Influence of blood sampling methods on dopamine-receptor-blocking activities as determined by a radioreceptor assay.

PubMed

Lai, A A; Fleck, R J; Patzke, J V; Glueck, B G; Shaskan, E G; Rosenberg, B J

1982-01-01

The influence of blood collection methods on dopamine-receptor-blocking activities as determined by a radioreceptor assay kit was investigated. Thirty-one patients treated with one of six neuroleptic drugs (thioridazine, trifluoperazine, haloperidol, chlorpromazine, thiothixene, or fluphenazine) participated in this study. Blood samples were drawn from each patient into five different evacuated blood collection tubes made by the same manufacturer (red-stoppered tube containing no additives, lavender-stoppered tube containing EDTA, green-stoppered tube containing heparin, dark blue-stoppered tube containing no additives, and dark blue-stoppered tube containing heparin). The results show that for five drugs (chlorpromazine, fluphenazine, haloperidol, thiothixene, and trifluoperazine), the dark blue-stoppered tubes without additives resulted in significantly higher dopamine-receptor-blocking activities than the red-, lavender-, or green-stoppered tubes. For thioridazine, the green-stoppered tubes resulted in significantly higher blocking activities than the blue- and red-stoppered tubes. The possible effect of tris(2-butoxyethyl) phosphate, a plasticizer, on dopamine-receptor-blocking activities by neuroleptic drugs is discussed.

BDNF Up-Regulates α7 Nicotinic Acetylcholine Receptor Levels on Subpopulations of Hippocampal Interneurons

PubMed Central

Massey, Kerri A.; Zago, Wagner M.; Berg, Darwin K.

2006-01-01

In the hippocampus, brain-derived neurotrophic factor (BDNF) regulates a number of synaptic components. Among these are nicotinic acetylcholine receptors containing α7 subunits (α7-nAChRs), which are interesting because of their relative abundance in the hippocampus and their high relative calcium permeability. We show here that BDNF elevates surface and intracellular pools of α7-nAChRs on cultured hippocampal neurons and that glutamatergic activity is both necessary and sufficient for the effect. Blocking transmission through NMDA receptors with APV blocked the BDNF effect; increasing spontaneous excitatory activity with the GABAA receptor antagonist bicuculline replicated the BDNF effect. BDNF antibodies blocked the BDNF-mediated increase but not the bicuculline one, consistent with enhanced glutamatergic activity acting downstream from BDNF. Increased α7-nAChR clusters were most prominent on interneuron subtypes known to innervate directly excitatory neurons. The results suggest that BDNF, acting through glutamatergic transmission, can modulate hippocampal output in part by controlling α7-nAChR levels. PMID:17029981

Inhibitory effect of D3 dopamine receptors on neuropeptide Y‑induced migration in vascular smooth muscle cells.

PubMed

Xia, Xue-Wei; Zhou, Yong-Qiao; Luo, Hao; Zeng, Chunyu

2017-10-01

Abnormal migration of vascular smooth muscle cells (VSMCs) serves an important role in hypertension, atherosclerosis and restenosis following angioplasty, which is regulated numerous hormonal and humoral factors, including neuropeptide Y (NPY) and dopamine. Dopamine and NPY are both sympathetic neurotransmitters, and a previous study reported that NPY increased VSMC proliferation, while dopamine receptor inhibited it. Therefore, the authors wondered whether or not there is an inhibitory effect of dopamine receptor on NPY‑mediated VSMC migration. The present study demonstrated that stimulation with NPY dose‑dependence (10‑10‑10‑7M, 24 h) increased VSMC migration, the stimulatory effect of NPY was via the Y1 receptor. This is because, in the presence of the Y1 receptor antagonist, BIBP3226 (10‑7 M), the stimulatory effect of NPY on VSMC migration was blocked. Activation of the D3 receptor by PD128907 dose‑dependence (10‑11‑10‑8 M) reduced the stimulatory effect of NPY on VSMC migration. The effect of PD128907 was via the D3 receptor, because the inhibitory effect of PD128907 on NPY‑mediated migration was blocked by the D3 receptor antagonist, U99194. The authors' further study suggested that the inhibitory effect of the D3 receptor was via the PKA signaling pathway, in the presence of the PKA inhibitor, 14‑22 (10‑6 M), the inhibitory effect of PD128907 on VSMC migration was blocked. Moreover, the inhibitory effect of PD128907 was imitated by PKA activator, Sp‑cAMP [S], in the presence of Sp‑cAMP [S], the NPY‑mediated stimulatory effect on VSMC migration was abolished. The present study indicated that activation of the D3 receptor inhibits NPY Y1‑mediated migration on VSMCs, PKA is involved in the signaling pathway.

Glutaraldehyde pretreatment blocks phospholipase A2 modulation of adrenergic receptors.

PubMed

Cohen, R M; McLellan, C; Dauphin, M; Hirata, F

1985-01-07

Treatment of rat cerebral cortical membranes with phospholipase A2 affects, in a parallel fashion, beta-, alpha 1- and alpha 2-adrenergic receptor binding, but not the affinity of these receptors for their respective ligands. Pretreatment of membranes with 0.1 percent glutaraldehyde blocks the effects of phospholipase A2 on adrenergic receptor binding. The results support the hypothesis that desensitization or "masking" of adrenergic receptors may involve changes in membrane lipid composition. Furthermore, glutaraldehyde may prove a useful tool in the investigation of the dynamic roles of lipids in receptor function and more specifically, their regulation and coupling to physiological events.

Capsaicin and N-arachidonoyl-dopamine (NADA) decrease tension by activating both cannabinoid and vanilloid receptors in fast skeletal muscle fibers of the frog.

PubMed

Trujillo, Xóchitl; Ortiz-Mesina, Mónica; Uribe, Tannia; Castro, Elena; Montoya-Pérez, Rocío; Urzúa, Zorayda; Feria-Velasco, Alfredo; Huerta, Miguel

2015-02-01

Previous studies have indicated that vanilloid receptor (VR1) mRNA is expressed in muscle fibers. In this study, we evaluated the functional effects of VR1 activation. We measured caffeine-induced contractions in bundles of the extensor digitorum longus muscle of Rana pipiens. Isometric tension measurements showed that two VR1 agonists, capsaicin (CAP) and N-arachidonoyl-dopamine (NADA), reduced muscle peak tension to 57 ± 4 % and 71 ± 3% of control, respectively. The effect of CAP was partially blocked by a VR1 blocker, capsazepine (CPZ), but the effect of NADA was not changed by CPZ. Because NADA is able to act on cannabinoid receptors, which are also present in muscle fibers, we tested the cannabinoid antagonist AM281. We found that AM281 antagonized both CAP and NADA effects. AM281 alone reduced peak tension to 80 ± 6 % of control. With both antagonists, the CAP effect was completely blocked, and the NADA effect was partially blocked. These results provide pharmacological evidence of the functional presence of the VR1 receptor in fast skeletal muscle fibers of the frog and suggest that capsaicin and NADA reduce tension by activating both cannabinoid and vanilloid receptors.

Role of Mas receptor antagonist (A779) in renal hemodynamics in condition of blocked angiotensin II receptors in rats.

PubMed

Mansoori, A; Oryan, S; Nematbakhsh, M

2016-03-01

The vasodilatory effect of angiotensin 1-7 (Ang 1-7) is exerted in the vascular bed via Mas receptor (MasR) gender dependently. However, the crosstalk between MasR and angiotensin II (Ang II) types 1 and 2 receptors (AT1R and AT2R) may change some actions of Ang 1-7 in renal circulation. In this study by blocking AT1R and AT2R, the role of MasR in kidney hemodynamics was described. In anaesthetized male and female Wistar rats, the effects of saline as vehicle and MasR blockade (A779) were tested on mean arterial pressure (MAP), renal perfusion pressure (RPP), renal blood flow (RBF), and renal vascular resistance (RVR) when both AT1R and AT2R were blocked by losartan and PD123319, respectively. In male rats, when AT1R and AT2R were blocked, there was a tendency for the increase in RBF/wet kidney tissue weight (RBF/KW) to be elevated by A779 as compared with the vehicle (P=0.08), and this was not the case in female rats. The impact of MasR on renal hemodynamics appears not to be sexual dimorphism either when Ang II receptors were blocked. It seems that co-blockade of all AT1R, AT2R, and MasR may alter RBF/ KW in male more than in female rats. These findings support a crosstalk between MasR and Ang II receptors in renal circulation.

Rapid relief of block by mecamylamine of neuronal nicotinic acetylcholine receptors of rat chromaffin cells in vitro: an electrophysiological and modeling study.

PubMed

Giniatullin, R A; Sokolova, E M; Di Angelantonio, S; Skorinkin, A; Talantova, M V; Nistri, A

2000-10-01

The mechanism responsible for the blocking action of mecamylamine on neuronal nicotinic acetylcholine receptors (nAChRs) was studied on rat isolated chromaffin cells recorded under whole-cell patch clamp. Mecamylamine strongly depressed (IC(50) = 0.34 microM) inward currents elicited by short pulses of nicotine, an effect slowly reversible on wash. The mecamylamine block was voltage-dependent and promptly relieved by a protocol combining membrane depolarization with a nicotine pulse. Either depolarization or nicotine pulses were insufficient per se to elicit block relief. Block relief was transient; response depression returned in a use-dependent manner. Exposure to mecamylamine failed to block nAChRs if they were not activated by nicotine or if they were activated at positive membrane potentials. These data suggest that mecamylamine could not interact with receptors either at rest or at depolarized level. Other nicotinic antagonists like dihydro-beta-erythroidine or tubocurarine did not share this action of mecamylamine although proadifen partly mimicked it. Mecamylamine is suggested to penetrate and block open nAChRs that would subsequently close and trap this antagonist. Computer modeling indicated that the mechanism of mecamylamine blocking action could be described by assuming that 1) mecamylamine-blocked receptors possessed a much slower, voltage-dependent isomerization rate, 2) the rate constant for mecamylamine unbinding was large and poorly voltage dependent. Hence, channel reopening plus depolarization allowed mecamylamine escape and block relief. In the presence of mecamylamine, therefore, nAChRs acquire the new property of operating as coincidence detectors for concomitant changes in membrane potential and receptor occupancy.

Blocking NMDA receptors delays death in rats with acute liver failure by dual protective mechanisms in kidney and brain.

PubMed

Cauli, Omar; González-Usano, Alba; Cabrera-Pastor, Andrea; Gimenez-Garzó, Carla; López-Larrubia, Pilar; Ruiz-Sauri, Amparo; Hernández-Rabaza, Vicente; Duszczyk, Malgorzata; Malek, Michal; Lazarewicz, Jerzy W; Carratalá, Arturo; Urios, Amparo; Miguel, Alfonso; Torregrosa, Isidro; Carda, Carmen; Montoliu, Carmina; Felipo, Vicente

2014-06-01

Treatment of patients with acute liver failure (ALF) is unsatisfactory and mortality remains unacceptably high. Blocking NMDA receptors delays or prevents death of rats with ALF. The underlying mechanisms remain unclear. Clarifying these mechanisms will help to design more efficient treatments to increase patient's survival. The aim of this work was to shed light on the mechanisms by which blocking NMDA receptors delays rat's death in ALF. ALF was induced by galactosamine injection. NMDA receptors were blocked by continuous MK-801 administration. Edema and cerebral blood flow were assessed by magnetic resonance. The time course of ammonia levels in brain, muscle, blood, and urine; of glutamine, lactate, and water content in brain; of glomerular filtration rate and kidney damage; and of hepatic encephalopathy (HE) and intracranial pressure was assessed. ALF reduces kidney glomerular filtration rate (GFR) as reflected by reduced inulin clearance. GFR reduction is due to both reduced renal perfusion and kidney tubular damage as reflected by increased Kim-1 in urine and histological analysis. Blocking NMDA receptors delays kidney damage, allowing transient increased GFR and ammonia elimination which delays hyperammonemia and associated changes in brain. Blocking NMDA receptors does not prevent cerebral edema or blood-brain barrier permeability but reduces or prevents changes in cerebral blood flow and brain lactate. The data show that dual protective effects of MK-801 in kidney and brain delay cerebral alterations, HE, intracranial pressure increase and death. NMDA receptors antagonists may increase survival of patients with ALF by providing additional time for liver transplantation or regeneration.

Neurotrophins play differential roles in short and long-term recognition memory.

PubMed

Callaghan, Charlotte K; Kelly, Aine M

2013-09-01

The neurotrophin family of proteins are believed to mediate various forms of synaptic plasticity in the adult brain. Here we have assessed the roles of these proteins in object recognition memory in the rat, using icv infusions of function-blocking antibodies or the tyrosine kinase antagonist, tyrphostin AG879, to block Trk receptors. We report that tyrphostin AG879 impairs both short-term and long-term recognition memory, indicating a requirement for Trk receptor activation in both processes. The effect of inhibition of each of the neurotrophins with activity-blocking neutralising antibodies was also tested. Treatment with anti-BDNF, anti-NGF or anti-NT4 had no effect on short-term memory, but blocked long-term recognition memory. Treatment with anti-NT3 had no effect on either process. We also assessed changes in expression of neurotrophins and their respective receptors in the hippocampus, dentate gyrus and perirhinal cortex over a 24 h period following training in the object recognition task. We observed time-dependent changes in expression of the Trk receptors and their ligands in the dentate gyrus and perirhinal cortex. The data are consistent with a pivotal role for neurotrophic factors in the expression of recognition memory. Copyright © 2013 Elsevier Inc. All rights reserved.

Hyperactivity induced by stimulation of separate dopamine D-1 and D-2 receptors in rats with bilateral 6-OHDA lesions.

PubMed

Arnt, J

1985-08-26

The effects of DA agonists and antagonists with different dopamine (DA) D-1 and D-2 receptor selectivity have been studied in rats with bilateral 6-OHDA lesions. The D-1 agonist SK & F 38393, the D-2 agonist pergolide and the mixed agonist apomorphine all induced marked hyperactivity in lesioned rats in doses which were without stimulant effect in sham-operated animals. The hyperactivity induced by SK & F 38393 was blocked by the DA D-1 antagonist SCH 23390, but unaffected by the D-2 antagonists spiroperidol or clebopride. Pergolide-induced hyperactivity showed the reverse selectivity. The mixed D-1/D-2 antagonists, cis(Z)-flupentixol and cis(Z)-clopenthixol, however blocked the effect of both agonists. Apomorphine-induced hyperactivity was neither blocked by selective D-1 nor D-2 antagonists, but was dose-dependently inhibited by cis(Z)-flupentixol and cis(Z)-clopenthixol. Potent blockade was also obtained by combined treatment with SCH 23390 and spiroperidol, indicating the need of blocking both D-1 and D-2 receptors simultaneously. The results indicate that D-1 and D-2 receptor function can be independently manipulated in denervated rats and they confirm similar results obtained in rats with unilateral 6-OHDA lesions using circling behaviour.

[Impact of rotational stress on development of local immune response in mice. The role of k-opiate receptors].

PubMed

Geĭn, S V; Siatchikhin, A A

2008-01-01

It was established that in an inductive phase of immune response rotational stress increases the number of APC, intensifies DTH and suppresses proliferation in the regional lymph node. K-Opiate receptors block by nor-BNI in the inductive period does not prevent changes of immune parameters. In a productive phase of the immune response, rotational stress activates formation of APC and DTH reaction. Block of k-opiate receptors abolished stress effects on the above parameters.

Kainate receptor pore‐forming and auxiliary subunits regulate channel block by a novel mechanism

PubMed Central

Brown, Patricia M. G. E.; Aurousseau, Mark R. P.; Musgaard, Maria; Biggin, Philip C.

2016-01-01

Key points Kainate receptor heteromerization and auxiliary subunits, Neto1 and Neto2, attenuate polyamine ion‐channel block by facilitating blocker permeation.Relief of polyamine block in GluK2/GluK5 heteromers results from a key proline residue that produces architectural changes in the channel pore α‐helical region.Auxiliary subunits exert an additive effect to heteromerization, and thus relief of polyamine block is due to a different mechanism.Our findings have broad implications for work on polyamine block of other cation‐selective ion channels. Abstract Channel block and permeation by cytoplasmic polyamines is a common feature of many cation‐selective ion channels. Although the channel block mechanism has been studied extensively, polyamine permeation has been considered less significant as it occurs at extreme positive membrane potentials. Here, we show that kainate receptor (KAR) heteromerization and association with auxiliary proteins, Neto1 and Neto2, attenuate polyamine block by enhancing blocker permeation. Consequently, polyamine permeation and unblock occur at more negative and physiologically relevant membrane potentials. In GluK2/GluK5 heteromers, enhanced permeation is due to a single proline residue in GluK5 that alters the dynamics of the α‐helical region of the selectivity filter. The effect of auxiliary proteins is additive, and therefore the structural basis of polyamine permeation and unblock is through a different mechanism. As native receptors are thought to assemble as heteromers in complex with auxiliary proteins, our data identify an unappreciated impact of polyamine permeation in shaping the signalling properties of neuronal KARs and point to a structural mechanism that may be shared amongst other cation‐selective ion channels. PMID:26682513

A key agonist-induced conformational change in the cannabinoid receptor CB1 is blocked by the allosteric ligand Org 27569.

PubMed

Fay, Jonathan F; Farrens, David L

2012-09-28

Allosteric ligands that modulate how G protein-coupled receptors respond to traditional orthosteric drugs are an exciting and rapidly expanding field of pharmacology. An allosteric ligand for the cannabinoid receptor CB1, Org 27569, exhibits an intriguing effect; it increases agonist binding, yet blocks agonist-induced CB1 signaling. Here we explored the mechanism behind this behavior, using a site-directed fluorescence labeling approach. Our results show that Org 27569 blocks conformational changes in CB1 that accompany G protein binding and/or activation, and thus inhibit formation of a fully active CB1 structure. The underlying mechanism behind this behavior is that simultaneous binding of Org 27569 produces a unique agonist-bound conformation, one that may resemble an intermediate structure formed on the pathway to full receptor activation.

Participation of mitochondrial diazepam binding inhibitor receptors in the anticonflict, antineophobic and anticonvulsant action of 2-aryl-3-indoleacetamide and imidazopyridine derivatives.

PubMed

Auta, J; Romeo, E; Kozikowski, A; Ma, D; Costa, E; Guidotti, A

1993-05-01

The 2-hexyl-indoleacetamide derivative, FGIN-1-27 [N,N-di-n-hexyl-2- (4-fluorophenyl)indole-3-acetamide], and the imidazopyridine derivative, alpidem, both bind with high affinity to glial mitochondrial diazepam binding inhibitor receptors (MDR) and increase mitochondrial steroidogenesis. Although FGIN-1-27 is selective for the MDR, alpidem also binds to the allosteric modulatory site of the gamma-aminobutyric acidA receptor where the benzodiazepines bind. FGIN-1-27 and alpidem, like the neurosteroid 3 alpha,21-dehydroxy-5 alpha-pregnane-20-one (THDOC), clonazepam and zolpidem (the direct allosteric modulators of gamma-aminobutyric acidA receptors) delay the onset of isoniazid and metrazol-induced convulsions. The anti-isoniazid convulsant action of FGIN-1-27 and alpidem, but not that of THDOC, is blocked by PK 11195. In contrast, flumazenil blocked completely the anticonvulsant action of clonazepam and zolpidem and partially blocked that of alpidem, but it did not affect the anticonvulsant action of THDOC and FGIN-1-27. Alpidem, like clonazepam, zolpidem and diazepam, but not THDOC or FGIN-1-27, delay the onset of bicuculline-induced convulsions. In two animal models of anxiety, the neophobic behavior in the elevated plus maze test and the conflict-punishment behavior in the Vogel conflict test, THDOC and FGIN-1-27 elicited anxiolytic-like effects in a manner that is flumazenil insensitive, whereas alpidem elicited a similar anxiolytic effect, but is partially blocked by flumazenil. Whereas PK 11195 blocked the effect of FGIN-1-27 and partially blocked alpidem, it did not affect THDOC in both animal models of anxiety.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabotropic glutamate receptor-mediated signaling dampens the HPA axis response to restraint stress

PubMed Central

Evanson, Nathan K.; Herman, James P.

2015-01-01

Glutamate is an important neurotransmitter in regulation of the neural portion of hypothalamus-pituitary-adrenal (HPA) axis activity, and signals through ionotropic and metabotropic receptors. In the current studies we investigated the role of hypothalamic paraventricular group I metabotropic glutamate receptors in regulation of the HPA axis response to restraint stress in rats. Direct injection of the group I metabotropic glutamate receptor agonist 3,5-dihydroxyphenylglycine (DHPG) into the PVN prior to restraint leads to blunting of the HPA axis response in awake animals. Consistent with this result, infusion of the group I receptor antagonist hexyl-homoibotenic acid (HIBO) potentiates the HPA axis response to restraint. The excitatory effect of blocking paraventricular group I metabotropic glutamate signaling is blocked by co-administration of dexamethasone into the PVN. However, the inhibitory effect of DHPG is not affected by co-administration of the cannabinoid CB1 receptor antagonist AM-251 into the PVN. Together, these results suggest that paraventricular group I metabotropic glutamate receptor signaling acts to dampen HPA axis reactivity. This effect appears to be similar to the rapid inhibitory effect of glucocorticoids at the PVN, but is not mediated by endocannabinoid signaling. PMID:25701594

Metabotropic glutamate receptor-mediated signaling dampens the HPA axis response to restraint stress.

PubMed

Evanson, Nathan K; Herman, James P

2015-10-15

Glutamate is an important neurotransmitter in the regulation of the neural portion of hypothalamus-pituitary-adrenal (HPA) axis activity, and signals through ionotropic and metabotropic receptors. In the current studies we investigated the role of hypothalamic paraventricular group I metabotropic glutamate receptors in the regulation of the HPA axis response to restraint stress in rats. Direct injection of the group I metabotropic glutamate receptor agonist 3,5-dihydroxyphenylglycine (DHPG) into the PVN prior to restraint leads to blunting of the HPA axis response in awake animals. Consistent with this result, infusion of the group I receptor antagonist hexyl-homoibotenic acid (HIBO) potentiates the HPA axis response to restraint. The excitatory effect of blocking paraventricular group I metabotropic glutamate signaling is blocked by co-administration of dexamethasone into the PVN. However, the inhibitory effect of DHPG is not affected by co-administration of the cannabinoid CB1 receptor antagonist AM-251 into the PVN. Together, these results suggest that paraventricular group I metabotropic glutamate receptor signaling acts to dampen HPA axis reactivity. This effect appears to be similar to the rapid inhibitory effect of glucocorticoids at the PVN, but is not mediated by endocannabinoid signaling. Copyright © 2015 Elsevier Inc. All rights reserved.

The effects of the selective 5-HT(2C) receptor antagonist SB 242084 on learned helplessness in male Fischer 344 rats.

PubMed

Strong, Paul V; Greenwood, Benjamin N; Fleshner, Monika

2009-05-01

Rats exposed to an uncontrollable stressor demonstrate a constellation of behaviors such as exaggerated freezing and deficits in shuttle box escape learning. These behaviors in rats have been called learned helplessness and have been argued to model human stress-related mood disorders. Learned helplessness is thought to be caused by hyperactivation of serotonin (5-HT) neurons in the dorsal raphe nucleus (DRN) and a subsequent exaggerated release of 5-HT in DRN projection sites. Blocking 5-HT(2C) receptors in the face of an increase in serotonin can alleviate anxiety behaviors in some animal models. However, specific 5-HT receptor subtypes involved in learned helplessness remain unknown. The current experiments tested the hypothesis that 5-HT(2C) receptor activation is necessary and sufficient for the expression of learned helplessness. The selective 5-HT(2C) receptor antagonist SB 242084 (1.0 mg/kg) administered i.p. to adult male Fischer 344 rats prior to shuttle box behavioral testing, but not before stress, blocked stress-induced deficits in escape learning but had no effect on the exaggerated shock-elicited freezing. The selective 5-HT(2C) receptor agonist CP-809101 was sufficient to produce learned helplessness-like behaviors in the absence of prior stress and these effects were blocked by pretreatment with SB 242084. Results implicate the 5-HT(2C) receptor subtype in mediating the shuttle box escape deficits produced by exposure to uncontrollable stress and suggest that different postsynaptic 5-HT receptor subtypes underlie the different learned helplessness behaviors.

Evidence that the adenosine A3 receptor may mediate the protection afforded by preconditioning in the isolated rabbit heart.

PubMed

Liu, G S; Richards, S C; Olsson, R A; Mullane, K; Walsh, R S; Downey, J M

1994-07-01

Agonists selective for the A1 adenosine receptor mimic the protective effect of ischaemic preconditioning against infarction in the rabbit heart. Unselective adenosine antagonists block this protection but, paradoxically, the A1 adenosine receptor selective antagonist 8-cyclopentyl- 1,3-dipropylxanthine (DPCPX) does not. The aim of this study was to test the hypothesis that the newly described A3 adenosine receptor, which has an agonist profile similar to the A1 receptor but is insensitive to DPCPX, might mediate preconditioning. Isolated rabbit hearts perfused with Krebs buffer experienced 30 min of regional ischaemia followed by 120 min of reperfusion. Infarct size was measured by tetrazolium staining. In control hearts infarction was 32.2(SEM 1.5)% of the risk zone. Preconditioning by 5 min ischaemia and 10 min reperfusion reduced infarct size to 8.8(2.3)%. Replacing the regional ischaemia with 5 min perfusion with 10 microM adenosine or 65 nM N6-[2-(4-aminophenyl)ethyl]adenosine (APNEA), an adenosine A3 receptor agonist, was equally protective. The unselective antagonist 8-p-sulphophenyl theophylline at 100 microM abolished protection by preconditioning, adenosine, and APNEA, but 200 nM DPCPX did not block protection by any of the interventions. Likewise the potent but unselective A3 receptor antagonist 8-(4-carboxyethenylphenyl)-1,3-dipropylxanthine (BW A1433) completely blocked protection from ischaemic preconditioning. Because protection against infarction afforded by ischaemic preconditioning, adenosine, or the A3 receptor agonist APNEA could not be blocked by DPCPX and because the potent A3 receptor antagonist BW A1433 blocked protection from ischaemic preconditioning, these data indicate that the protection of preconditioning is not exclusively mediated by the adenosine A1 receptor in rabbit heart and could involve the A3 receptor.

Ability of the new AT1 receptor blocker azilsartan to block angiotensin II-induced AT1 receptor activation after wash-out.

PubMed

Miura, Shin-ichiro; Matsuo, Yoshino; Nakayama, Asuka; Tomita, Sayo; Suematsu, Yasunori; Saku, Keijiro

2014-03-01

The recently approved angiotensin II (Ang II) type 1 (AT1) receptor blocker (ARB) azilsartan strongly reduces blood pressure (BP) in patients with hypertension. We previously reported that azilsartan showed unique binding behavior to the AT1 receptor because of its 5-oxo-1,2,4-oxadiazole moiety. However, the ability of azilsartan to block Ang II-dependent AT1 receptor activation is not yet clear. Azilsartan and a derivative of azilsartan (azilsartan-7H) that lacks a carboxyl group at the benzimidazole ring were used. Ang II-induced inositol phosphate (IP) production and extracellular signal-regulated kinase (ERK) activation were analyzed in a cell-based wash-out assay. Azilsartan, but not azilsartan-7H, completely blocked Ang II-induced IP production and ERK activation. Our previous report demonstrated that azilsartan mainly interacts with Tyr(113), Lys(199), and Gln(257) in the AT1 receptor. The interactions between azilsartan and Tyr(113) and Gln(257), but not Lys(199), were critical for blocking Ang II-induced IP production and ERK activation after wash-out. Although our findings regarding the molecule-specific effects of azilsartan are based on basic research, they may lead to an exciting insight into the mechanism of azilsartan.

Hyoscine butylbromide potently blocks human nicotinic acetylcholine receptors in SH-SY5Y cells.

PubMed

Weiser, Thomas; Just, Stefan

2009-02-06

Hyoscine butylbromide (HBB; tradenames: Buscopan/Buscapina is an antispasmodic drug for the treatment of abdominal pain associated with gastrointestinal cramping. As a hyoscine derivative, this compound competitively inhibits muscarinic acetylcholine (ACh) receptors on smooth muscle cells in the gastrointestinal tract. Preliminary investigations suggested that it might also inhibit nicotinic ACh receptors. This study investigated the effect of HBB on nicotinic ACh receptor-mediated membrane currents in SH-SY5Y cells. ACh and nicotine application-induced comparable membrane currents with EC(50) values of 25.9+/-0.6 and 40.1+/-0.4microM, respectively. When coapplied with 100microM ACh, HBB concentration-dependently suppressed currents with an IC(50) value of 0.19+/-0.04microM, and was approximately seven-times more potent than the ganglionic blocker, hexamethonium (IC(50)=1.3+/-0.3microM). Increasing the agonist concentration to 5mM did not affect the amount of block by HBB, which suggests a non-competitive mode of action. These functional in vitro data demonstrate for the first time that HBB blocks neuronal nicotinic ACh receptors in the same concentration range as it inhibits muscarinic ACh receptors. If one hypothesizes that HBB might also affect nicotinic receptors in autonomic neurons in vivo (e. g. in the enteric nervous system), this effect could contribute to its spasmolytic activity.

Mechanism of the cardiovascular effects of the GABAA receptors of the ventral tegmental area of the rat brain.

PubMed

Yeganeh, Fahimeh; Ranjbar, Afsaneh; Hatam, Masoumeh; Nasimi, Ali

2015-07-23

The ventral tegmental area (VTA) contains GABA terminals involved in the regulation of the cardiovascular system. Previously, we demonstrated that blocking GABAA but not GABAB receptors produced a pressor response accompanied by marked bradycardia. This study was performed to find the possible mechanisms involved in these responses by blocking ganglionic nicotinic receptors, peripheral muscarinic receptors or peripheral V1 vasopressin receptors. Experiments were performed on urethane anesthetized male Wistar rats. Drugs were microinjected unilaterally into the VTA (100 nl). The average changes in mean arterial pressure (MAP) and heart rate (HR) were compared between pre- and post-treatment using paired t-test. Injection of bicuculline methiodide (BMI), a GABAA antagonist, into the VTA caused a significant increase in MAP and a decrease in HR. Administration (i.v.) of the nicotinic receptor blocker, hexamethonium, enhanced the pressor response but abolished the bradycardic response to BMI, which ruled out involvement of the sympathetic nervous system. Blockade of the peripheral muscarinic receptors by homatropine (i.v.) abolished the bradycardic effect of BMI, but had no effect on the pressor response, indicating that bradycardia was produced by the parasympathetic outflow to the heart. Both the pressor and bradycardic responses to BMI were blocked by V1 receptor antagonist (i.v.), indicating that administration of BMI in the VTA disinhibited the release of vasopressin into the circulation. In conclusion, we demonstrated that GABAergic mechanism of the VTA exerts a tonic inhibition on vasopressin release through activation of GABAA receptors. The sympathetic system is not involved in the decrease of blood pressure by GABA of the VTA. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Evidence for involvement of nitric oxide and GABAB receptors in MK-801- stimulated release of glutamate in rat prefrontal cortex

PubMed Central

Roenker, Nicole L.; Gudelsky, Gary A.; Ahlbrand, Rebecca; Horn, Paul S.; Richtand, Neil M.

2012-01-01

Systemic administration of NMDA receptor antagonists elevates extracellular glutamate within prefrontal cortex. The cognitive and behavioral effects of NMDA receptor blockade have direct relevance to symptoms of schizophrenia, and recent studies demonstrate an important role for nitric oxide and GABAB receptors in mediating the effects of NMDA receptor blockade on these behaviors. We sought to extend those observations by directly measuring the effects of nitric oxide and GABAB receptor mechanisms on MK-801-induced glutamate release in the prefrontal cortex. Systemic MK-801 injection (0.3 mg/kg) to male Sprague-Dawley rats significantly increased extracellular glutamate levels in prefrontal cortex, as determined by microdialysis. This effect was blocked by pretreatment with the nitric oxide synthase inhibitor L-NAME (60 mg/kg). Reverse dialysis of the nitric oxide donor SNAP (0.5 – 5 mM) directly into prefrontal cortex mimicked the effect of systemic MK-801, dose-dependently elevating cortical extracellular glutamate. The effect of MK-801 was also blocked by systemic treatment with the GABAB receptor agonist baclofen (5 mg/kg). In combination, these data suggest increased nitric oxide formation is necessary for NMDA antagonist-induced elevations of extracellular glutamate in the prefrontal cortex. Additionally, the data suggest GABAB receptor activation can modulate the NMDA antagonist-induced increase in cortical glutamate release. PMID:22579658

Mechanism of action of the insecticides, lindane and fipronil, on glycine receptor chloride channels

PubMed Central

Islam, Robiul; Lynch, Joseph W

2012-01-01

BACKGROUND AND PURPOSE Docking studies predict that the insecticides, lindane and fipronil, block GABAA receptors by binding to 6′ pore-lining residues. However, this has never been tested at any Cys-loop receptor. The neurotoxic effects of these insecticides are also thought to be mediated by GABAA receptors, although a recent morphological study suggested glycine receptors mediated fipronil toxicity in zebrafish. Here we investigated whether human α1, α1β, α2 and α3 glycine receptors were sufficiently sensitive to block by either compound as to represent possible neurotoxicity targets. We also investigated the mechanisms by which lindane and fipronil inhibit α1 glycine receptors. EXPERIMENTAL APPROACH Glycine receptors were recombinantly expressed in HEK293 cells and insecticide effects were studied using patch-clamp electrophysiology. KEY RESULTS Both compounds completely inhibited all tested glycine receptor subtypes with IC50 values ranging from 0.2–2 µM, similar to their potencies at vertebrate GABAA receptors. Consistent with molecular docking predictions, both lindane and fipronil interacted with 6′ threonine residues via hydrophobic interactions and hydrogen bonds. In contrast with predictions, we found no evidence for lindane interacting at the 2′ level. We present evidence for fipronil binding in a non-blocking mode in the anaesthetic binding pocket, and for lindane as an excellent pharmacological tool for identifying the presence of β subunits in αβ heteromeric glycine receptors. CONCLUSIONS AND IMPLICATIONS This study implicates glycine receptors as novel vertebrate toxicity targets for fipronil and lindane. Furthermore, lindane interacted with pore-lining 6′ threonine residues, whereas fipronil may have both pore and non-pore binding sites. PMID:22035056

Mechanism of action of the insecticides, lindane and fipronil, on glycine receptor chloride channels.

PubMed

Islam, Robiul; Lynch, Joseph W

2012-04-01

Docking studies predict that the insecticides, lindane and fipronil, block GABA(A) receptors by binding to 6' pore-lining residues. However, this has never been tested at any Cys-loop receptor. The neurotoxic effects of these insecticides are also thought to be mediated by GABA(A) receptors, although a recent morphological study suggested glycine receptors mediated fipronil toxicity in zebrafish. Here we investigated whether human α1, α1β, α2 and α3 glycine receptors were sufficiently sensitive to block by either compound as to represent possible neurotoxicity targets. We also investigated the mechanisms by which lindane and fipronil inhibit α1 glycine receptors. Glycine receptors were recombinantly expressed in HEK293 cells and insecticide effects were studied using patch-clamp electrophysiology. Both compounds completely inhibited all tested glycine receptor subtypes with IC(50) values ranging from 0.2-2 µM, similar to their potencies at vertebrate GABA(A) receptors. Consistent with molecular docking predictions, both lindane and fipronil interacted with 6' threonine residues via hydrophobic interactions and hydrogen bonds. In contrast with predictions, we found no evidence for lindane interacting at the 2' level. We present evidence for fipronil binding in a non-blocking mode in the anaesthetic binding pocket, and for lindane as an excellent pharmacological tool for identifying the presence of β subunits in αβ heteromeric glycine receptors. This study implicates glycine receptors as novel vertebrate toxicity targets for fipronil and lindane. Furthermore, lindane interacted with pore-lining 6' threonine residues, whereas fipronil may have both pore and non-pore binding sites. © 2011 The Authors. British Journal of Pharmacology © 2011 The British Pharmacological Society.

Effect and tolerability of blonanserin in severe delusion with various types of dementia.

PubMed

Takaki, Manabu; Honda, Hajime; Terada, Seishi; Uchitomi, Yosuke

2015-06-01

Low-dose blonanserin was effective for treating severe delusions in six patients with various types of dementia, and it was also well tolerated. Delusion and hallucination scores, as measured by the Neuropsychiatric Inventory, improved, and extrapyramidal symptom scores, as measured by the Drug-Induced Extrapyramidal Symptoms Scale, were unchanged. Blonanserin has strong dopamine D 2 receptor-, 5-hydroxytryptamine 2A receptor-, and dopamine D 3 receptor-blocking activities and weak 5-hydroxytryptamine-2C, α 1 -, histamine H 1 -, and muscarinic M 1 -blocking activities. Its unique characteristics may make it suitable for treating severe delusions and hallucination in patients with dementia. © 2014 The Authors. Psychogeriatrics © 2014 Japanese Psychogeriatric Society.

Tamoxifen regulation of bone growth and endocrine function in the ovariectomized rat: discrimination of responses involving estrogen receptor α/estrogen receptor β, G protein-coupled estrogen receptor, or estrogen-related receptor γ using fulvestrant (ICI 182780).

PubMed

Fitts, James M; Klein, Robert M; Powers, C Andrew

2011-07-01

Tamoxifen is a selective estrogen receptor (ER) modulator, but it is also a deactivating ligand for estrogen-related receptor-γ (ERRγ) and a full agonist for the G protein-coupled estrogen receptor (GPER). Fulvestrant is a selective ER down-regulator that lacks agonist effects on ERα/ERβ, is inactive on ERRγ, but acts as a full agonist on GPER. Fulvestrant effects on tamoxifen actions on uterine and somatic growth, bone, the growth hormone (GH)-insulin-like growth factor I (IGF-I) axis, and pituitary prolactin were analyzed to pharmacologically discriminate tamoxifen effects that may be mediated by ERα/ERβ versus ERRγ versus GPER. Ovariectomized rats received tamoxifen (0.6 mg/kg/daily) plus fulvestrant at 0, 3, 6, or 12 mg/kg/daily for 5 weeks; controls received vehicle or 6 mg/kg fulvestrant daily. Tamoxifen effects to increase uterine weight, decrease serum IGF-I, increase pituitary prolactin, and increase bone mineral density could be fully blocked by fulvestrant, indicating mediation by ERα/ERβ. Tamoxifen effects to decrease pituitary GH, tibia length, and body weight were only partially blocked by fulvestrant, indicating involvement of mechanisms unrelated to ERα/ERβ. Fulvestrant did not inhibit tamoxifen actions to reduce total pituitary protein, again indicating effects not mediated by ERα/ERβ. Tamoxifen actions to reduce serum GH were mimicked rather than inhibited by fulvestrant, pharmacological features consistent with GPER involvement. However, fulvestrant alone increased IGF-I and also blocked tamoxifen-evoked IGF-I decreases; thus fulvestrant effects on serum GH might reflect increased IGF-I feedback inhibition. Fulvestrant alone had no effect on the other parameters. The findings indicate that mechanisms unrelated to ERα/ERβ contribute to tamoxifen effects on body weight, bone growth, and pituitary function.

Glutamatergic postsynaptic block by Pamphobeteus spider venoms in crayfish.

PubMed

Araque, A; Ferreira, W; Lucas, S; Buño, W

1992-01-31

The effects of toxins from venom glands of two south american spiders (Pamphobeteus platyomma and P. soracabae) on glutamatergic excitatory synaptic transmission were studied in the neuromuscular junction of the opener muscle of crayfish. The toxins selectively and reversibly blocked both excitatory postsynaptic currents and potentials in a dose-dependent manner. They also reversibly abolished glutamate-induced postsynaptic membrane depolarization. They had no effect on resting postsynaptic membrane conductance nor on postsynaptic voltage-gated currents. The synaptic facilitation and the frequency of miniature postsynaptic potentials were unaffected by the toxins, indicating that presynaptic events were not modified. Picrotoxin, a selective antagonist of the gamma-aminobutyric acid (GABA)A receptor, did not modify toxin effects. We conclude that both toxins specifically block the postsynaptic glutamate receptor-channel complex.

Low-frequency electroacupuncture suppresses focal epilepsy and improves epilepsy-induced sleep disruptions.

PubMed

Yi, Pei-Lu; Lu, Chin-Yu; Jou, Shuo-Bin; Chang, Fang-Chia

2015-07-07

The positive effects of acupuncture at Feng-Chi acupoints on treating epilepsy and insomnia have been well-documented in ancient Chinese literature. However, there is a lack of scientific evidence to elucidate the underlying mechanisms behind these effects. Our previous study demonstrated that high-frequency (100 Hz) electroacupuncture (EA) at Feng-Chi acupoints deteriorates both pilocarpine-induced focal epilepsy and sleep disruptions. This study investigated the effects of low-frequency (10 Hz) EA on epileptic activities and epilepsy-induced sleep disruptions. In rats, the Feng-Chi acupoint is located 3 mm away from the center of a line between the two ears. Rats received 30 min of 10 Hz EA stimuli per day before each day's dark period for three consecutive days. Our results indicated that administration of pilocarpine into the left CeA at the beginning of the dark period induced focal epilepsy and decreased both rapid eye movement (REM) sleep and non-REM (NREM) sleep during the consequent light period. Low-frequency (10 Hz) EA at Feng-Chi acupoints suppressed pilocarpine-induced epileptiform EEGs, and this effect was in turn blocked by naloxone (a broad-spectrum opioid receptor antagonist), but not by naloxonazine (a μ-receptor antagonist), naltrindole (a δ-receptor antagonist) and nor-binaltorphimine (a κ-receptor antagonist). Ten Hz EA enhanced NREM sleep during the dark period, and this enhancement was blocked by all of the opioid receptor antagonists. On the other hand, 10 Hz EA reversed pilocarpine-induced NREM suppression during the light period, and the EA's effect on the sleep disruption was only blocked by naloxonazine. These results indicate that low-frequency EA stimulation of Feng-Chi acupoints is beneficial in improving epilepsy and epilepsy-induced sleep disruptions, and that opioid receptors in the CeA mediate EA's therapeutic effects.

K(Ca)3.1 channels facilitate K+ secretion or Na+ absorption depending on apical or basolateral P2Y receptor stimulation.

PubMed

Palmer, Melissa L; Peitzman, Elizabeth R; Maniak, Peter J; Sieck, Gary C; Prakash, Y S; O'Grady, Scott M

2011-07-15

Human mammary epithelial (HME) cells express several P2Y receptor subtypes located in both apical and basolateral membranes. Apical UTP or ATP-γ-S stimulation of monolayers mounted in Ussing chambers evoked a rapid, but transient decrease in short circuit current (I(sc)), consistent with activation of an apical K+ conductance. In contrast, basolateral P2Y receptor stimulation activated basolateral K+ channels and increased transepithelial Na+ absorption. Chelating intracellular Ca2+ using the membrane-permeable compound BAPTA-AM, abolished the effects of purinoceptor activation on I(sc). Apical pretreatment with charybdotoxin also blocked the I(sc) decrease by >90% and similar magnitudes of inhibition were observed with clotrimazole and TRAM-34. In contrast, iberiotoxin and apamin did not block the effects of apical P2Y receptor stimulation. Silencing the expression of K(Ca)3.1 produced ∼70% inhibition of mRNA expression and a similar reduction in the effects of apical purinoceptor agonists on I(sc). In addition, silencing P2Y2 receptors reduced the level of P2Y2 mRNA by 75% and blocked the effects of ATP-γ-S by 65%. These results suggest that P2Y2 receptors mediate the effects of purinoceptor agonists on K+ secretion by regulating the activity of K(Ca)3.1 channels expressed in the apical membrane of HME cells. The results also indicate that release of ATP or UTP across the apical or basolateral membrane elicits qualitatively different effects on ion transport that may ultimately determine the [Na+]/[K+] composition of fluid within the mammary ductal network.

Aleglitazar, a dual peroxisome proliferator-activated receptor-α and -γ agonist, protects cardiomyocytes against the adverse effects of hyperglycaemia.

PubMed

Chen, Yan; Chen, Hongmei; Birnbaum, Yochai; Nanhwan, Manjyot K; Bajaj, Mandeep; Ye, Yumei; Qian, Jinqiao

2017-03-01

To assess the effects of Aleglitazar on hyperglycaemia-induced apoptosis. We incubated human cardiomyocytes, cardiomyocytes from cardiac-specific peroxisome proliferator-activated receptor-γ knockout or wild-type mice in normoglycaemic or hyperglycaemic conditions (glucose 25 mM). Cells were treated with different concentrations of Aleglitazar for 48 h. We measured viability, apoptosis, caspase-3 activity, cytochrome-C release, total antioxidant capacity and reactive oxygen species formation in the treated cardiomyocytes. Human cardiomyocytes were transfected with short interfering RNA against peroxisome proliferator-activated receptor-α or peroxisome proliferator-activated receptor-γ. Aleglitazar attenuated hyperglycaemia-induced apoptosis, caspase-3 activity and cytochrome-C release and increased viability in human cardiomyocyte, cardiomyocytes from cardiac-specific peroxisome proliferator-activated receptor-γ knockout and wild-type mice. Hyperglycaemia reduced the antioxidant capacity and Aleglitazar significantly blunted this effect. Hyperglycaemia-induced reactive oxygen species production was attenuated by Aleglitazar in both human cardiomyocyte and wild-type mice cardiomyocytes. Aleglitazar improved cell viability in cells exposed to hyperglycaemia. The protective effect was partially blocked by short interfering RNA against peroxisome proliferator-activated receptor-α alone and short interfering RNA against peroxisome proliferator-activated receptor-γ alone and completely blocked by short interfering RNA to both peroxisome proliferator-activated receptor-α and peroxisome proliferator-activated receptor-γ. Aleglitazar protects cardiomyocytes against hyperglycaemia-induced apoptosis by combined activation of both peroxisome proliferator-activated receptor-α and peroxisome proliferator-activated receptor-γ in a short-term vitro model.

The effects of intraperitoneal and intracerebroventricular administration of the GABAB receptor antagonist CGP 35348 on food intake in rats.

PubMed

Patel, Sunit M; Ebenezer, Ivor S

2004-10-25

In order to test the hypothesis that endogenous gamma-aminobutyric acid (GABA), acting at central GABAB receptors, plays a physiological role in the control of feeding behaviour, it was reasoned that blocking these receptors with a centrally active GABAB receptor antagonist should reduce food intake in hungry rats. In the present study, experiments were carried out to test this possibility using the GABAB receptor antagonist 3-aminopropyl-diethoxy-methyl-phosphinic acid (CGP 35348), which is water-soluble and can penetrate the blood-brain barrier from the systemic circulation. CGP 35348 (50 and 100 mg/kg, i.p.) had no effect on food intake in 22-h fasted rats, but a higher dose (i.e. 500 mg/kg., i.p.) significantly reduced cumulative food consumption. These findings are consistent with previous observations that high systemic doses of CGP 35348 are needed to block central GABAB receptors. However, to eliminate the possibility that the 500 mg/kg dose of CGP 35348 decreased food intake by a peripheral, rather than a central mode of action, further experiments were undertaken where the drug was given directly into the brain by the intracerebroventricular (i.c.v.) route. I.c.v. administration of CGP 35348 (5 and 10 microg) significantly decreased cumulative food intake food intake in rats that had been fasted for 22 h. By contrast, i.c.v. administration of CGP 35348 (10 microg) had no effect on water intake in 16-h water-deprived rats. The results indicate that CGP 35348 reduces food consumption in hungry rats by blocking central GABAB receptors in a behaviourally specific manner. These findings suggest that endogenous GABA acting at central GABAB receptors plays a physiological role in the regulation of feeding behaviour.

