcitability and spontaneous activity that was accompanied by hyperalgesia in the ipsilateral hind paw. By the 5th day after onset of CCD, there was a novel upregulation in neuronal expression of the chemokine, monocyte chemoattractant protein-1 (MCP-1 or CCL2) and also its receptor, CCR2. The neurons developed, in response to topically applied MCP-1, an excitatory response that they normally do not have. CCD also activated non-neuronal cells including, for example, the endothelial cells as evidenced by angiogenesis in the form of an increased number of capillaries in the DRG after 7 days. A working hypothesis is that the CCD induced changes in neurons and non-neuronal cells that may act together to promote the survival of the injured tissue. The release of ligands such as CCL2, in addition to possibly activating nociceptive neurons (maintaining the pain), may also act to preserve injured cells in the face of ischemia and hypoxia, for example, by promoting angiogenesis. Thus, somal hyperexcitability, as often said of inflammation, may represent a double edged sword. PMID:18958366

Acetaminophen and non-steroidal anti-inflammatory drugs interact with morphine and tramadol analgesia for the treatment of neuropathic pain in rats.

PubMed

Shinozaki, Tomonari; Yamada, Toshihiko; Nonaka, Takahiro; Yamamoto, Tatsuo

2015-06-01

Although non-steroidal anti-inflammatory drugs and acetaminophen have no proven efficacy against neuropathic pain, they are frequently prescribed for neuropathic pain patients. We examined whether the combination of opioids (tramadol and morphine) with indomethacin or acetaminophen produce favorable effects on neuropathic pain and compared the efficacy for neuropathic pain with that for inflammatory pain. The carrageenan model was used as the inflammatory pain model while the tibial neuroma transposition (TNT) model was used as the neuropathic pain model. The tibial nerve is transected in the TNT model, with the tibial nerve stump then transpositioned to the lateral aspect of the hindlimb. Neuropathic pain (mechanical allodynia and neuroma pain) is observed after TNT injury. Drugs were administered orally. In the carrageenan model, all drugs produced anti-allodynic effects and all drug combinations, but not tramadol + indomethacin combination, produced synergistic anti-allodynic effects. In the TNT model, tramadol and morphine, but not acetaminophen and indomethacin, produced anti-neuropathic pain effects. In the combination, with the exception of morphine + acetaminophen combination, both acetaminophen and indomethacin reduced the 50% effective dose (ED50) of tramadol and morphine as compared with the ED50s for the single drug study in the TNT model. The ED50s of tramadol and morphine in the carrageenan combination test were not statistically significantly different from the ED50s in the TNT model combination study. The combination of opioids with indomethacin or acetaminophen produced a synergistic analgesic effect both in inflammatory and neuropathic pain with some exceptions. The efficacy of these combinations for neuropathic pain was not different from that for inflammatory pain.

Lacosamide inhibits calcitonin gene-related peptide production and release at trigeminal level in the rat.

PubMed

Greco, M C; Capuano, A; Navarra, P; Tringali, G

2016-07-01

Several classes of drugs are effective in prevention and treatment of migraine, although they may differ among each other in their mode of action and in indications. One such class is represented by antiepileptics. Lacosamide is an approved antiepileptic drug that also shows antinociceptive activity in animal models, including analgesic efficacy in central and trigeminal pain. Calcitonin gene-related peptide (CGRP) is considered the main neuro-mediator of trigeminal signalling, playing an essential role in headache, migraine in particular. Here, we investigated the effects of lacosamide on CGRP signalling in both in vitro and ex vivo/vitro models in the rat. We assessed: (1) CGRP released from brainstem explants at baseline or after pharmacological challenges; and (2) CGRP levels in brain areas after in vivo treatments with test drugs. We found that: (1) lacosamide inhibits CGRP release from brainstem explants under basal conditions as well as after stimulation by 56 mM KCl, 10 μM veratridine or 1 μM capsaicin; and (2) the i.p. administration of nitroglycerine produces an increase in CGRP levels in the brainstem and trigeminal ganglia, which is inhibited by a pre-treatment with lacosamide. These findings provide preliminary evidence suggesting that lacosamide is able to control pain transmission under conditions affecting the trigeminal system, such as migraine. © 2015 European Pain Federation - EFIC®

[Expression of hemokinin-1 in rat spinal cord after peripheral inflammation].