Propranolol blocks the stimulatory effects of naloxone on ventilation and oxygen consumption in hamsters.

PubMed

Schlenker, E H; Eikanger, J

1997-06-01

The purposes of these studies were: 1) to determine the effects of various doses of propranolol, a nonspecific beta-adrenergic antagonist, on ventilation, oxygen consumption, and body temperature in hamsters, and 2) to test the hypothesis that in hamsters the stimulatory effects of naloxone, an opioid receptor antagonist, on ventilation and oxygen consumption occur, at least in part, through the release of catecholamines that act via beta-adrenergic receptors. Propranolol, a non-specific beta adrenergic receptor antagonist, at a 20 mg/kg depressed body temperature, oxygen consumption, tidal volume, and ventilation relative to saline. The lower dose of 10 mg/kg had only transitory effects on tidal volume at 60 min and ventilation at 30 min post-injection-Naloxone (1 mg/kg) relative to saline stimulated ventilation and oxygen consumption. These effects were blocked by propranolol pretreatment. The results of these experiments demonstrate that in the hamster, 1) body temperature, oxygen consumption, and ventilation appear to be modulated by beta-adrenergic receptors, and 2) the stimulatory effects of naloxone on oxygen consumption and ventilation may occur through the interaction of endogenous opioids and beta-adrenergic receptor systems.

Cannabinoid 2 (CB2) receptor agonism reduces lithium chloride-induced vomiting in Suncus murinus and nausea-induced conditioned gaping in rats.

PubMed

Rock, Erin M; Boulet, Nathalie; Limebeer, Cheryl L; Mechoulam, Raphael; Parker, Linda A

2016-09-05

We aimed to investigate the potential anti-emetic and anti-nausea properties of targeting the cannabinoid 2 (CB2) receptor. We investigated the effect of the selective CB2 agonist, HU-308, on lithium chloride- (LiCl) induced vomiting in Suncus murinus (S. murinus) and conditioned gaping (nausea-induced behaviour) in rats. Additionally, we determined whether these effects could be prevented by pretreatment with AM630 (a selective CB2 receptor antagonist/inverse agonist). In S. murinus, HU-308 (2.5, 5mg/kg, i.p.) reduced, but did not completely block, LiCl-induced vomiting; an effect that was prevented with AM630. In rats, HU-308 (5mg/kg, i.p.) suppressed, but did not completely block, LiCl-induced conditioned gaping to a flavour; an effect that was prevented by AM630. These findings are the first to demonstrate the ability of a selective CB2 receptor agonist to reduce nausea in animal models, indicating that targeting the CB2 receptor may be an effective strategy, devoid of psychoactive effects, for managing toxin-induced nausea and vomiting. Copyright © 2016 Elsevier B.V. All rights reserved.

Neurite outgrowth mediated by the heat shock protein Hsp90α: a novel target for the antipsychotic drug aripiprazole

PubMed Central

Ishima, T; Iyo, M; Hashimoto, K

2012-01-01

Aripiprazole is an atypical antipsychotic drug approved for the treatment of psychiatric disorders such as schizophrenia, bipolar disorder, major depressive disorder and autism. The drug shows partial agonistic activity at dopamine D2 receptors and 5-hydroxytryptamine (5-HT) 5-HT1A receptors, and antagonistic activity at 5-HT2A receptors. However, the precise mechanistic pathways remain unclear. In this study, we examined the effects of aripiprazole on neurite outgrowth. Aripiprazole significantly potentiated nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells, in a concentration-dependent manner. The 5-HT1A receptor antagonist WAY-100635, but not the dopamine D2 receptor antagonist sulpiride, blocked the effects of aripiprazole, although, only partially. Specific inhibitors of inositol 1,4,5-triphosphate (IP3) receptors and BAPTA-AM, a chelator of intracellular Ca2+, blocked the effects of aripiprazole. Moreover, specific inhibitors of several common signaling pathways phospholipase C-γ (PLC-γ), phosphatidylinositol-3 kinase (PI3K), mammalian target of rapamycin, p38 MAPK, c-Jun N-terminal kinase, Akt, Ras, Raf, ERK, MAPK) also blocked the effects of aripiprazole. Using proteomic analysis, we found that aripiprazole significantly increased levels of the heat shock protein Hsp90α in cultured cells. The effects of aripiprazole on NGF-induced neurite outgrowth were significantly attenuated by treatment with Hsp90α RNA interference, but not by the negative control of Hsp90α. These findings suggest that both 5-HT1A receptor activation and Ca2+ signaling via IP3 receptors, as well as their downstream cellular signaling pathways play a role in the promotion of aripiprazole-induced neurite outgrowth. Furthermore, aripiprazole-induced increases in Hsp90α protein expression may form part of the therapeutic mechanism for this drug. PMID:23047241

Stimulation of postsynapse adrenergic α2A receptor improves attention/cognition performance in an animal model of attention deficit hyperactivity disorder.

PubMed

Kawaura, Kazuaki; Karasawa, Jun-ichi; Chaki, Shigeyuki; Hikichi, Hirohiko

2014-08-15

A 5-trial inhibitory avoidance test using spontaneously hypertensive rat (SHR) pups has been used as an animal model of attention deficit hyperactivity disorder (ADHD). However, the roles of noradrenergic systems, which are involved in the pathophysiology of ADHD, have not been investigated in this model. In the present study, the effects of adrenergic α2 receptor stimulation, which has been an effective treatment for ADHD, on attention/cognition performance were investigated in this model. Moreover, neuronal mechanisms mediated through adrenergic α2 receptors were investigated. We evaluated the effects of both clonidine, a non-selective adrenergic α2 receptor agonist, and guanfacine, a selective adrenergic α2A receptor agonist, using a 5-trial inhibitory avoidance test with SHR pups. Juvenile SHR exhibited a shorter transfer latency, compared with juvenile Wistar Kyoto (WKY) rats. Both clonidine and guanfacine significantly prolonged the transfer latency of juvenile SHR. The effects of clonidine and guanfacine were significantly blocked by pretreatment with an adrenergic α2A receptor antagonist. In contrast, the effect of clonidine was not attenuated by pretreatment with an adrenergic α2B receptor antagonist, or an adrenergic α2C receptor antagonist, while it was attenuated by a non-selective adrenergic α2 receptor antagonist. Furthermore, the effects of neither clonidine nor guanfacine were blocked by pretreatment with a selective noradrenergic neurotoxin. These results suggest that the stimulation of the adrenergic α2A receptor improves the attention/cognition performance of juvenile SHR in the 5-trial inhibitory avoidance test and that postsynaptic, rather than presynaptic, adrenergic α2A receptor is involved in this effect. Copyright © 2014 Elsevier B.V. All rights reserved.

Glucocorticoid acts on a putative G protein-coupled receptor to rapidly regulate the activity of NMDA receptors in hippocampal neurons.

PubMed

Zhang, Yanmin; Sheng, Hui; Qi, Jinshun; Ma, Bei; Sun, Jihu; Li, Shaofeng; Ni, Xin

2012-04-01

Glucocorticoids (GCs) have been demonstrated to act through both genomic and nongenomic mechanisms. The present study demonstrated that corticosterone rapidly suppressed the activity of N-methyl-D-aspartate (NMDA) receptors in cultured hippocampal neurons. The effect was maintained with corticosterone conjugated to bovine serum albumin and blocked by inhibition of G protein activity with intracellular GDP-β-S application. Corticosterone increased GTP-bound G(s) protein and cyclic AMP (cAMP) production, activated phospholipase Cβ(3) (PLC-β(3)), and induced inositol-1,4,5-triphosphate (IP(3)) production. Blocking PLC and the downstream cascades with PLC inhibitor, IP(3) receptor antagonist, Ca(2+) chelator, and protein kinase C (PKC) inhibitors prevented the actions of corticosterone. Blocking adenylate cyclase (AC) and protein kinase A (PKA) caused a decrease in NMDA-evoked currents. Application of corticosterone partly reversed the inhibition of NMDA currents caused by blockage of AC and PKA. Intracerebroventricular administration of corticosterone significantly suppressed long-term potentiation (LTP) in the CA1 region of the hippocampus within 30 min in vivo, implicating the possibly physiological significance of rapid effects of GC on NMDA receptors. Taken together, our results indicate that GCs act on a putative G protein-coupled receptor to activate multiple signaling pathways in hippocampal neurons, and the rapid suppression of NMDA activity by GCs is dependent on PLC and downstream signaling.

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

TrpC5 Mediates Acute Leptin and Serotonin Effects via Pomc Neurons.

PubMed

Gao, Yong; Yao, Ting; Deng, Zhuo; Sohn, Jong-Woo; Sun, Jia; Huang, Yiru; Kong, Xingxing; Yu, Kai-Jiang; Wang, Rui-Tao; Chen, Hong; Guo, Hongbo; Yan, Jianqun; Cunningham, Kathryn A; Chang, Yongsheng; Liu, Tiemin; Williams, Kevin W

2017-01-17

The molecular mechanisms underlying acute leptin and serotonin 2C receptor-induced hypophagia remain unclear. Here, we show that neuronal and pro-opiomelanocortin (Pomc)-specific loss of transient receptor potential cation 5 (TrpC5) subunits is sufficient to decrease energy expenditure and increase food intake resulting in elevated body weight. Deficiency of Trpc5 subunits in Pomc neurons is also sufficient to block the anorexigenic effects of leptin and serotonin 2C receptor (Ht2Cr) agonists. The loss of acute anorexigenic effects of these receptors is concomitant with a blunted electrophysiological response to both leptin and Ht2Cr agonists in arcuate Pomc neurons. We also demonstrate that the Ht2Cr agonist lorcaserin-induced improvements in glucose and insulin tolerance are blocked by TrpC5 deficiency in Pomc neurons. Together, our results link TrpC5 subunits in the brain with leptin- and serotonin 2C receptor-dependent changes in neuronal activity, as well as energy balance, feeding behavior, and glucose metabolism. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Role of the thrombin receptor in restenosis and atherosclerosis.

PubMed

Baykal, D; Schmedtje, J F; Runge, M S

1995-02-23

Thrombus generation is central to thrombosis at vascular lesion sites, including post-PCTA acute reocclusion and chronic restenosis. Thrombin stimulates platelet activation, monocyte and neutrophil chemotaxis, and endothelial production of prothrombotic factors. The varied physiologic effects of thrombin are due to the widespread presence of thrombin receptors in many cell types. The receptor is uniquely activated: thrombin binds to the receptor at the thrombin anion-binding exosite, the receptor ligand ("tethered ligand") apparently being a sequence of 6 amino acids (SFLLRN). Thus, peptides corresponding to the sequence of the tethered ligand can stimulate almost all functions of native thrombin itself. Several intracellular signaling pathways have been identified as important in the restenosis process: the G protein-related pathway, cyclic adenosine monophosphate (cAMP) mediator pathway, and tyrosine kinase activation pathway. In situ hybridization has demonstrated an increase in thrombin receptor mRNA throughout the period of neointimal and vascular lesion development. The mechanism of this increase is unknown, but may be mediated by multiple inflammatory modulators. Several strategies have been tested in animal models for inhibiting thrombin: (1) Hirudin not only prevents thrombin from cleaving fibrinogen, but also prevents thrombin receptor activation. (2) Thrombin receptor antagonist peptides block platelet aggregation effects of thrombin. (3) Mono- and polyclonal antibodies inhibit thrombin receptor activation. (4) Antisense oligonucleotides block thrombin receptor expression.

The angiotensin II type 1 receptor-neprilysin inhibitor LCZ696 blocked aldosterone synthesis in a human adrenocortical cell line.

PubMed

Miura, Shin-Ichiro; Suematsu, Yasunori; Matsuo, Yoshino; Tomita, Sayo; Nakayama, Asuka; Goto, Masaki; Arimura, Tadaaki; Kuwano, Takashi; Yahiro, Eiji; Saku, Keijiro

2016-11-01

A recent clinical study indicated that an angiotensin II (Ang II) type 1 (AT 1 ) receptor-neprilysin inhibitor (ARNi) designated LCZ696 (sacubitril/valsartan, as combined sodium complex) was superior to enalapril at reducing the risks of death and hospitalization due to heart failure. Therefore, we investigated the possible mechanisms of the beneficial effect of LCZ696, in which the inhibition of neprilysin enhances atrial natriuretic peptide (NP) or brain NP (ANP or BNP)-evoked signals that can block Ang II/AT 1 receptor-induced aldosterone (Ald) synthesis in human adrenocortical cells. The binding affinity of valsartan+LBQ657 (active moiety of sacubitril) to the AT 1 receptor was greater than that of valsartan alone in an AT 1 receptor-expressing human embryonic kidney cell-based assay. There was no difference in the dissociation from the AT 1 receptor between valsartan+LBQ657 and valsartan alone. In Ang II-sensitized human adrenocortical cells, ANP or BNP alone, but not LBQ657 or valsartan alone, significantly decreased Ald synthesis. The level of suppression of Ald synthesis by ANP or BNP with LBQ657 was greater than that by ANP or BNP without LBQ657. The suppression of ANP was blocked by inhibitors of regulator of G-protein signaling proteins and cyclic GMP-dependent protein kinase. The inhibition of neprilysin did not change the mRNA levels of the AT 1 receptor, ANP receptor A, regulator of G-protein signaling protein, renin or 3β-hydroxysteroid dehydrogenases. In conclusion, the inhibition of neprilysin by LBQ657 enhances the NP-evoked signals that can block Ang II/AT 1 receptor-induced Ald synthesis in human adrenocortical cells.

Endoplasmic reticulum stress contributes to acetylcholine receptor degradation by promoting endocytosis in skeletal muscle cells.

PubMed

Du, Ailian; Huang, Shiqian; Zhao, Xiaonan; Zhang, Yun; Zhu, Lixun; Ding, Ji; Xu, Congfeng

2016-01-15

After binding by acetylcholine released from a motor neuron, a nicotinic acetylcholine receptor at the neuromuscular junction produces a localized end-plate potential, which leads to muscle contraction. Improper turnover and renewal of acetylcholine receptors contributes to the pathogenesis of myasthenia gravis. In the present study, we demonstrate that endoplasmic reticulum (ER) stress contributes to acetylcholine receptor degradation in C2C12 myocytes. We further show that ER stress promotes acetylcholine receptor endocytosis and lysosomal degradation, which was dampened by blocking endocytosis or treating with lysosome inhibitor. Knockdown of ER stress proteins inhibited acetylcholine receptor endocytosis and degradation, while rescue assay restored its endocytosis and degradation, confirming the effects of ER stress on promoting endocytosis-mediated degradation of junction acetylcholine receptors. Thus, our studies identify ER stress as a factor promoting acetylcholine receptor degradation through accelerating endocytosis in muscle cells. Blocking ER stress and/or endocytosis might provide a novel therapeutic approach for myasthenia gravis. Copyright © 2015 Elsevier B.V. All rights reserved.

Opioid receptor subtypes mediating the noise-induced decreases in high-affinity choline uptake in the rat brain.

PubMed

Lai, H; Carino, M A

1992-07-01

Acute (20 min) exposure to 100-dB white noise elicits a naltrexone-sensitive decrease in sodium-dependent high-affinity choline uptake in the frontal cortex and hippocampus of the rat. In the present study, the subtypes of opioid receptors involved were investigated by pretreating rats with microinjection of specific opioid-receptor antagonists into the lateral cerebroventricle before noise exposure. We found that the noise-induced decrease in high-affinity choline uptake in the hippocampus was blocked by pretreatment with either mu-, delta-, or kappa-opioid-receptor antagonists, whereas the effect of noise on frontal cortical high-affinity choline uptake was blocked by a mu- and delta- but not by a kappa-antagonist. These data further confirm the role of endogenous opioids in mediating the effects of noise on central cholinergic activity and indicate that different neural mechanisms are involved in the effects of noise on the frontal cortical and hippocampal cholinergic systems.

GABA/sub B/ receptor activation inhibits Ca/sup 2 +/-activated potassium channels in synaptosomes: involvement of G-proteins

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

Ticku, M.K.; Delgado, A.

1989-01-01

/sup 86/Rb-efflux assay from preloaded synaptosomes of rat cerebral cortex was developed to study the effect of GABA/sub B/ receptor agonist baclofen on Ca/sup 2 +/-activated K/sup +/-channels. Depolarization of /sup 86/Rb-loaded synaptosomes in physiological buffer increased Ca/sup 2 +/-activated /sup 86/Rb-efflux by 400%. The /sup 86/Rb-efflux was blocked by quinine sulfate, tetraethylammonium, and La/sup 3 +/ indicating the involvement of Ca/sup 2 +/-activated K/sup +/-channels. (-)Baclofen inhibited Ca/sup 2 +/-activated /sup 86/Rb-efflux in a stereospecific manner. The inhibitory effect of (-)baclofen was mediated by GABA/sub B/ receptor activation, since it was blocked by GABA/sub B/ antagonist phaclofen, but notmore » by bicuculline. Further, pertussis toxin also blocked the ability of baclofen or depolarizing action to affect Ca/sup 2 +/-activated K/sup +/-channels. These results suggest that baclofen inhibits Ca/sup 2 +/-activated K/sup +/-channels in synaptosomes and these channels are regulated by G-proteins. This assay may provide an ideal in vitro model to study GABA/sub B/ receptor pharmacology.« less

5-HT receptors as novel targets for optimizing pigmentary responses in dorsal skin melanophores of frog, Hoplobatrachus tigerinus

PubMed Central

Ali, Sharique A; Salim, Saima; Sahni, Tarandeep; Peter, Jaya; Ali, Ayesha S

2012-01-01

BACKGROUND AND PURPOSE Biochemical identification of 5-HT has revealed similar projection patterns across vertebrates. In CNS, 5-HT regulates major physiological functions but its peripheral functions are still emerging. The pharmacology of 5-HT is mediated by a diverse range of receptors that trigger different responses. Interestingly, 5-HT receptors have been detected in pigment cells indicating their role in skin pigmentation. Hence, we investigated the role of this monoaminergic system in amphibian pigment cells, melanophores, to further our understanding of its role in pigmentation biology together with its evolutionary significance. EXPERIMENTAL APPROACH Pharmacological profiling of 5-HT receptors was achieved using potent/selective agonists and antagonists. In vitro responses of melanophores were examined by Mean Melanophores Size Index assay. The melanophores of lower vertebrates are highly sensitive to external stimuli. The immediate cellular responses to drugs were defined in terms of pigment translocation within the cells. KEY RESULTS 5-HT exerted strong concentration-dependent pigment dispersion at threshold dose of 1 × 10−6 g·mL−1. Specific 5-HT1 and 5-HT2 receptor agonists, sumatriptan and myristicin. also induced dose-dependent dispersion. Yohimbine and metergoline synergistically antagonized sumatriptan-mediated dispersion, whereas trazodone partially blocked myristicin-induced dispersion. Conversely, 5-HT3 and 5-HT4 receptor agonists, 1 (3 chlorophenyl) biguanide (1,3 CPB) and 5-methoxytryptamine (5-MT), caused a dose-dependent pigment aggregation. The aggregatory effect of 1,3 CPB was completely blocked by ondansetron, whereas L-lysine partially blocked the effect of 5-MT. CONCLUSIONS AND IMPLICATIONS The results suggest that 5-HT-induced physiological effects are mediated via distinct classes of receptors, which possibly participate in the modulation of pigmentary responses in amphibian. PMID:21880033

Cyproheptadine Enhances the I K of Mouse Cortical Neurons through Sigma-1 Receptor-Mediated Intracellular Signal Pathway

PubMed Central

He, Yan-Lin; Zhang, Chun-Lei; Gao, Xiao-Fei; Yao, Jin-Jing; Hu, Chang-Long; Mei, Yan-Ai

2012-01-01

Cyproheptadine (CPH) is a histamine- and serotonin-receptor antagonist, and its effects are observed recently in the modulation of multiple intracellular signals. In this study, we used cortical neurons and HEK-293 cells transfected with Kv2.1 α-subunit to address whether CPH modify neural voltage-gated K+ channels by a mechanism independent of its serotonergic and histaminergic properties. Our results demonstrate that intracellularly delivered CPH increased the I K by reducing the activity of protein kinas A (PKA). Inhibition of Gi eliminated the CPH-induced effect on both the I K and PKA. Blocking of 5-HT-, M-, D2-, H1- or H2- type GPCR receptors with relevant antagonists did not eliminate the CPH-induced effect on the I K. Antagonists of the sigma-1 receptor, however, blocked the effect of CPH. Moreover, the inhibition of sigma-1 by siRNA knockdown significantly reduced the CPH-induced effect on the I K. On the contrary, sigma-1 receptor agonist mimicked the effects of CPH on the induction of I K. A ligand-receptor binding assay indicated that CPH bound to the sigma-1 receptor. Similar effect of CPH were obtained from HEK-293 cells transfected with the α-subunit of Kv2.1. In overall, we reveal for the first time that CPH enhances the I K by modulating activity of PKA, and that the associated activation of the sigma-1 receptor/Gi-protein pathway might be involved. Our findings illustrate an uncharacterized effect of CPH on neuron excitability through the I K, which is independent of histamine H1 and serotonin receptors. PMID:22844454

Asialoglycoprotein receptor mediates the toxic effects of an asialofetuin-diphtheria toxin fragment A conjugate on cultured rat hepatocytes

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

Cawley, D.B.; Simpson, D.L.; Herschman, H.R.

1981-06-01

We have constructed a toxic hybrid protein that is recognized by asialoglycoprotein (ASGP) receptors of cultured rat hepatocytes. The conjugate consists of fragment A of diphtheria toxin (DTA) linked by a disulfide bond to asialofetuin (ASF). This conjugate is highly toxic, inhibiting protein synthesis in primary rat hepatocytes at concentrations as low as 10 pM. The ASF-DTA conjugate was 600 and 1800 times as toxic as diphtheria toxin and DTA, respectively, on primary rat hepatocytes. The ASGP receptor recognizes galactose-terminated proteins. We tested a series of glycoproteins for their ability to block the action of the ASF-DTA conjugate. Fetuin andmore » orosomucoid, two glycoproteins with terminal sialic acid on their oligosaccharide chains, did not block the action of the conjugate. Their galactose-terminated asialo derivatives, ASF and asialoorosomucoid, as expected, did block the action of the conjugate. The N-acetylglucosaminyl-terminated derivative (asialoagalactoorosomucoid) had no appreciable effect on the activity of the conjugate. We tested the ASF-DTA conjugate on six cell types; except for primary rat hepatocytes, none of them were affected by a high concentration (10 nM) of ASF-DTA conjugate. A fetuin-DTA conjugate was less toxic by a factor of 300 than the ASF-DTA conjugate and exerted its effects primarily through non-receptor-mediated mechanisms. The highly toxic ASF-DTA conjugate is cell-type specific, and its action is mediated by a well-characterized receptor, whose mechanism of receptor-ligand internalization has been extensively investigated.« less

Asialoglycoprotein receptor mediates the toxic effects of an asialofetuin-diphtheria toxin fragment A conjugate on cultured rat hepatocytes.

PubMed Central

Cawley, D B; Simpson, D L; Herschman, H R

1981-01-01

We have constructed a toxic hybrid protein that is recognized by asialoglycoprotein (ASGP) receptors of cultured rat hepatocytes. The conjugate consists of fragment A of diphtheria toxin (DTA) linked by a disulfide bond to asialofetuin (ASF). This conjugate is highly toxic, inhibiting protein synthesis in primary rat hepatocytes at concentrations as low as 10 pM. The ASF-DTA conjugate was 600 and 1800 times as toxic as diphtheria toxin and DTA, respectively, on primary rat hepatocytes. The ASGP receptor recognizes galactose-terminated proteins. We tested a series of glycoproteins for their ability to block the action of the ASF-DTA conjugate. Fetuin and orosomucoid, two glycoproteins with terminal sialic acid on their oligosaccharide chains, did not block the action of the conjugate. Their galactose-terminated asialo derivatives, ASF and asialoorosomucoid, as expected, did block the action of the conjugate. The N-acetylglucosaminyl-terminated derivative (asialogalactoorsomucoid) had no appreciable effect on the activity of the conjugate. We tested the ASF-DTA conjugate on six cell types; except for primary rat hepatocytes, none of them were affected by a high concentration (10 nM) of ASF-DTA conjugate. A fetuin-DTA conjugate was less toxic by a factor of 300 than the ASF-DTA conjugate and exerted its effects primarily through non-receptor-mediated mechanisms. The highly toxic ASF-DTA conjugate is cell-type specific, and its action is mediated by a well-characterized receptor, whose mechanism of receptor-ligand internalization has been extensively investigated. Images PMID:6167984

Oxotremorine-M potentiates NMDA receptors by muscarinic receptor dependent and independent mechanisms.

PubMed

Zwart, Ruud; Reed, Hannah; Sher, Emanuele

2018-01-01

Muscarinic acetylcholine M1 receptors play an important role in synaptic plasticity in the hippocampus and cortex. Potentiation of NMDA receptors as a consequence of muscarinic acetylcholine M1 receptor activation is a crucial event mediating the cholinergic modulation of synaptic plasticity, which is a cellular mechanism for learning and memory. In Alzheimer's disease, the cholinergic input to the hippocampus and cortex is severely degenerated, and agonists or positive allosteric modulators of M1 receptors are therefore thought to be of potential use to treat the deficits in cognitive functions in Alzheimer's disease. In this study we developed a simple system in which muscarinic modulation of NMDA receptors can be studied in vitro. Human M1 receptors and NR1/2B NMDA receptors were co-expressed in Xenopus oocytes and various muscarinic agonists were assessed for their modulatory effects on NMDA receptor-mediated responses. As expected, NMDA receptor-mediated responses were potentiated by oxotremorine-M, oxotremorine or xanomeline when the drugs were applied between subsequent NMDA responses, an effect which was fully blocked by the muscarinic receptor antagonist atropine. However, in oocytes expressing NR1/2B NMDA receptors but not muscarinic M1 receptors, oxotremorine-M co-applied with NMDA also resulted in a potentiation of NMDA currents and this effect was not blocked by atropine, demonstrating that oxotremorine-M is able to directly potentiate NMDA receptors. Oxotremorine, which is a close analogue of oxotremorine-M, and xanomeline, a chemically distinct muscarinic agonist, did not potentiate NMDA receptors by this direct mechanism. Comparing the chemical structures of the three different muscarinic agonists used in this study suggests that the tri-methyl ammonium moiety present in oxotremorine-M is important for the compound's interaction with NMDA receptors. Copyright © 2017 Elsevier Inc. All rights reserved.

Blocking endocytosis in Drosophila's circadian pacemaker neurons interferes with the endogenous clock in a PDF-dependent way.

PubMed

Wülbeck, Corinna; Grieshaber, Eva; Helfrich-Förster, Charlotte

2009-10-01

The neuropeptide pigment-dispersing factor (PDF) plays an essential role in the circadian clock of the fruit fly Drosophila melanogaster, but many details of PDF signaling in the clock network are still unknown. We tried to interfere with PDF signaling by blocking the GTPase Shibire in PDF neurons. Shibire is an ortholog of the mammalian Dynamins and is essential for endocytosis of clathrin-coated vesicles at the plasma membrane. Such endocytosis is used for neurotransmitter reuptake by presynaptic neurons, which is a prerequisite of synaptic vesicle recycling, and receptor-mediated endocytosis in the postsynaptic neuron, which leads to signal termination. By blocking Shibire function via overexpression of a dominant negative mutant form of Shibire in PDF neurons, we slowed down the behavioral rhythm by 3 h. This effect was absent in PDF receptor null mutants, indicating that we interfered with PDF receptor-mediated endocytosis. Because we obtained similar behavioral phenotypes by increasing the PDF level in regions close to PDF neurons, we conclude that blocking Shibire did prolong PDF signaling in the neurons that respond to PDF. Obviously, terminating the PDF signaling via receptor-mediated endocytosis is a crucial step in determining the period of behavioral rhythms.

Activation of µ-opioid receptors and block of KIR3 potassium channels and NMDA receptor conductance by l- and d-methadone in rat locus coeruleus

PubMed Central

Matsui, Aya; Williams, John T

2010-01-01

BACKGROUND AND PURPOSE Methadone activates opioid receptors to increase a potassium conductance mediated by G-protein-coupled, inwardly rectifying, potassium (KIR3) channels. Methadone also blocks KIR3 channels and N-methyl-D-aspartic acid (NMDA) receptors. However, the concentration dependence and stereospecificity of receptor activation and channel blockade by methadone on single neurons has not been characterized. EXPERIMENTAL APPROACH Intracellular and whole-cell recording were made from locus coeruleus neurons in brain slices and the activation of µ-opioid receptors and blockade of KIR3 and NMDA channels with l- and d-methadone was examined. KEY RESULTS The potency of l-methadone, measured by the amplitude of hyperpolarization was 16.5-fold higher than with d-methadone. A maximum hyperpolarization was caused by both enantiomers (∼30 mV); however, the maximum outward current measured with whole-cell voltage-clamp recording was smaller than the current induced by [Met]5enkephalin. The KIR3 conductance induced by activation of α2-adrenoceptors was decreased with high concentrations of l- and d-methadone (10–30 µM). In addition, methadone blocked the resting inward rectifying conductance (KIR). Both l- and d-methadone blocked the NMDA receptor-dependent current. The block of NMDA receptor-dependent current was voltage-dependent suggesting that methadone acted as a channel blocker. CONCLUSIONS AND IMPLICATIONS Methadone activated µ-opioid receptors at low concentrations in a stereospecific manner. KIR3 and NMDA receptor channel block was not stereospecific and required substantially higher concentrations. The separation in the concentration range suggests that the activation of µ-opioid receptors rather than the channel blocking properties mediate both the therapeutic and toxic actions of methadone. PMID:20659105

NK1 receptor activation in rat rostral ventrolateral medulla selectively attenuates somato-sympathetic reflex while antagonism attenuates sympathetic chemoreflex.

PubMed

Makeham, John M; Goodchild, Ann K; Pilowsky, Paul M

2005-06-01

The effects of activation and blockade of the neurokinin 1 (NK1) receptor in the rostral ventrolateral medulla (RVLM) on arterial blood pressure (ABP), splanchnic sympathetic nerve activity (sSNA), phrenic nerve activity, the somato-sympathetic reflex, baroreflex, and chemoreflex were studied in urethane-anesthetized and artificially ventilated Sprague-Dawley rats. Bilateral microinjection of either the stable substance P analog (pGlu5, MePhe8, Sar9)SP(5-11) (DiMe-SP) or the highly selective NK1 agonist [Sar9, Met (O(2))11]SP into the RVLM resulted in an increase in ABP, sSNA, and heart rate and an abolition of phrenic nerve activity. The effects of [Sar9, Met (O(2))11]SP were blocked by the selective nonpeptide NK1 receptor antagonist WIN 51708. NK1 receptor activation also dramatically attenuated the somato-sympathetic reflex elicited by tibial nerve stimulation, while leaving the baroreflex and chemoreflex unaffected. This effect was again blocked by WIN 51708. NK1 receptor antagonism in the RVLM, with WIN 51708 significantly attenuated the sympathoexcitatory response to hypoxia but had no effect on baseline respiratory function. Our findings suggest that substance P and the NK1 receptor play a significant role in the cardiorespiratory reflexes integrated within the RVLM.

Panicolytic-like action of bradykinin in the dorsal periaqueductal gray through μ-opioid and B2-kinin receptors.

PubMed

Sestile, Caio César; Maraschin, Jhonatan Christian; Gama, Vanessa Scalco; Zangrossi, Hélio; Graeff, Frederico Guilherme; Audi, Elisabeth Aparecida

2017-09-01

A wealth of evidence has shown that opioid and kinin systems may control proximal defense in the dorsal periaqueductal gray matter (dPAG), a critical panic-associated area. Studies with drugs that interfere with serotonin-mediated neurotransmission suggest that the μ-opioid receptor (MOR) synergistically interacts with the 5-HT 1A receptor in the dPAG to inhibit escape, a panic-related behavior. A similar inhibitory effect has also been reported after local administration of bradykinin (BK), which is blocked by the non-selective opioid receptor antagonist naloxone. The latter evidence, points to an interaction between BK and opioids in the dPAG. We further explored the existence of this interaction through the dPAG electrical stimulation model of panic. We also investigated whether intra-dPAG injection of captopril, an inhibitor of the angiotensin-converting enzyme (ACE) that also degrades BK, causes a panicolytic-like effect. Our results showed that intra-dPAG injection of BK inhibited escape performance in a dose-dependent way, and this panicolytic-like effect was blocked by the BK type 2 receptor (B2R) antagonist HOE-140, and by the selective MOR antagonist CTOP. Conversely, the panicolytic-like effect caused by local administration of the selective MOR agonist DAMGO was antagonized by pre-treatment with either CTOP or HOE-140, indicating cross-antagonism between MOR and B2R. Finally, intra-dPAG injection of captopril also impaired escape in a dose-dependent way, and this panicolytic-like effect was blocked by pretreatment with HOE-140, suggesting mediation by endogenous BK. The panicolytic-like effect of captopril indicates that the use of ACE inhibitors in the clinical management of panic disorder may be worth exploring. Copyright © 2017 Elsevier Ltd. All rights reserved.

Epitope mapping of tsh receptor-blocking antibodies in Graves' disease that appear during pregnancy.

PubMed

Kung, A W; Lau, K S; Kohn, L D

2001-08-01

Spontaneous remission of Graves' disease during pregnancy is thought to be due to a reduction of thyroid-stimulating antibody activity. We suspected, however, that a broader change in TSH receptor antibody characteristics might play an important role in modulating disease activity during pregnancy. We measured TSH binding inhibitory Ig, thyroid-stimulating antibody, and thyroid stimulating-blocking antibody activities in 13 pregnant Graves' disease patients at first, second, and third trimesters and 4 months postpartum. To measure and epitope-map thyroid-stimulating antibody and thyroid stimulating-blocking antibody activities, we used CHO cells transfected with wild-type human TSH receptor or with several TSH receptor-LH/hCG receptor chimeras: Mc1+2, Mc2, and Mc4. These chimeric cells have their respective TSH receptor residues 9-165, 90-165, and 261-370 substituted with equivalent residues of the LH/hCG receptor. Overall thyroid-stimulating antibody decreased, whereas thyroid stimulating-blocking antibody increased progressively during pregnancy. TSH binding inhibitory Ig fluctuated in individual patients, but overall the activities remained statistically unchanged. Thyroid stimulating-blocking antibody appeared in subjects who were either negative for thyroid-stimulating antibody or whose thyroid-stimulating antibody activity increased or decreased during pregnancy. Epitope mapping showed that the thyroid-stimulating antibodies were mainly directed against residues 9-165 of the N-terminus of the TSH receptor extracellular domain. All thyroid stimulating-blocking antibodies had blocking activities against residues 261-370 of the C-terminus of the ectodomain. However, the majority of the thyroid stimulating-blocking antibodies had a hybrid conformational epitope directed against N-terminal residues 9-89 or 90-165 as well. Despite a change in the activity level, we did not observe any change in the epitope of either the stimulatory or blocking Abs as pregnancy advanced. In conclusion, a change in the specificity of TSH receptor antibody from stimulatory to blocking activity was observed during pregnancy, and the appearance of thyroid stimulating-blocking antibody may contribute to the remission of Graves' disease during pregnancy.

Evidence that central dopamine receptors modulate sympathetic neuronal activity to the adrenal medulla to alter glucoregulatory mechanisms.

PubMed

Arnerić, S P; Chow, S A; Bhatnagar, R K; Webb, R L; Fischer, L J; Long, J P

1984-02-01

Previous reports suggest that analogs of dopamine (DA) can produce hyperglycemia in rats by interacting with DA receptors. Experiments reported here indicate the site of action and describe the metabolic sequalae associated with the hyperglycemic effect of apomorphine (APO), produced in conscious unrestrained rats. Apomorphine was more potent when administered by intracerebroventricular (i.c.v.) injection than when given subcutaneously (s.c.). Very small doses of the DA receptor antagonist pimozide, given intraventricularly, blocked the hyperglycemic effect of apomorphine administered subcutaneously. Sectioning of the spinal cord at thoracic vertebra T1-2 or sectioning the greater splanchnic nerve blocked apomorphine-induced hyperglycemia; whereas section of the superior colliculus or section at T5-6 had no effect. A dose of apomorphine or epinephrine (EPI) producing a similar degree of hyperglycemia elevated the concentration of EPI in serum to a similar degree, and the increase in EPI in serum preceded the increase in glucose in serum. Fasting animals for 2 or 18 hr had no significant effect on EPI- or apomorphine-induced hyperglycemia despite a reduction (91-93%) of the glycogen content of liver and skeletal muscle during the 18 hr fast. 5-Methoxyindole-2-carboxylic acid (MICA), an inhibitor of gluconeogenesis, blocked EPI- and apomorphine-induced hyperglycemia in rats fasted for 18 hr. However, 5-methoxyindole-2-carboxylic acid was ineffective in blocking hyperglycemia in animals fasted for 2 hr. Changes in insulin or glucagon in serum alone cannot account for the hyperglycemic action of apomorphine. These data demonstrate that apomorphine interacts with central DA receptors located in the hindbrain to activate sympathetic neuronal activity to the adrenal gland which subsequently releases epinephrine to alter homeostasis of glucose. Epinephrine may then, depending on the nutritional status, facilitate glycogenolytic or gluconeogenic processes to produce hyperglycemia.

Interdependence of Platelet-Derived Growth Factor and Estrogen-Signaling Pathways in Inducing Neonatal Rat Testicular Gonocytes Proliferation1

PubMed Central

Thuillier, Raphael; Mazer, Monty; Manku, Gurpreet; Boisvert, Annie; Wang, Yan; Culty, Martine

2010-01-01

We previously found that platelet-derived growth factor (PDGF) and 17beta-estradiol stimulate gonocyte proliferation in a dose-dependent, nonadditive manner. In the present study, we report that gonocytes express RAF1, MAP2K1, and MAPK1/3. Inhibition of RAF1 and MAP2K1/2, but not phosphoinositide-3-kinase, blocked PDGF-induced proliferation. AG-370, an inhibitor of PDGF receptor kinase activity, suppressed not only PDGF-induced proliferation but also that induced by 17beta-estradiol. In addition, RAF1 and MAP2K1/2 inhibitors blocked 17beta-estradiol-activated proliferation. The estrogen receptor antagonist ICI 182780 inhibited both the effects of 17beta-estradiol and PDGF. PDGF lost its stimulatory effect when steroid-depleted serum or no serum was used. Similarly, 17beta-estradiol did not induce gonocyte proliferation in the absence of PDGF. The xenoestrogens genistein, bisphenol A, and DES, but not coumestrol, stimulated gonocyte proliferation in a dose-dependent and PDGF-dependent manner similarly to 17beta-estradiol. Their effects were blocked by ICI 182780, suggesting that they act via the estrogen receptor. AG-370 blocked genistein and bisphenol A effects, demonstrating their requirement of PDGF receptor activation in a manner similar to 17beta-estradiol. These results demonstrate the interdependence of PDGF and estrogen pathways in stimulating in vitro gonocyte proliferation, suggesting that this critical step in gonocyte development might be regulated in vivo by the coordinated action of PDGF and estrogen. Thus, the inappropriate exposure of gonocytes to xenoestrogens might disrupt the crosstalk between the two pathways and potentially interfere with gonocyte development. PMID:20089883

Opioid receptor activation triggering downregulation of cAMP improves effectiveness of anti-cancer drugs in treatment of glioblastoma

PubMed Central

Friesen, Claudia; Hormann, Inis; Roscher, Mareike; Fichtner, Iduna; Alt, Andreas; Hilger, Ralf; Debatin, Klaus-Michael; Miltner, Erich

2014-01-01

Glioblastoma are the most frequent and malignant human brain tumors, having a very poor prognosis. The enhanced radio- and chemoresistance of glioblastoma and the glioblastoma stem cells might be the main reason why conventional therapies fail. The second messenger cyclic AMP (cAMP) controls cell proliferation, differentiation, and apoptosis. Downregulation of cAMP sensitizes tumor cells for anti-cancer treatment. Opioid receptor agonists triggering opioid receptors can activate inhibitory Gi proteins, which, in turn, block adenylyl cyclase activity reducing cAMP. In this study, we show that downregulation of cAMP by opioid receptor activation improves the effectiveness of anti-cancer drugs in treatment of glioblastoma. The µ-opioid receptor agonist D,L-methadone sensitizes glioblastoma as well as the untreatable glioblastoma stem cells for doxorubicin-induced apoptosis and activation of apoptosis pathways by reversing deficient caspase activation and deficient downregulation of XIAP and Bcl-xL, playing critical roles in glioblastomas’ resistance. Blocking opioid receptors using the opioid receptor antagonist naloxone or increasing intracellular cAMP by 3-isobutyl-1-methylxanthine (IBMX) strongly reduced opioid receptor agonist-induced sensitization for doxorubicin. In addition, the opioid receptor agonist D,L-methadone increased doxorubicin uptake and decreased doxorubicin efflux, whereas doxorubicin increased opioid receptor expression in glioblastomas. Furthermore, opioid receptor activation using D,L-methadone inhibited tumor growth significantly in vivo. Our findings suggest that opioid receptor activation triggering downregulation of cAMP is a promising strategy to inhibit tumor growth and to improve the effectiveness of anti-cancer drugs in treatment of glioblastoma and in killing glioblastoma stem cells. PMID:24626197

A role of nucleus accumbens dopamine receptors in the nucleus accumbens core, but not shell, in fear prediction error.

PubMed

Li, Susan S Y; McNally, Gavan P

2015-08-01

Two experiments used an associative blocking design to study the role of dopamine receptors in the nucleus accumbens shell (AcbSh) and core (AcbC) in fear prediction error. Rats in the experimental groups were trained to a visual fear-conditioned stimulus (conditional stimulus [CS]) A in Stage I, whereas rats in the control groups were not. In Stage II, all rats received compound fear conditioning of the visual CSA and an auditory CSB. Rats were later tested for their fear responses to CSB. All rats received microinjections of saline or the D1-D2 receptor antagonist cis-(z)-flupenthixol prior to Stage II. These microinjections targeted either the AcbSh (Experiment 1) or the AcbC (Experiment 2). In each experiment, Stage I fear conditioning of CSA blocked fear learning to CSB. Microinjection of cis-(z)-flupenthixol (10 or 20 μg) into the AcbSh (Experiment 1) had no effect on fear learning or associative blocking. In contrast, microinjection of cis-(z)-flupenthixol (10 or 20 μg) into the AcbC (Experiment 2) attenuated blocking and so enabled fear learning to CSB. These results identify the AcbC as the critical locus for dopamine receptor contributions to fear prediction error and the associative blocking of fear learning. (c) 2015 APA, all rights reserved).

Hashimoto's thyroiditis with heterogeneous antithyrotropin receptor antibodies: unique epitopes may contribute to the regulation of thyroid function by the antibodies.

PubMed

Akamizu, T; Kohn, L D; Hiratani, H; Saijo, M; Tahara, K; Nakao, K

2000-06-01

Blocking-type TSH-binding inhibitor Igs (TBIIs) are known to cause hypothyroidism and an atrophic thyroid gland in patients with primary myxedema. They can block the activity of thyroid-stimulating antibodies (TSAbs) in Graves' patients as well as the activity of TSH. The majority of the epitopes for these blocking-type TBIIs have been, and are shown herein, to be present on the C-terminal region of the extracellular domain of the human TSH receptor (TSHR), whereas those for Graves' TSAbs are on the N-terminus. We report on a patient with Hashimoto's thyroiditis who suffered from mild hypothyroidism and a moderately sized goiter. Her serum had a potent blocking-type TBII and a weak TSAb in human and porcine TSHR systems. Using human TSHR/lutropin-CG receptor chimeras, we determined that the functional epitope of her blocking-type TBII was uniquely present on the N-terminal, rather than the C-terminal, region of the extracellular domain of the TSHR, unlike the case for blocking-type TBIIs in primary myxedema patients. The epitope of her TSAb was also unusual. Although the functional epitopes of most TSAbs are known to involve the N-terminal region of the receptor, her TSAb epitope did not seem to be present solely on the N- or C-terminus of the extracellular domain of the receptor. Blocking-type TBIIs from patients with primary myxedema blocked her TSAb activity as well as stimulation by TSH; her blocking-type TBII was able to only partially block her TSAb. In contrast, her blocking-type TBII almost completely blocked TSAbs from Graves' patients. Thus, we suggest that the unique epitopes of this patient's heterogeneous population of TSH receptor antibodies, at least in part, contribute to regulation of her thyroid function.

Alcohol and Caffeine: The Perfect Storm

PubMed Central

O'Brien, Mary Claire

2011-01-01

Although it is widely believed that caffeine antagonizes the intoxicating effects of alcohol, the molecular mechanisms underlying their interaction are incompletely understood. It is known that both caffeine and alcohol alter adenosine neurotransmission, but the relationship is complex, and may be dose dependent. In this article, we review the available literature on combining caffeine and alcohol. Ethical constraints prohibit laboratory studies that would mimic the high levels of alcohol intoxication achieved by many young people in real-world settings, with or without the addition of caffeine. We propose a possible neurochemical mechanism for the increase in alcohol consumption and alcohol-related consequences that have been observed in persons who simultaneously consume caffeine. Caffeine is a nonselective adenosine receptor antagonist. During acute alcohol intake, caffeine antagonizes the “unwanted” effects of alcohol by blocking the adenosine A1 receptors that mediate alcohol's somnogenic and ataxic effects. The A1 receptor–mediated “unwanted” anxiogenic effects of caffeine may be ameliorated by alcohol-induced increase in the extracellular concentration of adenosine. Moreover, by means of interactions between adenosine A2A and dopamine D2 receptors, caffeine-mediated blockade of adenosine A2A receptors can potentiate the effects of alcohol-induced dopamine release. Chronic alcohol intake decreases adenosine tone. Caffeine may provide a “treatment” for the withdrawal effects of alcohol by blocking the effects of upregulated A1 receptors. Finally, blockade of A2A receptors by caffeine may contribute to the reinforcing effects of alcohol. PMID:24761263

Constitutively active 5-HT2/α1 receptors facilitate muscle spasms after human spinal cord injury

PubMed Central

D'Amico, Jessica M.; Murray, Katherine C.; Li, Yaqing; Chan, K. Ming; Finlay, Mark G.; Bennett, David J.

2013-01-01

In animals, the recovery of motoneuron excitability in the months following a complete spinal cord injury is mediated, in part, by increases in constitutive serotonin (5-HT2) and norepinephrine (α1) receptor activity, which facilitates the reactivation of calcium-mediated persistent inward currents (CaPICs) without the ligands serotonin and norepinephrine below the injury. In this study we sought evidence for a similar role of constitutive monoamine receptor activity in the development of spasticity in human spinal cord injury. In chronically injured participants with partially preserved sensory and motor function, the serotonin reuptake inhibitor citalopram facilitated long-lasting reflex responses (spasms) previously shown to be mediated by CaPICs, suggesting that in incomplete spinal cord injury, functional descending sources of monoamines are present to activate monoamine receptors below the lesion. However, in participants with motor or motor/sensory complete injuries, the inverse agonist cyproheptadine, which blocks both ligand and constitutive 5-HT2/α1 receptor activity, decreased long-lasting reflexes, whereas the neutral antagonist chlorpromazine, which only blocks ligand activation of these receptors, had no effect. When tested in noninjured control participants having functional descending sources of monoamines, chlorpromazine was effective in reducing CaPIC-mediated motor unit activity. On the basis of these combined results, it appears that in severe spinal cord injury, facilitation of persistent inward currents and muscle spasms is mainly mediated by the activation of constitutive 5-HT2 and α1 receptor activity. Drugs that more selectively block these constitutively active monoamine receptors may provide better oral control of spasticity, especially in motor complete spinal cord injury where reducing motoneuron excitability is the primary goal. PMID:23221402

Further evidence that tachykinin-induced contraction of human isolated bronchus is mediated only by NK2-receptors.

PubMed

Sheldrick, R L; Rabe, K F; Fischer, A; Magnussen, H; Coleman, R A

1995-11-01

The tachykinin-receptors mediating contraction of human bronchus have been characterized using both tachykinin-receptor selective agonists and blocking drugs under conditions where tachykinin metabolism by endogenous peptidases has been controlled, and true equilibrium conditions have been established. The findings that neurokinin A (EC50 = 2 nM) is the most potent agonist, and the NK2-receptor selective agonist, GR64349, is only 3-fold weaker, whereas agonists selective for NK1-receptors, substance P methyl ester, or NK3-receptors, senktide, are inactive, suggest that this effect is mediated exclusively by NK2-receptors. This is supported by observations that GR64349 is antagonised by the selective NK2-receptor blocking drugs, MEN10207 (pA2 = 6.7), R396 (pA2 = 6.1), (+/-)SR48968 (pA2 = 8.4) and GR159897 (pA2 = 8.6), but not by the NK1-receptor blocking drug, GR82334 (pA2 < 5). In approximately half of the preparations, the peptidase inhibitors, phosphoramidon (1 microM) and bestatin (100 microM), caused a marked and well-maintained contraction (approximately 20% of neurokinin A maximum), which may indicate a role for endogenous tachykinins in the regulation of tone in this preparation. This is supported by the finding that neurokinin A-immunoreactive nerve fibres are located around intrinsic neurones of local ganglia and within the smooth muscle layer of this preparation.

Bisphenol A and Related Alkylphenols Exert Nongenomic Estrogenic Actions Through a G Protein-Coupled Estrogen Receptor 1 (Gper)/Epidermal Growth Factor Receptor (Egfr) Pathway to Inhibit Meiotic Maturation of Zebrafish Oocytes1

PubMed Central

Fitzgerald, Amanda C.; Peyton, Candace; Dong, Jing; Thomas, Peter

2015-01-01

Xenobiotic estrogens, such as bisphenol A (BPA), disrupt a wide variety of genomic estrogen actions, but their nongenomic estrogen actions remain poorly understood. We investigated nongenomic estrogenic effects of low concentrations of BPA and three related alkylphenols on the inhibition of zebrafish oocye maturation (OM) mediated through a G protein-coupled estrogen receptor 1 (Gper)-dependent epidermal growth factor receptor (Egfr) pathway. BPA (10–100 nM) treatment for 3 h mimicked the effects of estradiol-17beta (E2) and EGF, decreasing spontaneous maturation of defolliculated zebrafish oocytes, an effect not blocked by coincubation with actinomycin D, but blocked by coincubation with a Gper antibody. BPA displayed relatively high binding affinity (15.8% that of E2) for recombinant zebrafish Gper. The inhibitory effects of BPA were attenuated by inhibition of upstream regulators of Egfr, intracellular tyrosine kinase (Src) with PP2, and matrix metalloproteinase with ilomastat. Treatment with an inhibitor of Egfr transactivation, AG1478, and an inhibitor of the mitogen-activated protein kinase (MAPK) 3/1 pathway, U0126, increased spontaneous OM and blocked the inhibitory effects of BPA, E2, and the selective GPER agonist, G-1. Western blot analysis showed that BPA (10–200 nM) mimicked the stimulatory effects of E2 and EGF on Mapk3/1 phosphorylation. Tetrabromobisphenol A, 4-nonylphenol, and tetrachlorobisphenol A (5–100 nM) also inhibited OM, an effect blocked by cotreatment with AG1478, as well as with the GPER antagonist, G-15, and displayed similar binding affinities as BPA to zebrafish Gper. The results suggest that BPA and related alkylphenols disrupt zebrafish OM by a novel nongenomic estrogenic mechanism involving activation of the Gper/Egfr/Mapk3/1 pathway. PMID:26490843

Bisphenol A and Related Alkylphenols Exert Nongenomic Estrogenic Actions Through a G Protein-Coupled Estrogen Receptor 1 (Gper)/Epidermal Growth Factor Receptor (Egfr) Pathway to Inhibit Meiotic Maturation of Zebrafish Oocytes.

PubMed

Fitzgerald, Amanda C; Peyton, Candace; Dong, Jing; Thomas, Peter

2015-12-01

Xenobiotic estrogens, such as bisphenol A (BPA), disrupt a wide variety of genomic estrogen actions, but their nongenomic estrogen actions remain poorly understood. We investigated nongenomic estrogenic effects of low concentrations of BPA and three related alkylphenols on the inhibition of zebrafish oocye maturation (OM) mediated through a G protein-coupled estrogen receptor 1 (Gper)-dependent epidermal growth factor receptor (Egfr) pathway. BPA (10-100 nM) treatment for 3 h mimicked the effects of estradiol-17beta (E2) and EGF, decreasing spontaneous maturation of defolliculated zebrafish oocytes, an effect not blocked by coincubation with actinomycin D, but blocked by coincubation with a Gper antibody. BPA displayed relatively high binding affinity (15.8% that of E2) for recombinant zebrafish Gper. The inhibitory effects of BPA were attenuated by inhibition of upstream regulators of Egfr, intracellular tyrosine kinase (Src) with PP2, and matrix metalloproteinase with ilomastat. Treatment with an inhibitor of Egfr transactivation, AG1478, and an inhibitor of the mitogen-activated protein kinase (MAPK) 3/1 pathway, U0126, increased spontaneous OM and blocked the inhibitory effects of BPA, E2, and the selective GPER agonist, G-1. Western blot analysis showed that BPA (10-200 nM) mimicked the stimulatory effects of E2 and EGF on Mapk3/1 phosphorylation. Tetrabromobisphenol A, 4-nonylphenol, and tetrachlorobisphenol A (5-100 nM) also inhibited OM, an effect blocked by cotreatment with AG1478, as well as with the GPER antagonist, G-15, and displayed similar binding affinities as BPA to zebrafish Gper. The results suggest that BPA and related alkylphenols disrupt zebrafish OM by a novel nongenomic estrogenic mechanism involving activation of the Gper/Egfr/Mapk3/1 pathway. © 2015 by the Society for the Study of Reproduction, Inc.

Dopamine D2 receptors mediate the increase in reinstatement of the conditioned rewarding effects of cocaine induced by acute social defeat.

PubMed

Reguilón, Marina Daiana; Montagud-Romero, Sandra; Ferrer-Pérez, Carmen; Roger-Sánchez, Concepción; Aguilar, María Asunción; Miñarro, José; Rodríguez-Arias, Marta

2017-03-15

Social stress modifies the activity of brain areas involved in the rewarding effects of psychostimulants, inducing neuroadaptations in the dopaminergic mesolimbic system and modifying the sensitivity of dopamine receptors. In the present study we evaluated the effect of the dopamine D 1 - and D 2 -like receptor antagonists (SCH23390 and raclopride, respectively) on the short-time effects of acute social defeat (ASD). Male OF1 mice were socially defeated before each conditioning session of the conditioned place preference (CPP) induced by 1mg/kg or 25mg/kg of cocaine plus the corresponding dopamine antagonist. A final experiment was designed to evaluate the effect of the dopamine antagonists on the CPP induced by 3mg/kg of cocaine with or without a stress experience. Mice exposed to ASD showed an increase in reinstatement of the conditioned reinforcing effects of cocaine that was blocked by all of the dopamine receptor antagonists. Blockade of dopamine D 2 -like receptors with raclopride specifically prevented the effects of stress without affecting the rewarding properties of cocaine. However, SCH23390 inhibited cocaine-induced preference in the control groups and even induced aversion in defeated mice conditioned with the lower dose of cocaine. Moreover, the lowest dose of SCH23390 blocked the rewarding effects of 3mg/kg of cocaine-induced CPP. Our results confirm that the dopamine D 2 receptor is involved in the short-term effects of ASD on the rewarding effects of cocaine. The dopamine D 1 receptor is clearly involved in the rewarding effects of cocaine, but its role in the effects of ASD remains to be demonstrated. Copyright © 2017 Elsevier B.V. All rights reserved.

Naloxone-blocked depriming effect of anxiolytic selank on apomorphine-induced behavioral manifestations of hyperfunction of dopamine system.

PubMed

Meshavkin, V K; Kost, N V; Sokolov, O Yu; Zolotarev, Yu A; Myasoedov, N F; Zozulya, A A

2006-11-01

Peptide anxiolytic selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro) applied intraperitoneally in doses of 0.01, 0.1, 1.0, and 10.0 mg/kg to mice reduces behavioral manifestations of dopaminergic system induced by apomorphine in the verticalization test. This effect was comparable to that of atypical antipsychotic olanzapine in near-therapeutic doses (0.1 and 1.0 mg/kg, intraperitoneally) and was blocked with nonselective opioid receptor antagonist naloxone (10 mg/kg, intraperitoneally). Radioreceptor assay showed that selank did not displace nonselective D2-dopamine receptor antagonist (3)H-spiperone (EC50>100 microM) and delta- and micro-opioid receptor ligand 3H-DADLE (EC50>40 microM) from specific binding sites on rat brain membranes. It is hypothesized that the revealed behavioral effect of selank is mediated by its modulating effect on the endogenous opioid system and specifically, by its effect on activity of enkephalin-degrading enzymes.

LSD and DOB: interaction with 5-HT2A receptors to inhibit NMDA receptor-mediated transmission in the rat prefrontal cortex.

PubMed

Arvanov, V L; Liang, X; Russo, A; Wang, R Y

1999-09-01

Both the phenethylamine hallucinogen (-)-1-2, 5-dimethoxy-4-bromophenyl-2-aminopropane (DOB), a selective serotonin 5-HT2A,2C receptor agonist, and the indoleamine hallucinogen D-lysergic acid diethylamide (LSD, which binds to 5-HT1A, 1B, 1D, 1E, 1F, 2A, 2C, 5, 6, 7, dopamine D1 and D2, and alpha1 and alpha2 adrenergic receptors), but not their non-hallucinogenic congeners, inhibited N-methyl-D-aspartate (NMDA)-induced inward current and NMDA receptor-mediated synaptic responses evoked by electrical stimulation of the forceps minor in pyramidal cells of the prefrontal cortical slices. The inhibitory effect of hallucinogens was mimicked by 5-HT in the presence of selective 5-HT1A and 5-HT3 receptor antagonists. The inhibitory action of DOB, LSD and 5-HT on the NMDA transmission was blocked by the 5-HT2A receptor antagonists R-(+)-alpha-(2, 3-dimethoxyphenil)-1-[4-fluorophenylethyl]-4-piperidineme thanol (M100907) and ketanserin. However, at low concentrations, when both LSD and DOB by themselves only partially depressed the NMDA response, they blocked the inhibitory effect of 5-HT, suggesting a partial agonist action. Whereas N-(4-aminobutyl)-5-chloro-2-naphthalenesulphonamide (W-7, a calmodulin antagonist) and N-[2-[[[3-(4'-chlorophenyl)- 2-propenyl]methylamino]methyl]phenyl]-N-(2-hydroxyethyl)-4'-methoxy-b enzenesulphonamide phosphate (KN-93, a Ca2+/CaM-KII inhibitor), but not the negative control 2-[N-4'methoxybenzenesulphonyl]amino-N-(4'-chlorophenyl)-2-propeny l-N -methylbenzylamine phosphate (KN-92), blocked the inhibitory action of LSD and DOB, the selective protein kinase C inhibitor chelerythrine was without any effect. We conclude that phenethylamine and indoleamine hallucinogens may exert their hallucinogenic effect by interacting with 5-HT2A receptors via a Ca2+/CaM-KII-dependent signal transduction pathway as partial agonists and modulating the NMDA receptors-mediated sensory, perceptual, affective and cognitive processes.

Activation of P2Y6 receptors increases the voiding frequency in anaesthetized rats by releasing ATP from the bladder urothelium.

PubMed

Carneiro, Inês; Timóteo, M Alexandrina; Silva, Isabel; Vieira, Cátia; Baldaia, Catarina; Ferreirinha, Fátima; Silva-Ramos, Miguel; Correia-de-Sá, Paulo

2014-07-01

Despite the abundant expression of the UDP-sensitive P2Y6 receptor in urothelial cells and sub-urothelial myofibroblasts its role in the control of bladder function is not well understood. We compared the effects of UDP and of the selective P2Y6 receptor agonist, PSB0474, on bladder urodynamics in anaesthetized rats; the voided fluid was tested for ATP bioluminescence. The isolated urinary bladder was used for in vitro myographic recordings and [(3) H]-ACh overflow experiments. Instillation of UDP or PSB0474 into the bladder increased the voiding frequency (VF) without affecting the amplitude (A) and the duration (Δt) of bladder contractions; an effect blocked by the P2Y6 receptor antagonist, MRS2578. Effects mediated by urothelial P2Y6 receptors required extrinsic neuronal circuitry as they were not detected in the isolated bladder. UDP-induced bladder hyperactvity was also prevented by blocking P2X3 and P2Y1 receptors, respectively, with A317491 and MRS2179 applied i.v.. UDP decreased [(3) H]-ACh release from stimulated bladder strips with urothelium, but not in its absence. Inhibitory effects of UDP were converted into facilitation by the P2Y1 receptor antagonist, MRS2179. The P2Y6 receptor agonist increased threefold ATP levels in the voided fluid. Activation of P2Y6 receptors increased the voiding frequency indirectly by releasing ATP from the urothelium and activation of P2X3 receptors on sub-urothelial nerve afferents. Bladder hyperactivity may be partly reversed following ATP hydrolysis to ADP by E-NTPDases, thereby decreasing ACh release from cholinergic nerves expressing P2Y1 receptors. © 2014 The British Pharmacological Society.

Convergent Pathways for Steroid Hormone-and Neurotransmitter-Induced Rat Sexual Behavior

NASA Astrophysics Data System (ADS)

Mani, S. K.; Allen, J. M. C.; Clark, J. H.; Blaustein, J. D.; O'Malley, B. W.

1994-08-01

Estrogen and progesterone modulate gene expression in rodents by activation of intracellular receptors in the hypothalamus, which regulate neuronal networks that control female sexual behavior. However, the neurotransmitter dopamine has been shown to activate certain steroid receptors in a ligand-independent manner. A dopamine receptor stimulant and a D_1 receptor agonist, but not a D_2 receptor agonist, mimicked the effects of progesterone in facilitating sexual behavior in female rats. The facilitatory effect of the neurotransmitter was blocked by progesterone receptor antagonists, a D_1 receptor antagonist, or antisense oligonucleotides to the progesterone receptor. The results suggest that in rodents neurotransmitters may regulate in vivo gene expression and behavior by means of cross-talk with steroid receptors in the brain.

Inhibition of mechanotransducer currents in crayfish sensory neuron by CGS 9343B, a calmodulin antagonist.

PubMed

Lin, J H; Rydqvist, B

2000-05-26

The effects of CGS 9343B (zaldaride maleate), a calmodulin antagonist, on mechanosensitive channels were examined in crayfish slowly adapting sensory neurons using the two-electrode voltage clamp technique. In addition to its inhibition of voltage-gated Na(+) and K(+) currents, CGS 9343B (<30 microM) blocked reversibly the receptor current in a dose-dependent and voltage-dependent manner with a dissociation constant (K(d)) of 26.8 microM. The time course of the block was 265 s. Within the extension range of 3-30%, the reduction in receptor current was stimulus-independent and the gating mechanisms were not affected. Extracellular Ca(2+) was not necessary for its blocking effects. No changes in passive muscle tension were observed in the presence of 20 microM CGS 9343B. These results suggest that CGS 9343B, as a calmodulin antagonist, can also block mechanosensitive channels, possibly by being incorporated into the lipid membrane and/or interacting with the channel protein.

Optomotor-blind negatively regulates Drosophila eye development by blocking Jak/STAT signaling.

PubMed

Tsai, Yu-Chen; Grimm, Stefan; Chao, Ju-Lan; Wang, Shih-Chin; Hofmeyer, Kerstin; Shen, Jie; Eichinger, Fred; Michalopoulou, Theoni; Yao, Chi-Kuang; Chang, Chih-Hsuan; Lin, Shih-Han; Sun, Y Henry; Pflugfelder, Gert O

2015-01-01

Organ formation requires a delicate balance of positive and negative regulators. In Drosophila eye development, wingless (wg) is expressed at the lateral margins of the eye disc and serves to block retinal development. The T-box gene optomotor-blind (omb) is expressed in a similar pattern and is regulated by Wg. Omb mediates part of Wg activity in blocking eye development. Omb exerts its function primarily by blocking cell proliferation. These effects occur predominantly in the ventral margin. Our results suggest that the primary effect of Omb is the blocking of Jak/STAT signaling by repressing transcription of upd which encodes the Jak receptor ligand Unpaired.

Antidepressant and anxiolytic properties of the methanolic extract of Momordica charantia Linn (Cucurbitaceae) and its mechanism of action.

PubMed

Ishola, I O; Akinyede, A A; Sholarin, A M

2014-07-01

The whole plant of Momordica charantia Linn (Cucurbitaceae) is used in traditional African medicine in the management of depressive illness. Momordica charantia (MC) (50-400 mg/kg, p.o.) was administered 1 h before behavioural studies using the forced swimming test (FST) and tail suspension test (TST) to investigate antidepressant-like effect while the anxiolytic-like effect was evaluated with elevated plus maze test (EPM), hole-board test (HBT), and light-dark test (LDT). Acute treatment with MC (50-400 mg/kg) significantly increased swimming time (86.51%) and reduced the duration of immobility (52.35%) in FST and TST with peak effects observed at 200 mg/kg, respectively, in comparison to control. The pretreatment of mice with either sulpiride (dopamine D2 receptor antagonist), or metergoline (5-HT2 receptor antagonist), or cyproheptadine (5-HT2 receptor antagonist), or prazosin (α1-adrenoceptor antagonist), or yohimbine (α2-adrenoceptor antagonist), and atropine (muscarinic cholinergic receptor antagonist) 15 min before oral administration of MC (200 mg/kg) significantly blocked its anti-immobility effect. Similarly, MC (200 mg/kg) significantly reduced anxiety by increasing the open arm exploration (64.27%) in EPM, number of head-dips in HBT (34.38%), and time spent in light compartment (29.38%) in the LDT. However, pretreatment with flumazenil (GABAA receptor antagonist) 15 min before MC (200 mg/kg) significantly blocked (54.76%) its anxiolytic effect. The findings in this study showed that MC possesses antidepressant-like effect that is dependent on the serotonergic (5-HT2 receptor), noradrenergic (α1- and α2-adrenoceptors), dopaminergic (D2 receptor), and muscarinic cholinergic systems and an anxiolytic-like effect that might involve an action on benzodiazepine-type receptor. © Georg Thieme Verlag KG Stuttgart · New York.

Facilitatory effects of selective agonists for tachykinin receptors on cholinergic neurotransmission: evidence for species differences.

PubMed Central

Belvisi, M. G.; Patacchini, R.; Barnes, P. J.; Maggi, C. A.

1994-01-01

1. Exogenous tachykinins modulate cholinergic neurotransmission in rabbit and guinea-pig airways. We have investigated the effect of selective tachykinin receptor agonists and antagonists on cholinergic neurotransmission evoked by electrical field stimulation (EFS) of bronchial rings in rabbit, guinea-pig and human airways in vitro to assess which type of tachykinin receptor is mediating this facilitatory effect. 2. Bronchial rings were set up for isometric tension recording. Contractile responses to EFS (60 V, 0.4 ms, 2 Hz for 10 s every min) and exogenous acetylcholine (ACh) were obtained and the effects of selective tachykinin agonists and antagonists were investigated. 3. In rabbit bronchi the endogenous tachykinins, substance P (SP) and neurokinin A (NKA) (10 nM) potentiated cholinergic responses to EFS (by 287.6 +/- 121%, P < 0.01 and 181.4 +/- 56.5%, P < 0.001 respectively). 4. The NK1 receptor selective agonist, [Sar9]SP sulphone (10 nM) evoked a maximal facilitatory action on cholinergic responses of 334.9 +/- 63% (P < 0.01) (pD2 = 8.5 +/- 0.06) an effect which was blocked by the selective NK1-receptor antagonist, CP 96,345 (100 nM) (P < 0.05) but not by the NK2 receptor antagonist, MEN 10,376 (100 nM). The NK2 receptor selective agonist, [beta Ala8]NKA(4-10) (10 nM), produced a maximum enhancement of 278 +/- 83.5% (P < 0.01) (pD2 = 8.7 +/- 0.1) an effect which was blocked by MEN 10,376 (100 nM) (P < 0.05) and not by CP 96,345. [MePhe7]NKB, an NK3 receptor selective agonist was without effect.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7516799

Antagonism of corticotropin-releasing factor CRF1 receptors blocks the enhanced response to cocaine after social stress.

PubMed

Ferrer-Pérez, Carmen; Reguilón, Marina D; Manzanedo, Carmen; Aguilar, M Asunción; Miñarro, José; Rodríguez-Arias, Marta

2018-03-15

Numerous studies have shown that social defeat stress induces an increase in the rewarding effects of cocaine. In this study we have investigated the role played by the main hypothalamic stress hormone, corticotropin-releasing factor (CRF), in the effects that repeated social defeat (RSD) induces in the conditioned rewarding effects and locomotor sensitization induced by cocaine. A total of 220 OF1 mice were divided into experimental groups according to the treatment received before each social defeat: saline, 5 or 10 mg/kg of the nonpeptidic corticotropin-releasing factor CRF 1 receptor antagonist CP-154,526, or 15 or 30 µg/kg of the peptidic corticotropin-releasing factor CRF 2 receptor antagonist Astressin 2 -B. Three weeks after the last defeat, conditioned place preference (CPP) induced by 1 mg/kg of cocaine was evaluated. Motor response to 10 mg/kg of cocaine was also studied after a sensitization induction. Blockade of corticotropin-releasing factor CRF 1 receptor reversed the increase in cocaine CPP induced by social defeat. Conversely, peripheral corticotropin-releasing factor CRF 2 receptor blockade produced similar effects to those observed in socially stressed animals. The effect of RSD on cocaine sensitization was again blocked by the corticotropin-releasing factor CRF 1 receptor antagonist, while peripheral CRF 2 receptor antagonist did not show effect. Acute administration of Astressin 2 -B induced an anxiogenic response. Our results confirm that CRF modulates the effects of social stress on reinforcement and sensitization induced by cocaine in contrasting ways. These findings highlight CRF receptors as potential therapeutic targets to be explored by research about stress-related addiction problems. Copyright © 2018 Elsevier B.V. All rights reserved.

The G‐protein biased partial κ opioid receptor agonist 6′‐GNTI blocks hippocampal paroxysmal discharges without inducing aversion

PubMed Central

Zangrandi, Luca; Burtscher, Johannes; MacKay, James P; Colmers, William F

2016-01-01

Background and Purpose With a prevalence of 1–2%, epilepsies belong to the most frequent neurological diseases worldwide. Although antiepileptic drugs are available since several decades, the incidence of patients that are refractory to medication is still over 30%. Antiepileptic effects of κ opioid receptor (κ receptor) agonists have been proposed since the 1980s. However, their clinical use was hampered by dysphoric side effects. Recently, G‐protein biased κ receptor agonists were developed, suggesting reduced aversive effects. Experimental Approach We investigated the effects of the κ receptor agonist U‐50488H and the G‐protein biased partial κ receptor agonist 6′‐GNTI in models of acute seizures and drug‐resistant temporal lobe epilepsy and in the conditioned place avoidance (CPA) test. Moreover, we performed slice electrophysiology to understand the functional mechanisms of 6′‐GNTI. Key Results As previously shown for U‐50488H, 6′‐GNTI markedly increased the threshold for pentylenetetrazole‐induced seizures. All treated mice displayed reduced paroxysmal activity in response to U‐50488H (20 mg·kg−1) or 6′‐GNTI (10–30 nmoles) treatment in the mouse model of intra‐hippocampal injection of kainic acid. Single cell recordings on hippocampal pyramidal cells revealed enhanced inhibitory signalling as potential mechanisms causing the reduction of paroxysmal activity. Effects of 6′‐GNTI were blocked in both seizure models by the κ receptor antagonist 5′‐GNTI. Moreover, 6′‐GNTI did not induce CPA, a measure of aversive effects, while U‐50488H did. Conclusions and Implications Our data provide the proof of principle that anticonvulsant/antiseizure and aversive effects of κ receptor activation can be pharmacologically separated in vivo. PMID:26928671

VEGF-Trap: a VEGF blocker with potent antitumor effects.

PubMed

Holash, Jocelyn; Davis, Sam; Papadopoulos, Nick; Croll, Susan D; Ho, Lillian; Russell, Michelle; Boland, Patricia; Leidich, Ray; Hylton, Donna; Burova, Elena; Ioffe, Ella; Huang, Tammy; Radziejewski, Czeslaw; Bailey, Kevin; Fandl, James P; Daly, Tom; Wiegand, Stanley J; Yancopoulos, George D; Rudge, John S

2002-08-20

Vascular endothelial growth factor (VEGF) plays a critical role during normal embryonic angiogenesis and also in the pathological angiogenesis that occurs in a number of diseases, including cancer. Initial attempts to block VEGF by using a humanized monoclonal antibody are beginning to show promise in human cancer patients, underscoring the importance of optimizing VEGF blockade. Previous studies have found that one of the most effective ways to block the VEGF-signaling pathway is to prevent VEGF from binding to its normal receptors by administering decoy-soluble receptors. The highest-affinity VEGF blocker described to date is a soluble decoy receptor created by fusing the first three Ig domains of VEGF receptor 1 to an Ig constant region; however, this fusion protein has very poor in vivo pharmacokinetic properties. By determining the requirements to maintain high affinity while extending in vivo half life, we were able to engineer a very potent high-affinity VEGF blocker that has markedly enhanced pharmacokinetic properties. This VEGF-Trap effectively suppresses tumor growth and vascularization in vivo, resulting in stunted and almost completely avascular tumors. VEGF-Trap-mediated blockade may be superior to that achieved by other agents, such as monoclonal antibodies targeted against the VEGF receptor.

How do eggs get fat? Insights into ovarian fatty acid accumulation in the shortfinned eel, Anguilla australis.

PubMed

Damsteegt, Erin L; Mizuta, Hiroko; Hiramatsu, Naoshi; Lokman, P Mark

2015-09-15

Previous research using eels has shown that 11-ketotestosterone can induce ovarian triacylglyceride accumulation both in vivo and in vitro. Further, accumulation is dramatically enhanced in the presence of very-low density lipoprotein. This study examined the involvement of the low density lipoprotein receptor and vitellogenin receptor in oocyte lipid accumulation. Specific antisera were used in an attempt to block the vitellogenin receptor and/or the low density lipoprotein receptor. Accordingly, incubation with the low density lipoprotein receptor antiserum clearly reduced the oocyte diameter and the amount of oil present within the oocyte. In contrast, blocking the vitellogenin receptor had little effect on either oocyte surface area or the abundance of oil droplets in the cytosol. In keeping with birds, we conclude that the low density lipoprotein receptor is a major player involved in mediating ovarian fatty acid accumulation in the eel. However, lipoprotein lipase-mediated fatty acid accumulation also remains conceivable, for example through interactions between this enzyme and the low density lipoprotein receptor. Copyright © 2015 Elsevier Inc. All rights reserved.

The Role of 5-HT2A, 5-HT2C and mGlu2 Receptors in the Behavioral Effects of Tryptamine Hallucinogens N,N-Dimethyltryptamine and N,N-Diisopropyltryptamine in Rats and Mice

PubMed Central

Carbonaro, Theresa M.; Eshleman, Amy J.; Forster, Michael J.; Cheng, Kejun; Rice, Kenner C.; Gatch, Michael B.

2014-01-01

Rationale: Serotonin 5-HT2A and 5-HT2C receptors are thought to be the primary pharmacological mechanisms for serotonin-mediated hallucinogenic drugs, but recently there has been interest in metabotropic glutamate (mGluR2) receptors as contributors to the mechanism of hallucinogens. Objective: The present study assesses the role of these 5-HT and glutamate receptors as molecular targets for two tryptamine hallucinogens, N,N-dimethyltryptamine (DMT) and N,N-diisopropyltryptamine (DiPT). Methods: Drug discrimination, head twitch and radioligand binding assays were used. A 5-HT2AR inverse agonist (MDL100907), 5-HT2CR antagonist (SB242084) and mGluR2/3 agonist (LY379268) were tested for their ability to attenuate the discriminative stimulus effects of DMT and DiPT; an mGluR2/3 antagonist (LY341495) was tested for potentiation. MDL100907 was used to attenuate head twitches induced by DMT and DiPT. Radioligand binding studies and inosital-1-phosphate (IP-1) accumulation were performed at the 5-HT2CR for DiPT. Results: MDL100907 fully blocked the discriminative stimulus effects of DMT, but only partially blocked DiPT. SB242084 partially attenuated the discriminative stimulus effects of DiPT, but produced minimal attenuation of DMT’s effects. LY379268 produced potent, but only partial blockade of the discriminative stimulus effects of DMT. LY341495 facilitated DMT- and DiPT-like effects. Both compounds elicited head twitches (DiPT>DMT) which were blocked by MDL1000907. DiPT was a low potency full agonist at 5-HT2CR in vitro. Conclusions: The 5-HT2AR likely plays a major role in mediating the effects of both compounds. 5-HT2C and mGluR2 receptors likely modulate the discriminative stimulus effects of both compounds to some degree. PMID:24985890

The role of 5-HT2A, 5-HT 2C and mGlu2 receptors in the behavioral effects of tryptamine hallucinogens N,N-dimethyltryptamine and N,N-diisopropyltryptamine in rats and mice.

PubMed

Carbonaro, Theresa M; Eshleman, Amy J; Forster, Michael J; Cheng, Kejun; Rice, Kenner C; Gatch, Michael B

2015-01-01

Serotonin 5-HT2A and 5-HT2C receptors are thought to be the primary pharmacological mechanisms for serotonin-mediated hallucinogenic drugs, but recently there has been interest in metabotropic glutamate (mGluR2) receptors as contributors to the mechanism of hallucinogens. The present study assesses the role of these 5-HT and glutamate receptors as molecular targets for two tryptamine hallucinogens, N,N-dimethyltryptamine (DMT) and N,N-diisopropyltryptamine (DiPT). Drug discrimination, head twitch, and radioligand binding assays were used. A 5-HT2AR inverse agonist (MDL100907), 5-HT2CR antagonist (SB242084), and mGluR2/3 agonist (LY379268) were tested for their ability to attenuate the discriminative stimulus effects of DMT and DiPT; an mGluR2/3 antagonist (LY341495) was tested for potentiation. MDL100907 was used to attenuate head twitches induced by DMT and DiPT. Radioligand binding studies and inosital-1-phosphate (IP-1) accumulation were performed at the 5-HT2CR for DiPT. MDL100907 fully blocked the discriminative stimulus effects of DMT, but only partially blocked DiPT. SB242084 partially attenuated the discriminative stimulus effects of DiPT, but produced minimal attenuation of DMT's effects. LY379268 produced potent, but only partial blockade of the discriminative stimulus effects of DMT. LY341495 facilitated DMT- and DiPT-like effects. Both compounds elicited head twitches (DiPT>DMT) which were blocked by MDL1000907. DiPT was a low-potency full agonist at 5-HT2CR in vitro. The 5-HT2AR likely plays a major role in mediating the effects of both compounds. 5-HT2C and mGluR2 receptors likely modulate the discriminative stimulus effects of both compounds to some degree.

Baclofen blocks the acquisition and expression of mitragynine-induced conditioned place preference in rats.

PubMed

Yusoff, Nurul H M; Mansor, Sharif M; Müller, Christian P; Hassan, Zurina

2018-06-01

Mitragynine is the major alkaloid found in the leaves of M. speciosa Korth (Rubiaceae), a plant that is native to Southeast Asia. This compound has been used, either traditionally or recreationally, due to its psychostimulant and opioid-like effects. Recently, mitragynine has been shown to exert conditioned place preference (CPP), indicating the rewarding and motivational properties of M. speciosa. Here, the involvement of GABA B receptors in mediating mitragynine reward is studied using a CPP paradigm in rats. First, we examined the effects of GABA B receptor agonist baclofen (1.25, 2.5 and 5 mg/kg) on the acquisition of mitragynine (10 mg/kg)-induced CPP. Second, the involvement of GABA B receptors in the expression of mitragynine-induced CPP was tested. We found that the acquisition of mitragynine-induced CPP could be blocked by higher doses (2.5 and 5 mg/kg) of baclofen. Baclofen at a high dose inhibited locomotor activity and caused a CPP. Furthermore, we found that baclofen (2.5 and 5 mg/kg) also blocked the expression of mitragynine-induced CPP. These findings suggest that both, the acquisition and expression of mitragynine's reinforcing properties is controlled by the GABA B receptor. Copyright © 2018 Elsevier B.V. All rights reserved.

Effects of Intra-Amygdala Infusion of CB1 Receptor Agonists on the Reconsolidation of Fear-Potentiated Startle

ERIC Educational Resources Information Center

Lin, Hui-Ching; Mao, Sheng-Chun; Gean, Po-Wu

2006-01-01

The cannabinoid CB1 receptor has been shown to be critically involved in the extinction of fear memory. Systemic injection of a CB1 receptor antagonist prior to extinction training blocked extinction. Conversely, administration of the cannabinoid uptake inhibitor AM404 facilitated extinction in a dose-dependent manner. Here we show that bilateral…

Role of group II metabotropic glutamate receptors 2/3 and group I metabotropic glutamate receptor 5 in developing rat medial vestibular nuclei.

PubMed

Grassi, Silvarosa; Frondaroli, Adele; Pettorossi, Vito Enrico

2005-08-22

In brainstem slices from developing rats, metabotropic glutamate receptors mGluR2/3 and mGluR5 play different inhibitory roles in synaptic transmission and plasticity of the medial vestibular nuclei. The mGluR2/3 block (LY341495) reduces the occurrence of long-term depression after vestibular afferent high frequency stimulation at P8-P10, and increases that of long-term potentiation, while the mGluR5 block prevents high frequency stimulation long-term depression. Later on, the receptor block does not influence high frequency stimulation effects. In addition, while mGluR2/3 agonist (APDC) always provokes a transient reduction of synaptic responses, that of mGluR5 (CHPG) induces long-term depression per se at P8-P10. These results show a key role of mGluR5 in inducing high frequency stimulation long-term depression in developing medial vestibular nuclei, while mGluR2/3 modulate synaptic transmission, probably through presynaptic control of glutamate release.

Histamine H2 receptor - Involvement in gastric ulceration

NASA Technical Reports Server (NTRS)

Brown, P. A.; Vernikos-Danellis, J.; Brown, T. H.

1976-01-01

The involvement of the H1 and H2 receptors for histamine in the pathogenesis of gastric ulcers was investigated in rats. Metiamide, an H2 receptor antagonist, reliably reduced ulceration produced by stress alone or by a combination of stress and aspirin. In contrast, pyrilamine, which blocks only the H1 receptor, was without effect under these same conditions. The results support the hypothesis that histamine mediates both stress and stress plus aspirin induced ulceration by a mechanism involving the H2 receptor.

Effects of cannabinoids on tension induced by acetylcholine and choline in slow skeletal muscle fibers of the frog.

PubMed

Trujillo, Xóchitl; Sánchez-Pastor, Enrique; Andrade, Felipa; Huerta, Miguel

2014-01-01

We investigated the effects of cannabinoids on acetylcholine (ACh) or choline contractures in slow skeletal muscle fibers from Rana pipiens. Bundles of cruralis muscle fibers were incubated with the cannabinoid receptor 1 (CB1) agonist, arachidonylcyclopropylamide (ACPA), which diminished the maximum isometric tension by 10 % and the total tension by 5 % of the ACh contracture, and 40 and 22 % of the choline contracture, respectively. Preincubation with the CB1 antagonist, AM281, or with pertussis toxin (PTX) completely blocked the effect of ACPA on the ACh contracture. On the other hand, the decrease in choline contracture by ACPA was only partially blocked by AM281 (~16 % decrease), PTX (20 %), or by dantrolene (~46 %). Our results show that ACPA modulates ACh and choline contractures, and suggest that this effect involves the participation of CB1, the ACh receptor, and -RyR in ACh contractures. For choline contractures, ACPA may also be acting through cannabinoid receptor-independent mechanisms.

Effects of 5-hydroxytryptamine on isolated strips of the guinea-pig stomach

PubMed Central

Yamaguchi, T.

1972-01-01

1. The effects of 5-hydroxytryptamine (5-HT) on isolated strips of the longitudinal and circular muscles of the guinea-pig stomach were investigated. 2. 5-HT (0·1-1 μg/ml) increased the resting tension of the longitudinal muscle while it decreased that of the circular muscle. These effects were blocked by lysergic acid diethylamide (LSD), but were not affected by tetrodotoxin, hyoscine or morphine. 3. Electrical stimulation caused contraction in the longitudinal muscle, and contraction followed by relaxation in the circular muscle. In both the longitudinal and circular muscles, the evoked contractions were potentiated by 5-HT. This effect was blocked by tetrodotoxin, hyoscine and morphine, but was not affected by LSD. 4. It is concluded that, in the stomach as well as the intestine of the guinea-pig, there are two kinds of 5-HT receptors: the morphine-sensitive M receptor is situated on the intramural nerves and the D-receptor on the smooth muscle cells. PMID:5015031

Effect of intrathecal non-NMDA EAA receptor antagonist LY293558 in rats: a new class of drugs for spinal anesthesia.

PubMed

Von Bergen, Nicholas H; Subieta, Alberto; Brennan, Timothy J

2002-07-01

Excitatory amino acid receptors are important for both sensory and motor function in the spinal cord. We studied the effects of intrathecal LY293558, a competitive non-N-methyl-D-aspartate excitatory amino acid receptor antagonist, on motor and sensory function in rats to determine whether drugs blocking these receptors could potentially be used as alternative agents to local anesthetics for spinal anesthesia. Rats were tested before and 15-240 min after intrathecal injection of 5 nmol (in 10 microl) LY293558. Sensory function was tested at the hind paw using withdrawal response to pin prick and withdrawal to pinch with sharp forceps. Motor performance (ambulation, placing reflex, and Rotorod time), blood pressure, and heart rate were also evaluated. Some tests were repeated the next day. Responses after LY293558 were compared to injection of 40 microl bupivacaine, 0.75%. Pin-prick responses at the forepaw, chest, abdomen, hind leg, and hind paw were also examined after intrathecal LY293558. Intrathecal LY293558 blocked both sensory and motor responses through 180 min; complete recovery was present the following day. No change in blood pressure or heart rate occurred. The effects of LY293558 were more pronounced and sustained than those of bupivacaine. Segmental blockade of the response to pin prick was present after LY293558. Drugs like LY293558 that block alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA)/kainate receptors may be an alternative to local anesthetics for spinal anesthesia in humans.

Alpha 2-adrenergic receptor stimulation of phospholipase A2 and of adenylate cyclase in transfected Chinese hamster ovary cells is mediated by different mechanisms

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

Jones, S.B.; Halenda, S.P.; Bylund, D.B.

1991-02-01

The effect of alpha 2-adrenergic receptor activation on adenylate cyclase activity in Chinese hamster ovary cells stably transfected with the alpha 2A-adrenergic receptor gene is biphasic. At lower concentrations of epinephrine forskolin-stimulated cyclic AMP production is inhibited, but at higher concentrations the inhibition is reversed. Both of these effects are blocked by the alpha 2 antagonist yohimbine but not by the alpha 1 antagonist prazosin. Pretreatment with pertussis toxin attenuates inhibition at lower concentrations of epinephrine and greatly potentiates forskolin-stimulated cyclic AMP production at higher concentrations of epinephrine. alpha 2-Adrenergic receptor stimulation also causes arachidonic acid mobilization, presumably via phospholipasemore » A2. This effect is blocked by yohimbine, quinacrine, removal of extracellular Ca2+, and pretreatment with pertussis toxin. Quinacrine and removal of extracellular Ca2+, in contrast, have no effect on the enhanced forskolin-stimulated cyclic AMP production. Thus, it appears that the alpha 2-adrenergic receptor in these cells can simultaneously activate distinct signal transduction systems; inhibition of adenylate cyclase and stimulation of phospholipase A2, both via G1, and potentiation of cyclic AMP production by a different (pertussis toxin-insensitive) mechanism.« less

[The relationships among raphe magnus nucleus, locus coeruleus and dorsal motor nucleus of vagus in the descending regulation of gastric motility].

PubMed

Qiao, Hui; An, Shu-Cheng; Xu, Chang

2011-02-01

To explore the interrelationship among dorsal motor nucleus of the vagus (DMV), locus coeruleus (LC) and raphe magnus nucleus (NRM) in the mechanism of the descending regulation on gastric motility, which may constitute a parasympathetic local circuit, work as a neural center of gastric modulation in brainstem. Using nucleus location, electric stimulation and lesion, together with microinjection, and recording the inter-gastric pressure. (1) LC stimulation could inhibit the gastric motility significantly (P < 0.01), DMV lesion weaken this effect, while blocking the a receptor on DMV could reverse the effect. (2) NRM stimulation reduced the amplitude of gastric constriction (P < 0.01), DMV lesion could abolish the effect, but blocking the 5-HT2A receptor on DMV depressed the gastric motility heavily (P < 0.01) like NRM stimulation. While LC lesion could abolish the effect of NRM stimulation, and microinjection of ritanserin into LC could likewise abolish it. (1) LC inhibit the gastric motility via a receptor in DMV, and meanwhile may excite it through 5-HT2A receptor in DMV, these two ways work together to keeping the gastric motility amplitude normally. (2) NRM inhibit the gastric motility via 5-HT2A receptor in LC.

Modulation by bicuculline and penicillin of the block by t-butyl-bicyclo-phosphorothionate (TBPS) of GABAA-receptor mediated Cl−-current responses in rat striatal neurones

PubMed Central

Behrends, Jan C

2000-01-01

T-butyl-bicyclo-phosphorothionate (TBPS) is a prototypical representative of the cage-convulsants which act through a use-dependent block of the GABAA-receptor-ionophore complex. Using current recordings from cultured neurones of rat striatum the manner was investigated in which two antagonists, bicuculline and penicillin, presumably acting at the agonist binding site and in the ionic channel, respectively, modify the rate of block by TBPS. Penicillin (5 or 10 mM) did not slow the rate of block by TBPS, but produced a significant enhancement of block rate, which, however, was inversely related to the degree of antagonism by penicillin of the GABA-induced current. Bicuculline (10 μM) reduced the rate of block by TBPS. However, this effect was 3 fold weaker than its GABA-antagonistic action. The slowing of block rate and the current antagonism exhibited a biphasic, positive-negative relationship. Co-application of bicuculline (100 μM) in a concentration that produced nearly complete antagonism and TBPS (10 μM) resulted in a marked (∼40%) reduction of subsequent GABA response amplitudes compatible with a direct, bicuculline-induced conformational change in the receptor required for the binding of and block by TBPS. The lack of protection afforded by the channel blocker penicillin as well as the lack of correlation between bicuculline antagonism of the Cl−-current and its efficiency in protecting against TBPS block is evidence against an open channel blocking mechanism for TBPS. TBPS does, therefore, not appear to gain access to its binding site via the open pore but through alternative routes regulated from the agonist binding site. PMID:10694249

Enzalutamide

MedlinePlus

... androgen receptor inhibitors. It works by blocking the effects of androgen (a male reproductive hormone) to stop ... decrease your dose if you experience serious side effects during your treatment. Be sure to talk to ...

Apalutamide

MedlinePlus

... androgen receptor inhibitors. It works by blocking the effects of androgen (a male reproductive hormone) to stop ... decrease your dose if you experience serious side effects during your treatment. Be sure to talk to ...

Role of 5-HT3 Receptor on Food Intake in Fed and Fasted Mice

PubMed Central

Li, Bingjin; Shao, Dongyuan; Luo, Yungang; Wang, Pu; Liu, Changhong; Zhang, Xingyi; Cui, Ranji

2015-01-01

Background Many studies have shown that 5-hydroxytryptamine (5-HT) receptor subtypes are involved in the regulation of feeding behavior. However, the relative contribution of 5-HT3 receptor remains unclear. The present study was aimed to investigate the role of 5-HT3 receptor in control of feeding behavior in fed and fasted mice. Methodology/Principal Findings Food intake and expression of c-Fos, tyrosine hydroxylase (TH), proopiomelanocortin (POMC) and 5-HT in the brain were examined after acute treatment with 5-HT3 receptor agonist SR-57227 alone or in combination with 5-HT3 receptor antagonist ondansetron. Food intake was significantly inhibited within 3 h after acute treatment with SR 57227 in fasted mice but not fed mice, and this inhibition was blocked by ondansetron. Immunohistochemical study revealed that fasting-induced c-Fos expression was further enhanced by SR 57227 in the brainstem and the hypothalamus, and this enhancement was also blocked by ondansetron. Furthermore, the fasting-induced downregulation of POMC expression in the hypothalamus and the TH expression in the brain stem was blocked by SR 57227 in the fasted mice, and this effect of SR 57227 was also antagonized by ondansetron. Conclusion/Significance Taken together, our findings suggest that the effect of SR 57227 on the control of feeding behavior in fasted mice may be, at least partially, related to the c-Fos expression in hypothalamus and brain stem, as well as POMC system in the hypothalamus and the TH system in the brain stem. PMID:25789930

Antinociceptive action of isolated mitragynine from Mitragyna Speciosa through activation of opioid receptor system.

PubMed

Shamima, Abdul Rahman; Fakurazi, Sharida; Hidayat, Mohamad Taufik; Hairuszah, Ithnin; Moklas, Mohamad Aris Mohd; Arulselvan, Palanisamy

2012-01-01

Cannabinoids and opioids systems share numerous pharmacological properties and antinociception is one of them. Previous findings have shown that mitragynine (MG), a major indole alkaloid found in Mitragyna speciosa (MS) can exert its antinociceptive effects through the opioids system. In the present study, the action of MG was investigated as the antinociceptive agent acting on Cannabinoid receptor type 1 (CB1) and effects on the opioids receptor. The latency time was recorded until the mice showed pain responses such as shaking, licking or jumping and the duration of latency was measured for 2 h at every 15 min interval by hot plate analysis. To investigate the beneficial effects of MG as antinociceptive agent, it was administered intraperitoneally 15 min prior to pain induction with a single dosage (3, 10, 15, 30, and 35 mg/kg b.wt). In this investigation, 35 mg/kg of MG showed significant increase in the latency time and this dosage was used in the antagonist receptor study. The treated groups were administered with AM251 (cannabinoid receptor-1 antagonist), naloxone (non-selective opioid antagonist), naltrindole (δ-opioid antagonist) naloxonazine (μ(1)-receptor antagonist) and norbinaltorpimine (κ-opioid antagonist) respectively, prior to administration of MG (35 mg/kg). The results showed that the antinociceptive effect of MG was not antagonized by AM251; naloxone and naltrindole were effectively blocked; and norbinaltorpimine partially blocked the antinociceptive effect of MG. Naloxonazine did inhibit the effect of MG, but it was not statistically significant. These results demonstrate that CB1 does not directly have a role in the antinociceptive action of MG where the effect was observed with the activation of opioid receptor.