PubMed

Ando, Yuko

2009-06-01

Hemokinin-1 (HK-1) is a novel peptide described as a member of the tachykinin family. Substance P (SP), a representative member of the tachykinin family, has been well characterized and is thought to play a part in inflammation and pain. While several studies indicate that HK-1 is involved in inflammation and pain, the biological functions of HK-1 are not fully understood. In the present study we investigated the expression of HK-1 mRNA (TAC4) and SP mRNA (TAC1) in the dorsal spinal cord of rat after inducing peripheral inflammation by administering complete Freund's adjuvant (CFA) into the hind paw, using real-time RT-PCR. In the behavioral studies, the thresholds of withdrawal response of the hind paw to thermal stimulation significantly decreased on the ipsilateral side, but not on the contralateral side, 6 hours after CFA injection and thermal hyperalgesia persisted until 4 days after CFA injection. The level of HK-1 mRNA expression significantly increased on the bilateral sides of the dorsal spinal cord 6 hours after CFA injection and returned to the base level 1 day after injection. On the other hand, the level of SP mRNA expression did not change in the spinal cord 6 hours and 1 day after CFA injection. These results indicate that HK-1 may contribute to inflammatory pain, in the early phase, in a different manner from SP.

Strain-Specific Induction of Experimental Autoimmune Prostatitis (EAP) in Mice

PubMed Central

Jackson, Christopher M.; Flies, Dallas B.; Mosse, Claudio A.; Parwani, Anil; Hipkiss, Edward L.; Drake, Charles G.

2013-01-01

BACKGROUND Prostatitis, a clinical syndrome characterized by pelvic pain and inflammation, is common in adult males. Although several induced and spontaneous murine models of prostatitis have been explored, the role of genetic background on induction has not been well-defined. METHODS Using a standard methodology for the induction of experimental autoimmune prostatitis (EAP), we investigated both acute and chronic inflammation on several murine genetic backgrounds. RESULTS In our colony, nonobese diabetic (NOD) mice evinced spontaneous prostatitis that was not augmented by immunization with rat prostate extract (RPE). In contrast, the standard laboratory strain Balb/c developed chronic inflammation in response to RPE immunization. Development of EAP in other strains was variable. CONCLUSIONS These data suggest that Balb/c mice injected with RPE may provide a useful model for chronic prostatic inflammation. PMID:23129407

Physiologically based kinetic modeling of bioactivation and detoxification of the alkenylbenzene methyleugenol in human as compared with rat

DOE Office of Scientific and Technical Information (OSTI.GOV)

Al-Subeihi, Ala' A.A., E-mail: ala.alsubeihi@wur.nl; BEN-HAYYAN-Aqaba International Laboratories, Aqaba Special Economic Zone Authority; Spenkelink, Bert

2012-05-01

This study defines a physiologically based kinetic (PBK) model for methyleugenol (ME) in human based on in vitro and in silico derived parameters. With the model obtained, bioactivation and detoxification of methyleugenol (ME) at different doses levels could be investigated. The outcomes of the current model were compared with those of a previously developed PBK model for methyleugenol (ME) in male rat. The results obtained reveal that formation of 1′-hydroxymethyleugenol glucuronide (1′HMEG), a major metabolic pathway in male rat liver, appears to represent a minor metabolic pathway in human liver whereas in human liver a significantly higher formation of 1′-oxomethyleugenolmore » (1′OME) compared with male rat liver is observed. Furthermore, formation of 1′-sulfooxymethyleugenol (1′HMES), which readily undergoes desulfonation to a reactive carbonium ion (CA) that can form DNA or protein adducts (DA), is predicted to be the same in the liver of both human and male rat at oral doses of 0.0034 and 300 mg/kg bw. Altogether despite a significant difference in especially the metabolic pathways of the proximate carcinogenic metabolite 1′-hydroxymethyleugenol (1′HME) between human and male rat, the influence of species differences on the ultimate overall bioactivation of methyleugenol (ME) to 1′-sulfooxymethyleugenol (1′HMES) appears to be negligible. Moreover, the PBK model predicted the formation of 1′-sulfooxymethyleugenol (1′HMES) in the liver of human and rat to be linear from doses as high as the benchmark dose (BMD{sub 10}) down to as low as the virtual safe dose (VSD). This study shows that kinetic data do not provide a reason to argue against linear extrapolation from the rat tumor data to the human situation. -- Highlights: ► A PBK model is made for bioactivation and detoxification of methyleugenol in human. ► Comparison to the PBK model in male rat revealed species differences. ► PBK results support linear extrapolation from high to low dose and from rat to human.« less

Physical exercise prevents motor disorders and striatal oxidative imbalance after cerebral ischemia-reperfusion.

PubMed

Sosa, P M; Schimidt, H L; Altermann, C; Vieira, A S; Cibin, F W S; Carpes, F P; Mello-Carpes, P B

2015-09-01

Stroke is the third most common cause of death worldwide, and most stroke survivors present some functional impairment. We assessed the striatal oxidative balance and motor alterations resulting from stroke in a rat model to investigate the neuroprotective role of physical exercise. Forty male Wistar rats were assigned to 4 groups: a) control, b) ischemia, c) physical exercise, and d) physical exercise and ischemia. Physical exercise was conducted using a treadmill for 8 weeks. Ischemia-reperfusion surgery involved transient bilateral occlusion of the common carotid arteries for 30 min. Neuromotor performance (open-field and rotarod performance tests) and pain sensitivity were evaluated beginning at 24 h after the surgery. Rats were euthanized and the corpora striata was removed for assay of reactive oxygen species, lipoperoxidation activity, and antioxidant markers. Ischemia-reperfusion caused changes in motor activity. The ischemia-induced alterations observed in the open-field test were fully reversed, and those observed in the rotarod test were partially reversed, by physical exercise. Pain sensitivity was similar among all groups. Levels of reactive oxygen species and lipoperoxidation increased after ischemia; physical exercise decreased reactive oxygen species levels. None of the treatments altered the levels of antioxidant markers. In summary, ischemia-reperfusion resulted in motor impairment and altered striatal oxidative balance in this animal model, but those changes were moderated by physical exercise.