Correlation of 125I-LSD autoradiographic labeling with serotonin voltage clamp responses in Aplysia neurons

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

Evans, M.L.; Kadan, M.J.; Hartig, P.R.

Autoradiographic receptor binding studies using 125I-LSD (2-(125I)lysergic acid diethyamide) revealed intense labelling on the soma of a symmetrically located pair of cells in the abdominal ganglion of Aplysia californica. This binding was blocked by micromolar concentrations of serotonin and lower concentrations of the serotonergic antagonists, cyproheptadine and mianserin. Electrophysiological investigation of responses to serotonin of neurons in the left upper quadrant, where one of the labeled neurons is located, revealed a range of serotonin responses. Cells L3 and L6 have a K+ conductance increase in response to serotonin that is not blocked by cyproheptadine or mianserin. Cells L2 and L4more » have a biphasic response to serotonin: a Na+ conductance increase, which can be blocked by cyproheptadine and mianserin, followed by a voltage dependent Ca2+ conductance which is blocked by Co2+ but not the serotonergic antagonists. Cell L1, and its symmetrical pair, R1, have in addition to the Na+ and Ca2+ responses observed in L2 and L4, a Cl- conductance increase blocked by LSD, cyproheptadine and mianserin. LSD had little effect on the other responses. The authors conclude that the symmetrically located cells L1 and R1 have a Cl- channel linked to a cyproheptadine- and mianserin-sensitive serotonin receptor that is selectively labelled by 125I-LSD. This receptor has many properties in common with the mammalian serotonin 1C receptor.« less

Naloxone Antagonizes Soman-induced Central Respiratory Depression in Rats.

PubMed

Škrbić, Ranko; Stojiljković, Miloš P; Ćetković, Slavko S; Dobrić, Silva; Jeremić, Dejan; Vulović, Maja

2017-06-01

The influence of naloxone on respiration impaired by the highly toxic organophosphate nerve agent soman in anaesthetized rats was investigated. Soman, administered in a dose that was ineffective in blocking the electrically induced contractions of the phrenic nerve-diaphragm preparation in situ, induced a complete block of the spontaneous respiratory movements of the diaphragm, indicating the domination of central over the peripheral effects. Naloxone dose-dependently antagonized the soman-induced respiratory blockade. Atropine, at a dose that was per se ineffective in counteracting soman-induced respiratory depression, potentiated the protective effects of naloxone and completely restored respiration. Naloxone remained completely ineffective in antagonizing respiratory depression induced by the muscarinic receptor agonist the oxotremorine. It is assumed that naloxone antagonizes soman-induced respiratory inhibition by blocking endogenous opioidergic respiratory control pathways that are independent of the stimulation of muscarinic receptors. © 2016 Nordic Association for the Publication of BCPT (former Nordic Pharmacological Society).

Effects of the NMDA receptor antagonist memantine on the expression and development of acute opiate dependence as assessed by withdrawal-potentiated startle and hyperalgesia.

PubMed

Harris, Andrew C; Rothwell, Patrick E; Gewirtz, Jonathan C

2008-03-01

While the N-methyl-D: -aspartate (NMDA) glutamate receptor has been strongly implicated in chronic opiate dependence, relatively few studies have examined the effects of NMDA receptor antagonists on withdrawal from acute opiate exposure. The current study examined the effects of memantine, a well-tolerated NMDA receptor antagonist, on acute opiate dependence as assessed by elevations in rodent startle responding (i.e., "withdrawal-potentiated startle") and increased pain sensitivity (i.e., hyperalgesia). Administration of memantine either attenuated (5 mg/kg) or blocked (10 mg/kg) the expression of withdrawal-potentiated startle during naloxone (2.5 mg/kg)-precipitated withdrawal from a single dose of morphine sulfate (10 mg/kg). Pre-treatment with the NMDA receptor antagonist also inhibited the exacerbation of withdrawal-potentiated startle across repeated acute opiate exposures. Memantine blocked the expression of acute dependence, but was less effective in inhibiting its escalation, when hyperalgesia was used as a measure of withdrawal. These doses of memantine did not affect startle responding or nociception in otherwise drug-free animals. Data from additional control groups indicated that the effects of memantine on the expression of withdrawal were not influenced by nonspecific interactions between the NMDA antagonist and either morphine or naloxone. These findings suggest that the NMDA receptor may play a key role in the earliest stages of opiate dependence and provide further evidence that memantine may be useful for the treatment of opiate withdrawal.

Involvement of α₂-adrenoceptors, imidazoline, and endothelin-A receptors in the effect of agmatine on morphine and oxycodone-induced hypothermia in mice.

PubMed

Bhalla, Shaifali; Andurkar, Shridhar V; Gulati, Anil

2013-10-01

Potentiation of opioid analgesia by endothelin-A (ET(A)) receptor antagonist, BMS182874, and imidazoline receptor/α₂-adrenoceptor agonists such as clonidine and agmatine are well known. It is also known that agmatine blocks morphine hyperthermia in rats. However, the effect of agmatine on morphine or oxycodone hypothermia in mice is unknown. The present study was carried out to study the role of α₂-adrenoceptors, imidazoline, and ET(A) receptors in morphine and oxycodone hypothermia in mice. Body temperature was determined over 6 h in male Swiss Webster mice treated with morphine, oxycodone, agmatine, and combination of agmatine with morphine or oxycodone. Yohimbine, idazoxan, and BMS182874 were used to determine involvement of α₂-adrenoceptors, imidazoline, and ET(A) receptors, respectively. Morphine and oxycodone produced significant hypothermia that was not affected by α₂-adrenoceptor antagonist yohimbine, imidazoline receptor/α₂ adrenoceptor antagonist idazoxan, or ET(A) receptor antagonist, BMS182874. Agmatine did not produce hypothermia; however, it blocked oxycodone but not morphine-induced hypothermia. Agmatine-induced blockade of oxycodone hypothermia was inhibited by idazoxan and yohimbine. The blockade by idazoxan was more pronounced compared with yohimbine. Combined administration of BMS182874 and agmatine did not produce changes in body temperature in mice. However, when BMS182874 was administered along with agmatine and oxycodone, it blocked agmatine-induced reversal of oxycodone hypothermia. This is the first report demonstrating that agmatine does not affect morphine hypothermia in mice, but reverses oxycodone hypothermia. Imidazoline receptors and α₂-adrenoceptors are involved in agmatine-induced reversal of oxycodone hypothermia. Our findings also suggest that ET(A) receptors may be involved in blockade of oxycodone hypothermia by agmatine. © 2012 The Authors Fundamental and Clinical Pharmacology © 2012 Société Française de Pharmacologie et de Thérapeutique.

Optomotor-Blind Negatively Regulates Drosophila Eye Development by Blocking Jak/STAT Signaling

PubMed Central

Tsai, Yu-Chen; Grimm, Stefan; Chao, Ju-Lan; Wang, Shih-Chin; Hofmeyer, Kerstin; Shen, Jie; Eichinger, Fred; Michalopoulou, Theoni; Yao, Chi-Kuang; Chang, Chih-Hsuan; Lin, Shih-Han; Sun, Y. Henry; Pflugfelder, Gert O.

2015-01-01

Organ formation requires a delicate balance of positive and negative regulators. In Drosophila eye development, wingless (wg) is expressed at the lateral margins of the eye disc and serves to block retinal development. The T-box gene optomotor-blind (omb) is expressed in a similar pattern and is regulated by Wg. Omb mediates part of Wg activity in blocking eye development. Omb exerts its function primarily by blocking cell proliferation. These effects occur predominantly in the ventral margin. Our results suggest that the primary effect of Omb is the blocking of Jak/STAT signaling by repressing transcription of upd which encodes the Jak receptor ligand Unpaired. PMID:25781970

Effects of antidepressant drugs on histamine-H/sub 1/ receptors in the brain

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

Hall, H.; Oegren, S.O.

1984-02-06

The histamine-H/sub 1/ receptor blocking properties of a number of structurally different antidepressant drugs have been evaluated using a /sup 3/H-mepyramine binding assay and a guinea-pig ileum preparation. The tricyclic antidepressants all inhibited the histamine-H/sub 1/ receptor. Some newer antidepressant drugs, such as zimeldine and nomifensine were devoid of activity while others, such as iprindole and mianserin were very potent. It is concluded that antagonistic effects on the histamine-H/sub 1/ receptor is not associated with the therapeutic efficacy in depression, but may contribute to the sedative effects of the antidepressant drugs.

Panicolytic-like effect of tramadol is mediated by opioid receptors in the dorsal periaqueductal grey.

PubMed

Fiaes, Gislaine Cardoso de Souza; Roncon, Camila Marroni; Sestile, Caio Cesar; Maraschin, Jhonatan Christian; Souza, Rodolfo Luis Silva; Porcu, Mauro; Audi, Elisabeth Aparecida

2017-05-30

Tramadol is a synthetic opioid prescribed for the treatment of moderate to severe pain, acting as agonist of μ-opioid receptors and serotonin (5-HT) and noradrenaline (NE) reuptake inhibitor. This study evaluated the effects of tramadol in rats submitted to the elevated T-maze (ETM), an animal model that evaluates behavioural parameters such as anxiety and panic. Male Wistar rats were intraperitoneally (i.p.) treated acutely with tramadol (16 and 32mg/kg) and were submitted to the ETM. Tramadol (32mg/kg) promoted a panicolytic-like effect. Considering that dorsal periaqueductal grey (dPAG) is the main brain structure related to the pathophysiology of panic disorder (PD), this study also evaluated the participation of 5-HT and opioid receptors located in the dPAG in the panicolytic-like effect of tramadol. Seven days after stereotaxic surgery for implantation of a cannula in the dPAG, the animals were submitted to the test. To assess the involvement of 5-HT 1A receptors on the effect of tramadol, we combined the 5-HT 1A receptor antagonist, WAY100635 (0.37nmol), microinjected intra-dPAG, 10min prior to the administration of tramadol (32mg/kg, i.p.). WAY100635 did not block the panicolytic-like effect of tramadol. We also associated the non-selective opioid receptor antagonist, naloxone, systemically (1mg/kg, i.p.) or intra-dPAG (0.5nmol) administered 10min prior to tramadol (32mg/kg, i.p.). Naloxone blocked the panicolytic-like effect of tramadol in both routes of administrations, showing that tramadol modulates acute panic defensive behaviours through its interaction with opioid receptors located in the dPAG. Copyright © 2017 Elsevier B.V. All rights reserved.

Neurophysiological Analysis of Circadian Rhythm Entrainment

DTIC Science & Technology

1994-05-24

on activations in response to the ionotropic agonist NMDA (25). These results point to a previously uninvestigated role for metabotropic receptors in...are selective agonists of the metabotropic type of glutamate receptor . Selective metabotropic antagonists can block these effects but do not alter...glutamate receptors on SCN cell activity. In slice preparations, our initial findings are that the selective metabotropic agonist 1S,3R-ACPD has very potent

Differential block of nicotinic synapses on B versus C neurones in sympathetic ganglia of frog by alpha-conotoxins MII and ImI.

PubMed

Tavazoie, S F; Tavazoie, M F; McIntosh, J M; Olivera, B M; Yoshikami, D

1997-03-01

1. The effects of two new acetylcholine receptor antagonists, alpha-conotoxin MII and alpha-conotoxin ImI, on nicotinic synaptic transmission in the 10th paravertebral sympathetic ganglion of the leopard frog (Rana pipiens) were examined. The preganglionic nerve was electrically stimulated (at low frequency, < or = 1 min-1, to avoid use-dependent changes) while compound action potentials of B and C neurones were monitored from the postganglionic nerve. 2. alpha-Conotoxins MII and ImI, at low micromolar concentrations, reversibly blocked both B and C waves, alpha-Conotoxin MII blocked the C wave more effectively than the B wave, whereas the potency of alpha-conotoxin ImI was opposite that of MII. The observation that nicotinic antagonists can differentially block synaptic transmission of B versus C neurones with opposite selectivities strongly suggests that these neurones possess distinct nicotinic receptors. 3. In addition to fast and slow B waves described by others. C waves with two temporally distinguishable components were present in our recordings. Each alpha-conotoxin affected fast and slow B waves similarly. Likewise, toxins did not discriminate between the two components of C waves. This suggests that all neurones within each major class (B or C) may have the same nicotinic receptors. 4. Synthetic forms of alpha-conotoxins MII and ImI were used in the present study. Their ease of synthesis and their specificities should make these toxins useful probes to investigate the various subtypes of neuronal nicotinic acetylcholine receptors.

Presynaptic Muscarinic M2 Receptors Modulate Glutamatergic Transmission in the Bed Nucleus of the Stria Terminalis

PubMed Central

Guo, Ji-Dong; Hazra, Rimi; Dabrowska, Joanna; Muly, E. Chris; Wess, Jürgen; Rainnie, Donald G.

2012-01-01

The anterolateral cell group of the bed nucleus of the stria terminalis (BNSTALG) serves as an important relay station in stress circuitry. Limbic inputs to the BNSTALG are primarily glutamatergic and activity-dependent changes in this input have been implicated in abnormal behaviors associated with chronic stress and addiction. Significantly, local infusion of acetylcholine (ACh) receptor agonists into the BNST trigger stress-like cardiovascular responses, however, little is known about the effects of these agents on glutamatergic transmission in the BNSTALG. Here, we show that glutamate- and ACh-containing fibers are found in close association in the BNSTALG. Moreover, in the presence of the acetylcholinesterase inhibitor, eserine, endogenous ACh release evoked a long-lasting reduction of the amplitude of stimulus-evoked EPSCs. This effect was mimicked by exogenous application of the ACh analogue, carbachol, which caused a reversible, dose-dependent, reduction of the evoked EPSC amplitude, and an increase in both the paired pulse ratio and coefficient of variation, suggesting a presynaptic site of action. Uncoupling of postsynaptic G-proteins with intracellular GDP-β-S, or application of the nicotinic receptor antagonist, tubocurarine, failed to block the carbachol effect. In contrast, the carbachol effect was blocked by prior application of atropine or M2 receptor-preferring antagonists, and was absent in M2/M4 receptor knockout mice, suggesting that presynaptic M2 receptors mediate the effect of ACh. Immuno-electron microscopy studies further revealed the presence of M2 receptors on axon terminals that formed asymmetric synapses with BNST neurons. Our findings suggest that presynaptic M2 receptors might be an important modulator of the stress circuit and hence a novel target for drug development. PMID:22166222

[The effects of epinephrine and adrenergic antagonists on adenosine 3', 5'-monophosphate level of bovine trabecular cells in vitro].

PubMed

Lu, Y; Li, M; Shen, Y

1998-03-01

To determine the effects of epinephrine (EPI) and adrenergic antagonists on adenosine 3', 5'-monophosphate (cAMP) level of bovine trabecular cells (BTC) in vitro. (3)H-cAMP was used in protein binding assay for measuring the intracellular level of cAMP. (1) 10(-5) mol/L EPI induced a fold increase of cAMP in cultured BTC in vitro; (2) Timilol and ICI 118, 551 blocked efficiently the effect of EPI at a lower concentration (10(-6) mol/L). (3) Bisoprolol did not efficiently block the effect of EPI unless at high concentrations (>or= 10(-5) mol/L). The effects of EPI increasing outflow facility may be associated with its increase of cAMP in trabecular cells; BTC contains beta-adrenergic receptors, and beta(2)-adrenergic receptors are dominant.

Depolarizing Effects of Daikenchuto on Interstitial Cells of Cajal from Mouse Small Intestine

PubMed Central

Kim, Hyungwoo; Kim, Hyun Jung; Yang, Dongki; Jung, Myeong Ho; Kim, Byung Joo

2017-01-01

Background: Daikenchuto (DKT; TJ-100, TU-100), a traditional herbal medicineis used in modern medicine to treat gastrointestinal (GI) functional disorders. Interstitial cells of Cajal (ICCs) are the pacemaker cells of the GI tract and play important roles in the regulation of GI motility. Objective: The objective of this study was to investigate the effects of DKT on the pacemaker potentials (PPs) of cultured ICCs from murine small intestine. Materials and Methods: Enzymatic digestions were used to dissociate ICCs from mouse small intestine tissues. All experiments on ICCs were performed after 12 h of culture. The whole-cell patch-clamp configuration was used to record ICC PPs (current clamp mode). All experiments were performed at 30-32°C. Results: In current-clamp modeDKT depolarized and concentration-dependently decreased the amplitudes of PPs. Y25130 (a 5-HT3 receptor antagonist) or SB269970 (a 5-HT7 receptor antagonist) did not block DKT-induced PP depolarization, but RS39604 (a 5-HT4 receptor antagonist) did. Methoctramine (a muscarinic M2 receptor antagonist) failed to block DKT-induced PP depolarization, but pretreating 4-diphenylacetoxy-N-methylpiperidine methiodide (a muscarinic M3 receptor antagonist) facilitated blockade of DKT-induced PP depolarization. Pretreatment with an external Ca2+-free solution or thapsigargin abolished PPsand under these conditions, DKT did not induce PP depolarization. Furthermore Ginseng radix and Zingiberis rhizomes depolarized PPs, whereas Zanthoxyli fructus fruit (the third component of DKT) hyperpolarized PPs. Conclusion: These results suggest that DKT depolarizes ICC PPs in an internal or external Ca2+-dependent manner by stimulating 5-HT4 and M3 receptors. Furthermore, the authors suspect that the component in DKT largely responsible for depolarization is probably also a component of Ginseng radix and Zingiberis rhizomes. SUMMARY Daikenchuto (DKT) depolarized and concentration-dependently decreased the amplitudes of pacemaker potentials (PPs)Y25130 (a 5-HT3 receptor antagonist) or SB269970 (a 5-HT7 receptor antagonist) did not block DKT-induced PP depolarization, but RS39604 (a 5-HT4 receptor antagonist) didMethoctramine (a muscarinic M2 receptor antagonist) failed to block DKT-induced PP depolarization, but pretreating 4-DAMP (a muscarinic M3 receptor antagonist) facilitated blockade of DKT-induced PP depolarizationGinseng radix and Zingiberis rhizomes depolarized PPswhereas Zanthoxyli fructus fruit (the third component of DKT) hyperpolarized PPs. Abbreviation used: DKT: Daikenchuto, GI: Gastrointestinal, ICCs: Interstitial cells of Cajal, PPs: Pacemaker Potentials. PMID:28216898

Depolarizing Effects of Daikenchuto on Interstitial Cells of Cajal from Mouse Small Intestine.

PubMed

Kim, Hyungwoo; Kim, Hyun Jung; Yang, Dongki; Jung, Myeong Ho; Kim, Byung Joo

2017-01-01

Daikenchuto (DKT; TJ-100, TU-100), a traditional herbal medicineis used in modern medicine to treat gastrointestinal (GI) functional disorders. Interstitial cells of Cajal (ICCs) are the pacemaker cells of the GI tract and play important roles in the regulation of GI motility. The objective of this study was to investigate the effects of DKT on the pacemaker potentials (PPs) of cultured ICCs from murine small intestine. Enzymatic digestions were used to dissociate ICCs from mouse small intestine tissues. All experiments on ICCs were performed after 12 h of culture. The whole-cell patch-clamp configuration was used to record ICC PPs (current clamp mode). All experiments were performed at 30-32°C. In current-clamp modeDKT depolarized and concentration-dependently decreased the amplitudes of PPs. Y25130 (a 5-HT 3 receptor antagonist) or SB269970 (a 5-HT 7 receptor antagonist) did not block DKT-induced PP depolarization, but RS39604 (a 5-HT 4 receptor antagonist) did. Methoctramine (a muscarinic M 2 receptor antagonist) failed to block DKT-induced PP depolarization, but pretreating 4-diphenylacetoxy-N-methylpiperidine methiodide (a muscarinic M 3 receptor antagonist) facilitated blockade of DKT-induced PP depolarization. Pretreatment with an external Ca 2+ -free solution or thapsigargin abolished PPsand under these conditions, DKT did not induce PP depolarization. Furthermore Ginseng radix and Zingiberis rhizomes depolarized PPs, whereas Zanthoxyli fructus fruit (the third component of DKT) hyperpolarized PPs. These results suggest that DKT depolarizes ICC PPs in an internal or external Ca 2+ -dependent manner by stimulating 5-HT 4 and M 3 receptors. Furthermore, the authors suspect that the component in DKT largely responsible for depolarization is probably also a component of Ginseng radix and Zingiberis rhizomes. Daikenchuto (DKT) depolarized and concentration-dependently decreased the amplitudes of pacemaker potentials (PPs)Y25130 (a 5-HT 3 receptor antagonist) or SB269970 (a 5-HT 7 receptor antagonist) did not block DKT-induced PP depolarization, but RS39604 (a 5-HT 4 receptor antagonist) didMethoctramine (a muscarinic M 2 receptor antagonist) failed to block DKT-induced PP depolarization, but pretreating 4-DAMP (a muscarinic M 3 receptor antagonist) facilitated blockade of DKT-induced PP depolarizationGinseng radix and Zingiberis rhizomes depolarized PPswhereas Zanthoxyli fructus fruit (the third component of DKT) hyperpolarized PPs. Abbreviation used: DKT: Daikenchuto, GI: Gastrointestinal, ICCs: Interstitial cells of Cajal, PPs: Pacemaker Potentials.

Effects of adrenergic stimulation on ventilation in man

PubMed Central

Heistad, Donald D.; Wheeler, Robert C.; Mark, Allyn L.; Schmid, Phillip G.; Abboud, Francois M.

1972-01-01

The mechanism by which catecholamines affect ventilation in man is not known. Ventilatory responses to catecholamines were observed in normal subjects before and after adrenergic receptor blockade. Intravenous infusions of norepinephrine and isoproterenol caused significant increases in minute volume and decreases in end-tidal PCo2 which were blocked by the administration of propranolol, a beta adrenergic receptor blocker. The hyperventilatory response to hypoxia was not altered by propranolol. Intravenous infusion of phenylephrine caused a small but significant decrease in minute volume which was antagonized by phentolamine, an alpha adrenergic receptor blocker. Angiotensin, a nonadrenergic pressor agent, also decreased minute volume significantly. 100% oxygen was administered to suppress arterial chemoreceptors. Increases in minute volume and decreases in arterial PCo2 in response to norepinephrine and isoproterenol were blocked by breathing 100% oxygen. The decrease in minute volume during phenylephrine was not altered by 100% oxygen. The results indicate that: (a) beta adrenergic receptors mediate the hyperventilatory response to norepinephrine and isoproterenol but not to hypoxia. (b) the pressor agents phenylephrine and angiotensin decrease ventilation, and (c) suppression of chemoreceptors blocks the ventilatory response to norepinephrine and isoproterenol but not to phenylephrine. Implications concerning the interaction of adrenergic receptors and chemoreceptors with respect to the hyperventilatory response to catecholamines are discussed. PMID:4336940

TRPV1 channels in the nucleus of the solitary tract mediate thermal prolongation of the LCR in decerebrate piglets

PubMed Central

Xia, Luxi; Bartlett, Donald; Leiter, J.C.

2011-01-01

Elevating body temperature or just the temperature of the dorsal medulla by approximately 2 °C prolongs the laryngeal chemoreflex (LCR) in decerebrate neonatal piglets. We tested the hypothesis that transient receptor potential vanilloid 1 (TRPV1) receptors in the nucleus of the solitary tract (NTS) mediate thermal prolongation of the LCR. We studied the effect of a selective TRPV1 receptor antagonist on thermal prolongation of the LCR, and we tested the effect of a TRPV1 agonist on the duration of the LCR under normothermic conditions. We studied 37 decerebrate neonatal piglets between the ages of post-natal days 4 and 7. The TRPV1 receptor antagonist, 5−iodoresiniferatoxin (65 microM/L in 100 nL), blocked thermal prolongation of the LCR when injected bilaterally into the region of the NTS. The TRPV1 agonist, resiniferatoxin (0.65-1.0 mM/L in 100 nL), prolonged the LCR after bilateral injection into the NTS even when the body temperature of each piglet was normal. The effect of the TRPV1 agonists could be blocked by treatment with the GABAA receptor antagonist, bicuculline, whether given intravenously (0.3 mg/kg) or focally injected bilaterally into the NTS (10 mM in 100nL). We conclude that TRPV1 receptors in the NTS mediate thermal prolongation of the LCR. PMID:21276877

Is vitronectin the velcro that binds the gametes together?

PubMed

Fusi, F M; Bernocchi, N; Ferrari, A; Bronson, R A

1996-11-01

Evidence has been presented that the adhesion of human spermatozoa to the oolemma is mediated by integrins recognizing the Arg-Gly-Asp sequence (RGD). Fibronectin and vitronectin, glycoproteins that contain functional RGD sequences, are both present on human spermatozoa, and integrins that recognize these ligands have been detected on spermatozoa and eggs. In this work, we studied the effects of oligopeptides specifically designed to block fibronectin or vitronectin receptors on the interaction of human spermatozoa with zona-free hamster oocytes. GRGDdSP, a peptide blocking cell attachment to fibronectin, was without effect, while GdRGDSP, which blocks both fibronectin and vitronectin receptors, significantly inhibited the binding of human spermatozoa to the oolemma of zona-free hamster eggs, in a concentration-dependent manner, over a range 1-100 microM. As these experiments suggested that a vitronectin receptor plays a role in sperm-oolemmal adhesion, we performed a series of experiments studying the effects of exogenous vitronectin, when added to spermatozoa and oocytes, on gamete interactions. Sperm-oolemmal adherence, as well as sperm aggregation, was promoted by vitronectin, over range of 2.2 nM to 1 microM, but only in the presence of calcium ions. We propose that vitronectin released during the sperm acrosome reaction is recognized by both gametes and plays a role in their adhesion.

Recent insights into the mode of action of memantine and ketamine

PubMed Central

Johnson, Jon W.; Glasgow, Nathan G.; Povysheva, Nadezhda V.

2014-01-01

The clinical benefits of the glutamate receptor antagonists memantine and ketamine have helped sustain optimism that glutamate receptors represent viable targets for development of therapeutic drugs. Both memantine and ketamine antagonize N-methyl-d-aspartate receptors (NMDARs), a glutamate receptor subfamily, by blocking the receptor-associated ion channel. Although many of the basic characteristics of NMDAR inhibition by memantine and ketamine appear similar, their effects on humans and to a lesser extent on rodents are strongly divergent. Some recent research suggests that preferential inhibition by memantine and ketamine of distinct NMDAR subpopulations may contribute to the drugs' differential clinical effects. Here we review studies that shed light on possible explanations for differences between the effects of memantine and ketamine. PMID:25462293

Influence of pHo on calcium channel block by amlodipine, a charged dihydropyridine compound. Implications for location of the dihydropyridine receptor

PubMed Central

1989-01-01

We have investigated the modulation of L-type calcium channel currents in isolated ventricular cells by the dihydropyridine derivative amlodipine, a weak base with a pKa of 8.6. Under conditions that favor neutral drug molecules, amlodipine block resembles other, previously described, neutral dihydropyridine derivatives: block is more pronounced at depolarized voltages, repetitive pulsing is not needed to promote block, and recovery is complete at hyperpolarized voltages. When the drug is ionized, depolarized voltages still enhance block, however, the time course is slow and speeded by repetitive pulses that open channels. Recovery from block by ionized drug molecules is very slow and incomplete, but can be rapidly modified by changes in external hydrogen ion concentration. We conclude from these observations that the degree of ionization of the drug molecule can affect access to the dihydropyridine receptor and that external protons can interact with the drug-receptor complex even if channels are blocked and closed. These observations place limitations on the location of this receptor in the ventricular cell membrane. PMID:2549176

Guanosine-5'-monophosphate induces cell death in rat hippocampal slices via ionotropic glutamate receptors activation and glutamate uptake inhibition.

PubMed

Molz, Simone; Dal-Cim, Tharine; Tasca, Carla I

2009-12-01

Guanine derivatives modulate the glutamatergic system through displacement of binding of glutamate to its receptors acting as antagonist of glutamate receptors in moderate to high micromolar concentrations. Guanosine-5'-monophosphate (GMP) is shown to be neuroprotective against glutamate- or oxygen/glucose deprivation-induced neurotoxicity and also against NMDA-induced apoptosis in hippocampal slices. However, in this study we are showing that high extracellular GMP concentrations (5mM) reduced cell viability in hippocampal brain slices. The toxic effect of GMP was not blocked by dipyridamole, a nucleoside transport inhibitor, nor mimicked by guanosine, suggesting an extracellular mode of action to GMP which does not involve its hydrolysis to guanosine. GMP-dependent cell damage was not blocked by P1 purinergic receptor antagonists, neither altered by adenosine A(1) or A(2A) receptor agonists. The blockage of the ionotropic glutamate receptors AMPA or NMDA, but not KA or metabotropic glutamate receptors, reversed the toxicity induced by GMP. GMP (5mM) induced a decrease in glutamate uptake into hippocampal slices, which was reversed by dl-TBOA. Therefore, GMP-induced hippocampal cell damage involves activation of ionotropic glutamate receptors and inhibition of glutamate transporters activity.

G protein-coupled receptor 30 in tumor development.

PubMed

Wang, Dengfeng; Hu, Lina; Zhang, Guonan; Zhang, Lin; Chen, Chen

2010-08-01

Estrogen plays several important physiological and pathological functions in not only reproductive system but many other systems as well. Its transcriptional activation has been traditionally described as being mediated by classic nuclear estrogen receptors (ERs). It is however established recently that a novel functional estrogen transmembrane receptor, G protein-coupled receptor 30 (GPR30), modulates both rapid non-genomic events and genomic transcriptional events of estrogen. It has been demonstrated that GPR30 promotes the progress of estrogen-related tumors through mitogen-activated protein kinase (MAPK) signaling pathways. Effects mediated by GPR30 are maintained when classic ERs are absent or blocked. In addition, GPR30 is involved in drug resistance, which is often occurring during cancer treatments. All these new findings strongly imply that GPR30 may be an important therapeutic target for estrogen-related tumors. Simultaneously blocking both GPR30 and classic ERs may be a better strategy for the treatment of estrogen-related tumors.

Evidence that NMDA-dependent limbic neural plasticity in the right hemisphere mediates pharmacological stressor (FG-7142)-induced lasting increases in anxiety-like behavior. Study 2--The effects on behavior of block of NMDA receptors prior to injection of FG-7142.

PubMed

Adamec, R E

1998-01-01

The hypothesis that N-methyl-D-aspartate (NMDA) receptors mediate initiation of lasting behavioral changes induced by the anxiogenic beta-carboline, FG-7142, was supported in this study. Behavioral changes normally induced by FG-7142 were blocked when the competitive NMDA receptor blocker, 7-amino-phosphono-heptanoic acid, was given prior to administration of FG-7142. When cats were subsequently given FG-7142 alone, the drug produced lasting behavioral changes like those reported previously. Flumazenil, a benzodiazepine receptor antagonist, reversed an increase in defensiveness produced by FG-7142 alone, replicating previous findings. The data are consistent with the hypothesis that NMDA-dependent long-term potentiation in limbic pathways subserving defensive response to threat mediates lasting increases in defensiveness produced by FG-7142.

Azadirachtin interacts with the tumor necrosis factor (TNF) binding domain of its receptors and inhibits TNF-induced biological responses.

PubMed

Thoh, Maikho; Kumar, Pankaj; Nagarajaram, Hampathalu A; Manna, Sunil K

2010-02-19

The role of azadirachtin, an active component of a medicinal plant Neem (Azadirachta indica), on TNF-induced cell signaling in human cell lines was investigated. Azadirachtin blocks TNF-induced activation of nuclear factor kappaB (NF-kappaB) and also expression of NF-kappaB-dependent genes such as adhesion molecules and cyclooxygenase 2. Azadirachtin inhibits the inhibitory subunit of NF-kappaB (IkappaB alpha) phosphorylation and thereby its degradation and RelA (p65) nuclear translocation. It blocks IkappaB alpha kinase (IKK) activity ex vivo, but not in vitro. Surprisingly, azadirachtin blocks NF-kappaB DNA binding activity in transfected cells with TNF receptor-associated factor (TRAF)2, TNF receptor-associated death domain (TRADD), IKK, or p65, but not with TNFR, suggesting its effect is at the TNFR level. Azadirachtin blocks binding of TNF, but not IL-1, IL-4, IL-8, or TNF-related apoptosis-inducing ligand (TRAIL) with its respective receptors. Anti-TNFR antibody or TNF protects azadirachtin-mediated down-regulation of TNFRs. Further, in silico data suggest that azadirachtin strongly binds in the TNF binding site of TNFR. Overall, our data suggest that azadirachtin modulates cell surface TNFRs thereby decreasing TNF-induced biological responses. Thus, azadirachtin exerts an anti-inflammatory response by a novel pathway, which may be beneficial for anti-inflammatory therapy.

Azadirachtin Interacts with the Tumor Necrosis Factor (TNF) Binding Domain of Its Receptors and Inhibits TNF-induced Biological Responses*

PubMed Central

Thoh, Maikho; Kumar, Pankaj; Nagarajaram, Hampathalu A.; Manna, Sunil K.

2010-01-01

The role of azadirachtin, an active component of a medicinal plant Neem (Azadirachta indica), on TNF-induced cell signaling in human cell lines was investigated. Azadirachtin blocks TNF-induced activation of nuclear factor κB (NF-κB) and also expression of NF-κB-dependent genes such as adhesion molecules and cyclooxygenase 2. Azadirachtin inhibits the inhibitory subunit of NF-κB (IκBα) phosphorylation and thereby its degradation and RelA (p65) nuclear translocation. It blocks IκBα kinase (IKK) activity ex vivo, but not in vitro. Surprisingly, azadirachtin blocks NF-κB DNA binding activity in transfected cells with TNF receptor-associated factor (TRAF)2, TNF receptor-associated death domain (TRADD), IKK, or p65, but not with TNFR, suggesting its effect is at the TNFR level. Azadirachtin blocks binding of TNF, but not IL-1, IL-4, IL-8, or TNF-related apoptosis-inducing ligand (TRAIL) with its respective receptors. Anti-TNFR antibody or TNF protects azadirachtin-mediated down-regulation of TNFRs. Further, in silico data suggest that azadirachtin strongly binds in the TNF binding site of TNFR. Overall, our data suggest that azadirachtin modulates cell surface TNFRs thereby decreasing TNF-induced biological responses. Thus, azadirachtin exerts an anti-inflammatory response by a novel pathway, which may be beneficial for anti-inflammatory therapy. PMID:20018848

Effect of the anti-receptor ligand-blocking 225 monoclonal antibody on EGF receptor endocytosis and sorting

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

Jaramillo, Maria L.; Leon, Zully; Grothe, Suzanne

The anti-receptor antibody, 225 mAb, is known to block binding of ligand to the epidermal growth factor receptor (EGFR). However, the effect of this neutralizing antibody on EGFR endocytosis, trafficking and degradation remains unclear. Here, we demonstrate that endocytosis of {sup 125}I-225 mAb occurs, albeit with a slower rate than that of EGF. Using pulse chase assays, we show that internalized {sup 125}I-225 mAb is recycled to the surface much more efficiently than internalized {sup 125}I-EGF. Also, we found that internalization of {sup 125}I-225 mAb, in contrast to that of EGF, is independent of receptor tyrosine kinase activity, as evidencedmore » by its insensitivity to AG1478, a specific EGFR tyrosine kinase inhibitor. Analysis of the levels of cell surface and total EGFR showed that treatment with 225 mAb results in a 30-40% decrease in surface EGFR and a relatively slow downregulation of total EGFR. Taken together, these data indicate that 225 mAb induces internalization and downregulation of EGFR via a mechanism distinct from that underlying EGF-induced EGFR internalization and downregulation.« less

Octopamine and tyramine regulate the activity of reproductive visceral muscles in the adult female blood-feeding bug, Rhodnius prolixus.

PubMed

Hana, Sam; Lange, Angela B

2017-05-15

The role of octopamine and tyramine in regulating spontaneous contractions of reproductive tissues was examined in the female Rhodnius prolixus Octopamine decreased the amplitude of spontaneous contractions of the oviducts and reduced RhoprFIRFa-induced contractions in a dose-dependent manner, whereas tyramine only reduced the RhoprFIRFa-induced contractions. Both octopamine and tyramine decreased the frequency of spontaneous bursal contractions and completely abolished the contractions at 5×10 -7  mol l -1 and above. Phentolamine, an octopamine receptor antagonist, attenuated the inhibition induced by octopamine on the oviducts and the bursa. Octopamine also increased the levels of cAMP in the oviducts, and this effect was blocked by phentolamine. Dibutyryl cyclic AMP mimicked the effects of octopamine by reducing the frequency of bursal contractions, suggesting that the octopamine receptor may act by an Octβ receptor. The tyramine receptor antagonist yohimbine failed to block the inhibition of contractions induced by tyramine on the bursa, suggesting that tyramine may be acting on the Octβ receptor in the bursa. © 2017. Published by The Company of Biologists Ltd.

H1- and H2-receptor characterization in the tracheal circulation of sheep.

PubMed Central

Webber, S. E.; Salonen, R. O.; Widdicombe, J. G.

1988-01-01

1. The effects of histamine, the specific H1-agonist SKF 71481-A2 and the H2-agonist dimaprit were examined on tracheal vascular resistance in sheep anaesthetized with pentobarbitone. Tracheal vascular resistance was determined by perfusing the cranial tracheal arteries at constant flows and measuring inflow pressures. Changes in tracheal smooth muscle tone were also measured. 2. Histamine and SKF 71481-A2 contracted the tracheal smooth muscle and this effect was blocked by the H1-antagonist mepyramine. Stimulation of H2-receptors with dimaprit had no effect on tracheal smooth muscle tone. 3. Histamine had a complex action on the tracheal vasculature producing either a triphasic change (early dilatation then constriction followed by late dilatation) or just a constriction. SKF 71481-A2 always produced a biphasic change in vascular resistance (dilatation followed by constriction). Dimaprit dilated the tracheal vasculature. 4. The late dilatation produced by histamine in some sheep was blocked by bilateral cervical vagotomy but the mechanism for this effect is not known. No other responses to histamine, SKF 71481-A2 or dimaprit were affected by vagotomy. 5. The vasoconstriction produced by histamine and SKF 71481-A2 was antagonized by mepyramine indicating a H1-receptor-mediated effect. Cimetidine had no effect on the vasoconstriction to histamine suggesting a lack of involvement of H2-receptors. 6. The vasodilatation produced by histamine and SKF 71481-A2 was also antagonized by mepyramine, again suggesting a H1-receptor-mediated action. Cimetidine had no effect on the vasodilator response to histamine indicating no involvement of H2-receptors in this response. 7. The dilator effect of dimaprit was antagonized by cimetidine suggesting this effect was mediated by H2-receptors. 8. We conclude that H1-receptors in the various parts of the sheep tracheal vasculature can cause increases and decreases in total tracheal vascular resistance; that H2-receptors decrease resistance; and that the tracheal smooth muscle contracts on activation of H1-receptors but has no response to H2-agonists. PMID:2906559

Pharmacological properties of excitatory amino acid induced changes in extracellular calcium concentration in rat hippocampal slices.

PubMed

Arens, J; Stabel, J; Heinemann, U

1992-01-01

We have studied extracellular ionic changes induced by iontophoretic application of excitatory amino acids in rat hippocampal slices. In contrast to kinetics of changes in [Ca2+]o, kinetics of changes in [K+]o, [Na+]o, [Cl-]o as well as in extracellular space size were comparable for different glutamate receptor agonists. Thus, alpha-amino-3-hydroxy-5-methylisoxazolepropionic acid (AMPA), quisqualate (quis), and kainate caused reductions in [Ca2+]o followed by an increase of [Ca2+]o above baseline, whereas glutamate, aspartate, N-methyl-D-aspartate (NMDA), and DL-homocysteic acid caused only reductions in [Ca2+]o. After blocking the NMDA receptors with ketamine and 2-amino-5- phosphonovaleric acid (2-APV), glutamate-induced decreases in [Ca2+]o were followed by an overshoot. Reduction of the transmembrane Na+ gradient by lowering [Na+]o, blocking of the Na(+)-K+ ATPase by lowering [K+]o, and application of ouabain blocked the overshoots after quis application, whereas vanadate, a blocker of the Ca(2+)-Mg2+ ATPase, had no effects. Lithium enhanced the reductions in [Ca2+]o and blocked the overshoots. Amiloride also reduced the overshoots. All organic Ca2+ entry blockers diminished reductions of [Ca2+]o but increased the overshoots. Inorganic Ca2+ antagonists had variable effects. Ni2+ had similar effects as the organic Ca2+ entry blockers while Cd2+ reduced both the [Ca2+]o decreases as well as the subsequent overshoots. Co2+ had initially a similar action as Ni2+. With prolonged application, [Ca2+]o decreases became augmented and, during wash, overshoots could no longer be elicited. We suggest that the overshoots in [Ca2+]o are due to a combined effect of extracellular space shrinkage and activation of the Na+/Ca2+ exchangers. This would imply that NMDA receptor activation blocks extrusion of Ca2+ from the cells. We tested the hypothesis that quis-induced intracellular Ca2+ release and extrusion of Ca2+ from the cells contributed to the overshoots. Dantrolene was without effect on the quis-induced signals, while ryanodine reduced the overshoots. Caffeine on the other hand diminished the [Ca2+]o decreases with no effects on the overshoots. To test for possible second messenger routes by which NMDA receptor activation might slow Ca2+ extrusion from cells, we investigated the effects of arachidonic acid and N-monomethyl-D- arginine on the quis-induced signals. While these agents reduced decreases in [Ca2+]o, they had no clear effects on the overshoots. Thus a possible route by which NMDA receptor activation may affect Ca2+ extrusion from cells has still to be elucidated.

Inhibition of Ebola and Marburg Virus Entry by G Protein-Coupled Receptor Antagonists

PubMed Central

Cheng, Han; Lear-Rooney, Calli M.; Johansen, Lisa; Varhegyi, Elizabeth; Chen, Zheng W.; Olinger, Gene G.

2015-01-01

ABSTRACT Filoviruses, consisting of Ebola virus (EBOV) and Marburg virus (MARV), are among the most lethal infectious threats to mankind. Infections by these viruses can cause severe hemorrhagic fevers in humans and nonhuman primates with high mortality rates. Since there is currently no vaccine or antiviral therapy approved for humans, there is an urgent need to develop prophylactic and therapeutic options for use during filoviral outbreaks and bioterrorist attacks. One of the ideal targets against filoviral infection and diseases is at the entry step, which is mediated by the filoviral glycoprotein (GP). In this report, we screened a chemical library of small molecules and identified numerous inhibitors, which are known G protein-coupled receptor (GPCR) antagonists targeting different GPCRs, including histamine receptors, 5-HT (serotonin) receptors, muscarinic acetylcholine receptor, and adrenergic receptor. These inhibitors can effectively block replication of both infectious EBOV and MARV, indicating a broad antiviral activity of the GPCR antagonists. The time-of-addition experiment and microscopic studies suggest that GPCR antagonists block filoviral entry at a step following the initial attachment but prior to viral/cell membrane fusion. These results strongly suggest that GPCRs play a critical role in filoviral entry and GPCR antagonists can be developed as an effective anti-EBOV/MARV therapy. IMPORTANCE Infection of Ebola virus and Marburg virus can cause severe illness in humans with a high mortality rate, and currently there is no FDA-approved vaccine or therapeutic treatment available. The 2013-2015 epidemic in West Africa underscores a lack of our understanding in the infection and pathogenesis of these viruses and the urgency of drug discovery and development. In this study, we have identified numerous inhibitors that are known G protein-coupled receptor (GPCR) antagonists targeting different GPCRs. These inhibitors can effectively block replication of both infectious EBOV and MARV, indicating a broad antiviral activity of the GPCR antagonists. Our results strongly suggest that GPCRs play a critical role in filoviral entry and GPCR antagonists can be developed as an effective anti-EBOV/MARV therapy. PMID:26202243

Inhibition of Ebola and Marburg Virus Entry by G Protein-Coupled Receptor Antagonists.

PubMed

Cheng, Han; Lear-Rooney, Calli M; Johansen, Lisa; Varhegyi, Elizabeth; Chen, Zheng W; Olinger, Gene G; Rong, Lijun

2015-10-01

Filoviruses, consisting of Ebola virus (EBOV) and Marburg virus (MARV), are among the most lethal infectious threats to mankind. Infections by these viruses can cause severe hemorrhagic fevers in humans and nonhuman primates with high mortality rates. Since there is currently no vaccine or antiviral therapy approved for humans, there is an urgent need to develop prophylactic and therapeutic options for use during filoviral outbreaks and bioterrorist attacks. One of the ideal targets against filoviral infection and diseases is at the entry step, which is mediated by the filoviral glycoprotein (GP). In this report, we screened a chemical library of small molecules and identified numerous inhibitors, which are known G protein-coupled receptor (GPCR) antagonists targeting different GPCRs, including histamine receptors, 5-HT (serotonin) receptors, muscarinic acetylcholine receptor, and adrenergic receptor. These inhibitors can effectively block replication of both infectious EBOV and MARV, indicating a broad antiviral activity of the GPCR antagonists. The time-of-addition experiment and microscopic studies suggest that GPCR antagonists block filoviral entry at a step following the initial attachment but prior to viral/cell membrane fusion. These results strongly suggest that GPCRs play a critical role in filoviral entry and GPCR antagonists can be developed as an effective anti-EBOV/MARV therapy. Infection of Ebola virus and Marburg virus can cause severe illness in humans with a high mortality rate, and currently there is no FDA-approved vaccine or therapeutic treatment available. The 2013-2015 epidemic in West Africa underscores a lack of our understanding in the infection and pathogenesis of these viruses and the urgency of drug discovery and development. In this study, we have identified numerous inhibitors that are known G protein-coupled receptor (GPCR) antagonists targeting different GPCRs. These inhibitors can effectively block replication of both infectious EBOV and MARV, indicating a broad antiviral activity of the GPCR antagonists. Our results strongly suggest that GPCRs play a critical role in filoviral entry and GPCR antagonists can be developed as an effective anti-EBOV/MARV therapy. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Activation of P2Y6 receptors increases the voiding frequency in anaesthetized rats by releasing ATP from the bladder urothelium

PubMed Central

Carneiro, Inês; Timóteo, M Alexandrina; Silva, Isabel; Vieira, Cátia; Baldaia, Catarina; Ferreirinha, Fátima; Silva-Ramos, Miguel; Correia-de-Sá, Paulo

2014-01-01

BACKGROUND AND PURPOSE Despite the abundant expression of the UDP-sensitive P2Y6 receptor in urothelial cells and sub-urothelial myofibroblasts its role in the control of bladder function is not well understood. EXPERIMENTAL APPROACH We compared the effects of UDP and of the selective P2Y6 receptor agonist, PSB0474, on bladder urodynamics in anaesthetized rats; the voided fluid was tested for ATP bioluminescence. The isolated urinary bladder was used for in vitro myographic recordings and [3H]-ACh overflow experiments. KEY RESULTS Instillation of UDP or PSB0474 into the bladder increased the voiding frequency (VF) without affecting the amplitude (A) and the duration (Δt) of bladder contractions; an effect blocked by the P2Y6 receptor antagonist, MRS2578. Effects mediated by urothelial P2Y6 receptors required extrinsic neuronal circuitry as they were not detected in the isolated bladder. UDP-induced bladder hyperactvity was also prevented by blocking P2X3 and P2Y1 receptors, respectively, with A317491 and MRS2179 applied i.v.. UDP decreased [3H]-ACh release from stimulated bladder strips with urothelium, but not in its absence. Inhibitory effects of UDP were converted into facilitation by the P2Y1 receptor antagonist, MRS2179. The P2Y6 receptor agonist increased threefold ATP levels in the voided fluid. CONCLUSIONS AND IMPLICATIONS Activation of P2Y6 receptors increased the voiding frequency indirectly by releasing ATP from the urothelium and activation of P2X3 receptors on sub-urothelial nerve afferents. Bladder hyperactivity may be partly reversed following ATP hydrolysis to ADP by E-NTPDases, thereby decreasing ACh release from cholinergic nerves expressing P2Y1 receptors. PMID:24697602

Muscarinic receptor M4 positive allosteric modulators attenuate central effects of cocaine.

PubMed

Dall, Camilla; Weikop, Pia; Dencker, Ditte; Molander, Anna C; Wörtwein, Gitta; Conn, P Jeffrey; Fink-Jensen, Anders; Thomsen, Morgane

2017-07-01

Cocaine addiction is a chronic brain disease affecting neurotransmission. Muscarinic cholinergic receptors modulate dopaminergic signaling in the reward system, and muscarinic receptor stimulation can block direct reinforcing effects of cocaine. Here, we tested the hypothesis that specific muscarinic M 4 receptor stimulation can attenuate the discriminative stimulus effects and conditioned rewarding effects of cocaine, measures believed to predict the ability of cocaine and cocaine-associated cues to elicit relapse to drug taking. We tested the M 4 -selective positive allosteric modulators VU0152100 and VU0467154 in a drug discrimination assay and a conditioned place preference assay, including extinction and reinstatement of place preference. Specificity of the cocaine discrimination effect was verified using knockout mice lacking either M 1 or M 4 receptors (M 1 -/- , M 4 -/- ). We also replicated previous findings in cocaine-induced locomotor hyperactivity and striatal dopamine microdialysis assays. VU0152100 attenuated the discriminative stimulus effect of cocaine in wild-type mice and M 1 -/- mice, but not in M 4 -/- mice, without affecting rates of responding. As previously shown with VU0152100, VU0467154 almost eliminated cocaine-induced hyperactivity and striatal dopamine efflux. VU0467154 failed to attenuate acquisition of cocaine-conditioned place preference, but facilitated extinction and prevented reinstatement of the conditioned place preference. These findings further support the notion that M 4 receptors are promising targets for the treatment of cocaine addiction, by showing that results can be replicated using distinct ligands, and that in addition to blocking reinforcing effects of cocaine relevant to ongoing drug taking, M 4 positive allosteric modulators can also attenuate subjective and conditioned effects relevant to relapse. Copyright © 2017. Published by Elsevier B.V.

Circulating Estradiol Regulates Brain-Derived Estradiol via Actions at GnRH Receptors to Impact Memory in Ovariectomized Rats.

PubMed

Nelson, Britta S; Black, Katelyn L; Daniel, Jill M

2016-01-01

Systemic estradiol treatment enhances hippocampus-dependent memory in ovariectomized rats. Although these enhancements are traditionally thought to be due to circulating estradiol, recent data suggest these changes are brought on by hippocampus-derived estradiol, the synthesis of which depends on gonadotropin-releasing hormone (GnRH) activity. The goal of the current work is to test the hypothesis that peripheral estradiol affects hippocampus-dependent memory through brain-derived estradiol regulated via hippocampal GnRH receptor activity. In the first experiment, intracerebroventricular infusion of letrozole, which prevents the synthesis of estradiol, blocked the ability of peripheral estradiol administration in ovariectomized rats to enhance hippocampus-dependent memory in a radial-maze task. In the second experiment, hippocampal infusion of antide, a long-lasting GnRH receptor antagonist, blocked the ability of peripheral estradiol administration in ovariectomized rats to enhance hippocampus-dependent memory. In the third experiment, hippocampal infusion of GnRH enhanced hippocampus-dependent memory, the effects of which were blocked by letrozole infusion. Results indicate that peripheral estradiol-induced enhancement of cognition is mediated by brain-derived estradiol via hippocampal GnRH receptor activity.

Potentiation of the actions of bradykinin by angiotensin I-converting enzyme inhibitors. The role of expressed human bradykinin B2 receptors and angiotensin I-converting enzyme in CHO cells.

PubMed

Minshall, R D; Tan, F; Nakamura, F; Rabito, S F; Becker, R P; Marcic, B; Erdös, E G

1997-11-01

Part of the beneficial effects of angiotensin I-converting enzyme (ACE) inhibitors are due to augmenting the actions of bradykinin (BK). We studied this effect of enalaprilat on the binding of [3H]BK to Chinese hamster ovary (CHO) cells stably transfected to express the human BK B2 receptor alone (CHO-3B) or in combination with ACE (CHO-15AB). In CHO-15AB cells, enalaprilat (1 mumol/L) increased the total number of low-affinity [3H]BK binding sites on the cells at 37 degrees C, but not at 4 degrees C, from 18.4 +/- 4.3 to 40.3 +/- 11.9 fmol/10(6) cells (P < .05; Kd, 2.3 +/- 0.8 and 5.9 +/- 1.3 nmol/L; n = 4). Enalaprilat preserved a portion of the receptors in high-affinity conformation (Kd, 0.17 +/- 0.08 nmol/L; 8.1 +/- 0.9 fmol/10(6) cells). Enalaprilat decreased the IC50 of [Hyp3-Tyr(Me)8]BK, the BK analogue more resistant to ACE, from 3.2 +/- 0.8 to 0.41 +/- 0.16 nmol/L (P < .05, n = 3). The biphasic displacement curve of the binding of [3H]BK also suggested the presence of high-affinity BK binding sites. Enalaprilat (5 nmol to 1 mumol/L) potentiated the release of [3H]arachidonic acid and the liberation of inositol 1,4,5-trisphosphate (IP3) induced by BK and [Hyp3-Tyr(Me)8]BK. Moreover, enalaprilat (1 mumol/L) completely and immediately restored the response of the B2 receptor, desensitized by the agonist (1 mumol/L [Hyp3-Tyr(Me)8]BK); this effect was blocked by the antagonist, HOE 140. Finally, enalaprilat, but not the prodrug enalapril, decreased internalization of the receptor from 70 +/- 9% to 45 +/- 9% (P < .05, n = 7). In CHO-3B cells, enalaprilat was ineffective. ACE inhibitors in the presence of both the B2 receptor and ACE enhance BK binding, protect high-affinity receptors, block receptor desensitization, and decrease internalization, thereby potentiating BK beyond blocking its hydrolysis.

Differential effects of glucocorticoid and mineralocorticoid antagonism on anxiety behavior in mild traumatic brain injury.

PubMed

Fox, Laura C; Davies, Daniel R; Scholl, Jamie L; Watt, Michael J; Forster, Gina L

2016-10-01

Mild traumatic brain injuries (TBIs) comprise three-quarters of all TBIs occurring in the United States annually, and psychological symptoms arising from them can last years after injury. One commonly observed symptom following mild TBI is generalized anxiety. Most mild TBIs happen in stressful situations (sports, war, domestic violence, etc.) when glucocorticoids are elevated in the brain at the time of impact, and glucocorticoids have negative effects on neuronal health following TBI. Therefore, blocking glucocorticoid receptors might prevent emergence of anxiety symptoms post-injury. Adult male rats received mifepristone (20mg/kg) or spironolactone (50mg/kg) to block glucocorticoid and mineralocorticoid receptors, respectively, 40min prior to being exposed to acute social defeat stress followed immediately by mild TBI. In defeated rats with concomitant mild TBI, mifepristone restored time spent in the open arms of an elevated plus maze to control levels, demonstrating for the first time that glucocorticoid receptors play a critical role in the development of anxiety after mild TBI. Future treatments could target these receptors, alleviating anxiety as a major side effect in victims of mild TBI sustained in stressful situations. Copyright © 2016 Elsevier B.V. All rights reserved.

Are monoaminergic systems involved in the lethargy induced by a parasitoid wasp in the cockroach prey?

PubMed

Weisel-Eichler, A; Libersat, F

2002-05-01

The venom of the parasitoid wasp Ampulex compressa induces long-lasting hypokinesia in the cockroach prey. Previous work indicates that the venom acts in the subesophageal ganglion to indirectly affect modulation of thoracic circuits for locomotion. However, the target of the venom in the subesophageal ganglion, and the mechanism by which the venom achieves its effects are as yet unknown. While the stung cockroaches appear generally lethargic, not all behaviors were affected, indicating that the venom targets specific motor systems and not behavior in general. Stung cockroaches were observed "freezing" in abnormal positions. Reserpine, which depletes monoamines, mimics the behavioral effects of the venom. We treated cockroaches with antagonists to dopamine and octopamine receptors, and found that the dopamine system is required for normal escape response. Dopamine injection induces prolonged grooming in normal cockroaches, but not in stung, suggesting that the venom is affecting dopamine receptors, or targets downstream of these receptors, in the subesophageal ganglion. This dopamine blocking effect fades slowly over the course of several weeks, similar to the time course of recovery from hypokinesia. The similarity in the time courses suggests that the mechanism underlying the hypokinesia may be the block of the dopamine receptors.

Micromolar-Affinity Benzodiazepine Receptors Regulate Voltage-Sensitive Calcium Channels in Nerve Terminal Preparations

NASA Astrophysics Data System (ADS)

Taft, William C.; Delorenzo, Robert J.

1984-05-01

Benzodiazepines in micromolar concentrations significantly inhibit depolarization-sensitive Ca2+ uptake in intact nerve-terminal preparations. Benzodiazepine inhibition of Ca2+ uptake is concentration dependent and stereospecific. Micromolar-affinity benzodiazepine receptors have been identified and characterized in brain membrane and shown to be distinct from nanomolar-affinity benzodiazepine receptors. Evidence is presented that micromolar, and not nanomolar, benzodiazepine binding sites mediate benzodiazepine inhibition of Ca2+ uptake. Irreversible binding to micromolar benzodiazepine binding sites also irreversibly blocked depolarization-dependent Ca2+ uptake in synaptosomes, indicating that these compounds may represent a useful marker for identifying the molecular components of Ca2+ channels in brain. Characterization of benzodiazepine inhibition of Ca2+ uptake demonstrates that these drugs function as Ca2+ channel antagonists, because benzodiazepines effectively blocked voltage-sensitive Ca2+ uptake inhibited by Mn2+, Co2+, verapamil, nitrendipine, and nimodipine. These results indicate that micromolar benzodiazepine binding sites regulate voltage-sensitive Ca2+ channels in brain membrane and suggest that some of the neuronal stabilizing effects of micromolar benzodiazepine receptors may be mediated by the regulation of Ca2+ conductance.

Micromolar-affinity benzodiazepine receptors regulate voltage-sensitive calcium channels in nerve terminal preparations.

PubMed Central

Taft, W C; DeLorenzo, R J

1984-01-01

Benzodiazepines in micromolar concentrations significantly inhibit depolarization-sensitive Ca2+ uptake in intact nerve-terminal preparations. Benzodiazepine inhibition of Ca2+ uptake is concentration dependent and stereospecific. Micromolar-affinity benzodiazepine receptors have been identified and characterized in brain membrane and shown to be distinct from nanomolar-affinity benzodiazepine receptors. Evidence is presented that micromolar, and not nanomolar, benzodiazepine binding sites mediate benzodiazepine inhibition of Ca2+ uptake. Irreversible binding to micromolar benzodiazepine binding sites also irreversibly blocked depolarization-dependent Ca2+ uptake in synaptosomes, indicating that these compounds may represent a useful marker for identifying the molecular components of Ca2+ channels in brain. Characterization of benzodiazepine inhibition of Ca2+ uptake demonstrates that these drugs function as Ca2+ channel antagonists, because benzodiazepines effectively blocked voltage-sensitive Ca2+ uptake inhibited by Mn2+, Co2+, verapamil, nitrendipine, and nimodipine. These results indicate that micromolar benzodiazepine binding sites regulate voltage-sensitive Ca2+ channels in brain membrane and suggest that some of the neuronal stabilizing effects of micromolar benzodiazepine receptors may be mediated by the regulation of Ca2+ conductance. PMID:6328498

Insulin induces alpha1B-adrenergic receptor phosphorylation and desensitization.

PubMed

García-Sáinz, J Adolfo; Romero-Avila, M Teresa; Molina-Muñoz, Tzindilú; Medina, Luz del Carmen

2004-09-03

The ability of insulin to induce alpha1B-adrenoceptor phosphorylation and desensitization was tested in two model systems: rat-1 cells that stably express alpha1B-adrenoceptors, through transfection, and endogenously express insulin receptors and DDT1 MF2 cells that endogenously express both receptors. Insulin induced concentration-dependent increases in the phosphorylation state of the adrenergic receptors in the two models with similar EC50 values (0.5-2 nM). The effect was rapid in the two systems but it was sustained in rat-1 cells and transient in DDT1 MF2 cells. In both cell lines, the insulin-mediated phosphorylation of alpha1B-adrenoceptors was blocked by wortmannin and LY 294002, and by staurosporine and bisindolylmaleimide I, indicating that the effect involved phosphoinositide 3-kinase and protein kinase C activities. The adrenoceptor phosphorylation induced by insulin was associated to desensitization as evidences by a diminished elevation of intracellular calcium in response to noradrenaline. Inhibitors of phosphoinositide 3-kinase and protein kinase C blocked the functional desensitization induced by insulin.

Role of IL-1 beta and 5-HT2 receptors in midbrain periaqueductal gray (PAG) in potentiating defensive rage behavior in cat.

PubMed

Bhatt, Suresh; Bhatt, Rekha; Zalcman, Steven S; Siegel, Allan

2008-02-01

Feline defensive rage, a form of aggressive behavior that occurs in response to a threat can be elicited by electrical stimulation of the medial hypothalamus or midbrain periaqueductal gray (PAG). Our laboratory has recently begun a systematic examination of the role of cytokines in the regulation of rage and aggressive behavior. It was shown that the cytokine, interleukin-2 (IL-2), differentially modulates defensive rage when microinjected into the medial hypothalamus and PAG by acting through separate neurotransmitter systems. The present study sought to determine whether a similar relationship exists with respect to interleukin 1-beta (IL-1 beta), whose receptor activation in the medial hypothalamus potentiates defensive rage. Thus, the present study identified the effects of administration of IL-1 beta into the PAG upon defensive rage elicited from the medial hypothalamus. Microinjections of IL-1 beta into the dorsal PAG significantly facilitated defensive rage behavior elicited from the medial hypothalamus in a dose and time dependent manner. In addition, the facilitative effects of IL-1 beta were blocked by pre-treatment with anti-IL-1 beta receptor antibody, while IL-1 beta administration into the PAG had no effect upon predatory attack elicited from the lateral hypothalamus. The findings further demonstrated that IL-1 beta's effects were mediated through 5-HT(2) receptors since pretreatment with a 5-HT(2C) receptors antagonist blocked the facilitating effects of IL-1 beta. An extensive pattern of labeling of IL-1 beta and 5-HT(2C) receptors in the dorsal PAG supported these findings. The present study demonstrates that IL-beta in the dorsal PAG, similar to the medial hypothalamus, potentiates defensive rage behavior and is mediated through a 5-HT(2C) receptor mechanism.

In vitro profile of the antidepressant candidate OPC-14523 at rat and human 5-HT1A receptors.

PubMed

Jordan, Shaun; Chen, Ruoyan; Koprivica, Vuk; Hamilton, Ronald; Whitehead, Richard E; Tottori, Katsura; Kikuchi, Tetsuro

2005-07-11

This study determined the in vitro functional profile of 1-[3-[4-(3-chlorophenyl)-1-piperazinyl]propyl]-5-methoxy-3,4-dihydro-2-quinolinone monomethanesulfonate (OPC-14523) at rat and human serotonin (5-HT) 5-HT1A receptors and binding affinity of OPC-14523 at human frontocortical 5-HT1A receptors. OPC-14523 (1 microM) increased guanosine-5'-O-(3-[35S]thio)-triphosphate ([35S]GTPgammaS) binding to 5-HT1A receptor-containing regions of rat brain tissue sections (approximately 53% of the effect of 1 microM (+)8-hydroxy-2-(di-n-propylamino)tetralin ((+)8-OH-DPAT) that were blocked by the selective 5-HT1A receptor antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-2-pyridinylcyclohexanecarboxamide (WAY-100635). OPC-14523 also behaved as a partial agonist in its stimulation of [35S]GTPgammaS binding to membranes from rat hippocampus (pEC50=7.60+/-0.23, Emax=41.1% of the effect of 10 microM (+)8-OH-DPAT), human frontal cortex (pEC50=7.89+/-0.08; Emax=64% of the effect of 10 microM (+)8-OH-DPAT), and Chinese Hamster Ovary cells expressing cloned human 5-HT1A receptors (pEC50=8.0+/-0.11; Emax=85.5% of the effect of 10 microM 5-HT), and all of these effects of OPC-14523 were blocked by WAY-100635. Taken together, these data support the development of OPC-14523 as an antidepressant whose mechanism of action involves potent partial agonist activity at 5-HT1A receptors.

Effects of tianeptine on onset time of pentylenetetrazole-induced seizures in mice: possible role of adenosine A1 receptors.

PubMed

Uzbay, Tayfun I; Kayir, Hakan; Ceyhan, Mert

2007-02-01

Depression is a common psychiatric problem in epileptic patients. Thus, it is important that an antidepressant agent has anticonvulsant activity. This study was organized to investigate the effects of tianeptine, an atypical antidepressant, on pentylenetetrazole (PTZ)-induced seizure in mice. A possible contribution of adenosine receptors was also evaluated. Adult male Swiss-Webster mice (25-35 g) were subjects. PTZ (80 mg/kg, i.p.) was injected to mice 30 min after tianeptine (2.5-80 mg/kg, i.p.) or saline administration. The onset times of 'first myoclonic jerk' (FMJ) and 'generalized clonic seizures' (GCS) were recorded. Duration of 600 s was taken as a cutoff time in calculation of the onset time of the seizures. To evaluate the contribution of adenosine receptors in the effect of tianeptine, a nonspecific adenosine receptor antagonist caffeine, a specific A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), a specific A2A receptor antagonist 8-(3-chlorostyryl) caffeine (CSC) or their vehicles were administered to the mice 15 min before tianeptine (80 mg/kg) or saline treatments. Tianeptine (40 and 80 mg/kg) pretreatment significantly delayed the onset time of FMJ and GCS. Caffeine (10-60 mg/kg, i.p.) dose-dependently blocked the retarding effect of tianeptine (80 mg/kg) on the onset times of FMJ and GCS. DPCPX (20 mg/kg) but not CSC (1-8 mg/kg) blocked the effect of tianeptine (80 mg/kg) on FMJ. Our results suggest that tianeptine delayed the onset time of PTZ-induced seizures via adenosine A1 receptors in mice. Thus, this drug may be a useful choice for epileptic patients with depression.

Acute Stress Suppresses Synaptic Inhibition and Increases Anxiety via Endocannabinoid Release in the Basolateral Amygdala

PubMed Central

Itoga, Christy A.; Fisher, Marc O.; Solomonow, Jonathan; Roltsch, Emily A.; Gilpin, Nicholas W.

2016-01-01

Stress and glucocorticoids stimulate the rapid mobilization of endocannabinoids in the basolateral amygdala (BLA). Cannabinoid receptors in the BLA contribute to anxiogenesis and fear-memory formation. We tested for rapid glucocorticoid-induced endocannabinoid regulation of synaptic inhibition in the rat BLA. Glucocorticoid application to amygdala slices elicited a rapid, nonreversible suppression of spontaneous, but not evoked, GABAergic synaptic currents in BLA principal neurons; the effect was also seen with a membrane-impermeant glucocorticoid, but not with intracellular glucocorticoid application, implicating a membrane-associated glucocorticoid receptor. The glucocorticoid suppression of GABA currents was not blocked by antagonists of nuclear corticosteroid receptors, or by inhibitors of gene transcription or protein synthesis, but was blocked by inhibiting postsynaptic G-protein activity, suggesting a postsynaptic nongenomic steroid signaling mechanism that stimulates the release of a retrograde messenger. The rapid glucocorticoid-induced suppression of inhibition was prevented by blocking CB1 receptors and 2-arachidonoylglycerol (2-AG) synthesis, and it was mimicked and occluded by CB1 receptor agonists, indicating it was mediated by the retrograde release of the endocannabinoid 2-AG. The rapid glucocorticoid effect in BLA neurons in vitro was occluded by prior in vivo acute stress-induced, or prior in vitro glucocorticoid-induced, release of endocannabinoid. Acute stress also caused an increase in anxiety-like behavior that was attenuated by blocking CB1 receptor activation and inhibiting 2-AG synthesis in the BLA. Together, these findings suggest that acute stress causes a long-lasting suppression of synaptic inhibition in BLA neurons via a membrane glucocorticoid receptor-induced release of 2-AG at GABA synapses, which contributes to stress-induced anxiogenesis. SIGNIFICANCE STATEMENT We provide a cellular mechanism in the basolateral amygdala (BLA) for the rapid stress regulation of anxiogenesis in rats. We demonstrate a nongenomic glucocorticoid induction of long-lasting suppression of synaptic inhibition that is mediated by retrograde endocannabinoid release at GABA synapses. The rapid glucocorticoid-induced endocannabinoid suppression of synaptic inhibition is initiated by a membrane-associated glucocorticoid receptor in BLA principal neurons. We show that acute stress increases anxiety-like behavior via an endocannabinoid-dependent mechanism centered in the BLA. The stress-induced endocannabinoid modulation of synaptic transmission in the BLA contributes, therefore, to the stress regulation of anxiety, and may play a role in anxiety disorders of the amygdala. PMID:27511017

Effects of tetraethylammonium on potassium currents in a molluscan neurons

PubMed Central

1981-01-01

The effects of tetraethylammonium (TEA) on the delayed K+ current and on the Ca2+-activated K+ current of the Aplysia pacemaker neurons R-15 and L-6 were studied. The delayed outward K+ current was measured in Ca2+-free ASW containing tetrodotoxin (TTX), using brief depolarizing clamp pulses. External TEA blocks the delayed K+ current reversibly in a dose-dependent manner. The experimental results are well fitted with a Michaelis-Menten expression, assuming a one-to-one reaction between TEA and a receptor site, with an apparent dissociation constant of 6.0 mM. The block depends on membrane voltage and is reduced at positive membrane potentials. The Ca2+-activated K+ current was measured in Ca2+- free artificial seawater (ASW) containing TTX, using internal Ca2+ ion injection to directly activate the K+ conductance. External TEA and a number of other quaternary ammonium ions block the Ca2+-activated K+ current reversibly in a dose-dependent manner. TEA is the most effective blocker, with an apparent dissociation constant, for a one-to- one reaction with a receptor site, of 0.4 mM. The block decreases with depolarization. The Ca2+-activated K+ current was also measured after intracellular iontophoretic TEA injection. Internal TEA blocks the Ca2+- activated K+ current (but the block is only apparent at positive membrane potentials), is increased by depolarization, and is irreversible. The effects of external and internal TEA can be seen in measurements of the total outward K+ current at different membrane potentials in normal ASW. PMID:6265594

Treating inflammation by blocking interleukin-1 in a broad spectrum of diseases.

PubMed

Dinarello, Charles A; Simon, Anna; van der Meer, Jos W M

2012-08-01

Interleukin-1 (IL-1) is a highly active pro-inflammatory cytokine that lowers pain thresholds and damages tissues. Monotherapy blocking IL-1 activity in autoinflammatory syndromes results in a rapid and sustained reduction in disease severity, including reversal of inflammation-mediated loss of sight, hearing and organ function. This approach can therefore be effective in treating common conditions such as post-infarction heart failure, and trials targeting a broad spectrum of new indications are underway. So far, three IL-1-targeted agents have been approved: the IL-1 receptor antagonist anakinra, the soluble decoy receptor rilonacept and the neutralizing monoclonal anti-IL-1β antibody canakinumab. In addition, a monoclonal antibody directed against the IL-1 receptor and a neutralizing anti-IL-1α antibody are in clinical trials.

Nicotinic Acetylcholine Receptors Mediate the Suppressive Effect of an Injection of Diluted Bee Venom into the GV3 Acupoint on Oxaliplatin-Induced Neuropathic Cold Allodynia in Rats.

PubMed

Yoon, Heera; Kim, Min Joon; Yoon, Insoo; Li, Dong Xing; Bae, Hyunsu; Kim, Sun Kwang

2015-01-01

Oxaliplatin, a platinum-based chemotherapy drug, often induces acute neuropathic pain, especially cold allodynia, even after a single administration. Subcutaneous injection of diluted bee venom (BV) into acupoints has been used to treat various pain symptoms in traditional oriental medicine. Although we previously demonstrated the suppressive effect of BV injection on oxaliplatin-induced cold allodynia in rats, its neurochemical mechanism remained unclear. This study investigates whether and how the cholinergic system mediates the relieving effect of BV injection on cold allodynia in oxaliplatin-administered rats. The behavioral signs of cold allodynia induced by an oxaliplatin administration (6 mg/kg, intraperitoneally (i.p.)) were evaluated by a tail immersion test in cold water (4°C). BV (0.25 mg/kg, subcutaneously (s.c.)) injection into the Yaoyangguan acupoint, located between the spinous processes of the fourth and fifth lumbar vertebrae, significantly alleviated the cold allodynia. This relieving effect of BV injection on oxaliplatin-induced cold allodynia was blocked by a pretreatment with mecamylamine (a non-selective nicotinic receptor antagonist, 2 mg/kg, i.p.), but not by atropine (a non-selective muscarinic receptor antagonist, 1 mg/kg, i.p.). Further, dihydro-β-erythroidinehydrobromide (DHβE, an α4β2 nicotinic antagonist, 5 mg/kg, i.p.) prevented the anti-allodynic effect of BV, whereas methyllycaconitine (an α7 nicotinic antagonist, 6 mg/kg, i.p.) did not. Finally, intrathecal administration of DHβE (10 nM) blocked the BV-induced anti-allodynic effect. These results suggest that nicotinic acetylcholine receptors, especially spinal α4β2 receptors, but not muscarinic receptors, mediate the suppressive effect of BV injection on oxaliplatin-induced acute cold allodynia in rats.

NO-producing compounds transform neuron responses to glutamate.

PubMed

D'yakonova, T L

2000-01-01

We have previously shown that NO increases the excitatory effects of glutamate and blocks the desensitization of neurons to glutamate in the brain of the common snail. The aim of the present work was to identify the possible effect of NO on inhibitory responses to glutamate in the neurons of this mollusk. Electrophysiological investigations were performed on three identified neurons. The results showed that glutamate (0.05-0.1 mM) initially induced hyperpolarization and blocked the spike activity of these neurons. Simultaneous exposure to glutamate and the NO donor nitroprusside or preincubation with an NO donor had the effect that cells again responded to glutamate with depolarization and excitation. The transformed excitatory response lasted several minutes and could be reproduced even after 24 h of washing. The NO synthase blocker monomethylarginine blocked the excitatory response to glutamate. Another agonist of glutamate receptors, N-methyl-D-aspartate (NMDA, 0.1-1 mM), initially had excitatory effects on these neurons; this effect was significantly enhanced after transformation of the response to glutamate by NO donors. The results obtained here show that NO is involved in transforming the inhibitory responses to glutamate to excitatory responses, and that this effect may be mediated by NMDA-type receptors.

Blockade of Cocaine or σ Receptor Agonist Self Administration by Subtype-Selective σ Receptor Antagonists

PubMed Central

Hiranita, Takato; Kopajtic, Theresa A.; Rice, Kenner C.; Mesangeau, Christophe; Narayanan, Sanju; Abdelazeem, Ahmed H.; McCurdy, Christopher R.

2016-01-01

The identification of sigma receptor (σR) subtypes has been based on radioligand binding and, despite progress with σ1R cellular function, less is known about σR subtype functions in vivo. Recent findings that cocaine self administration experience will trigger σR agonist self administration was used in this study to assess the in vivo receptor subtype specificity of the agonists (+)-pentazocine, PRE-084 [2-(4-morpholinethyl) 1-phenylcyclohexanecarboxylate hydrochloride], and 1,3-di-o-tolylguanidine (DTG) and several novel putative σR antagonists. Radioligand binding studies determined in vitro σR selectivity of the novel compounds, which were subsequently studied for self administration and antagonism of cocaine, (+)-pentazocine, PRE-084, or DTG self administration. Across the dose ranges studied, none of the novel compounds were self administered, nor did they alter cocaine self administration. All compounds blocked DTG self administration, with a subset also blocking (+)-pentazocine and PRE-084 self administration. The most selective of the compounds in binding σ1Rs blocked cocaine self administration when combined with a dopamine transport inhibitor, either methylphenidate or nomifensine. These drug combinations did not decrease rates of responding maintained by food reinforcement. In contrast, the most selective of the compounds in binding σ2Rs had no effect on cocaine self administration in combination with either dopamine transport inhibitor. Thus, these results identify subtype-specific in vivo antagonists, and the utility of σR agonist substitution for cocaine self administration as an assay capable of distinguishing σR subtype selectivity in vivo. These results further suggest that effectiveness of dual σR antagonism and dopamine transport inhibition in blocking cocaine self administration is specific for σ1Rs and further support this dual targeting approach to development of cocaine antagonists. PMID:27189970

NR4A nuclear receptors support memory enhancement by histone deacetylase inhibitors

PubMed Central

Hawk, Joshua D.; Bookout, Angie L.; Poplawski, Shane G.; Bridi, Morgan; Rao, Allison J.; Sulewski, Michael E.; Kroener, Brian T.; Manglesdorf, David J.; Abel, Ted

2012-01-01

The formation of a long-lasting memory requires a transcription-dependent consolidation period that converts a short-term memory into a long-term memory. Nuclear receptors compose a class of transcription factors that regulate diverse biological processes, and several nuclear receptors have been implicated in memory formation. Here, we examined the potential contribution of nuclear receptors to memory consolidation by measuring the expression of all 49 murine nuclear receptors after learning. We identified 13 nuclear receptors with increased expression after learning, including all 3 members of the Nr4a subfamily. These CREB-regulated Nr4a genes encode ligand-independent “orphan” nuclear receptors. We found that blocking NR4A activity in memory-supporting brain regions impaired long-term memory but did not impact short-term memory in mice. Further, expression of Nr4a genes increased following the memory-enhancing effects of histone deacetylase (HDAC) inhibitors. Blocking NR4A signaling interfered with the ability of HDAC inhibitors to enhance memory. These results demonstrate that the Nr4a gene family contributes to memory formation and is a promising target for improving cognitive function. PMID:22996661

Tolerance to the anticonvulsant effect of morphine in mice: blockage by ultra-low dose naltrexone.

PubMed

Roshanpour, Maryam; Ghasemi, Mehdi; Riazi, Kiarash; Rafiei-Tabatabaei, Neda; Ghahremani, Mohammad Hossein; Dehpour, Ahmad Reza

2009-02-01

The present study evaluated the development of tolerance to the anticonvulsant effect of morphine in a mouse model of clonic seizures induced by pentylenetetrazole, and whether ultra-low doses of the opioid receptor antagonist naltrexone which selectively block G(s) opioid receptors were capable of preventing the observed tolerance. The results showed that the morphine anticonvulsant effect could be subject to tolerance after repeated administration. Both the development and expression of tolerance were inhibited by ultra-low doses of naltrexone, suggesting the possible involvement of G(s)-coupled opioid receptors in the development of tolerance to the anticonvulsant effect of morphine.

Resolvin D1 and D2 Reverse Lipopolysaccharide-Induced Depression-Like Behaviors Through the mTORC1 Signaling Pathway.

PubMed

Deyama, Satoshi; Ishikawa, Yuka; Yoshikawa, Kotomi; Shimoda, Kento; Ide, Soichiro; Satoh, Masamichi; Minami, Masabumi

2017-07-01

Resolvin D1 and D2 are bioactive lipid mediators that are generated from docosahexaenoic acid. Although recent preclinical studies suggest that these compounds have antidepressant effects, their mechanisms of action remain unclear. We investigated mechanisms underlying the antidepressant effects of resolvin D1 and resolvin D2 in lipopolysaccharide (0.8 mg/kg, i.p.)-induced depression model mice using a tail suspension test. I.c.v. infusion of resolvin D1 (10 ng) and resolvin D2 (10 ng) produced antidepressant effects; these effects were significantly blocked by a resolvin D1 receptor antagonist WRW4 (10 µg, i.c.v.) and a resolvin D2 receptor antagonist O-1918 (10 µg, i.c.v.), respectively. The mammalian target of rapamycin complex 1 inhibitor rapamycin (10 mg/kg, i.p.) and a mitogen-activated protein kinase kinase inhibitor U0126 (5 µg, i.c.v.) significantly blocked the antidepressant effects of resolvin D1 and resolvin D2. An AMPA receptor antagonist NBQX (10 mg/kg, i.p.) and a phosphoinositide 3-kinase inhibitor LY294002 (3 µg, i.c.v.) blocked the antidepressant effects of resolvin D1 significantly, but not of resolvin D2. Bilateral infusions of resolvin D1 (0.3 ng/side) or resolvin D2 (0.3 ng/side) into the medial prefrontal cortex or dentate gyrus of the hippocampus produced antidepressant effects. These findings demonstrate that resolvin D1 and resolvin D2 produce antidepressant effects via the mammalian target of rapamycin complex 1 signaling pathway, and that the medial prefrontal cortex and dentate gyrus are important brain regions for these antidepressant effects. These compounds and their receptors may be promising targets for the development of novel rapid-acting antidepressants, like ketamine and scopolamine. © The Author 2017. Published by Oxford University Press on behalf of CINP.

Bud extracts from Tilia tomentosa Moench inhibit hippocampal neuronal firing through GABAA and benzodiazepine receptors activation.

PubMed

Allio, Arianna; Calorio, Chiara; Franchino, Claudio; Gavello, Daniela; Carbone, Emilio; Marcantoni, Andrea

2015-08-22

Tilia tomentosa Moench bud extracts (TTBEs) is used in traditional medicine for centuries as sedative compound. Different plants belonging to the Tilia genus have shown their efficacy in the treatment of anxiety but still little is known about the mechanism of action of their bud extracts. To evaluate the action of TTBEs as anxiolytic and sedative compound on in vitro hippocampal neurons. The anxiolytic effect of TTBEs was assayed by testing the effects of these compounds on GABAA receptor-activated chloride current of hippocampal neurons by means of the patch-clamp technique and microelectrode-arrays (MEAs). TTBEs acutely administered on mouse hippocampal neurons, activated a chloride current comparable to that measured in the presence of GABA (100 µM). Bicuculline (100 µM) and picrotoxin (100 µM) blocked about 90% of this current, while the remaining 10% was blocked by adding the benzodiazepine (BDZ) antagonist flumazenil (30 µM). Flumazenil alone blocked nearly 60% of the TTBEs activated current, suggesting that TTBEs binds to both GABAA and BDZ receptor sites. Application of high-doses of TTBEs on spontaneous active hippocampal neurons grown for 3 weeks on MEAs blocked the synchronous activity of these neurons. The effects were mimicked by GABA and prevented by picrotoxin (100µM) and flumazenil (30 µM). At minimal doses, TTBEs reduced the frequency of synchronized bursts and increased the cross-correlation index of synchronized neuronal firing. Our data suggest that TTBEs mimics GABA and BDZ agonists by targeting hippocampal GABAergic synapses and inhibiting network excitability by increasing the strength of inhibitory synaptic outputs. Our results contribute toward the validation of TTBEs as effective sedative and anxiolytic compound. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Addition of a Nitric Oxide Donor to an Angiotensin II Type 1 Receptor Blocker May Cancel Its Blood Pressure-Lowering Effects.

PubMed

Yahiro, Eiji; Miura, Shin-Ichiro; Suematsu, Yasunori; Matsuo, Yoshino; Arimura, Tadaaki; Kuwano, Takashi; Imaizumi, Satoshi; Iwata, Atsushi; Uehara, Yoshinari; Saku, Keijiro

2015-01-01

While physiological levels of nitric oxide (NO) protect the endothelium and have vasodilatory effects, excessive NO has adverse effects on the cardiovascular system. Recently, new NO-releasing pharmacodynamic hybrids of angiotensin II (Ang II) type 1 (AT1) receptor blockers (ARBs) have been developed.We analyzed whether olmesartan with NO-donor side chains (Olm-NO) was superior to olmesartan (Olm) for the control of blood pressure (BP). Although there was no significant difference in binding affinity to AT1 wild-type (WT) receptor between Olm and Olm-NO in a cell-based binding assay, the suppressive effect of Olm-NO on Ang II-induced inositol phosphate (IP) production was significantly weaker than that of Olm in AT1 WT receptor-expressing cells. While Olm had a strong inverse agonistic effect on IP production, Olm-NO did not. Next, we divided 18 C57BL mice into 3 groups: Ang II (infusion using an osmotic mini-pump) as a control group, Ang II (n = 6) + Olm, and Ang II (n = 6) + Olm-NO groups (n = 6). Olm-NO did not block Ang II-induced high BP after 10 days, whereas Olm significantly decreased BP. In addition, Olm, but not Olm-NO, significantly reduced the ratio of heart weight to body weight (HW/BW) with downregulation of the mRNA levels of atrial natriuretic peptide.An ARB with a NO-donor may cancel BP-lowering effects probably due to excessive NO and a weak blocking effect by Olm-NO toward AT1 receptor activation.

The Vasopressin 1b Receptor Antagonist A-988315 Blocks Stress Effects on the Retrieval of Object-Recognition Memory

PubMed Central

Barsegyan, Areg; Atsak, Piray; Hornberger, Wilfried B; Jacobson, Peer B; van Gaalen, Marcel M; Roozendaal, Benno

2015-01-01

Stress-induced activation of the hypothalamo–pituitary–adrenocortical (HPA) axis and high circulating glucocorticoid levels are well known to impair the retrieval of memory. Vasopressin can activate the HPA axis by stimulating vasopressin 1b (V1b) receptors located on the pituitary. In the present study, we investigated the effect of A-988315, a selective and highly potent non-peptidergic V1b-receptor antagonist with good pharmacokinetic properties, in blocking stress effects on HPA-axis activity and memory retrieval. To study cognitive performance, male Sprague-Dawley rats were trained on an object-discrimination task during which they could freely explore two identical objects. Memory for the objects and their location was tested 24 h later. A-988315 (20 or 60 mg/kg) or water was administered orally 90 min before retention testing, followed 60 min later by stress of footshock exposure. A-988315 dose-dependently dampened stress-induced increases in corticosterone plasma levels, but did not significantly alter HPA-axis activity of non-stressed control rats. Most importantly, A-988315 administration prevented stress-induced impairment of memory retrieval on both the object-recognition and the object-location tasks. A-988315 did not alter the retention of non-stressed rats and did not influence the total time spent exploring the objects or experimental context in either stressed or non-stressed rats. Thus, these findings indicate that direct antagonism of V1b receptors is an effective treatment to block stress-induced activation of the HPA axis and the consequent impairment of retrieval of different aspects of recognition memory. PMID:25669604

TRPV1 channels in the nucleus of the solitary tract mediate thermal prolongation of the LCR in decerebrate piglets.

PubMed

Xia, Luxi; Bartlett, Donald; Leiter, J C

2011-04-30

Elevating body temperature or just the temperature of the dorsal medulla by approximately 2°C prolongs the laryngeal chemoreflex (LCR) in decerebrate neonatal piglets. We tested the hypothesis that transient receptor potential vanilloid 1 (TRPV1) receptors in the nucleus of the solitary tract (NTS) mediate thermal prolongation of the LCR. We studied the effect of a selective TRPV1 receptor antagonist on thermal prolongation of the LCR, and we tested the effect of a TRPV1 agonist on the duration of the LCR under normothermic conditions. We studied 37 decerebrate neonatal piglets between the ages of post-natal days 4 and 7. The TRPV1 receptor antagonist, 5'-iodoresiniferatoxin (65μM/L in 100nL), blocked thermal prolongation of the LCR when injected bilaterally into the region of the NTS. The TRPV1 agonist, resiniferatoxin (0.65-1.0mM/L in 100nL), prolonged the LCR after bilateral injection into the NTS even when the body temperature of each piglet was normal. The effect of the TRPV1 agonists could be blocked by treatment with the GABA(A) receptor antagonist, bicuculline, whether given intravenously (0.3mg/kg) or focally injected bilaterally into the NTS (10mM in 100nL). We conclude that TRPV1 receptors in the NTS mediate thermal prolongation of the LCR. Copyright © 2011 Elsevier B.V. All rights reserved.

Cardiovascular effects of spinal cord substance P: studies with a stable receptor agonist.

PubMed

Keeler, J R; Charlton, C G; Helke, C J

1985-06-01

The role of spinal cord substance P (SP) in regulating sympathetic outflow to the cardiovascular system was assessed with the stable active analog [pGlu5,MePhE8,MeGly9]-SP(5-11) (DiME-SP). The interaction of DiME-SP with spinal cord SP receptors was evaluated initially in binding studies. Saturable, high-affinity binding of [125I]Bolton-Hunter-SP to rat spinal cord membranes was dose-dependently inhibited by DiME-SP (IC50 = 1.5 microM). Intrathecal (i.t.) injections of DiME-SP (1.0-33 nmol) in anesthetized rats produced dose-dependent increases in blood pressure and heart rate that were accompanied by increases in plasma epinephrine and norepinephrine. Intravenous injections of the ganglionic blocker pentolinium blocked the cardiovascular and plasma catecholamine responses to i.t. injections of DiME-SP. Bulbospinal sympathoexcitatory pathways originating in the ventral medulla and their mediation by SP were also assessed. As demonstrated previously, application of bicuculline, the gamma-aminobutyric acid receptor antagonist, to the ventral surface of the medulla produced sympathetic mediated increases in blood pressure and these effects were blocked by i.t. injection of the SP receptor antagonist [D-Arg1,D-Pro2,D-Trp7,9,Leu11]-SP. In this study, we studied the specificity of the SP antagonist for SP receptors by attempting to alter the actions of the SP antagonist with a SP agonist. Administration of DiME-SP (33 nmol i.t.) blocked the effects of [D-Arg1,D-Pro2,D-Trp7,9,Leu11]-SP (3.3 nmol i.t.). Specifically, the SP agonist countered the SP antagonist-mediated 1) hypotensive response and 2) inhibitory effect on bicuculline-induced sympathoexcitatory responses elicited from the ventral surface of the medulla. These data provide further evidence that SP transmits excitatory information to the cardiovascular system via spinal sympathetic pathways.

Expression and signaling of G protein-coupled estrogen receptor 1 (GPER) in rat sertoli cells.

PubMed

Lucas, Thaís F G; Royer, Carine; Siu, Erica R; Lazari, Maria Fatima M; Porto, Catarina S

2010-08-01

The aim of the present study was to investigate the expression and signaling of the G protein-coupled estrogen receptor 1 (GPER) in cultured immature rat Sertoli cells--in which we have previously described the classical estrogen receptors (ESR1 and ESR2). Expression of GPER in cultured Sertoli cells from 15-day-old rats was detected by RT-PCR and immunoassays. Gper transcripts also were present in testes from 5-, 15-, and 120-day-old rats. Short-term treatment of Sertoli cells with 17beta-estradiol (E2), the GPER agonist G-1, or the ESR antagonist ICI 182,780 (ICI) rapidly activated MAPK3/1 (ERK1/2), even after down-regulation of ESR1 and ESR2, suggesting a role for GPER in the rapid E2 action in these cells. MAPK3/1 phosphorylation induced by ICI or G-1 was blocked by pertussis toxin, selective inhibitor of the SRC family of protein tyrosine kinases, metalloprotease inhibitor, MAP2K1/2 inhibitor, and epidermal growth factor receptor (EGFR) kinase inhibitor. Furthermore, E2, but not G-1, induced up-regulation of cyclin D1 in the Sertoli cells. This effect was blocked by ICI. E2 and G-1 decreased BAX and increased BCL2 expression and these effects were blocked by MAP2K1/2 inhibitor and EGFR kinase inhibitor. The pretreatment with ICI did not block the effect of E2. Taken together, these results indicate that in Sertoli cells 1) GPER-mediated MAPK3/1 activation occurs via EGFR transactivation through G protein beta gamma subunits that promote SRC-mediated metalloprotease-dependent release of EGFR ligands, which bind to EGFR and lead to MAPK3/1 phosphorylation; 2) E2-ESRs play a role in Sertoli cell proliferation; and 3) E2-GPER may regulate gene expression involved with apoptosis. ESR and GPER may mediate actions important for Sertoli cell function and maintenance of normal testis development and homeostasis.

Involvement of central opioid systems in human interferon-α induced immobility in the mouse forced swimming test

PubMed Central

Makino, Mitsuhiro; Kitano, Yutaka; Komiyama, Chika; Hirohashi, Masaaki; Takasuna, Kiyoshi

2000-01-01

We investigated the mechanism by which human interferon-α (IFN-α) increases the immobility time in a forced swimming test, an animal model of depression.Central administration of IFN-α (0.05–50 IU per mouse, i.cist.) increased the immobility time in the forced swimming test in mice in a dose-dependent manner.Neither IFN-β nor -γ possessed any effect under the same experimental conditions.Pre-treatment with an opioid receptor antagonist, naloxone (1 mg kg−1, s.c.) inhibited the prolonged immobility time induced by IFN-α (60 KIU kg−1, i.v. or 50 IU per mouse. i.cist.).Peripheral administration of naloxone methiodide (1 mg kg−1, s.c.), which does not pass the blood–brain barrier, failed to block the effect of IFN-α, while intracisternal administration of naloxone methiodide (1 nmol per mouse) completely blocked.The effect of IFN-α was inhibited by a μ1-specific opioid receptor antagonist, naloxonazine (35 mg kg−1, s.c.) and a μ1/μ2 receptor antagonist, β-FNA (40 mg kg−1, s.c.). A selective δ-opioid receptor antagonist, naltrindole (3 mg kg−1, s.c.) and a κ-opioid receptor antagonist, nor-binaltorphimine (20 mg kg−1, s.c.), both failed to inhibit the increasing effect of IFN-α.These results suggest that the activator of the central opioid receptors of the μ1-subtype might be related to the prolonged immobility time of IFN-α, but δ and κ-opioid receptors most likely are not involved. PMID:10903965

Aldosterone rapidly activates Src kinase in M-1 cells involving the mineralocorticoid receptor and HSP84.