Chimeric agents derived from the functionalized amino acid, lacosamide, and the α-aminoamide, safinamide: evaluation of their inhibitory actions on voltage-gated sodium channels, and antiseizure and antinociception activities and comparison with lacosamide and safinamide.

PubMed

Park, Ki Duk; Yang, Xiao-Fang; Dustrude, Erik T; Wang, Yuying; Ripsch, Matthew S; White, Fletcher A; Khanna, Rajesh; Kohn, Harold

2015-02-18

The functionalized amino acid, lacosamide ((R)-2), and the α-aminoamide, safinamide ((S)-3), are neurological agents that have been extensively investigated and have displayed potent anticonvulsant activities in seizure models. Both compounds have been reported to modulate voltage-gated sodium channel activity. We have prepared a series of chimeric compounds, (R)-7-(R)-10, by merging key structural units in these two clinical agents, and then compared their activities with (R)-2 and (S)-3. Compounds were assessed for their ability to alter sodium channel kinetics for inactivation, frequency (use)-dependence, and steady-state activation and fast inactivation. We report that chimeric compounds (R)-7-(R)-10 in catecholamine A-differentiated (CAD) cells and embryonic rat cortical neurons robustly enhanced sodium channel inactivation at concentrations far lower than those required for (R)-2 and (S)-3, and that (R)-9 and (R)-10, unlike (R)-2 and (S)-3, produce sodium channel frequency (use)-dependence at low micromolar concentrations. We further show that (R)-7-(R)-10 displayed excellent anticonvulsant activities and pain-attenuating properties in the animal formalin model. Of these compounds, only (R)-7 reversed mechanical hypersensitivity in the tibial-nerve injury model for neuropathic pain in rats.

Rat Genome and Model Resources.

PubMed

Shimoyama, Mary; Smith, Jennifer R; Bryda, Elizabeth; Kuramoto, Takashi; Saba, Laura; Dwinell, Melinda

2017-07-01

Rats remain a major model for studying disease mechanisms and discovery, validation, and testing of new compounds to improve human health. The rat's value continues to grow as indicated by the more than 1.4 million publications (second to human) at PubMed documenting important discoveries using this model. Advanced sequencing technologies, genome modification techniques, and the development of embryonic stem cell protocols ensure the rat remains an important mammalian model for disease studies. The 2004 release of the reference genome has been followed by the production of complete genomes for more than two dozen individual strains utilizing NextGen sequencing technologies; their analyses have identified over 80 million variants. This explosion in genomic data has been accompanied by the ability to selectively edit the rat genome, leading to hundreds of new strains through multiple technologies. A number of resources have been developed to provide investigators with access to precision rat models, comprehensive datasets, and sophisticated software tools necessary for their research. Those profiled here include the Rat Genome Database, PhenoGen, Gene Editing Rat Resource Center, Rat Resource and Research Center, and the National BioResource Project for the Rat in Japan. © The Author 2017. Published by Oxford University Press.

ACTH-like peptides increase pain sensitivity and antagonize opiate analgesia

NASA Technical Reports Server (NTRS)

Heybach, J. P.; Vernikos, J.

1981-01-01

The role of the pituitary and of ACTH in pain sensitivity was investigated in the rat. Pain sensitivity was assessed by measuring paw-lick and jump latencies in response to being placed on a grid at 55 C. Hypophysectomy reduced pain sensitivity, and this effect was reversed by the intracerebroventricular (ICV) injection of the opiate antagonist naloxone. Similarly, the analgesia produced by a dose of morphine was antagonized by the administration of ACTH or alpha-MSH. The peripheral injection of ACTH or alpha-MSH in normal rats did not increase pain sensitivity. However, ACTH administered ICV increased pain sensivity within 10 min. The results indicate that the pituitary is the source of an endogenous opiate antagonist and hyperalgesic factor and that this factor is ACTH or an ACTH-like peptide. This activity resides in the N-terminal portion of the ACTH molecule since ACTH sub 4-10 is not active in this respect, nor does this activity require a free N-terminal serine since alpha-MSH appears to be almost as potent as the ACTH sub 1-24 peptide. It is concluded that ACTH-like peptides of pituitary origin act as endogenous hyperalgesic and opiate antagonistic factors.