PubMed

Braun, Sabine; Lösel, Ralf; Wehling, Martin; Boldyreff, Brigitte

2004-07-16

We investigated the effect of aldosterone on Src kinase. In the kidney cell line, M-1 aldosterone leads to a >2-fold transient activation of Src kinase seen as early as 2 min after aldosterone administration. Maximal Src kinase activation was measured at an aldosterone concentration of 1 nM. In parallel to activation, autophosphorylation at Tyr-416 of Src kinase increased. Src kinase activation was blocked by spironolactone. Aldosterone led to increased association of Src with HSP84. Furthermore, rapamycin blocked aldosterone-induced Src activation. We conclude that Src activation by aldosterone is mediated through the mineralocorticoid receptor and HSP84.

Mouse Hepatitis Virus Strain A59 and Blocking Antireceptor Monoclonal Antibody Bind to the N-Terminal Domain of Cellular Receptor

NASA Astrophysics Data System (ADS)

Dveksler, Gabriela S.; Pensiero, Michael N.; Dieffenbach, Carl W.; Cardellichio, Christine B.; Basile, Alexis A.; Elia, Patrick E.; Holmes, Kathryn V.

1993-03-01

Mouse hepatitis virus (MHV) strain A59 uses as cellular receptors members of the carcinoembryonic antigen family in the immunoglobulin superfamily. Recombinant receptor proteins with deletions of whole or partial immunoglobulin domains were used to identify the regions of receptor glycoprotein recognized by virus and by antireceptor monoclonal antibody CC1, which blocks infection of murine cells. Monoclonal antibody CC1 and MHV-A59 virions bound only to recombinant proteins containing the entire first domain of MHV receptor. To determine which of the proteins could serve as functional virus receptors, receptor-negative hamster cells were transfected with recombinant deletion clones and then challenged with MHV-A59 virions. Receptor activity required the entire N-terminal domain with either the second or the fourth domain and the transmembrane and cytoplasmic domains. Recombinant proteins lacking the first domain or its C-terminal portion did not serve as viral receptors. Thus, like other virus receptors in the immunoglobulin superfamily, including CD4, poliovirus receptor, and intercellular adhesion molecule 1, the N-terminal domain of MHV receptor is recognized by the virus and the blocking monoclonal antibody.

P2X1 receptor-mediated inhibition of the proliferation of human coronary smooth muscle cells involving the transcription factor NR4A1.

PubMed

Hinze, Annette Viktoria; Mayer, Peter; Harst, Anja; von Kügelgen, Ivar

2013-12-01

Adenine nucleotides acting at P2X1 receptors are potent vasoconstrictors. Recently, we demonstrated that activation of adenosine A2B receptors on human coronary smooth muscle cells inhibits cell proliferation by the induction of the nuclear receptor subfamily 4, group A, member 1 (NR4A1; alternative notation Nur77). In the present study, we searched for long-term effects mediated by P2X1 receptors by analyzing receptor-mediated changes in cell proliferation and in the expression of NR4A1. Cultured human coronary smooth muscle cells were treated with selective receptor ligands. Effects on proliferation were determined by counting cells and measuring changes in impedance. The induction of transcription factors was assessed by qPCR. The P2X receptor agonist α,β-methylene-ATP and its analog β,γ-methylene-ATP inhibited cell proliferation by about 50 % after 5 days in culture with half-maximal concentrations of 0.3 and 0.08 μM, respectively. The effects were abolished or markedly attenuated by the P2X1 receptor antagonist NF449 (carbonylbis-imino-benzene-triylbis-(carbonylimino)tetrakis-benzene-1,3-disulfonic acid; 100 nM and 1 μM). α,β-methylene-ATP and β,γ-methylene-ATP applied for 30 min to 4 h increased the expression of NR4A1; NF449 blocked or attenuated this effect. Small interfering RNA directed against NR4A1 diminished the antiproliferative effects of α,β-methylene-ATP and β,γ-methylene-ATP. α,β-methylene-ATP (0.1 to 30 μM) decreased migration of cultured human coronary smooth muscle cells in a chamber measuring changes in impedance; NF449 blocked the effect. In conclusion, our results demonstrate for the first time that adenine nucleotides acting at P2X1 receptors inhibit the proliferation of human coronary smooth muscle cells via the induction of the early gene NR4A1.

Adenosine A₂A receptors inhibit delayed rectifier potassium currents and cell differentiation in primary purified oligodendrocyte cultures.

PubMed

Coppi, Elisabetta; Cellai, Lucrezia; Maraula, Giovanna; Pugliese, Anna Maria; Pedata, Felicita

2013-10-01

Oligodendrocyte progenitor cells (OPCs) are a population of cycling cells which persist in the adult central nervous system (CNS) where, under opportune stimuli, they differentiate into mature myelinating oligodendrocytes. Adenosine A(2A) receptors are Gs-coupled P1 purinergic receptors which are widely distributed throughout the CNS. It has been demonstrated that OPCs express A(2A) receptors, but their functional role in these cells remains elusive. Oligodendrocytes express distinct voltage-gated ion channels depending on their maturation. Here, by electrophysiological recordings coupled with immunocytochemical labeling, we studied the effects of adenosine A(2A) receptors on membrane currents and differentiation of purified primary OPCs isolated from the rat cortex. We found that the selective A(2A) agonist, CGS21680, inhibits sustained, delayed rectifier, K(+) currents (I(K)) without modifying transient (I(A)) conductances. The effect was observed in all cells tested, independently from time in culture. CGS21680 inhibition of I(K) current was concentration-dependent (10-200 nM) and blocked in the presence of the selective A(2A) antagonist SCH58261 (100 nM). It is known that I(K) currents play an important role during OPC development since their block decreases cell proliferation and differentiation. In light of these data, our further aim was to investigate whether A(2A) receptors modulate these processes. CGS21680, applied at 100 nM in the culture medium of oligodendrocyte cultures, inhibits OPC differentiation (an effect prevented by SCH58261) without affecting cell proliferation. Data demonstrate that cultured OPCs express functional A(2A) receptors whose activation negatively modulate I(K) currents. We propose that, by this mechanism, A(2A) adenosine receptors inhibit OPC differentiation. Copyright © 2013 Elsevier Ltd. All rights reserved.

R- and S-terbutaline activate large conductance and Ca2+ dependent K+ (BKCa) channel through interacting with β2 and M receptor respectively.

PubMed

Fan, Zhuo; Lin, Wei; Lv, Nanying; Ye, Yanrui; Tan, Wen

2016-11-01

This study investigated the effect of the β 2 receptor agonist terbutaline on the single channel activity of BK Ca channel. The effects of racemate and two isomers of terbutaline were all assessed. β 2 adrenoceptors were stably overexpressed on HEK293 cells by lentiviral transduction method and chicken BK Ca channels were transiently expressed on normal HEK293 cell line or HEK293 cells overexpressing β 2 receptors. Data showed that terbutaline significantly increased the single channel open probability of BK Ca channel within 10min. The channel activating effects of terbutaline are stereoselective and mainly stay with the R-enantiomers. The opening probability of BK Ca channel at 10min after drug application normalized to that just before drug application (Po10/Po0s) for R- and S-terbutaline were 7.85±3.20 and 1.06±0.45 respectively at 1μM concentration, corresponding to 28.37±9.96 and 2.68±1.09 at the higher concentration of 10μM. ICI 118551 blocked the effect of R- but not S-terbutaline (10μM), whereas atropine blocked the channel activating effects of S-terbutaline of higher concentration. In addition, the muscarinic receptor agonist carbachol increased the BK Ca channel activity in an atropine-sensitive manner as an positive control experiment, which indicate the involvement of M receptor in the channel activating effect of S-terbutaline. Copyright © 2016. Published by Elsevier B.V.

Estrogen receptor coregulator binding modulators (ERXs) effectively target estrogen receptor positive human breast cancers

PubMed Central

Raj, Ganesh V; Sareddy, Gangadhara Reddy; Ma, Shihong; Lee, Tae-Kyung; Viswanadhapalli, Suryavathi; Li, Rui; Liu, Xihui; Murakami, Shino; Chen, Chien-Cheng; Lee, Wan-Ru; Mann, Monica; Krishnan, Samaya Rajeshwari; Manandhar, Bikash; Gonugunta, Vijay K; Strand, Douglas; Tekmal, Rajeshwar Rao; Ahn, Jung-Mo; Vadlamudi, Ratna K

2017-01-01

The majority of human breast cancer is estrogen receptor alpha (ER) positive. While anti-estrogens/aromatase inhibitors are initially effective, resistance to these drugs commonly develops. Therapy-resistant tumors often retain ER signaling, via interaction with critical oncogenic coregulator proteins. To address these mechanisms of resistance, we have developed a novel ER coregulator binding modulator, ERX-11. ERX-11 interacts directly with ER and blocks the interaction between a subset of coregulators with both native and mutant forms of ER. ERX-11 effectively blocks ER-mediated oncogenic signaling and has potent anti-proliferative activity against therapy-sensitive and therapy-resistant human breast cancer cells. ERX-11 is orally bioavailable, with no overt signs of toxicity and potent activity in both murine xenograft and patient-derived breast tumor explant models. This first-in-class agent, with its novel mechanism of action of disrupting critical protein-protein interactions, overcomes the limitations of current therapies and may be clinically translatable for patients with therapy-sensitive and therapy-resistant breast cancers. DOI: http://dx.doi.org/10.7554/eLife.26857.001 PMID:28786813

The Serotonin 2C Receptor Agonist Lorcaserin Attenuates Intracranial Self-Stimulation and Blocks the Reward-Enhancing Effects of Nicotine.

PubMed

Zeeb, Fiona D; Higgins, Guy A; Fletcher, Paul J

2015-07-15

Lorcaserin, a serotonin (5-hydroxytryptamine, 5-HT) 2C receptor agonist, was recently approved for the treatment of obesity. We previously suggested that 5-HT2C receptor agonists affect reward processes and reduce the rewarding effects of drugs of abuse. Here, we determined whether lorcaserin (1) decreases responding for brain stimulation reward (BSR) and (2) prevents nicotine from enhancing the efficacy of BSR. Rats were trained on the intracranial self-stimulation (ICSS) paradigm to nosepoke for BSR of either the dorsal raphé nucleus or left medial forebrain bundle. In Experiment 1, lorcaserin (0.3-1.0 mg/kg) dose-dependently reduced the efficacy of BSR. This effect was blocked by prior administration of the 5-HT2C receptor antagonist SB242084. In Experiment 2, separate groups of rats received saline or nicotine (0.4 mg/kg) for eight sessions prior to testing. Although thresholds were unaltered in saline-treated rats, nicotine reduced reward thresholds. An injection of lorcaserin (0.3 mg/kg) prior to nicotine prevented the reward-enhancing effect of nicotine across multiple test sessions. These results demonstrated that lorcaserin reduces the rewarding value of BSR and also prevents nicotine from facilitating ICSS. Hence, lorcaserin may be effective in treating psychiatric disorders, including obesity and nicotine addiction, by reducing the value of food or drug rewards.

Dynamic Optical Filtration

NASA Technical Reports Server (NTRS)

Chretien, Jean-Loup (Inventor); Lu, Edward T. (Inventor)

2005-01-01

A dynamic optical filtration system and method effectively blocks bright light sources without impairing view of the remainder of the scene. A sensor measures light intensity and position so that selected cells of a shading matrix may interrupt the view of the bright light source by a receptor. A beamsplitter may be used so that the sensor may be located away from the receptor. The shading matrix may also be replaced by a digital micromirror device, which selectively sends image data to the receptor.

Dynamic optical filtration

NASA Technical Reports Server (NTRS)

Chretien, Jean-Loup (Inventor); Lu, Edward T. (Inventor)

2005-01-01

A dynamic optical filtration system and method effectively blocks bright light sources without impairing view of the remainder of the scene. A sensor measures light intensity and position so that selected cells of a shading matrix may interrupt the view of the bright light source by a receptor. A beamsplitter may be used so that the sensor may be located away from the receptor. The shading matrix may also be replaced by a digital micromirror device, which selectively sends image data to the receptor.

H2O2 attenuates IGF-1R tyrosine phosphorylation and its survival signaling properties in neuronal cells via NR2B containing NMDA receptor.

PubMed

Zeng, Zhiwen; Wang, Dejun; Gaur, Uma; Rifang, Liao; Wang, Haitao; Zheng, Wenhua

2017-09-12

Impairment of insulin-like growth factor I (IGF-I) signaling plays an important role in the development of neurodegeneration. In the present study, we investigated the effect of H 2 O 2 on the survival signaling of IGF-1 and its underlying mechanisms in human neuronal cells SH-SY5Y. Our results showed that IGF-1 promoted cell survival and stimulated phosphorylation of IGF-1R as well as its downstream targets like AKT and ERK1/2 in these cells. Meanwhile, these effects of IGF-1 were abolished by H 2 O 2 at 200μM concentration which did not cause any significant toxicity to cells itself in our experiments. Moreover, studies using various glutamate receptor subtype antagonists displayed that N-methyl-D -aspartate (NMDA) receptor antagonist dizocilpine maleate (MK-801) blocked the effects of H 2 O 2 , whereas other glutamate receptor subtype antagonists, such as non-NMDA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX), metabolic glutamate receptor antagonists LY341495 and CPCCOEt, had no effect. Further studies revealed that NR2B-containing NMDARs are responsible for these effects as its effects were blocked by pharmacological inhibitor Ro25-698 or specific siRNA for NR2B, but not NR2A. Finally, our data also showed that Ca 2+ influx contributes to the effects of H 2 O 2 . Similar results were obtained in primary cultured cortical neurons. Taken together, the results from the present study suggested that H 2 O 2 attenuated IGF-1R tyrosine phosphorylation and its survival signaling properties via NR2B containing NMDA receptors and Ca 2+ influx in SH-SY5Y cells. Therefore, NMDAR antagonists, especially NR2B-selective ones, combined with IGF-1 may serve as an alternative therapeutic agent for oxidative stress related neurodegenerative disease.

Cysteinyl leukotrienes C4 and D4 downregulate human mast cell expression of toll-like receptors 1 through 7.

PubMed

Karpov, V; Ilarraza, R; Catalli, A; Kulka, M

2018-01-01

Cysteinyl leukotrienes (CysLT) are potent inflammatory lipid molecules that mediate some of the pathophysiological responses associated with asthma such as bronchoconstriction, vasodilation and increased microvascular permeability. As a result, CysLT receptor antagonists (LRA), such as montelukast, have been used to effectively treat patients with asthma. We have recently shown that mast cells are necessary modulators of innate immune responses to bacterial infection and an important component of this innate immune response may involve the production of CysLT. However, the effect of LRA on innate immune receptors, particularly on allergic effector cells, is unknown. This study determined the effect of CysLT on toll-like receptor (TLR) expression by the human mast cell line LAD2. Real-time PCR analysis determined that LTC4, LTD4 and LTE4 downregulated mRNA expression of several TLR. Specifically in human CD34+-derived human mast cells (HuMC), LTC4 inhibited expression of TLR1, 2, 4, 5, 6 and 7 while LTD4 inhibited expression of TLR1-7. Montelukast blocked LTC4-mediated downregulation of all TLR, suggesting that these effects were mediated by activation of the CysLT1 receptor (CysLT1R). Flow cytometry analysis confirmed that LTC4 downregulated surface expression of TLR2 which was blocked by montelukast. These data show that CysLT can modulate human mast cell expression of TLR and that montelukast may be beneficial for innate immune responses mediated by mast cells.

Comparison of the antinociceptive action of crude Fuzei, the root of Aconitum, and its processed products.

PubMed

Liou, Shorong-Shii; Liu, I-Min; Lai, Mei Chou; Cheng, Juei-Tang

2005-07-14

The antinociceptive effects of crude Fuzei, the root of Aconitum carmichaeli and of Fuzei processed by three different methods were determined in mice and rats using the light tail-flick assay. A dose-dependent and significant increase in pain threshold was found at 60 min post treatment, with doses of 20-60 mg/kg crude Fuzei. The analgesic effects of processed Fuzei (20-60 mg/kg) exhibited a dose-dependent inhibition of tail-flick, but the effects were lower than those produced by crude Fuzei in the same tests. The analgesic effect of Yan-Fuzei, the salt baking product, was the most potent of the processed products and was nearly that provided by crude Fuzei. Although the concentrations of aconitine were significantly lower in the processed Fuzei than in the crude Fuzei, a higher oral LD50 was found for all of the processed Fuzei formulations. Moreover, antinociception of crude Fuzei and its processed products was attenuated but not totally blocked by naloxone at doses sufficient to block opioid mu-receptors. Furthermore, the analgesic effect of crude Fuzei and its processed products was decreased in opioid mu-receptor knockout mice, but the effect remained unaltered in mice with opioid mu-receptors, indicating that the analgesic effect of Fuzei is centrally mediated. These results demonstrate that Fuzei processed by salt baking possesses analgesic effects within a large therapeutic range, probably via a mechanism involving central opioid receptors that mediate the antinociception.

Tipepidine, a non-narcotic antitussive, exerts an antidepressant-like effect in the forced swimming test in adrenocorticotropic hormone-treated rats.

PubMed

Kawaura, Kazuaki; Ogata, Yukino; Honda, Sokichi; Soeda, Fumio; Shirasaki, Tetsuya; Takahama, Kazuo

2016-04-01

We investigated whether tipepidine exerts an antidepressant-like effect in the forced swimming test in adrenocorticotropic hormone (ACTH)-treated rats, which is known as a treatment-resistant depression model, and we studied the pharmacological mechanisms of the effects of tipepidine. Male Wistar rats (5-7 weeks old) were used in this study. Tipepidine (20 and 40 mg/kg, i.p.) decreased the immobility time in the forced swimming test in ACTH-treated rats. The anti-immobility effect of tipepidine was blocked by a catecholamine-depleting agent, alpha-methyl-p-tyrosine (300 mg/kg, s.c.), but not by a serotonin-depleting agent, p-chlorophenylalanine. The anti-immobility effect of tipepidine was also blocked by a dopamine D1 receptor antagonist, SCH23390 (0.02 mg/kg, s.c.) and an adrenaline α2 receptor antagonist, yohimbine (2 mg/kg, i.p.). In microdialysis technique, tipepidine (40 mg/kg, i.p.) increased the extracellular dopamine level of the nucleus accumbens (NAc) in ACTH-treated rats. These results suggest that tipepidine exerts an antidepressant-like effect in the forced swimming test in ACTH-treated rats, and that the effect of tipepidine is mediated by the stimulation of dopamine D1 receptors and adrenaline α2 receptors. The results also suggest that an increase in the extracellular dopamine level in the NAc may be involved in the antidepressant-like effect of tipepidine in ACTH-treated rats. Copyright © 2016. Published by Elsevier B.V.

Potentiating role of interleukin-1beta (IL-1beta) and IL-1beta type 1 receptors in the medial hypothalamus in defensive rage behavior in the cat.

PubMed

Hassanain, M; Bhatt, S; Zalcman, S; Siegel, A

2005-06-28

Recently, this laboratory provided evidence that interleukin-1beta (IL-1beta), an immune and brain-derived cytokine, microinjected into the medial hypothalamus, potentiates defensive rage behavior in the cat elicited from the midbrain periaqueductal gray (PAG), and that such effects are blocked by a 5-HT2 receptor antagonist. Since this finding represents the first time that a brain cytokine has been shown to affect defensive rage behavior, the present study replicated and extended these findings by documenting the specific potentiating role played by IL-1beta Type 1 receptor (IL-1RI), and the anatomical relationship between IL-1beta and 5-HT2 receptors in the medial hypothalamus. IL-1beta (10 ng) microinjected into the medial hypothalamus induced two separate phases of facilitation, one at 60 min and another at 180 min, post-injection. In turn, these effects were blocked with pretreatment of the selective IL-1 Type I receptor antagonist (IL-1ra) (10 ng), demonstrating the selectivity of the effects of IL-1beta on medial hypothalamic neurons upon PAG-elicited defensive rage behavior. The next stage of the study utilized immunohistochemical methods to demonstrate that IL-1beta and 5-HT2 receptors were present on the same neurons within regions of the medial hypothalamus where IL-1beta and the IL-1beta receptor antagonists were administered. This provided anatomical evidence suggesting a relationship between IL-1RI and 5-HT2 receptors in the medial hypothalamus that is consistent with the previous pharmacological observations in our laboratory. The overall findings show that activation of IL-1RI in the medial hypothalamus potentiates defensive rage behavior in the cat and that these effects may also be linked to the presence of 5-HT2 receptors on the same groups of neurons in this region of hypothalamus.

Cholesterol Regulates μ-Opioid Receptor-Induced β-Arrestin 2 Translocation to Membrane Lipid RaftsS⃞

PubMed Central

Qiu, Yu; Wang, Yan; Chen, Hong-Zhuan; Loh, Horace H.

2011-01-01

μ-Opioid receptor (OPRM1) is mainly localized in lipid raft microdomains but internalizes through clathrin-dependent pathways. Our previous studies demonstrated that disruption of lipid rafts by cholesterol-depletion reagent blocked the agonist-induced internalization of OPRM1 and G protein-dependent signaling. The present study demonstrated that reduction of cholesterol level decreased and culturing cells in excess cholesterol increased the agonist-induced internalization and desensitization of OPRM1, respectively. Further analyses indicated that modulation of cellular cholesterol level did not affect agonist-induced receptor phosphorylation but did affect membrane translocation of β-arrestins. The translocation of β-arrestins was blocked by cholesterol reduction, and the effect could be reversed by incubating with cholesterol. OptiPrep gradient separation of lipid rafts revealed that excess cholesterol retained more receptors in lipid raft domains and facilitated the recruitment of β-arrestins to these microdomains upon agonist activation. Moreover, excess cholesterol could evoke receptor internalization and protein kinase C-independent extracellular signal-regulated kinases activation upon morphine treatment. Therefore, these results suggest that cholesterol not only can influence OPRM1 localization in lipid rafts but also can effectively enhance the recruitment of β-arrestins and thereby affect the agonist-induced trafficking and agonist-dependent signaling of OPRM1. PMID:21518774

Opioid receptors regulate blocking and overexpectation of fear learning in conditioned suppression.

PubMed

Arico, Carolyn; McNally, Gavan P

2014-04-01

Endogenous opioids play an important role in prediction error during fear learning. However, the evidence for this role has been obtained almost exclusively using the species-specific defense response of freezing as the measure of learned fear. It is unknown whether opioid receptors regulate predictive fear learning when other measures of learned fear are used. Here, we used conditioned suppression as the measure of learned fear to assess the role of opioid receptors in fear learning. Experiment 1a studied associative blocking of fear learning. Rats in an experimental group received conditioned stimulus A (CSA) + training in Stage I and conditioned stimulus A and B (CSAB) + training in Stage II, whereas rats in a control group received only CSAB + training in Stage II. The prior fear conditioning of CSA blocked fear learning to conditioned stimulus B (CSB) in the experimental group. In Experiment 1b, naloxone (4 mg/kg) administered before Stage II prevented this blocking, thereby enabling normal fear learning to CSB. Experiment 2a studied overexpectation of fear. Rats received CSA + training and CSB + training in Stage I, and then rats in the experimental group received CSAB + training in Stage II whereas control rats did not. The Stage II compound training of CSAB reduced fear to CSA and CSB on test. In Experiment 2b, naloxone (4 mg/kg) administered before Stage II prevented this overexpectation. These results show that opioid receptors regulate Pavlovian fear learning, augmenting learning in response to positive prediction error and impairing learning in response to negative prediction error, when fear is assessed via conditioned suppression. These effects are identical to those observed when freezing is used as the measure of learned fear. These findings show that the role for opioid receptors in regulating fear learning extends across multiple measures of learned fear.

Pinoresinol-4,4'-di-O-beta-D-glucoside from Valeriana officinalis root stimulates calcium mobilization and chemotactic migration of mouse embryo fibroblasts.

PubMed

Do, Kee Hun; Choi, Young Whan; Kim, Eun Kyoung; Yun, Sung Ji; Kim, Min Sung; Lee, Sun Young; Ha, Jung Min; Kim, Jae Ho; Kim, Chi Dae; Son, Beung Gu; Kang, Jum Soon; Khan, Ikhlas A; Bae, Sun Sik

2009-06-01

Lignans are major constituents of plant extracts and have important pharmacological effects on mammalian cells. Here we showed that pinoresinol-4,4'-di-O-beta-D-glucoside (PDG) from Valeriana officinalis induced calcium mobilization and cell migration through the activation of lysophosphatidic acid (LPA) receptor subtypes. Stimulation of mouse embryo fibroblast (MEF) cells with 10 microM PDG resulted in strong stimulation of MEF cell migration and the EC(50) was about 2 microM. Pretreatment with pertussis toxin (PTX), an inhibitor of G(i) protein, completely blocked PDG-induced cell migration demonstrating that PDG evokes MEF cell migration through the activation of the G(i)-coupled receptor. Furthermore, pretreatment of MEF cells with Ki16425 (10 microM), which is a selective antagonist for LPA(1) and LPA(3) receptors, completely blocked PDG-induced cell migration. Likewise, PDG strongly induced calcium mobilization, which was also blocked by Ki16425 in a dose-dependent manner. Prior occupation of the LPA receptor with LPA itself completely blocked PDG-induced calcium mobilization. Finally, PDG-induced MEF cell migration was attenuated by pretreatment with a phosphatidylinositol 3-kinase (PI3K) inhibitor such as LY294002. Cells lacking downstream mediator of PI3K such as Akt1 and Akt2 (DKO cells) showed loss of PDG-induced migration. Re-expression of Akt1 (but not Akt2) completely restored PDG-induced DKO cell migration. Given these results, we conclude that PDG is a strong inducer of cell migration. We suggest that the pharmacological action of PDG may occur through the activation of an LPA receptor whereby activation of PI3K/Akt signaling pathway mediates PDG-induced MEF cell migration.

Cellular and synaptic effect of substance P on neonatal phrenic motoneurons.

PubMed

Ptak, K; Konrad, M; Di Pasquale, E; Tell, F; Hilaire, G; Monteau, R

2000-01-01

Experiments were carried out on the in vitro brainstem-spinal cord preparation of the newborn rat to analyse the effects of substance P (SP) on phrenic motoneuron (PMN) activity. In current-clamp mode, SP significantly depolarized PMNs, increased their input resistance, decreased the rheobase current and shifted the firing frequency-intensity relationships leftwards, but did not affect spike frequency adaptation or single spike configuration. The neurokinin receptor agonist NK1 had SP-mimetic effects, whereas the NK3 and NK2 receptor agonists were less effective and ineffective, respectively. In a tetrodotoxin-containing aCSF, only SP or the NK1 receptor agonist were still active. No depolarization was observed when the NK1 receptor agonist was applied in the presence of muscarine. In voltage-clamp mode, SP or the NK1 receptor agonist produced an inward current (ISP) which was not significantly reduced by extracellular application of tetraethylammonium, Co2+, 4-aminopyridine or Cs+. In aCSF containing tetrodotoxin, Co2+ and Cs+, ISP was blocked by muscarine. No PMN displayed any M-type potassium current but only a current showing no voltage sensitivity over the range -100 to 0 mV, reversing near the expected EK +, hence consistent with a leak current. SP application to the spinal cord only (using a partitioned chamber) significantly increased the phrenic activity. Pretreatment with the NMDA receptor antagonist DL-2-amino-5-phosphonovaleric acid (AP5) decreased the C4 discharge duration and blocked the effect of SP, thus exhibiting an NMDA potentiation by SP. In conclusion, SP modulates postsynaptically the response of phrenic motoneurons to the inspiratory drive through the reduction of a leak conductance and the potentiation of the NMDA component of the synaptic input.

Differential regulation of gonadotropin-releasing hormone (GnRH) neuron activity and membrane properties by acutely-applied estradiol: dependence on dose and estrogen receptor subtype

PubMed Central

Chu, Zhiguo; Andrade, Josefa; Shupnik, Margaret A.; Moenter, Suzanne M.

2009-01-01

GnRH neurons are critical to controlling fertility. In vivo, estradiol can inhibit or stimulate GnRH release depending on concentration and physiological state. We examined rapid, non-genomic effects of estradiol. Whole-cell recordings were made of GnRH neurons in brain slices from ovariectomized mice with ionotropic GABA and glutamate receptors blocked. Estradiol was bath-applied and measurements completed within 15 min. Estradiol from high physiological (preovulatory) concentrations (100pM) to 100nM enhanced action potential firing, reduced afterhyperpolarizing potential (AHP) and increased slow afterdepolarization (sADP) amplitudes, and reduced IAHP and enhanced IADP. The reduction of IAHP was occluded by prior blockade of calcium-activated potassium channels. These effects were mimicked by an estrogen receptor (ER) β-specific agonist and were blocked by the classical receptor antagonist ICI182780. ERα or GPR30 agonists had no effect. The acute stimulatory effect of high physiological estradiol on firing rate was dependent on signaling via protein kinase A. In contrast, low physiological levels of estradiol (10pM) did not affect intrinsic properties. Without blockade of ionotropic GABA and glutamate receptors, however, 10pM estradiol reduced firing of GnRH neurons; this was mimicked by an ERα agonist. ERα agonists reduced the frequency of GABA transmission to GnRH neurons; GABA can excite to these cells. In contrast, ERβ agonists increased GABA transmission and postsynaptic response. These data suggest rapid intrinsic and network modulation of GnRH neurons by estradiol is dependent upon both dose and receptor subtype. In cooperation with genomic actions, non-genomic effects may play a role in feedback regulation of GnRH secretion. PMID:19403828

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.

Antagonist action of progesterone at σ-receptors in the modulation of voltage-gated sodium channels

PubMed Central

Johannessen, Molly; Fontanilla, Dominique; Mavlyutov, Timur; Ruoho, Arnold E.

2011-01-01

σ-Receptors are integral membrane proteins that have been implicated in a number of biological functions, many of which involve the modulation of ion channels. A wide range of synthetic ligands activate σ-receptors, but endogenous σ-receptor ligands have proven elusive. One endogenous ligand, dimethyltryptamine (DMT), has been shown to act as a σ-receptor agonist. Progesterone and other steroids bind σ-receptors, but the functional consequences of these interactions are unclear. Here we investigated progesterone binding to σ1- and σ2-receptors and evaluated its effect on σ-receptor-mediated modulation of voltage-gated Na+ channels. Progesterone binds both σ-receptor subtypes in liver membranes with comparable affinities and blocks photolabeling of both subtypes in human embryonic kidney 293 cells that stably express the human cardiac Na+ channel Nav1.5. Patch-clamp recording in this cell line tested Na+ current modulation by the σ-receptor ligands ditolylguanidine, PB28, (+)SKF10047, and DMT. Progesterone inhibited the action of these ligands to varying degrees, and some of these actions were reduced by σ1-receptor knockdown with small interfering RNA. Progesterone inhibition of channel modulation by drugs was consistent with stronger antagonism of σ2-receptors. By contrast, progesterone inhibition of channel modulation by DMT was consistent with stronger antagonism of σ1-receptors. Progesterone binding to σ-receptors blocks σ-receptor-mediated modulation of a voltage-gated ion channel, and this novel membrane action of progesterone may be relevant to changes in brain and cardiovascular function during endocrine transitions. PMID:21084640

Antagonist action of progesterone at σ-receptors in the modulation of voltage-gated sodium channels.

PubMed

Johannessen, Molly; Fontanilla, Dominique; Mavlyutov, Timur; Ruoho, Arnold E; Jackson, Meyer B

2011-02-01

σ-Receptors are integral membrane proteins that have been implicated in a number of biological functions, many of which involve the modulation of ion channels. A wide range of synthetic ligands activate σ-receptors, but endogenous σ-receptor ligands have proven elusive. One endogenous ligand, dimethyltryptamine (DMT), has been shown to act as a σ-receptor agonist. Progesterone and other steroids bind σ-receptors, but the functional consequences of these interactions are unclear. Here we investigated progesterone binding to σ(1)- and σ(2)-receptors and evaluated its effect on σ-receptor-mediated modulation of voltage-gated Na(+) channels. Progesterone binds both σ-receptor subtypes in liver membranes with comparable affinities and blocks photolabeling of both subtypes in human embryonic kidney 293 cells that stably express the human cardiac Na(+) channel Na(v)1.5. Patch-clamp recording in this cell line tested Na(+) current modulation by the σ-receptor ligands ditolylguanidine, PB28, (+)SKF10047, and DMT. Progesterone inhibited the action of these ligands to varying degrees, and some of these actions were reduced by σ(1)-receptor knockdown with small interfering RNA. Progesterone inhibition of channel modulation by drugs was consistent with stronger antagonism of σ(2)-receptors. By contrast, progesterone inhibition of channel modulation by DMT was consistent with stronger antagonism of σ(1)-receptors. Progesterone binding to σ-receptors blocks σ-receptor-mediated modulation of a voltage-gated ion channel, and this novel membrane action of progesterone may be relevant to changes in brain and cardiovascular function during endocrine transitions.

Enhancement of bradykinin and resensitization of its B2 receptor.

PubMed

Marcic, B; Deddish, P A; Jackman, H L; Erdös, E G

1999-03-01

We studied the enhancement of the effects of bradykinin B2 receptor agonists by agents that react with active centers of angiotensin-converting enzyme (ACE) independent of enzymatic inactivation. The potentiation and the desensitization and resensitization of B2 receptor were assessed by measuring [3H]arachidonic acid release and [Ca2+]i mobilization in Chinese hamster ovary cells transfected to express human ACE and B2 receptor, or in endothelial cells with constitutively expressed ACE and receptor. Administration of bradykinin or its ACE-resistant analogue desensitized the receptor, but it was resensitized (arachidonic acid release or [Ca2+]i mobilization) by agents such as enalaprilat (1 micromol/L). Enalaprilat was inactive in the absence of ACE expression. La3+ (100 micromol/L) inhibited the apparent resensitization, probably by blocking the entry of extracellular calcium. Enalaprilat resensitized the receptor via ACE to release arachidonic acid by bradykinin at a lower concentration (5 nmol/L) than required to mobilize [Ca2+]i (1 micromol/L). Monoclonal antibodies inhibiting the ACE N-domain active center and polyclonal antiserum potentiated bradykinin. The snake venom peptide BPP5a and metabolites of angiotensin and bradykinin (angiotensin-[1-9], angiotensin-[1-7], bradykinin-[1-8]; 1 micromol/L) enhanced arachidonic acid release by bradykinin. Angiotensin-(1-9) and -(1-7) also resensitized the receptor. Enalaprilat potentiated the bradykinin effect in cells expressing a mutant ACE with a single N-domain active site. Agents that reacted with a single active site, on the N-domain or on the C-domain, potentiated bradykinin not by blocking its inactivation but by inducing crosstalk between ACE and the receptor. Enalaprilat enhanced signaling via ACE by Galphai in lower concentration than by Galphaq-coupled receptor.

Pharmacological Characterization of a Dopamine Transporter Ligand That Functions as a Cocaine Antagonist

PubMed Central

Desai, Rajeev I.; Grandy, David K.; Lupica, Carl R.

2014-01-01

An N-butyl analog of benztropine, JHW007 [N-(n-butyl)-3α-[bis(4′-fluorophenyl)methoxy]-tropane], binds to dopamine transporters (DAT) but has reduced cocaine-like behavioral effects and antagonizes various effects of cocaine. The present study further examined mechanisms underlying these effects. Cocaine dose-dependently increased locomotion, whereas JHW007 was minimally effective but increased activity 24 hours after injection. JHW007 (3–10 mg/kg) dose-dependently and fully antagonized the locomotor-stimulant effects of cocaine (5–60 mg/kg), whereas N-methyl and N-allyl analogs and the dopamine (DA) uptake inhibitor GBR12909 [1-(2-[bis(4-fluorophenyl)methoxy]ethyl)-4-(3-phenylpropyl)piperazine dihydrochloride] stimulated activity and failed to antagonize effects of cocaine. JHW007 also blocked the locomotor-stimulant effects of the DAT inhibitor GBR12909 but not stimulation produced by the δ-opioid agonist SNC 80 [4-[(R)-[(2S,5R)-4-allyl-2,5-dimethylpiperazin-1-yl](3-methoxyphenyl)methyl]-N,N-diethylbenzamide], which increases activity through nondopaminergic mechanisms. JHW007 blocked locomotor-stimulant effects of cocaine in both DA D2- and CB1-receptor knockout and wild-type mice, indicating a lack of involvement of these targets. Furthermore, JHW007 blocked effects of cocaine on stereotyped rearing but enhanced stereotyped sniffing, suggesting that interference with locomotion by enhanced stereotypies is not responsible for the cocaine-antagonist effects of JHW007. Time-course data indicate that administration of JHW007 antagonized the locomotor-stimulant effects of cocaine within 10 minutes of injection, whereas occupancy at the DAT, as determined in vivo, did not reach a maximum until 4.5 hours after injection. The σ1-receptor antagonist BD 1008 [N-[2-(3,4-dichlorophenyl)ethyl]-N-methyl-2-(1-pyrrolidinyl)ethylamine dihydrobromide] blocked the locomotor-stimulant effects of cocaine. Overall, these findings suggest that JHW007 has cocaine-antagonist effects that are deviate from its DAT occupancy and that some other mechanism, possibly σ-receptor antagonist activity, may contribute to the cocaine-antagonist effect of JHW007 and like drugs. PMID:24194528

Prostaglandin potentiates 5-HT responses in stomach and ileum innervating visceral afferent sensory neurons

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

Kim, Sojin; Jin, Zhenhua; Lee, Goeun

2015-01-02

Highlights: • Prostaglandin E2 (PGE{sub 2}) effect was tested on visceral afferent neurons. • PGE{sub 2} did not evoke response but potentiated serotonin (5-HT) currents up to 167%. • PGE{sub 2}-induced potentiation was blocked by E-prostanoid type 4 receptors antagonist. • PGE{sub 2} effect on 5-HT response was also blocked by protein kinase A inhibitor KT5720. • Thus, PGE{sub 2} modulate visceral afferent neurons via synergistic signaling with 5-HT. - Abstract: Gastrointestinal disorder is a common symptom induced by diverse pathophysiological conditions that include food tolerance, chemotherapy, and irradiation for therapy. Prostaglandin E{sub 2} (PGE{sub 2}) level increase was oftenmore » reported during gastrointestinal disorder and prostaglandin synthetase inhibitors has been used for ameliorate the symptoms. Exogenous administration of PGE{sub 2} induces gastrointestinal disorder, however, the mechanism of action is not known. Therefore, we tested PGE{sub 2} effect on visceral afferent sensory neurons of the rat. Interestingly, PGE{sub 2} itself did not evoked any response but enhanced serotonin (5-HT)-evoked currents up to 167% of the control level. The augmented 5-HT responses were completely inhibited by a 5-HT type 3 receptor antagonist, ondansetron. The PGE{sub 2}-induced potentiation were blocked by a selective E-prostanoid type4 (EP{sub 4}) receptors antagonist, L-161,982, but type1 and 2 receptor antagonist AH6809 has no effect. A membrane permeable protein kinase A (PKA) inhibitor, KT5720 also inhibited PGE{sub 2} effects. PGE{sub 2} induced 5-HT current augmentation was observed on 15% and 21% of the stomach and ileum projecting neurons, respectively. Current results suggest a synergistic signaling in visceral afferent neurons underlying gastrointestinal disorder involving PGE{sub 2} potentiation of 5-HT currents. Our findings may open a possibility for screen a new type drugs with lower side effects than currently using steroidal prostaglandin synthetase inhibitors by selectively targeting EP{sub 4} receptor/PKA pathway without interrupt prostaglandin synthesis.« less

Attenuation in rats of impairments of memory by scopolamine, a muscarinic receptor antagonist, by mecamylamine, a nicotinic receptor antagonist.

PubMed

Newman, L A; Gold, P E

2016-03-01

Scopolamine, a muscarinic antagonist, impairs learning and memory for many tasks, supporting an important role for the cholinergic system in these cognitive functions. The findings are most often interpreted to indicate that a decrease in postsynaptic muscarinic receptor activation mediates the memory impairments. However, scopolamine also results in increased release of acetylcholine in the brain as a result of blocking presynaptic muscarinic receptors. The present experiments assess whether scopolamine-induced increases in acetylcholine release may impair memory by overstimulating postsynaptic cholinergic nicotinic receptors, i.e., by reaching the high end of a nicotinic receptor activation inverted-U dose-response function. Rats tested in a spontaneous alternation task showed dose-dependent working memory deficits with systemic injections of mecamylamine and scopolamine. When an amnestic dose of scopolamine (0.15 mg/kg) was co-administered with a subamnestic dose of mecamylamine (0.25 mg/kg), this dose of mecamylamine significantly attenuated the scopolamine-induced memory impairments. We next assessed the levels of acetylcholine release in the hippocampus in the presence of scopolamine and mecamylamine. Mecamylamine injections resulted in decreased release of acetylcholine, while scopolamine administration caused a large increase in acetylcholine release. These findings indicate that a nicotinic antagonist can attenuate impairments in memory produced by a muscarinic antagonist. The nicotinic antagonist may block excessive activation of nicotinic receptors postsynaptically or attenuate increases in acetylcholine release presynaptically. Either effect of a nicotinic antagonist-to decrease scopolamine-induced increases in acetylcholine output or to decrease postsynaptic acetylcholine receptor activation-may mediate the negative effects on memory of muscarinic antagonists.

Δ⁹-tetrahydrocannabinol (Δ⁹-THC) exerts a direct neuroprotective effect in a human cell culture model of Parkinson's disease.

PubMed

Carroll, C B; Zeissler, M-L; Hanemann, C O; Zajicek, J P

2012-10-01

Δ⁹-tetrahydrocannabinol (Δ⁹-THC) is neuroprotective in models of Parkinson's disease (PD). Although CB1 receptors are increased within the basal ganglia of PD patients and animal models, current evidence suggests a role for CB1 receptor-independent mechanisms. Here, we utilized a human neuronal cell culture PD model to further investigate the protective properties of Δ⁹-THC. Differentiated SH-SY5Y neuroblastoma cells were exposed to PD-relevant toxins: 1-methyl-4-phenylpyridinium (MPP+), lactacystin and paraquat. Changes in CB1 receptor level were determined by quantitative polymerase chain reaction and Western blotting. Cannabinoids and modulatory compounds were co-administered with toxins for 48 h and the effects on cell death, viability, apoptosis and oxidative stress assessed. We found CB1 receptor up-regulation in response to MPP+, lactacystin and paraquat and a protective effect of Δ⁹-THC against all three toxins. This neuroprotective effect was not reproduced by the CB1 receptor agonist WIN55,212-2 or blocked by the CB1 antagonist AM251. Furthermore, the antioxidants α-tocopherol and butylhydroxytoluene as well as the antioxidant cannabinoids, nabilone and cannabidiol were unable to elicit the same neuroprotection as Δ⁹-THC. However, the peroxisome proliferator-activated receptor-gamma (PPARγ) antagonist T0070907 dose-dependently blocked the neuroprotective, antioxidant and anti-apoptotic effects of Δ⁹-THC, while the PPARγ agonist pioglitazone resulted in protection from MPP+-induced neurotoxicity. Furthermore, Δ⁹-THC increased PPARγ expression in MPP+-treated SH-SY5Y cells, another indicator of PPARγ activation. We have demonstrated up-regulation of the CB1 receptor in direct response to neuronal injury in a human PD cell culture model, and a direct neuronal protective effect of Δ⁹-THC that may be mediated through PPARγ activation. © 2011 The Authors. Neuropathology and Applied Neurobiology © 2011 British Neuropathological Society.

Influence of testosterone on synaptic transmission in the rat medial vestibular nuclei: estrogenic and androgenic effects.

PubMed

Grassi, S; Frondaroli, A; Di Mauro, M; Pettorossi, V E

2010-12-15

In brainstem slices of young male rat, we investigated the influence of the neuroactive steroid testosterone (T) on the synaptic responses by analyzing the field potential evoked in the medial vestibular nucleus (MVN) by vestibular afferent stimulation. T induced three distinct and independent long-term synaptic changes: fast long-lasting potentiation (fLP), slow long-lasting potentiation (sLP) and long-lasting depression (LD). The fLP was mediated by 17β-estradiol (E(2)) since it was abolished by blocking the estrogen receptors (ERs) or the enzyme converting T to E(2). Conversely, sLP and LD were mediated by 5α-dihydrotestosterone (DHT) since they were prevented by blocking the androgen receptors (ARs) or the enzyme converting T to DHT. Therefore, the synaptic effects of T were mediated by its androgenic or estrogenic metabolites. The pathways leading to estrogenic and androgenic conversion of T might be co-localized since, the occurrence of fLP under block of androgenic pathway, and that of sLP and LD under estrogenic block, were higher than those observed without blocks. In case of co-localization, the effect on synaptic transmission should depend on the prevailing enzymatic activity. We conclude that circulating and neuronal T can remarkably influence synaptic responses of the vestibular neurons in different and opposite ways, depending on its conversion to estrogenic or androgenic metabolites. Copyright © 2010 IBRO. Published by Elsevier Ltd. All rights reserved.

5-HT2 receptor blockade exhibits 5-HT vasodilator effects via nitric oxide, prostacyclin and ATP-sensitive potassium channels in rat renal vasculature.

PubMed

García-Pedraza, J A; García, M; Martín, M L; Rodríguez-Barbero, A; Morán, A

2016-04-01

The aim of this study was to determine whether orally sarpogrelate (selective 5-HT2 antagonist) treatment (30 mg/kg/day; 14 days) could modify 5-HT renal vasoconstrictor responses, characterizing 5-HT receptors and mediator mechanisms involved in serotonergic responses in the in situ autoperfused rat kidney. Intra-arterial (i.a.) injections of 5-HT (0.00000125 to 0.1 μg/kg) decreased renal perfusion pressure (RPP) but did not affect the mean blood pressure (MBP). i.a. agonists 5-CT (5-HT1/7), CGS-12066B (5-HT1B), L-694,247 (5-HT1D) or AS-19 (5-HT7) mimicked renal 5-HT vasodilator effect. However, neither 8-OH-DPAT (5-HT1A) nor 1-phenylbiguanide (5-HT3) modified RPP. Moreover: (i) GR-55562 (5-HT1B antagonist) and L-NAME (nitric oxide synthase [NOS] inhibitor) blocked CGS-12066B-induced vasodilator response, (ii) LY310762 (5-HT1D antagonist) and indomethacin (non-selective cyclooxygenase inhibitor) blocked L-694,247-induced vasodilator response; (iii) SB-258719 (5-HT7 antagonist) and glibenclamide (ATP-sensitive K+ channel blocker) blocked AS-19-induced vasodilator response; and (iv) 5-HT- or 5-CT-elicited renal vasodilation was significantly blocked by the mixture of GR-55562 + LY310762 + SB-258719. Furthermore, eNOS and iNOS proteins and prostacyclin levels are overexpressed in sarpogrelate-treated rats. Our data suggest that 5-HT exerts renal vasodilator effect in the in situ autoperfused sarpogrelate-treated rat kidney, mediated by 5-HT1D, 5-HT1B and 5-HT7 receptors, involving cyclooxygenase-derived prostacyclin, nitric oxide synthesis/release and ATP-sensitive K+ channels, respectively.

A role for sigma receptors in stimulant self-administration and addiction.

PubMed

Katz, Jonathan L; Hong, Weimin C; Hiranita, Takato; Su, Tsung-Ping

2016-04-01

Sigma-1 receptors (σ1Rs) are structurally unique intracellular proteins that function as chaperones. σ1Rs translocate from the mitochondria-associated membrane to other subcellular compartments, and can influence a host of targets, including ion channels, G-protein-coupled receptors, lipids, and other signaling proteins. Drugs binding to σRs can induce or block the actions of σRs. Studies indicate that stimulant self-administration induces the reinforcing effects of σR agonists, because of dopamine transporter actions. Once established, the reinforcing effects of σR agonists are independent of dopaminergic mechanisms traditionally thought to be critical to the reinforcing effects of stimulants. Self-administered doses of σR agonists do not increase dopamine concentrations in the nucleus accumbens shell, a transmitter and brain region considered important for the reinforcing effects of abused drugs. However, self-administration of σR agonists is blocked by σR antagonists. Several effects of stimulants have been blocked by σR antagonists, including the reinforcing effects, assessed by a place-conditioning procedure. However, the self-administration of stimulants is largely unaffected by σR antagonists, indicating fundamental differences in the mechanisms underlying these two procedures used to assess the reinforcing effects. When σR antagonists are administered in combination with dopamine uptake inhibitors, an effective and specific blockade of stimulant self-administration is obtained. Actions of stimulant drugs related to their abuse induce unique changes in σR activity and the changes induced potentially create redundant and, once established, independent reinforcement pathways. Concomitant targeting of both dopaminergic pathways and σR proteins produces a selective antagonism of stimulant self-administration, suggesting new avenues for combination chemotherapies to specifically combat stimulant abuse.

Effect of flecainide derivatives on sarcoplasmic reticulum calcium release suggests a lack of direct action on the cardiac ryanodine receptor.

PubMed

Bannister, Mark L; Alvarez-Laviada, Anita; Thomas, N Lowri; Mason, Sammy A; Coleman, Sharon; du Plessis, Christo L; Moran, Abbygail T; Neill-Hall, David; Osman, Hasnah; Bagley, Mark C; MacLeod, Kenneth T; George, Christopher H; Williams, Alan J

2016-08-01

Flecainide is a use-dependent blocker of cardiac Na(+) channels. Mechanistic analysis of this block showed that the cationic form of flecainide enters the cytosolic vestibule of the open Na(+) channel. Flecainide is also effective in the treatment of catecholaminergic polymorphic ventricular tachycardia but, in this condition, its mechanism of action is contentious. We investigated how flecainide derivatives influence Ca(2) (+) -release from the sarcoplasmic reticulum through the ryanodine receptor channel (RyR2) and whether this correlates with their effectiveness as blockers of Na(+) and/or RyR2 channels. We compared the ability of fully charged (QX-FL) and neutral (NU-FL) derivatives of flecainide to block individual recombinant human RyR2 channels incorporated into planar phospholipid bilayers, and their effects on the properties of Ca(2) (+) sparks in intact adult rat cardiac myocytes. Both QX-FL and NU-FL were partial blockers of the non-physiological cytosolic to luminal flux of cations through RyR2 channels but were significantly less effective than flecainide. None of the compounds influenced the physiologically relevant luminal to cytosol cation flux through RyR2 channels. Intracellular flecainide or QX-FL, but not NU-FL, reduced Ca(2) (+) spark frequency. Given its inability to block physiologically relevant cation flux through RyR2 channels, and its lack of efficacy in blocking the cytosolic-to-luminal current, the effect of QX-FL on Ca(2) (+) sparks is likely, by analogy with flecainide, to result from Na(+) channel block. Our data reveal important differences in the interaction of flecainide with sites in the cytosolic vestibules of Na(+) and RyR2 channels. © 2016 The Authors. British Journal of Pharmacology published by John Wiley & Sons Ltd on behalf of British Pharmacological Society.

Quercetin suppresses insulin receptor signaling through inhibition of the insulin ligand–receptor binding and therefore impairs cancer cell proliferation

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

Wang, Feng; Department of Nanomedicine, Houston Methodist Research Institute, Houston, TX 77030; Yang, Yong, E-mail: yyang@houstonmethodist.org

Graphical abstract: - Highlights: • Quercetin inhibits insulin ligand–receptor interactions. • Quercetin reduces downstream insulin receptor signaling. • Quercetin blocks insulin induced glucose uptake. • Quercetin suppresses insulin stimulated cancer cell proliferation and tumor growth. - Abstract: Although the flavonoid quercetin is known to inhibit activation of insulin receptor signaling, the inhibitory mechanism is largely unknown. In this study, we demonstrate that quercetin suppresses insulin induced dimerization of the insulin receptor (IR) through interfering with ligand–receptor interactions, which reduces the phosphorylation of IR and Akt. This inhibitory effect further inhibits insulin stimulated glucose uptake due to decreased cell membrane translocationmore » of glucose transporter 4 (GLUT4), resulting in impaired cancer cell proliferation. The effect of quercetin in inhibiting tumor growth was also evident in an in vivo model, indicating a potential future application for quercetin in the treatment of cancers.« less

Postsynaptic Synaptotagmins Mediate AMPA Receptor Exocytosis During LTP

PubMed Central

Wu, Dick; Bacaj, Taulant; Morishita, Wade; Goswami, Debanjan; Arendt, Kristin L.; Xu, Wei; Chen, Lu; Malenka, Robert C.; Südhof, Thomas C.

2017-01-01

Strengthening of synaptic connections by NMDA-receptor-dependent long-term potentiation (LTP) shapes neural circuits and mediates learning and memory. During NMDA-receptor-dependent LTP induction, Ca2+-influx stimulates recruitment of synaptic AMPA-receptors, thereby strengthening synapses. How Ca2+ induces AMPA-receptor recruitment, however, remains unclear. Here we show that, in pyramidal neurons of the hippocampal CA1-region, blocking postsynaptic expression of both synaptotagmin-1 and synaptotagmin-7, but not of synaptotagmin-1 or synaptotagmin-7 alone, abolished LTP. LTP was rescued by wild-type but not by Ca2+-binding-deficient mutant synaptotagmin-7. Blocking postsynaptic synaptotagmin-1/7 expression did not impair basal synaptic transmission, synaptic or extrasynaptic AMPA-receptor levels, or other AMPA-receptor trafficking events. Moreover, expression of dominant-negative mutant synaptotagmin-1 that inhibited Ca2+-dependent presynaptic vesicle exocytosis also blocked Ca2+-dependent postsynaptic AMPA-receptor exocytosis, thereby abolishing LTP. Our results suggest that postsynaptic synaptotagmin-1 and synaptotagmin-7 act as redundant Ca2+-sensors for Ca2+-dependent exocytosis of AMPA-receptors during LTP, thus delineating a simple mechanism for the recruitment of AMPA-receptors that mediates LTP. PMID:28355182

Etomidate blocks LTP and impairs learning but does not enhance tonic inhibition in mice carrying the N265M point mutation in the beta3 subunit of the GABAA receptor

PubMed Central

Oh, I; Rau, V; Lor, C; Laha, KT; Jurd, R; Rudolph, U; Eger, EI; Pearce, RA

2015-01-01

Enhancement of tonic inhibition mediated by extrasynaptic α5-subunit containing GABAA receptors (GABAARs) has been proposed as the mechanism by which a variety of anesthetics, including the general anesthetic etomidate, impair learning and memory. Since α5 subunits preferentially partner with β3 subunits, we tested the hypothesis that etomidate acts through β3-subunit containing GABAARs to enhance tonic inhibition, block LTP, and impair memory. We measured the effects of etomidate in wild type mice and in mice carrying a point mutation in the GABAAR β3-subunit (β3-N265M) that renders these receptors insensitive to etomidate. Etomidate enhanced tonic inhibition in CA1 pyramidal cells of the hippocampus in wild type but not in mutant mice, demonstrating that tonic inhibition is mediated by β3-subunit containing GABAARs. However, despite its inability to enhance tonic inhibition, etomidate did block LTP in brain slices from mutant mice as well as in those from wild type mice. Etomidate also impaired fear conditioning to context, with no differences between genotypes. In studies of recombinant receptors expressed in HEK293 cells, α5β1γ2L GABAARs were insensitive to amnestic concentrations of etomidate (1 [.proportional]M and below), whereas α5β2γ2L and α5β3γ2L GABAARs were enhanced. We conclude that etomidate enhances tonic inhibition in pyramidal cells through its action on α5β3-containing GABAA receptors, but blocks LTP and impairs learning by other means - most likely by modulating α5β2-containing GABAA receptors. The critical anesthetic targets underlying amnesia might include other forms of inhibition imposed on pyramidal neurons (e.g. slow phasic inhibition), or inhibitory processes on non-pyramidal cells (e.g. interneurons). PMID:25680234

Bicuculline, a GABAA-receptor antagonist, blocked HPA axis activation induced by ghrelin under an acute stress.

PubMed

Gastón, M S; Cid, M P; Salvatierra, N A

2017-03-01

Ghrelin is a peptide of 28 amino acids with a homology between species, which acts on the central nervous system to regulate different actions, including the control of growth hormone secretion and metabolic regulation. It has been suggested that central ghrelin is a mediator of behavior linked to stress responses and induces anxiety in rodents and birds. Previously, we observed that the anxiogenic-like behavior induced by ghrelin injected into the intermediate medial mesopallium (IMM) of the forebrain was blocked by bicuculline (a GABA A receptor competitive antagonist) but not by diazepam (a GABA A receptor allosteric agonist) in neonatal meat-type chicks (Cobb). Numerous studies have indicated that hypothalamic-pituitary-adrenal (HPA) axis activation mediates the response to stress in mammals and birds. However, it is still unclear whether this effect of ghrelin is associated with HPA activation. Therefore, we investigated whether anxiety behavior induced by intra-IMM ghrelin and mediated through GABA A receptors could be associated with HPA axis activation in the neonatal chick. In the present study, in an Open Field test, intraperitoneal bicuculline methiodide blocked anxiogenic-like behavior as well as the increase in plasma ACTH and corticosterone levels induced by ghrelin (30pmol) in neonatal chicks. Moreover, we showed for the first time that a competitive antagonist of GABA A receptor suppressed the HPA axis activation induced by an anxiogenic dose of ghrelin. These results show that the anxiogenic ghrelin action involves the activation of the HPA axis, with a complex functional interaction with the GABA A receptor. Copyright © 2016 Elsevier B.V. All rights reserved.

Endothelial barrier protection by local anesthetics: ropivacaine and lidocaine block tumor necrosis factor-α-induced endothelial cell Src activation.

PubMed

Piegeler, Tobias; Votta-Velis, E Gina; Bakhshi, Farnaz R; Mao, Mao; Carnegie, Graeme; Bonini, Marcelo G; Schwartz, David E; Borgeat, Alain; Beck-Schimmer, Beatrice; Minshall, Richard D

2014-06-01

Pulmonary endothelial barrier dysfunction mediated in part by Src-kinase activation plays a crucial role in acute inflammatory disease. Proinflammatory cytokines, such as tumor necrosis factor-α (TNFα), activate Src via phosphatidylinositide 3-kinase/Akt-dependent nitric oxide generation, a process initiated by recruitment of phosphatidylinositide 3-kinase regulatory subunit p85 to TNF-receptor-1. Because amide-linked local anesthetics have well-established anti-inflammatory effects, the authors hypothesized that ropivacaine and lidocaine attenuate inflammatory Src signaling by disrupting the phosphatidylinositide 3-kinase-Akt-nitric oxide pathway, thus blocking Src-dependent neutrophil adhesion and endothelial hyperpermeability. Human lung microvascular endothelial cells, incubated with TNFα in the absence or presence of clinically relevant concentrations of ropivacaine and lidocaine, were analyzed by Western blot, probing for phosphorylated/activated Src, endothelial nitric oxide synthase, Akt, intercellular adhesion molecule-1, and caveolin-1. The effect of ropivacaine on TNFα-induced nitric oxide generation, co-immunoprecipitation of TNF-receptor-1 with p85, neutrophil adhesion, and endothelial barrier disruption were assessed. Ropivacaine and lidocaine attenuated TNFα-induced Src activation (half-maximal inhibitory concentration [IC50] = 8.611 × 10 M for ropivacaine; IC50 = 5.864 × 10 M for lidocaine) and endothelial nitric oxide synthase phosphorylation (IC50 = 7.572 × 10 M for ropivacaine; IC50 = 6.377 × 10 M for lidocaine). Akt activation (n = 7; P = 0.006) and stimulus-dependent binding of TNF-receptor-1 and p85 (n = 6; P = 0.043) were blocked by 1 nM of ropivacaine. TNFα-induced neutrophil adhesion and disruption of endothelial monolayers via Src-dependent intercellular adhesion molecule-1- and caveolin-1-phosphorylation, respectively, were also attenuated. Ropivacaine and lidocaine effectively blocked inflammatory TNFα signaling in endothelial cells by attenuating p85 recruitment to TNF-receptor-1. The resultant decrease in Akt, endothelial nitric oxide synthase, and Src phosphorylation reduced neutrophil adhesion and endothelial hyperpermeability. This novel anti-inflammatory "side-effect" of ropivacaine and lidocaine may provide therapeutic benefit in acute inflammatory disease.

Blocking beta 2-adrenergic receptor inhibits dendrite ramification in a mouse model of Alzheimer's disease.

PubMed

Wu, Qin; Sun, Jin-Xia; Song, Xiang-He; Wang, Jing; Xiong, Cun-Quan; Teng, Fei-Xiang; Gao, Cui-Xiang

2017-09-01

Dendrite ramification affects synaptic strength and plays a crucial role in memory. Previous studies revealed a correlation between beta 2-adrenergic receptor dysfunction and Alzheimer's disease (AD), although the mechanism involved is still poorly understood. The current study investigated the potential effect of the selective β 2 -adrenergic receptor antagonist, ICI 118551 (ICI), on Aβ deposits and AD-related cognitive impairment. Morris water maze test results demonstrated that the performance of AD-transgenic (TG) mice treated with ICI (AD-TG/ICI) was significantly poorer compared with NaCl-treated AD-TG mice (AD-TG/NaCl), suggesting that β 2 -adrenergic receptor blockage by ICI might reduce the learning and memory abilities of mice. Golgi staining and immunohistochemical staining revealed that blockage of the β 2 -adrenergic receptor by ICI treatment decreased the number of dendritic branches, and ICI treatment in AD-TG mice decreased the expression of hippocampal synaptophysin and synapsin 1. Western blot assay results showed that the blockage of β 2 -adrenergic receptor increased amyloid-β accumulation by downregulating hippocampal α-secretase activity and increasing the phosphorylation of amyloid precursor protein. These findings suggest that blocking the β 2 -adrenergic receptor inhibits dendrite ramification of hippocampal neurons in a mouse model of AD.

Blocking beta 2-adrenergic receptor inhibits dendrite ramification in a mouse model of Alzheimer's disease

PubMed Central

Wu, Qin; Sun, Jin-xia; Song, Xiang-he; Wang, Jing; Xiong, Cun-quan; Teng, Fei-xiang; Gao, Cui-xiang

2017-01-01

Dendrite ramification affects synaptic strength and plays a crucial role in memory. Previous studies revealed a correlation between beta 2-adrenergic receptor dysfunction and Alzheimer's disease (AD), although the mechanism involved is still poorly understood. The current study investigated the potential effect of the selective β2-adrenergic receptor antagonist, ICI 118551 (ICI), on Aβ deposits and AD-related cognitive impairment. Morris water maze test results demonstrated that the performance of AD-transgenic (TG) mice treated with ICI (AD-TG/ICI) was significantly poorer compared with NaCl-treated AD-TG mice (AD-TG/NaCl), suggesting that β2-adrenergic receptor blockage by ICI might reduce the learning and memory abilities of mice. Golgi staining and immunohistochemical staining revealed that blockage of the β2-adrenergic receptor by ICI treatment decreased the number of dendritic branches, and ICI treatment in AD-TG mice decreased the expression of hippocampal synaptophysin and synapsin 1. Western blot assay results showed that the blockage of β2-adrenergic receptor increased amyloid-β accumulation by downregulating hippocampal α-secretase activity and increasing the phosphorylation of amyloid precursor protein. These findings suggest that blocking the β2-adrenergic receptor inhibits dendrite ramification of hippocampal neurons in a mouse model of AD. PMID:29089997

Tremor analysis separates Parkinson's disease and dopamine receptor blockers induced parkinsonism.

PubMed

Shaikh, Aasef G

2017-05-01

Parkinson's disease, the most common cause of parkinsonism is often difficult to distinguish from its second most common etiology due to exposure to dopamine receptor blocking agents such as antiemetics and neuroleptics. Dual axis accelerometry was used to quantify tremor in 158 patients with parkinsonism; 62 had Parkinson's disease and 96 were clinically diagnosed with dopamine receptor blocking agent-induced parkinsonism. Tremor was measured while subjects rested arms (resting tremor), outstretched arms in front (postural tremor), and reached a target (kinetic tremor). Cycle-by-cycle analysis was performed to measure cycle duration, oscillation amplitude, and inter-cycle variations in the frequency. Patients with dopamine receptor blocker induced parkinsonism had lower resting and postural tremor amplitude. There was a substantial increase of kinetic tremor amplitude in both disorders. Postural and resting tremor in subjects with dopamine receptor blocking agent-induced parkinsonism was prominent in the abduction-adduction plane. In contrast, the Parkinson's disease tremor had equal amplitude in all three planes of motion. Tremor frequency was comparable in both groups. Remarkable variability in the width of the oscillatory cycles suggested irregularity in the oscillatory waveforms in both subtypes of parkinsonism. Quantitative tremor analysis can distinguish Parkinson's disease from dopamine receptor blocking agent-induced parkinsonism.

Functionally Selective Signaling for Morphine and Fentanyl Antinociception and Tolerance Mediated by the Rat Periaqueductal Gray

PubMed Central

Morgan, Michael M.; Reid, Rachel A.; Saville, Kimber A.

2014-01-01

Functionally selective signaling appears to contribute to the variability in mechanisms that underlie tolerance to the antinociceptive effects of opioids. The present study tested this hypothesis by examining the contribution of G protein-coupled receptor kinase (GRK)/Protein kinase C (PKC) and C-Jun N-terminal kinase (JNK) activation on both the expression and development of tolerance to morphine and fentanyl microinjected into the ventrolateral periaqueductal gray of the rat. Microinjection of morphine or fentanyl into the periaqueductal gray produced a dose-dependent increase in hot plate latency. Microinjection of the non-specific GRK/PKC inhibitor Ro 32-0432 into the periaqueductal gray to block mu-opioid receptor phosphorylation enhanced the antinociceptive effect of morphine but had no effect on fentanyl antinociception. Microinjection of the JNK inhibitor SP600125 had no effect on morphine or fentanyl antinociception, but blocked the expression of tolerance to repeated morphine microinjections. In contrast, a microinjection of Ro 32-0432 blocked the expression of fentanyl, but not morphine tolerance. Repeated microinjections of Ro 32-0432 blocked the development of morphine tolerance and inhibited fentanyl antinociception whether rats were tolerant or not. Repeated microinjections of SP600125 into the periaqueductal gray blocked the development of tolerance to both morphine and fentanyl microinjections. These data demonstrate that the signaling molecules that contribute to tolerance vary depending on the opioid and methodology used to assess tolerance (expression vs. development of tolerance). This signaling difference is especially clear for the expression of tolerance in which JNK contributes to morphine tolerance and GRK/PKC contributes to fentanyl tolerance. PMID:25503060

Effects of vitamin D(3)-binding protein-derived macrophage activating factor (GcMAF) on angiogenesis.

PubMed

Kanda, Shigeru; Mochizuki, Yasushi; Miyata, Yasuyoshi; Kanetake, Hiroshi; Yamamoto, Nobuto

2002-09-04

The vitamin D(3)-binding protein (Gc protein)-derived macrophage activating factor (GcMAF) activates tumoricidal macrophages against a variety of cancers indiscriminately. We investigated whether GcMAF also acts as an antiangiogenic factor on endothelial cells. The effects of GcMAF on angiogenic growth factor-induced cell proliferation, chemotaxis, and tube formation were examined in vitro by using cultured endothelial cells (murine IBE cells, porcine PAE cells, and human umbilical vein endothelial cells [HUVECs]) and in vivo by using a mouse cornea micropocket assay. Blocking monoclonal antibodies to CD36, a receptor for the antiangiogenic factor thrombospondin-1, which is also a possible receptor for GcMAF, were used to investigate the mechanism of GcMAF action. GcMAF inhibited the endothelial cell proliferation, chemotaxis, and tube formation that were all stimulated by fibroblast growth factor-2 (FGF-2), vascular endothelial growth factor-A, or angiopoietin 2. FGF-2-induced neovascularization in murine cornea was also inhibited by GcMAF. Monoclonal antibodies against murine and human CD36 receptor blocked the antiangiogenic action of GcMAF on the angiogenic factor stimulation of endothelial cell chemotaxis. In addition to its ability to activate tumoricidal macrophages, GcMAF has direct antiangiogenic effects on endothelial cells independent of tissue origin. The antiangiogenic effects of GcMAF may be mediated through the CD36 receptor.

Glucocorticoid actions on L6 muscle cells in culture

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

Max, S.R.; Konagaya, M.; Konagaya, Y.

1986-05-01

Glucocorticoids exert striking catabolic effects on skeletal muscle. The mechanism of these effects remains poorly understood. They employed L6 muscle cells in culture to ascertain whether intracellular glucocorticoid receptors are involved. Studies in vitro permit exploration of glucocorticoid effects in the absence of other hormonal influences. L6 myoblasts were induced to form differentiated myotubes by growth in 1% serum. L6 myotubes were found to possess a high-affinity, limited capacity intracellular glucocorticoid receptor (apparent K/sub D/ = 5 x 10/sup -10/ M; B/sub max/ = 711 pmols/g protein) with ligand specificity similar to that of glucocorticoid receptors from classical glucocorticoid targetmore » tissues. Further, (/sup 3/H) triamcinolone acetonide specific binding to L6 cell homogenates was blocked by a glucocorticoid antagonist, RU38486 (11..beta..-(4-dimethyl-aminophenyl)-17..beta..-hydroxy-17..cap alpha..-(prop-l-ynyl)-estra-4,9-dien-3-one). Dexamethasone (10/sup -5/M) caused a 10-fold increase in the activity of gluatmine synthetase in L6 myotubes; this increase was prevented by RU38486. Similarly, dexamethasone (10/sup -5/M) caused a 20% decrease in (/sup 12/C) leucine incorporation into protein. This effect also was blocked by RU38486. Thus, induction of glutamine synthetase and diminution of protein synthesis by dexamethasone require intracellular glucocorticoid receptors. L6 cells should prove particularly valuable for further studies of glucocorticoid actions on skeletal muscle.« less

Involvement of brain-derived neurotrophic factor (BDNF) in the functional elimination of synaptic contacts at polyinnervated neuromuscular synapses during development.

PubMed

Garcia, N; Santafe, M M; Tomàs, M; Lanuza, M A; Besalduch, N; Tomàs, J

2010-05-15

We use immunohistochemistry to describe the localization of brain-derived neurotrophic factor (BDNF) and its receptors trkB and p75(NTR) in the neuromuscular synapses of postnatal rats (P6-P7) during the synapse elimination period. The receptor protein p75(NTR) is present in the nerve terminal, muscle cell and glial Schwann cell whereas BDNF and trkB proteins can be detected mainly in the pre- and postsynaptic elements. Exogenously applied BDNF (10 nM for 3 hr or 50 nM for 1 hr) increases ACh release from singly and dually innervated synapses. This effect may be specific for BDNF because the neurotrophin NT-4 (2-8 nM) does not modulate release at P6-P7. Blocking the receptors trkB and p75(NTR) (with K-252a and anti-p75-192-IgG, respectively) completely abolishes the potentiating effect of exogenous BDNF. In addition, exogenous BDNF transiently recruits functionally depressed silent terminals, and this effect seems to be mediated by trkB. Calcium ions, the L-type voltage-dependent calcium channels and protein kinase C are involved in BDNF-mediated nerve ending recruitment. Blocking experiments suggest that endogenous BDNF could operate through p75(NTR) receptors coupled to potentiate ACh release in all nerve terminals because the anti-p75-192-IgG reduces release. However, blocking the trkB receptor (K-252a) or neutralizing endogenous BDNF with the trkB-IgG fusion protein reveals a trkB-mediated release inhibition on almost mature strong endings in dual junctions. Taken together these results suggest that a BDNF-induced p75(NTR)-mediated ACh release potentiating mechanism and a BDNF-induced trkB-mediated release inhibitory mechanism may contribute to developmental synapse disconnection. (c) 2009 Wiley-Liss, Inc.

Xenon reduces glutamate-, AMPA-, and kainate-induced membrane currents in cortical neurones.

PubMed

Dinse, A; Föhr, K J; Georgieff, M; Beyer, C; Bulling, A; Weigt, H U

2005-04-01

The anaesthetic, analgesic, and neuroprotective effects of xenon (Xe) are believed to be mediated by a block of the NMDA (N-methyl-D-aspartate) receptor channel. Interestingly, the clinical profile of the noble gas differs markedly from that of specific NMDA receptor antagonists. The aim of this study was, therefore, to investigate whether Xe might be less specific, also inhibiting the two other subtypes of glutamate receptor channels, such as the alpha-amino-3-hydroxy-5-methyl-4-isoxazolole propionate (AMPA) and kainate receptors. The study was performed on voltage-clamped cortical neurones from embryonic mice and SH-SY5Y cells expressing GluR6 kainate receptors. Drugs were applied by a multi-barreled fast perfusion system. Xe, dissolved at approximately 3.45 mM in aqueous solution, diminished the peak and even more the plateau of AMPA and glutamate induced currents. At the control EC(50) value for AMPA (29 microM) these reductions were by about 40 and 56% and at 3 mM glutamate the reductions were by 45 and 66%, respectively. Currents activated at the control EC(50) value for kainate (57 microM) were inhibited by 42%. Likewise, Xe showed an inhibitory effect on kainate-induced membrane currents of SH-SY5Y cells transfected with the GluR6 subunit of the kainate receptor. Xe reduced kainate-induced currents by between 35 and 60%, depending on the kainate concentration. Xe blocks not only NMDA receptors, but also AMPA and kainate receptors in cortical neurones as well as GluR6-type receptors expressed in SH-SY5Y cells. Thus, Xe seems to be rather non-specific as a channel blocker and this may contribute to the analgesic and anaesthetic potency of Xe.

A novel muscarinic receptor-independent mechanism of KCNQ2/3 potassium channel blockade by Oxotremorine-M.

PubMed

Zwart, Ruud; Reed, Hannah; Clarke, Sophie; Sher, Emanuele

2016-11-15

Inhibition of KCNQ (Kv7) potassium channels by activation of muscarinic acetylcholine receptors has been well established, and the ion currents through these channels have been long known as M-currents. We found that this cross-talk can be reconstituted in Xenopus oocytes by co-transfection of human recombinant muscarinic M1 receptors and KCNQ2/3 potassium channels. Application of the muscarinic acetylcholine receptor agonist Oxotremorine-methiodide (Oxo-M) between voltage pulses to activate KCNQ2/3 channels caused inhibition of the subsequent KCNQ2/3 responses. This effect of Oxo-M was blocked by the muscarinic acetylcholine receptor antagonist atropine. We also found that KCNQ2/3 currents were inhibited when Oxo-M was applied during an ongoing KCNQ2/3 response, an effect that was not blocked by atropine, suggesting that Oxo-M inhibits KCNQ2/3 channels directly. Indeed, also in oocytes that were transfected with only KCNQ2/3 channels, but not with muscarinic M1 receptors, Oxo-M inhibited the KCNQ2/3 response. These results show that besides the usual muscarinic acetylcholine receptor-mediated inhibition, Oxo-M also inhibits KCNQ2/3 channels by a direct mechanism. We subsequently tested xanomeline, which is a chemically distinct muscarinic acetylcholine receptor agonist, and oxotremorine, which is a close analogue of Oxo-M. Both compounds inhibited KCNQ2/3 currents via activation of M1 muscarinic acetylcholine receptors but, in contrast to Oxo-M, they did not directly inhibit KCNQ2/3 channels. Xanomeline and oxotremorine do not contain a positively charged trimethylammonium moiety that is present in Oxo-M, suggesting that such a charged moiety could be a crucial component mediating this newly described direct inhibition of KCNQ2/3 channels. Copyright © 2016 Elsevier B.V. All rights reserved.

Influence of exogenous lactoferrin on the oxidant/antioxidant balance and molecular profile of hormone receptor-positive and -negative human breast cancer cells in vitro.

PubMed

Zalutskii, I V; Lukianova, N Y; Storchai, D M; Burlaka, A P; Shvets, Y V; Borikun, T V; Todor, I M; Lukashevich, V S; Rudnichenko, Y A; Chekhun, V F

2017-07-01

To investigate the mechanisms of cytotoxic activity and pro-/antioxidant effect of lactoferrin on hormone receptor-positive and receptor-negative breast cancer cells in vitro. The study was performed on receptor-positive (MCF-7, T47D) and receptor-negative (MDA-MB-231, MDA-MB-468) human breast cancer cell lines. Immunocytochemical staining, flow cytometry, low-temperature electron paramagnetic resonance, and the Comet assay were used. Upon treatment with lactoferrin, the increased levels of reactive oxygen species (ROS) (p < 0.05), NO generation rate by inducible NO-synthase (p < 0.05) and the level of "free" iron (p < 0.05) were observed. Moreover, the effects of lactoferrin were more pronounced in receptor-negative MDA-MB-231 and MDA-MB-468 cells. These changes resulted in increased expression of proapoptotic Bax protein (p < 0.05), reduced expression of the antiapoptotic Bcl-2 protein (p < 0.05) and level of not-oxidized mitochondrial cardiolipin (1.4-1.7-fold, p < 0.05). This, in turn, caused an increase in the percentage of apoptotic cells (by 14-24%, p < 0.05). Cytotoxic effects of lactoferrin were accompanied by an increase in the percentage of DNA in the comet tail and blocking cell cycle at G2/M phase, especially in receptor-negative cell lines. The study showed that exogenous lactoferrin causes a violation of an antioxidant balance by increasing the level of ROS, "free" iron and NO generation rate, resalting in the blocking of cell cycle at G2/M-phase and apoptosis of malignant cells.

Glutamatergic targets for new alcohol medications

PubMed Central

Spanagel, Rainer; Krystal, John H.

2013-01-01

Rationale An increasingly compelling literature points to a major role for the glutamate system in mediating the effects of alcohol on behavior and the pathophysiology of alcoholism. Preclinical studies indicate that glutamate signaling mediates certain aspects of ethanol’s intoxicating and rewarding effects, and undergoes adaptations following chronic alcohol exposure that may contribute to the withdrawal, craving and compulsive drug-seeking that drive alcohol abuse and alcoholism. Objectives We discuss the potential for targeting the glutamate system as a novel pharmacotherapeutic approach to treating alcohol use disorders, focusing on five major components of the glutamate system: the N-methyl-D-aspartate (NMDA) receptor and specific NMDA subunits, the glycineB site on the NMDA receptors (NMDAR), L-alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid ionotropic (AMPA) and kainate (KAR) receptors, metabotropic receptors (mGluR), and glutamate transporters. Results Chronic alcohol abuse produces a hyperglutamatergic state, characterized by elevated extracellular glutamate and altered glutamate receptors and transporters. Pharmacologically manipulating glutamatergic neurotransmission alters alcohol-related behaviors including intoxication, withdrawal, and alcohol-seeking, in rodents and human subjects. Blocking NMDA and AMPA receptors reduces alcohol consumption in rodents, but side-effects may limit this as a therapeutic approach. Selectively targeting NMDA and AMPA receptor subunits (e.g., GluN2B, GluA3), or the NMDAR glycineB site offers an alternative approach. Blocking mGluR5 potently affects various alcohol-related behaviors in rodents, and mGluR2/3 agonism also suppresses alcohol consumption. Finally, glutamate transporter upregulation may mitigate behavioral and neurotoxic sequelae of excess glutamate caused by alcohol. Conclusions Despite the many challenges that remain, targeting the glutamate system offers genuine promise for developing new treatments for alcoholism. PMID:23995381

Butyl benzyl phthalate suppresses the ATP-induced cell proliferation in human osteosarcoma HOS cells

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

Liu, P.-S., E-mail: pslediting@mail.scu.edu.t; Chen, C.-Y.

2010-05-01

Butyl benzyl phthalate (BBP), an endocrine disruptor present in the environment, exerts its genomic effects via intracellular steroid receptors and elicits non-genomic effects by interfering with membrane ion-channel receptors. We previously found that BBP blocks the calcium signaling coupled with P2X receptors in PC12 cells (Liu and Chen, 2006). Osteoblast P2X receptors were recently reported to play a role in cell proliferation and bone remodeling. In this present study, the effects of BBP on ATP-induced responses were investigated in human osteosarcoma HOS cells. These receptors mRNA had been detected, named P2X4, P2X7, P2Y2, P2Y4, P2Y5, P2Y9, and P2Y11, in humanmore » osteosarcoma HOS cells by RT-PCR. The enhancement of cell proliferation and the decrease of cytoviability had both been shown to be coupled to stimulation via different concentrations of ATP. BBP suppressed the ATP-induced calcium influx (mainly coupled with P2X) and cell proliferation but not the ATP-induced intracellular calcium release (mainly coupled with P2Y) and cytotoxicity in human osteosarcoma HOS cells. Suramin, a common P2 receptor's antagonist, blocked the ATP-induced calcium signaling, cell proliferation, and cytotoxicity. We suggest that P2X is mainly responsible for cell proliferation, and P2Y might be partially responsible for the observed cytotoxicity. BBP suppressed the calcium signaling coupled with P2X, suppressing cell proliferation. Since the importance of P2X receptors during bone metastasis has recently become apparent, the possible toxic risk of environmental BBP during bone remodeling is a public problem of concern.« less

The ventral tegmental area as a putative target for tachykinins in cardiovascular regulation

PubMed Central

Deschamps, Kathleen; Couture, Réjean

2005-01-01

Tachykinin receptor agonists and antagonists were microinjected into the ventral tegmental area (VTA) to study the relative participation of the three tachykinin receptors in cardiovascular regulation in freely behaving rat. Selective agonists (1–100 pmol) for NK1 ([Sar9, Met (O2)11]SP), NK2 ([β-Ala8]NKA (4–10)) and NK3 (senktide) receptors evoked increases in blood pressure, heart rate (HR) along with behavioural manifestations (face washing, sniffing, head scratching, rearing, wet dog shake). At 1 pmol, NK1 and NK3 agonists did not affect behaviour and blood pressure but only HR. Tachykinin agonists-induced cardiovascular responses were selectively and reversibly blocked by the prior injection of antagonists for NK1 receptors (LY 303870 ((R)-1-[N-(2-methoxybenzyl)acetylamino]-3-(1H-indol-3-yl)-2-[N-(2-(4-(piperidin-1-yl)piperidin-1-yl)acetyl)amino]propane), 5 nmol), NK2 receptors (SR 48968 ([(S)-N-methyl-N-[4-acetylamino-4-phenylpiperidino-2-(3,4-dichlorophenyl)butyl]benzamide]), 250 pmol) and NK3 receptors (SB 235375 ((−)-(S)-N-(α-ethylbenzyl)-3-(carboxymethoxy)-2-phenylquinoline-4-carboxamide), 25 nmol). With the exception of the NK2 agonist, most behavioural effects were also blocked by antagonists. Tachykinin agonists-induced cardiovascular responses were inhibited by intravenous (i.v.) treatments with antagonists for D1 dopamine receptor (SCH23390, 0.2 mg kg−1) and β1-adrenoceptor (atenolol, 5 mg kg−1) but not for D2 dopamine receptor (raclopride, 0.16 mg kg−1). Behavioural responses were blocked by SCH23390 only. The present study provides the first pharmacological evidence that the three tachykinin receptors in the rat VTA can affect the autonomic control of blood pressure and HR by increasing midbrain dopaminergic transmission. This mechanism may be involved in the coordination of behavioural and cardiovascular responses to stress and noxious stimulation. PMID:15895109

Nicotine blocks apomorphine-induced disruption of prepulse inhibition of the acoustic startle in rats: possible involvement of central nicotinic α7 receptors

PubMed Central

Suemaru, Katsuya; Yasuda, Kayo; Umeda, Kenta; Araki, Hiroaki; Shibata, Kazuhiko; Choshi, Tominari; Hibino, Satoshi; Gomita, Yutaka

2004-01-01

Nicotine has been reported to normalize deficits in auditory sensory gating in the cases of schizophrenia, suggesting an involvement of nicotinic acetylcholine receptors in attentional abnormalities. However, the mechanism remains unclear. The present study investigated the effects of nicotine on the disruption of prepulse inhibition (PPI) of the acoustic startle response induced by apomorphine or phencyclidine in rats. Over the dose range tested, nicotine (0.05–1 mg kg−1, s.c.) did not disrupt PPI. Neither methyllycaconitine (0.5–5 mg kg−1, s.c.), an α7 nicotinic receptor antagonist, nor dihydro-β-erythroidine (0.5–2 mg kg−1, s.c.), an α4β2 nicotinic receptor antagonist, had any effect on PPI. Nicotine (0.01–0.2 mg kg−1, s.c.) dose-dependently reversed the disruption of PPI induced by apomorphine (1 mg kg−1, s.c.), but had no effect on the disruption of PPI induced by phencyclidine (2 mg kg−1, s.c.). The reversal of apomorphine-induced PPI disruption by nicotine (0.2 mg kg−1) was eliminated by mecamylamine (1 mg kg−1, i.p.), but not by hexamethonium (10 mg kg−1, i.p.), indicating the involvement of central nicotinic receptors. The antagonistic action of nicotine on apomorphine-induced PPI disruption was dose-dependently blocked by methyllycaconitine (1 and 2 mg kg−1, s.c.). However, dihydro-β-erythroidine (1 and 2 mg kg−1, s.c.) had no effect. These results suggest that nicotine reverses the disruption of apomorphine-induced PPI through central α7 nicotinic receptors. PMID:15197106

Inhibition of the checkpoint protein PD-1 by the therapeutic antibody pembrolizumab outlined by quantum chemistry.

PubMed

Tavares, Ana Beatriz M L A; Lima Neto, José X; Fulco, Umberto L; Albuquerque, Eudenilson L

2018-01-30

Much of the recent excitement in the cancer immunotherapy approach has been generated by the recognition that immune checkpoint proteins, like the receptor PD-1, can be blocked by antibody-based drugs with profound effects. Promising clinical data have already been released pointing to the efficiency of the drug pembrolizumab to block the PD-1 pathway, triggering the T-lymphocytes to destroy the cancer cells. Thus, a deep understanding of this drug/receptor complex is essential for the improvement of new drugs targeting the protein PD-1. In this context, by employing quantum chemistry methods based on the Density Functional Theory (DFT), we investigate in silico the binding energy features of the receptor PD-1 in complex with its drug inhibitor. Our computational results give a better understanding of the binding mechanisms, being also an efficient alternative towards the development of antibody-based drugs, pointing to new treatments for cancer therapy.

The effects of stressful stimuli and hypothalamic-pituitary-adrenal axis activation are reversed by the melanin-concentrating hormone 1 receptor antagonist SNAP 94847 in rodents.

PubMed

Smith, Daniel G; Hegde, Laxminarayan G; Wolinsky, Toni D; Miller, Silke; Papp, Mariusz; Ping, Xiaoli; Edwards, Tanya; Gerald, Christophe P; Craig, Douglas A

2009-02-11

Melanin-concentrating hormone (MCH) is an orexigenic and dipsogenic neuropeptide that has been reported to mediate acute behavioral and neuroendocrine stress-related responses via MCH(1) receptor activation in rodents. The purpose of the present investigation was to use the MCH(1) receptor antagonist SNAP 94847 (N-(3-{1-[4-(3,4-difluoro-phenoxy)-benzyl]-piperidin-4-yl}-4-methyl-phenyl)-isobutyramide) to determine the effects of MCH(1) receptor blockade on MCH-evoked adrenocorticotropic hormone (ACTH) release, chronic mild stress-induced anhedonia, stress-induced hyperthermia and forced swim stress-induced immobility. The appropriate dose range for testing SNAP 94847 was determined by measuring MCH-evoked water drinking. The corresponding occupancy of MCH(1) receptors in rat striatum was also measured across a broad dose range. Orally administered (p.o.) SNAP 94847 (1-10 mg/kg) corresponds to 30-60% occupancy at MCH(1) receptors and significantly blocks water drinking induced by the intracerebroventricular (i.c.v.) injection of MCH. MCH (i.c.v.) significantly elevates plasma levels of ACTH in rats, and SNAP 94847 (2.5 mg/kg, p.o.) blocks MCH-evoked ACTH release. Using the chronic mild stress paradigm, we show that repeated daily exposure to environmental stressors for 5 weeks significantly suppresses sucrose intake in rats, and that SNAP 94847 (1 mg/kg, BID) for 1-5 weeks restores baseline sucrose intake. Moreover, a single administration of SNAP 94847 attenuates stress-induced hyperthermia and the behavioral effects of forced swim stress with minimal effective doses of 2.5 and 30 mg/kg (p.o.), respectively. The regulation of ACTH release and reversal of the effects of chronic and acute stress by SNAP 94847 are suggestive of a role for MCH(1) receptor blockade in the treatment of disorders characterized by high allostatic load.

Divergent Effects of Anandamide Transporter Inhibitors with Different Target Selectivity on Social Play Behavior in Adolescent Rats

PubMed Central

Trezza, Viviana; Vanderschuren, Louk J. M. J.

2009-01-01

The endocannabinoid system plays an important role in the modulation of affect, motivation, and emotion. Social play behavior is a natural reinforcer in adolescent rats, and we have recently shown that interacting endocannabinoid, opioid, and dopamine systems modulate social play. In the present study, we tested the hypothesis that, in contrast to administration of exogenous cannabinoid agonists, increasing local endocannabinoid signaling through anandamide transporter inhibition enhances social play. To this aim, we tested the effects of two anandamide transporter inhibitors with different target selectivity on social play behavior in adolescent rats. Interestingly, we found that the prototypical anandamide transporter inhibitor N-(4-hydroxyphenyl)-arachidonamide (AM404) reduced social play, whereas its more selective analog N-arachidonoyl-(2-methyl-4-hydroxyphenyl)amine (VDM11) enhanced it. The effects of AM404 were not mediated through its known pharmacological targets, since they were not blocked by the CB1 cannabinoid receptor antagonist N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride (SR141716A), the CB2 cannabinoid receptor antagonist N-(1,3,3-trimethylbicyclo(2.2.1)heptan-2-yl)-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)pyrazole-3-carboxamide (SR144528), or by the transient receptor potential vanilloid 1 receptor antagonist capsazepine. In contrast, the increase in social play induced by VDM11 was dependent on cannabinoid, opioid, and dopaminergic neurotransmission, since it was blocked by the CB1 cannabinoid receptor antagonist SR141716A, the opioid receptor antagonist naloxone, and the dopamine receptor antagonist α-flupenthixol. These findings support the notion that anandamide plays an important role in the modulation of social interaction in adolescent rats, and they suggest that selective anandamide transporter inhibitors might be useful for the treatment of social dysfunctions. Furthermore, these results suggest that off-target effects may be responsible for some of the conflicting effects of anandamide transporter inhibitors on behavior. PMID:18948500

Functional Expression of Two Neuronal Nicotinic Acetylcholine Receptors from cDNA Clones Identifies a Gene Family

NASA Astrophysics Data System (ADS)

Boulter, Jim; Connolly, John; Deneris, Evan; Goldman, Dan; Heinemann, Steven; Patrick, Jim

1987-11-01

A family of genes coding for proteins homologous to the α subunit of the muscle nicotinic acetylcholine receptor has been identified in the rat genome. These genes are transcribed in the central and peripheral nervous systems in areas known to contain functional nicotinic receptors. In this paper, we demonstrate that three of these genes, which we call alpha3, alpha4, and beta2, encode proteins that form functional nicotinic acetylcholine receptors when expressed in Xenopus oocytes. Oocytes expressing either alpha3 or alpha4 protein in combination with the beta2 protein produced a strong response to acetylcholine. Oocytes expressing only the alpha4 protein gave a weak response to acetylcholine. These receptors are activated by acetylcholine and nicotine and are blocked by Bungarus toxin 3.1. They are not blocked by α -bungarotoxin, which blocks the muscle nicotinic acetylcholine receptor. Thus, the receptors formed by the alpha3, alpha4, and beta2 subunits are pharmacologically similar to the ganglionic-type neuronal nicotinic acetylcholine receptor. These results indicate that the alpha3, alpha4, and beta2 genes encode functional nicotinic acetylcholine receptor subunits that are expressed in the brain and peripheral nervous system.

Role of the glucose-sensing receptor in insulin secretion.

PubMed

Kojima, Itaru; Medina, Johan; Nakagawa, Yuko

2017-09-01

Glucose is a primary stimulator of insulin secretion. It has been thought that glucose exerts its effect by a mechanism solely dependent on glucose metabolism. We show here that glucose induces rapid Ca 2+ and cyclic AMP signals in β-cells. These rapid signals are independent of glucose-metabolism and are reproduced by non-metabolizable glucose analogues. These results led us to postulate that glucose activates a cell-surface receptor, namely the glucose-sensing receptor. Rapid signals induced by glucose are blocked by inhibition of a sweet taste receptor subunit T1R3 and a calcium-sensing receptor subunit CaSR. In accordance with these observations, T1R3 and CaSR form a heterodimer. In addition, a heterodimer of T1R3 and CaSR is activated by glucose. These results suggest that a heterodimer of T1R3 and CaSR is a major component of the glucose-sensing receptor. When the glucose-sensing receptor is blocked, glucose-induced insulin secretion is inhibited. Also, ATP production is significantly attenuated by the inhibition of the receptor. Conversely, stimulation of the glucose-sensing receptor by either artificial sweeteners or non-metabolizable glucose analogue increases ATP. Hence, the glucose-sensing receptor signals promote glucose metabolism. Collectively, glucose activates the cell-surface glucose-sensing receptor and promotes its own metabolism. Glucose then enters the cells and is metabolized through already activated metabolic pathways. The glucose-sensing receptor is a key molecule regulating the action of glucose in β-cells. © 2017 John Wiley & Sons Ltd.

Mechanism of Tacrine Block at Adult Human Muscle Nicotinic Acetylcholine Receptors

PubMed Central

Prince, Richard J.; Pennington, Richard A.; Sine, Steven M.

2002-01-01

We used single-channel kinetic analysis to study the inhibitory effects of tacrine on human adult nicotinic receptors (nAChRs) transiently expressed in HEK 293 cells. Single channel recording from cell-attached patches revealed concentration- and voltage-dependent decreases in mean channel open probability produced by tacrine (IC50 4.6 μM at −70 mV, 1.6 μM at −150 mV). Two main effects of tacrine were apparent in the open- and closed-time distributions. First, the mean channel open time decreased with increasing tacrine concentration in a voltage-dependent manner, strongly suggesting that tacrine acts as an open-channel blocker. Second, tacrine produced a new class of closings whose duration increased with increasing tacrine concentration. Concentration dependence of closed-times is not predicted by sequential models of channel block, suggesting that tacrine blocks the nAChR by an unusual mechanism. To probe tacrine's mechanism of action we fitted a series of kinetic models to our data using maximum likelihood techniques. Models incorporating two tacrine binding sites in the open receptor channel gave dramatically improved fits to our data compared with the classic sequential model, which contains one site. Improved fits relative to the sequential model were also obtained with schemes incorporating a binding site in the closed channel, but only if it is assumed that the channel cannot gate with tacrine bound. Overall, the best description of our data was obtained with a model that combined two binding sites in the open channel with a single site in the closed state of the receptor. PMID:12198092

Potentiation of oxycodone antinociception in mice by agmatine and BMS182874 via an imidazoline I2 receptor-mediated mechanism.

PubMed

Bhalla, Shaifali; Ali, Izna; Lee, Hyaera; Andurkar, Shridhar V; Gulati, Anil

2013-01-01

The potentiation of oxycodone antinociception by BMS182874 (endothelin-A (ET(A)) receptor antagonist) and agmatine (imidazoline receptor/α(2)-adrenoceptor agonist) is well-documented. It is also known that imidazoline receptors but not α(2)-adrenoceptors are involved in potentiation of oxycodone antinociception by agmatine and BMS182874 in mice. However, the involvement of specific imidazoline receptor subtypes (I(1), I(2), or both) in this interaction is not clearly understood. The present study was conducted to determine the involvement of imidazoline I(1) and I(2) receptors in agmatine- and BMS182874-induced potentiation of oxycodone antinociception in mice. Antinociceptive (tail flick and hot-plate) latencies were determined in male Swiss Webster mice treated with oxycodone, agmatine, BMS182874, and combined administration of oxycodone with agmatine or BMS182874. Efaroxan (imidazoline I(1) receptor antagonist) and BU224 (imidazoline I(2) receptor antagonist) were used to determine the involvement of I(1) and I(2) imidazoline receptors, respectively. Oxycodone produced significant antinociceptive response in mice which was not affected by efaroxan but was blocked by BU224. Agmatine-induced potentiation of oxycodone antinociception was blocked by BU224 but not by efaroxan. Similarly, BMS182874-induced potentiation of oxycodone antinociception was blocked by BU224 but not by efaroxan. This is the first report demonstrating that BMS182874- or agmatine-induced enhancement of oxycodone antinociception is blocked by BU224 but not by efaroxan. We conclude that imidazoline I(2) receptors but not imidazoline I(1) receptors are involved in BMS182874- and agmatine-induced potentiation of oxycodone antinociception in mice. Copyright © 2012 Elsevier Inc. All rights reserved.

Regulation of Neuronal Muscarinic Acetylcholine Receptors

DTIC Science & Technology

1989-01-01

N1E - 115 cells with pertussis toxin blocks mAChR-mediated inhibition of adenylate cyclase but not mAChR-mediated stimulation of PI turnover...determine the effects of electrical depolarization on muscarinic acetylcholine receptors (mAChR) in the cultured neuroblastoma cell line, N E- 115 ...evidence that Gi and Go may differentially regulate cellular signaling mechanisms, these results suggest that depolarization may regulate specific

Pre-training administration of tianeptine, but not propranolol, protects hippocampus-dependent memory from being impaired by predator stress.

PubMed

Campbell, Adam M; Park, Collin R; Zoladz, Phillip R; Muñoz, Carmen; Fleshner, Monika; Diamond, David M

2008-02-01

Extensive research has shown that the antidepressant tianeptine blocks the adverse effects of chronic stress on hippocampal functioning. The current series of experiments extended this area of investigation by examining the influence of tianeptine on acute stress-induced impairments of spatial (hippocampus-dependent) memory. Tianeptine (10 mg/kg, ip) administered to adult male rats before, but not after, water maze training blocked the amnestic effects of predator stress (occurring between training and retrieval) on memory. The protective effects of tianeptine on memory occurred in rats which had extensive pre-stress training, as well as in rats which had only a single day of training. Tianeptine blocked stress effects on memory without altering the stress-induced increase in corticosterone levels. Propranolol, a beta-adrenergic receptor antagonist (5 and 10 mg/kg, ip), in contrast, did not block stress-induced amnesia. These findings indicate that treatment with tianeptine, unlike propanolol, provides an effective means with which to block the adverse effects of stress on cognitive functions of the hippocampus.

Fear Memory Recall Potentiates Opiate Reward Sensitivity through Dissociable Dopamine D1 versus D4 Receptor-Dependent Memory Mechanisms in the Prefrontal Cortex.

PubMed

Jing Li, Jing; Szkudlarek, Hanna; Renard, Justine; Hudson, Roger; Rushlow, Walter; Laviolette, Steven R

2018-05-09

Disturbances in prefrontal cortical (PFC) dopamine (DA) transmission are well established features of psychiatric disorders involving pathological memory processing, such as post-traumatic stress disorder and opioid addiction. Transmission through PFC DA D4 receptors (D4Rs) has been shown to potentiate the emotional salience of normally nonsalient emotional memories, whereas transmission through PFC DA D1 receptors (D1Rs) has been demonstrated to selectively block recall of reward- or aversion-related associative memories. In the present study, using a combination of fear conditioning and opiate reward conditioning in male rats, we examined the role of PFC D4/D1R signaling during the processing of fear-related memory acquisition and recall and subsequent sensitivity to opiate reward memory formation. We report that PFC D4R activation potentiates the salience of normally subthreshold fear conditioning memory cues and simultaneously potentiates the rewarding effects of systemic or intra-ventral tegmental area (VTA) morphine conditioning cues. In contrast, blocking the recall of salient fear memories with intra-PFC D1R activation, blocks the ability of fear memory recall to potentiate systemic or intra-VTA morphine place preference. These effects were dependent upon dissociable PFC phosphorylation states involving calcium-calmodulin-kinase II or extracellular signal-related kinase 1-2, following intra-PFC D4 or D1R activation, respectively. Together, these findings reveal new insights into how aberrant PFC DAergic transmission and associated downstream molecular signaling pathways may modulate fear-related emotional memory processing and concomitantly increase opioid addiction vulnerability. SIGNIFICANCE STATEMENT Post-traumatic stress disorder is highly comorbid with addiction. In this study, we use a translational model of fear memory conditioning to examine how transmission through dopamine D1 or D4 receptors, in the prefrontal cortex (PFC), may differentially control acquisition or recall of fear memories and how these mechanisms might regulate sensitivity to the rewarding effects of opioids. We demonstrate that PFC D4 activation not only controls the salience of fear memory acquisition, but potentiates the rewarding effects of opioids. In contrast, PFC D1 receptor activation blocks recall of fear memories and prevents potentiation of opioid reward effects. Together, these findings demonstrate novel PFC mechanisms that may account for how emotional memory disturbances might increase the addictive liability of opioid-class drugs. Copyright © 2018 the authors 0270-6474/18/384543-13$15.00/0.

Modulation of desensitization at glutamate receptors in isolated crucian carp horizontal cells by concanavalin A, cyclothiazide, aniracetam and PEPA.

PubMed

Shen, Y; Lu, T; Yang, X L

1999-03-01

In horizontal cells freshly dissociated from crucian carp (Carassius auratus) retina, we examined the effects of modulators of glutamate receptor desensitization, concanavalin A, cyclothiazide, aniracetam and 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluoro-phenoxyacetam ide (PEPA), on responses to rapid application of glutamate and kainate, using whole-cell voltage-clamp techniques. Incubation of concanavalin A suppressed the peak response but weakly potentiated the equilibrium response of horizontal cells to glutamate. Cyclothiazide blocked glutamate-induced desensitization in a dose-dependent manner, which resulted in a steady increase of the equilibrium current. The concentration of cyclothiazide causing a half-maximal potentiation for the equilibrium response was 85 microM. Furthermore, cyclothiazide shifted the dose-response relationship of the equilibrium current to the right, but slightly suppressed the kainate-induced sustained current. These effects of concanavalin A and cyclothiazide are consistent with the supposition that glutamate receptors of carp horizontal cells may be an alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-preferring subtype. In order to further characterize the AMPA receptors of horizontal cells, modulation by aniracetam and PEPA of glutamate- and kainate-induced currents was studied. Aniracetam, a preferential modulator of flop variants of AMPA receptors, considerably blocked desensitization of glutamate-induced currents, but only slightly potentiated kainate-induced currents. It was further found that PEPA, a flop-preferring allosteric modulator of AMPA receptor desensitization, slightly suppressed the peak current, while it dramatically potentiated the equilibrium current induced by glutamate in a dose-dependent manner. PEPA was much potent than aniracetam at these receptors and showed the effect on glutamate-induced desensitization even at a concentration as low as 3 microM. PEPA also potentiated non-desensitizing currents induced by kainate, but with much less extent. These modulatory effects of concanavalin A, cyclothiazide, aniracetam and PEPA on AMPA receptors in carp horizontal cells were rather similar to those obtained at AMPA receptors assembled from flop variants expressed in Xenopus oocyte and HEK cell. Consequently, we speculate that the AMPA receptor on carp horizontal cells may predominantly carry the flop splice variants.

F-spondin inhibits migration and differentiation of osteoclastic precursors.

PubMed

Oka, Hiroko; Mori, Maya; Kihara, Hisae

2011-12-01

Clinically, severe cemental resorption is a rare consequence of periodontitis, although alveolar bone resorption by osteoclasts is one of the main pathologic changes. F-spondin is a secreted neuronal glycoprotein that localizes to the cementum. F-spondin is among the cementum-specific factors in periodontal tissue that have been reported. However, the effects of F-spondin on osteoclastogenesis have not yet been established. We examined the effects of F-spondin on stages of osteoclastogenesis, migration, and differentiation in a mouse osteoclastic precursor model, RAW 264 cells. RAW 264 cells were treated with recombinant F-spondin. Macrophage colony stimulating factor (M-CSF)-induced cell migration was examined by migration assay performed with cell culture inserts. Osteoclastic differentiation was measured by counting tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells. In a transmigration assay, F-spondin significantly downregulated M-CSF-induced cell migration. Further, F-spondin significantly reduced the number of receptor activator of nuclear factor-kappa B ligand-induced TRAP-positive multinucleated cells. The receptor-associated protein, an antagonist of the low-density lipoprotein (LDL) receptor family, blocked the effects of F-spondin on M-CSF-induced migration. The suppressive effect of F-spondin on M-CSF-induced cell migration was blocked by knockdown of LDL receptor-related protein 8 (LRP8), a member of the LDL receptor family. Our findings suggest that F-spondin downregulates recruitment to the root side of periodontal tissue via LRP8 and inhibits differentiation of osteoclastic precursors. It is suggested that F-spondin is essential to protect the root surface from resorption.

ALLOPREGNANOLONE’S ATTENUATION OF THE LORDOSIS-INHIBITNG EFFECTS OF RESTRAINT IS BLOCKED BY THE ANTIPROGESTIN, CDB-4124

PubMed Central

Uphouse, Lynda; Hiegel, Cindy

2014-01-01

A brief restraint experience reduces lordosis behavior in ovariectomized females that have been hormonally primed with estradiol benzoate. The addition of progesterone to the priming prevents the lordosis inhibition. Based on prior studies with an inhibitor of progesterone metabolism, we have implicated the intracellular progesterone receptor, rather than progesterone metabolites, as responsible for this protection. However, the progesterone metabolite, allopregnanolone (3α-hydroxy-5α-pregnan-20-one), also prevents lordosis inhibition after restraint. In a prior study, we reported that the progestin receptor antagonist, RU486 (11β-(4-dimethylamino)phenyl-17β-hydroxy-17-(1-propynyl)estra-4,9-dien-3-one), attenuated the effect of allopregnanolone. Because RU486 can also block the glucocorticoid receptor, in the current studies, we evaluated the effect of the progestin receptor antagonist, CDB-4124 (17 α-acetoxy-21-methoxy-11β-[4-N,N-dimethyaminopheny]-19-norpregna-4,9-dione-3,20-dione), which is relatively devoid of antiglucocorticoid activity. Ovariectomized, Fischer rats were injected with 10 μg estradiol benzoate. Two days later, rats received either 60 mg/kg CDB-4124 or the 20% DMSO/propylene glycol vehicle 1 hr before injection with 4 mg/kg allopregnanolone. After a pretest to confirm sexual receptivity, rats were restrained for 5 min and immediately tested for sexual behavior. Lordosis behavior was reduced by the restraint and attenuated by allopregnanolone. Pretreatment with CDB-4124 reduced allopregnanolone’s effect. These findings support prior suggestions that allopreganolone reduces the response to restraint by mechanisms that require activation of the intracellular progesterone receptor. PMID:24650591

Allopregnanolone's attenuation of the lordosis-inhibiting effects of restraint is blocked by the antiprogestin, CDB-4124.

PubMed

Uphouse, Lynda; Hiegel, Cindy

2014-07-01

A brief restraint experience reduces lordosis behavior in ovariectomized females that have been hormonally primed with estradiol benzoate. The addition of progesterone to the priming prevents the lordosis inhibition. Based on prior studies with an inhibitor of progesterone metabolism, we have implicated the intracellular progesterone receptor, rather than progesterone metabolites, as responsible for this protection. However, the progesterone metabolite, allopregnanolone (3α-hydroxy-5α-pregnan-20-one), also prevents lordosis inhibition after restraint. In a prior study, we reported that the progestin receptor antagonist, RU486 (11β-(4-dimethylamino)phenyl-17β-hydroxy-17-(1-propynyl)estra-4,9-dien-3-one), attenuated the effect of allopregnanolone. Because RU486 can also block the glucocorticoid receptor, in the current studies, we evaluated the effect of the progestin receptor antagonist, CDB-4124 (17α-acetoxy-21-methoxy-11β-[4-N,N-dimethyaminopheny]-19-norpregna-4,9-dione-3,20-dione), which is relatively devoid of antiglucocorticoid activity. Ovariectomized, Fischer rats were injected with 10 μg estradiol benzoate. Two days later, rats received either 60 mg/kg CDB-4124 or 20% DMSO/propylene glycol vehicle 1 h before injection with 4 mg/kg allopregnanolone. After a pretest to confirm sexual receptivity, rats were restrained for 5min and immediately tested for sexual behavior. Lordosis behavior was reduced by the restraint and attenuated by allopregnanolone. Pretreatment with CDB-4124 reduced allopregnanolone's effect. These findings support prior suggestions that allopreganolone reduces the response to restraint by mechanisms that require activation of the intracellular progesterone receptor. Copyright © 2014 Elsevier Inc. All rights reserved.

Blocking of opioid receptors in experimental formaline-inactivated respiratory syncytial virus (FI-RSV) immunopathogenesis: from beneficial to harmful impacts.

PubMed

Salimi, Vahid; Mirzaei, Habib; Ramezani, Ali; Tahamtan, Alireza; Jamali, Abbas; Shahabi, Shahram; Golaram, Maryam; Minaei, Bagher; Gharagozlou, Mohammad Javad; Mahmoodi, Mahmood; Bont, Louis; Shokri, Fazel; Mokhtari-Azad, Talat

2018-04-01

Opioid system plays a significant role in pathophysiological processes, such as immune response and impacts on disease severity. Here, we investigated the effect of opioid system on the immunopathogenesis of respiratory syncytial virus (RSV) vaccine (FI-RSV)-mediated illness in a widely used mouse model. Female Balb/c mice were immunized at days 0 and 21 with FI-RSV (2 × 10 6  pfu, i.m.) and challenged with RSV-A2 (3 × 10 6  pfu, i.n.) at day 42. Nalmefene as a universal opioid receptors blocker administered at a dose of 1 mg/kg in combination with FI-RSV (FI-RSV + NL), and daily after live virus challenge (RSV + NL). Mice were sacrificed at day 5 after challenge and bronchoalveolar lavage (BAL) fluid and lungs were harvested to measure airway immune cells influx, T lymphocyte subtypes, cytokines/chemokines secretion, lung histopathology, and viral load. Administration of nalmefene in combination with FI-RSV (FI-RSV + NL-RSV) resulted in the reduction of the immune cells infiltration to the BAL fluid, the ratio of CD4/CD8 T lymphocyte, the level of IL-5, IL-10, MIP-1α, lung pathology, and restored weight loss after RSV infection. Blocking of opioid receptors during RSV infection in vaccinated mice (FI-RSV-RSV + NL) had no significant effects on RSV immunopathogenesis. Moreover, administration of nalmefene in combination with FI-RSV and blocking opioid receptors during RSV infection (FI-RSV + NL-RSV + NL) resulted in an increased influx of the immune cells to the BAL fluid, increases the level of IFN-γ, lung pathology, and weight loss in compared to control condition. Although nalmefene administration within FI-RSV vaccine decreases vaccine-enhanced infection during subsequent exposure to the virus, opioid receptor blocking during RSV infection aggravates the host inflammatory response to RSV infection. Thus, caution is required due to beneficial/harmful functions of opioid systems while targeting as potentially therapies.

The insecticide fipronil and its metabolite fipronil sulphone inhibit the rat α1β2γ2L GABAA receptor

PubMed Central

Li, P; Akk, G

2008-01-01

Background and purpose: Fipronil is the active ingredient in a number of widely used insecticides. Human exposure to fipronil leads to symptoms (headache, nausea and seizures) typically associated with the antagonism of GABAA receptors in the brain. In this study, we have examined the modulation of the common brain GABAA receptor subtype by fipronil and its major metabolite, fipronil sulphone. Experimental approach: Whole-cell and single-channel recordings were made from HEK 293 cells transiently expressing rat α1β2γ2L GABAA receptors. Key results: The major effect of fipronil was to increase the rate of current decay in macroscopic recordings. In single-channel recordings, the presence of fipronil resulted in shorter cluster durations without affecting the intracluster open and closed time distributions or the single-channel conductance. The α1V256S mutation, previously shown alleviate channel inhibition by inhibitory steroids and several insecticides, had a relatively small effect on channel block by fipronil. The mode of action of fipronil sulphone was similar to that of its parent compound but the metabolite was less potent at inhibiting the α1β2γ2L receptor. Conclusions and implications: We conclude that exposure to fipronil induces accumulation of receptors in a novel, long-lived blocked state. This process proceeds in parallel with and independently of, channel desensitization. The lower potency of fipronil sulphone indicates that the conversion serves as a detoxifying process in mammalian brain. PMID:18660823

The insecticide fipronil and its metabolite fipronil sulphone inhibit the rat alpha1beta2gamma2L GABA(A) receptor.

PubMed

Li, P; Akk, G

2008-11-01

Fipronil is the active ingredient in a number of widely used insecticides. Human exposure to fipronil leads to symptoms (headache, nausea and seizures) typically associated with the antagonism of GABA(A) receptors in the brain. In this study, we have examined the modulation of the common brain GABA(A) receptor subtype by fipronil and its major metabolite, fipronil sulphone. Whole-cell and single-channel recordings were made from HEK 293 cells transiently expressing rat alpha1beta2gamma2L GABA(A) receptors. The major effect of fipronil was to increase the rate of current decay in macroscopic recordings. In single-channel recordings, the presence of fipronil resulted in shorter cluster durations without affecting the intracluster open and closed time distributions or the single-channel conductance. The alpha1V256S mutation, previously shown alleviate channel inhibition by inhibitory steroids and several insecticides, had a relatively small effect on channel block by fipronil. The mode of action of fipronil sulphone was similar to that of its parent compound but the metabolite was less potent at inhibiting the alpha1beta2gamma2L receptor. We conclude that exposure to fipronil induces accumulation of receptors in a novel, long-lived blocked state. This process proceeds in parallel with and independently of, channel desensitization. The lower potency of fipronil sulphone indicates that the conversion serves as a detoxifying process in mammalian brain.

PKCepsilon-dependent potentiation of TTX-resistant Nav1.8 current by neurokinin-1 receptor activation in rat dorsal root ganglion neurons.

PubMed

Cang, Chun-Lei; Zhang, Hua; Zhang, Yu-Qiu; Zhao, Zhi-Qi

2009-06-30

Substance P (SP), which mainly exists in a subtype of small-diameter dorsal root ganglion (DRG) neurons, is an important signal molecule in pain processing in the spinal cord. Our previous results have proved the expression of SP receptor neurokinin-1 (NK-1) on DRG neurons and its interaction with transient receptor potential vanilloid 1 (TRPV1) receptor. In this study we investigated the effect of NK-1 receptor agonist on Na(v)1.8, a tetrodotoxin (TTX)-resistant sodium channel, in rat small-diameter DRG neurons employing whole-cell patch clamp recordings. NK-1 agonist [Sar(9), Met(O2)(11)]-substance P (Sar-SP) significantly enhanced the Na(v)1.8 currents in a subgroup of small-diameter DRG neurons under both the normal and inflammatory situation, and the enhancement was blocked by NK-1 antagonist Win51708 and protein kinase C (PKC) inhibitor bisindolylmaleimide (BIM), but not the protein kinase A (PKA) inhibitor H89. In particular, the inhibitor of PKCepsilon, a PKC isoform, completely blocked this effect. Under current clamp model, Sar-SP reduced the amount of current required to evoke action potentials and increased the firing rate in a subgroup of DRG neurons. These data suggest that activation of NK-1 receptor potentiates Na(v)1.8 sodium current via PKCepsilon-dependent signaling pathway, probably participating in the generation of inflammatory hyperalgesia.

Oleamide administered into the nucleus accumbens shell regulates feeding behaviour via CB1 and 5-HT2C receptors.

PubMed

Soria-Gómez, Edgar; Márquez-Diosdado, Marianela I; Montes-Rodríguez, Corinne J; Estrada-González, Vicente; Prospéro-García, Oscar

2010-10-01

The central nervous system control of food intake has been extensively studied, hence, several neurotransmitter systems regulating this function are now clearly identified, for example, the endocannabinoid and serotoninergic systems. The former stimulates feeding while the latter inhibits it. Oleamide (Ole) is a cannabimimetic molecule affecting both systems. In this work, we tested the orexigenic and anorectic potential of Ole when administered into the nucleus accumbens shell (NAcS), a brain region that has been related to the orexigenic effects of cannabinoids. Additionally, we tested if Ole administered into this nucleus affects the activity of the hypothalamic nuclei involved in feeding behaviour, just as other cannabinoids do. We found a hyperphagic effect of Ole that is mediated through CB1 activation. The combination of Ole and the CB1 antagonist, AM251, produced a hypophagia that was fully blocked by SB212084, a 5-HT2C receptor antagonist. We also show that blockade of 5-HT2C and 5-HT2A receptors in the NAcS stimulates food intake. Finally, the combination of Ole and AM251 activates hypothalamic nuclei, an effect also blocked by SB242084. In conclusion, we show, for the first time, that Ole administered into the NAcS has a dual effect on feeding behaviour, acting through cannabinoid and serotonin receptors. These effects probably result from a downstream interaction with the hypothalamus.

Direct block of native and cloned (Kir2.1) inward rectifier K+ channels by chloroethylclonidine

PubMed Central

Barrett-Jolley, R; Dart, C; Standen, N B

1999-01-01

We have investigated the inhibition of inwardly rectifying potassium channels by the α-adrenergic agonist/antagonist chloroethylclonidine (CEC). We used two preparations; two-electrode voltage-clamp of rat isolated flexor digitorum brevis muscle and whole-cell patch-clamp of cell lines transfected with Kir2.1 (IRK1).In skeletal muscle and at a membrane potential of −50 mV, chloroethylclonidine (CEC), an agonist at α2-adrenergic receptors and an antagonist at α1x-receptors, was found to inhibit the inward rectifier current with a Ki of 30 μM.The inhibition of skeletal muscle inward rectifier current by CEC was not mimicked by clonidine, adrenaline or noradrenaline and was not sensitive to high concentrations of α1-(prazosin) or α2-(rauwolscine) antagonists.The degree of current inhibition by CEC was found to vary with the membrane potential (approximately 70% block at −50 mV c.f. ∼10% block at −190 mV). The kinetics of this voltage dependence were further investigated using recombinant inward rectifier K+ channels (Kir2.1) expressed in the MEL cell line. Using a two pulse protocol, we calculated the time constant for block to be ∼8 s at 0 mV, and the rate of unblock was described by the relationship τ=exp((Vm+149)/22) s.This block was effective when CEC was applied to either the inside or the outside of patch clamped cells, but ineffective when a polyamine binding site (aspartate 172) was mutated to asparagine.The data suggest that the clonidine-like imidazoline compound, CEC, inhibits inward rectifier K+ channels independently of α-receptors by directly blocking the channel pore, possibly at an intracellular polyamine binding site. PMID:10516659

Peripheral 5-HT3 Receptors Are Involved in the Antinociceptive Effect of Bunodosine 391.

PubMed

Ferreira Junior, Wilson Alves; Zaharenko, Andre Junqueira; Kazuma, Kohei; Picolo, Gisele; Gutierrez, Vanessa Pacciari; de Freitas, Jose Carlos; Konno, Katsuhiro; Cury, Yara

2017-12-27

Bunodosine 391 (BDS 391), a low molecular weight compound isolated from the sea anemone Bunodosoma cangicum , increases the nociceptive threshold and inhibits inflammatory hyperalgesia. Serotonin receptors are involved in those effects. In this study, we have expanded the characterization of the antinociceptive effect of BDS 391 demonstrating that, in rats: (a) the compound inhibits (1.2-12 ng/paw) overt pain, in the formalin test, and mechanical hyperalgesia (0.6-6.0 ng/paw) detected in a model of neuropathic pain; (b) intraplantar administration of ondansetron, a selective 5-HT3 receptor antagonist, blocks the effect of BDS 391, whereas ketanserin, a 5-HT2 receptor antagonist, partially reversed this effect, indicating the involvement of peripheral 5-HT2 and 5-HT3 receptors in BDS 391 antinociception; and (c) in binding assay studies, BDS 391 was not able to displace the selective 5-HT receptor antagonists, suggesting that this compound does not directly bind to these receptors. The effect of biguanide, a selective 5-HT3 receptor agonist, was also evaluated. The agonist inhibited the formalin's nociceptive response, supporting an antinociceptive role for 5-HT3 receptors. Our study is the first one to show that a non-peptidic low molecular weight compound obtained from a sea anemone is able to induce antinociception and that activation of peripheral 5-HT3 receptors contributes to this effect.

Peripheral 5-HT3 Receptors Are Involved in the Antinociceptive Effect of Bunodosine 391

PubMed Central

Ferreira Junior, Wilson Alves; Zaharenko, Andre Junqueira; Kazuma, Kohei; Picolo, Gisele; Gutierrez, Vanessa Pacciari; de Freitas, Jose Carlos; Konno, Katsuhiro

2017-01-01

Bunodosine 391 (BDS 391), a low molecular weight compound isolated from the sea anemone Bunodosoma cangicum, increases the nociceptive threshold and inhibits inflammatory hyperalgesia. Serotonin receptors are involved in those effects. In this study, we have expanded the characterization of the antinociceptive effect of BDS 391 demonstrating that, in rats: (a) the compound inhibits (1.2–12 ng/paw) overt pain, in the formalin test, and mechanical hyperalgesia (0.6–6.0 ng/paw) detected in a model of neuropathic pain; (b) intraplantar administration of ondansetron, a selective 5-HT3 receptor antagonist, blocks the effect of BDS 391, whereas ketanserin, a 5-HT2 receptor antagonist, partially reversed this effect, indicating the involvement of peripheral 5-HT2 and 5-HT3 receptors in BDS 391 antinociception; and (c) in binding assay studies, BDS 391 was not able to displace the selective 5-HT receptor antagonists, suggesting that this compound does not directly bind to these receptors. The effect of biguanide, a selective 5-HT3 receptor agonist, was also evaluated. The agonist inhibited the formalin’s nociceptive response, supporting an antinociceptive role for 5-HT3 receptors. Our study is the first one to show that a non-peptidic low molecular weight compound obtained from a sea anemone is able to induce antinociception and that activation of peripheral 5-HT3 receptors contributes to this effect. PMID:29280949

Mixed nicotinic-muscarinic properties of the alpha9 nicotinic cholinergic receptor.

PubMed

Verbitsky, M; Rothlin, C V; Katz, E; Elgoyhen, A B

2000-10-01

The rat alpha9 nicotinic acetylcholine receptor (nAChR) was expressed in Xenopus laevis oocytes and tested for its sensitivity to a wide variety of cholinergic compounds. Acetylcholine (ACh), carbachol, choline and methylcarbachol elicited agonist-evoked currents, giving maximal or near maximal responses. Both the nicotinic agonist suberyldicholine as well as the muscarinic agonists McN-A-343 and methylfurtrethonium behaved as weak partial agonists of the receptor. Most classical cholinergic compounds tested, being either nicotinic (nicotine, epibatidine, cytisine, methyllycaconitine, mecamylamine, dihydro-beta-erythroidine), or muscarinic (muscarine, atropine, gallamine, pilocarpine, bethanechol) agonists and antagonists, blocked the recombinant alpha9 receptor. Block by nicotine, epibatidine, cytisine, methyllycaconitine and atropine was overcome at high ACh concentrations, suggesting a competitive type of block. The present results indicate that alpha9 displays mixed nicotinic-muscarinic features that resemble the ones described for the cholinergic receptor of cochlear outer hair cells (OHCs). We suggest that alpha9 contains the structural determinants responsible for the pharmacological properties of the native receptor.

The effect of centrally injected CDP-choline on respiratory system; involvement of phospholipase to thromboxane signaling pathway.

PubMed

Topuz, Bora B; Altinbas, Burcin; Yilmaz, Mustafa S; Saha, Sikha; Batten, Trevor F; Savci, Vahide; Yalcin, Murat

2014-05-01

CDP-choline is an endogenous metabolite in phosphatidylcholine biosynthesis. Exogenous administration of CDP-choline has been shown to affect brain metabolism and to exhibit cardiovascular, neuroendocrine neuroprotective actions. On the other hand, little is known regarding its respiratory actions and/or central mechanism of its respiratory effect. Therefore the current study was designed to investigate the possible effects of centrally injected CDP-choline on respiratory system and the mediation of the central cholinergic receptors and phospholipase to thromboxane signaling pathway on CDP-choline-induced respiratory effects in anaesthetized rats. Intracerebroventricularly (i.c.v.) administration of CDP-choline induced dose- and time-dependent increased respiratory rates, tidal volume and minute ventilation of male anaesthetized Spraque Dawley rats. İ.c.v. pretreatment with atropine failed to alter the hyperventilation responses to CDP-choline whereas mecamylamine, cholinergic nicotinic receptor antagonist, mepacrine, phospholipase A2 inhibitor, and neomycin phospholipase C inhibitor, blocked completely the hyperventilation induced by CDP-choline. In addition, central pretreatment with furegrelate, thromboxane A2 synthesis inhibitor, also partially blocked CDP-choline-evoked hyperventilation effects. These data show that centrally administered CDP-choline induces hyperventilation which is mediated by activation of central nicotinic receptors and phospholipase to thromboxane signaling pathway. Copyright © 2014 Elsevier B.V. All rights reserved.

Intranasal Opioid Administration in Rhesus Monkeys: PET Imaging and Antinociception.

PubMed

Saccone, Phillip A; Lindsey, Angela M; Koeppe, Robert A; Zelenock, Kathy A; Shao, Xia; Sherman, Phillip; Quesada, Carole A; Woods, James H; Scott, Peter J H

2016-11-01

The goal of this study was to evaluate the effects of intranasally administered opioids in rhesus monkeys using the tail-withdrawal assay, and to correlate these effects with measures of receptor occupancy using positron emission tomography (PET) imaging. Initial experiments characterized the antinociceptive effects of intranasal (IN) fentanyl and buprenorphine relative to intramuscular (IM) injection. Fentanyl (0.010-0.032 mg/kg) and buprenorphine (0.1-1.0 mg/kg) produced dose-dependent increases in tail-withdrawal latency that did not differ between routes of delivery. The second experiment compared the ability of IN and intravenous (IV) naloxone (NLX) to block the antinociceptive effects IV fentanyl, and to measure receptor occupancy at equipotent doses of NLX using PET imaging. IN and IV NLX (0.0032-0.032 mg/kg) produced dose-dependent decreases in fentanyl-induced antinociception. Again, there was no difference observed in overall potency between routes. PET imaging showed that IV and IN NLX produced similar decreases in receptor occupancy as measured by [ 11 C]carfentanil blocking, although there was a trend for IV NLX to produce marginally greater occupancy changes. This study validated the first procedures to evaluate the IN effects of opioids in rhesus monkeys. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

Blockade of Cocaine or σ Receptor Agonist Self Administration by Subtype-Selective σ Receptor Antagonists.

PubMed

Katz, Jonathan L; Hiranita, Takato; Kopajtic, Theresa A; Rice, Kenner C; Mesangeau, Christophe; Narayanan, Sanju; Abdelazeem, Ahmed H; McCurdy, Christopher R

2016-07-01

The identification of sigma receptor (σR) subtypes has been based on radioligand binding and, despite progress with σ1R cellular function, less is known about σR subtype functions in vivo. Recent findings that cocaine self administration experience will trigger σR agonist self administration was used in this study to assess the in vivo receptor subtype specificity of the agonists (+)-pentazocine, PRE-084 [2-(4-morpholinethyl) 1-phenylcyclohexanecarboxylate hydrochloride], and 1,3-di-o-tolylguanidine (DTG) and several novel putative σR antagonists. Radioligand binding studies determined in vitro σR selectivity of the novel compounds, which were subsequently studied for self administration and antagonism of cocaine, (+)-pentazocine, PRE-084, or DTG self administration. Across the dose ranges studied, none of the novel compounds were self administered, nor did they alter cocaine self administration. All compounds blocked DTG self administration, with a subset also blocking (+)-pentazocine and PRE-084 self administration. The most selective of the compounds in binding σ1Rs blocked cocaine self administration when combined with a dopamine transport inhibitor, either methylphenidate or nomifensine. These drug combinations did not decrease rates of responding maintained by food reinforcement. In contrast, the most selective of the compounds in binding σ2Rs had no effect on cocaine self administration in combination with either dopamine transport inhibitor. Thus, these results identify subtype-specific in vivo antagonists, and the utility of σR agonist substitution for cocaine self administration as an assay capable of distinguishing σR subtype selectivity in vivo. These results further suggest that effectiveness of dual σR antagonism and dopamine transport inhibition in blocking cocaine self administration is specific for σ1Rs and further support this dual targeting approach to development of cocaine antagonists. U.S. Government work not protected by U.S. copyright.

Non-NMDA receptor antagonist-induced drinking in rat

NASA Technical Reports Server (NTRS)

Xu, Z.; Johnson, A. K.

1998-01-01

Glutamate has been implicated in the central control of mechanisms that maintain body fluid homeostasis. The present studies demonstrate that intracerebroventricular (i.c.v.) injections of the non-N-methyl-d-aspartate (NMDA) receptor antagonists 6, 7-dinitroquinoxaline-2,3-dione (DNQX) and 6-cyano-7-nitroquinoxaline-2,3 dione (CNQX) induce drinking in rats. The dipsogenic effect of i.c.v. DNQX was antagonized by the non-NMDA receptor agonist alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA). The water intake induced by DNQX was also blocked by pretreatment with a NMDA receptor antagonist, MK-801, but not by angiotensin type 1 (AT1) or acetylcholine muscarinic receptor antagonists (losartan and atropine). The results indicate that non-NMDA receptors may exert a tonic inhibitory effect within brain circuits that control dipsogenic activity and that functional integrity of NMDA receptors may be required for the non-NMDA receptor antagonists to induce water intake. Copyright 1998 Published by Elsevier Science B.V.

Modulation of AMPA receptor mediated current by nicotinic acetylcholine receptor in layer I neurons of rat prefrontal cortex

PubMed Central

Tang, Bo; Luo, Dong; Yang, Jie; Xu, Xiao-Yan; Zhu, Bing-Lin; Wang, Xue-Feng; Yan, Zhen; Chen, Guo-Jun

2015-01-01

Layer I neurons in the prefrontal cortex (PFC) exhibit extensive synaptic connections with deep layer neurons, implying their important role in the neural circuit. Study demonstrates that activation of nicotinic acetylcholine receptors (nAChRs) increases excitatory neurotransmission in this layer. Here we found that nicotine selectively increased the amplitude of AMPA receptor (AMPAR)-mediated current and AMPA/NMDA ratio, while without effect on NMDA receptor-mediated current. The augmentation of AMPAR current by nicotine was inhibited by a selective α7-nAChR antagonist methyllycaconitine (MLA) and intracellular calcium chelator BAPTA. In addition, nicotinic effect on mEPSC or paired-pulse ratio was also prevented by MLA. Moreover, an enhanced inward rectification of AMPAR current by nicotine suggested a functional role of calcium permeable and GluA1 containing AMPAR. Consistently, nicotine enhancement of AMPAR current was inhibited by a selective calcium-permeable AMPAR inhibitor IEM-1460. Finally, the intracellular inclusion of synthetic peptide designed to block GluA1 subunit of AMPAR at CAMKII, PKC or PKA phosphorylation site, as well as corresponding kinase inhibitor, blocked nicotinic augmentation of AMPA/NMDA ratio. These results have revealed that nicotine increases AMPAR current by modulating the phosphorylation state of GluA1 which is dependent on α7-nAChR and intracellular calcium. PMID:26370265

Felbamate but not phenytoin or gabapentin reduces glutamate release by blocking presynaptic NMDA receptors in the entorhinal cortex

PubMed Central

Yang, Jian; Wetterstrand, Caroline; Jones, Roland S.G.

2007-01-01

Summary We have shown that a number of anticonvulsant drugs can reduce glutamate release at synapses in the rat entorhinal cortex (EC) in vitro. We have also shown that presynaptic NMDA receptors (NMDAr) tonically facilitate glutamate release at these synapses. In the present study we determined whether, phenytoin, gabapentin and felbamate may reduce glutamate release by blocking the presynaptic NMDAr. Whole cell patch clamp recordings of spontaneous excitatory postsynaptic currents (sEPSCs) were used as a monitor of presynaptic glutamate release. Postsynaptic NMDAr were blocked with internal dialysis with an NMDAr channel blocker. The antagonist, 2-AP5, reduced the frequency of sEPSCs by blocking the presynaptic facilitatory NMDAr, but did not occlude a reduction in sEPSC frequency by gabapentin or phenytoin. Felbamate also reduced sEPSC frequency, but this effect was occluded by prior application of 2-AP5. Thus, whilst all three drugs can reduce glutamate release, only the action of felbamate seems to be due to interaction with presynaptic NMDAr. PMID:17980555

Opioid receptors mediate direct predictive fear learning: evidence from one-trial blocking.

PubMed

Cole, Sindy; McNally, Gavan P

2007-04-01

Pavlovian fear learning depends on predictive error, so that fear learning occurs when the actual outcome of a conditioning trial exceeds the expected outcome. Previous research has shown that opioid receptors, including mu-opioid receptors in the ventrolateral quadrant of the midbrain periaqueductal gray (vlPAG), mediate such predictive fear learning. Four experiments reported here used a within-subject one-trial blocking design to study whether opioid receptors mediate a direct or indirect action of predictive error on Pavlovian association formation. In Stage I, rats were trained to fear conditioned stimulus (CS) A by pairing it with shock. In Stage II, CSA and CSB were co-presented once and co-terminated with shock. Two novel stimuli, CSC and CSD, were also co-presented once and co-terminated with shock in Stage II. The results showed one-trial blocking of fear learning (Experiment 1) as well as one-trial unblocking of fear learning when Stage II training employed a higher intensity footshock than was used in Stage I (Experiment 2). Systemic administrations of the opioid receptor antagonist naloxone (Experiment 3) or intra-vlPAG administrations of the selective mu-opioid receptor antagonist CTAP (Experiment 4) prior to Stage II training prevented one-trial blocking. These results show that opioid receptors mediate the direct actions of predictive error on Pavlovian association formation.

A cybernetic view on wind-up.

PubMed

Farajidavar, Aydin; Gharibzadeh, Shahriar; Towhidkhah, Farzad; Saeb, Sohrab

2006-01-01

Wind-up is described traditionally as a frequency dependent increase in the excitability of spinal cord neurons, evoked by electrical stimulation of afferent C-fibers. Different kinds of wind-up have been reported, but wind-up of Abeta fibers in hyperalgesic states has gained little attention. In this paper, we present a cybernetic view on Abeta fiber wind-up and consider the involved molecular mechanisms as feedback and feedforward processes. Furthermore, our previous hypothesis, the sprouting phenomenon, is included in this view. Considering the proposed model, wind-up in hyperalgesic states might leave out in three different ways: (1) blocking the NMDA receptors by increasing extracellular Mg2+, 2) blocking the receptors and channels that contribute to Ca2+ inward current, and 3) blocking the Abeta fibers by local anesthetics. It seems that wind-up may be inhibited more effectively by using these three blocking mechanisms simultaneously, because in this case, the feedback process (main controller), the feedforward process (trigger), and Abeta stimulation (trigger) would be inhibited concurrently. Wind up may aggravate the pain in clinical hyperalgesic situations such as post-surgical states, some neuropathic pains, fibromyalgia syndrome, and post-herpetic neuralgia. Surely, clinical studies are needed to validate the effectiveness of our abovementioned suggestions in relieving such clinical pains.

A Role for Sigma Receptors in Stimulant Self-Administration and Addiction.

PubMed

Katz, Jonathan L; Hiranita, Takato; Hong, Weimin C; Job, Martin O; McCurdy, Christopher R

2017-01-01

Sigma receptors (σRs) are structurally unique proteins that function intracellularly as chaperones. Historically, σRs have been implicated as modulators of psychomotor stimulant effects and have at times been proposed as potential avenues for modifying stimulant abuse. However, the influence of ligands for σRs on the effects of stimulants, such as cocaine or methamphetamine, in various preclinical procedures related to drug abuse has been varied. The present paper reviews the effects of σR agonists and antagonists in three particularly relevant procedures: stimulant discrimination, place conditioning, and self-administration. The literature to date suggests limited σR involvement in the discriminative-stimulus effects of psychomotor stimulants, either with σR agonists substituting for the stimulant or with σR antagonists blocking stimulant effects. In contrast, studies of place conditioning suggest that administration of σR antagonists or down-regulation of σR protein can block the place conditioning induced by stimulants. Despite place conditioning results, selective σR antagonists are inactive in blocking the self-administration of stimulants. However, compounds binding to the dopamine transporter and blocking σRs can selectively decrease stimulant self-administration. Further, after self-administration of stimulants, σR agonists are self-administered, an effect not seen in subjects without that specific history. These findings suggest that stimulants induce unique changes in σR activity, and once established, the changes induced create redundant, and dopamine independent reinforcement pathways. Concomitant targeting of both dopaminergic pathways and σR proteins produces a selective antagonism of those pathways, suggesting new avenues for combination chemotherapies to specifically combat stimulant abuse.

Lysophosphatidic Acid Signals through Multiple Receptors in Osteoclasts to Elevate Cytosolic Calcium Concentration, Evoke Retraction, and Promote Cell Survival*

PubMed Central

Lapierre, Danielle M.; Tanabe, Natsuko; Pereverzev, Alexey; Spencer, Martha; Shugg, Ryan P. P.; Dixon, S. Jeffrey; Sims, Stephen M.

2010-01-01

Lysophosphatidic acid (LPA) is a bioactive phospholipid whose functions are mediated by multiple G protein-coupled receptors. We have shown that osteoblasts produce LPA, raising the possibility that it mediates intercellular signaling among osteoblasts and osteoclasts. Here we investigated the expression, signaling and function of LPA receptors in osteoclasts. Focal application of LPA elicited transient increases in cytosolic calcium concentration ([Ca2+]i), with 50% of osteoclasts responding at ∼400 nm LPA. LPA-induced elevation of [Ca2+]i was blocked by pertussis toxin or the LPA1/3 receptor antagonist VPC-32183. LPA caused sustained retraction of osteoclast lamellipodia and disrupted peripheral actin belts. Retraction was insensitive to VPC-32183 or pertussis toxin, indicating involvement of a distinct signaling pathway. In this regard, inhibition of Rho-associated kinase stimulated respreading after LPA-induced retraction. Real-time reverse transcription-PCR revealed transcripts encoding LPA1 and to a lesser extent LPA2, LPA4, and LPA5 receptor subtypes. LPA induced nuclear translocation of NFATc1 and enhanced osteoclast survival, effects that were blocked by VPC-32183 or by a specific peptide inhibitor of NFAT activation. LPA slightly reduced the resorptive activity of osteoclasts in vitro. Thus, LPA binds to at least two receptor subtypes on osteoclasts: LPA1, which couples through Gi/o to elevate [Ca2+]i, activate NFATc1, and promote survival, and a second receptor that likely couples through G12/13 and Rho to evoke and maintain retraction through reorganization of the actin cytoskeleton. These findings reveal a signaling axis in bone through which LPA, produced by osteoblasts, acts on multiple receptor subtypes to induce pleiotropic effects on osteoclast activity and function. PMID:20551326

Attenuation in rats of impairments of memory by scopolamine, a muscarinic receptor antagonist, by mecamylamine, a nicotinic receptor antagonist

PubMed Central

Newman, L. A.

2015-01-01

Rationale Scopolamine, a muscarinic antagonist, impairs learning and memory for many tasks, supporting an important role for the cholinergic system in these cognitive functions. The findings are most often interpreted to indicate that a decrease in postsynaptic muscarinic receptor activation mediates the memory impairments. However, scopolamine also results in increased release of acetylcholine in the brain as a result of blocking presynaptic muscarinic receptors. Objectives The present experiments assess whether scopolamine-induced increases in acetylcholine release may impair memory by overstimulating postsynaptic cholinergic nicotinic receptors, i.e., by reaching the high end of a nicotinic receptor activation inverted-U dose-response function. Results Rats tested in a spontaneous alternation task showed dose-dependent working memory deficits with systemic injections of mecamylamine and scopolamine. When an amnestic dose of scopolamine (0.15 mg/kg) was co-administered with a subamnestic dose of mecamylamine (0.25 mg/kg), this dose of mecamylamine significantly attenuated the scopolamine-induced memory impairments. We next assessed the levels of acetylcholine release in the hippocampus in the presence of scopolamine and mecamylamine. Mecamylamine injections resulted in decreased release of acetylcholine, while scopolamine administration caused a large increase in acetylcholine release. Conclusions These findings indicate that a nicotinic antagonist can attenuate impairments in memory produced by a muscarinic antagonist. The nicotinic antagonist may block excessive activation of nicotinic receptors postsynaptically or attenuate increases in acetylcholine release presynaptically. Either effect of a nicotinic antagonist—to decrease scopolamine-induced increases in acetylcholine output or to decrease post-synaptic acetylcholine receptor activation—may mediate the negative effects on memory of muscarinic antagonists. PMID:26660295

Antidepressant-like responses to the combined sigma and 5-HT1A receptor agonist OPC-14523.

PubMed

Tottori, K; Miwa, T; Uwahodo, Y; Yamada, S; Nakai, M; Oshiro, Y; Kikuchi, T; Altar, C A

2001-12-01

The antidepressant-like activity of a novel compound, OPC-14523, was investigated in comparison with the conventional antidepressants, fluoxetine and imipramine. OPC-14523 bound with nanomolar affinities to sigma receptors (IC(50)=47-56 nM), the 5-HT(1A) receptor (IC(50)=2.3 nM), and the 5-HT transporter (IC(50)=80 nM). OPC-14523 inhibited the in vitro reuptake of 3H-5-HT (IC(50)=27 nM), but it showed very weak inhibitory activity on 3H-NE and 3H-DA reuptake. OPC-14523 did not inhibit MAO A or B activities or muscarinic receptors. A single oral administration of OPC-14523 produced a marked antidepressant-like effect in the forced swimming test (FST) with rats (ED(50)=27 mg/kg) and mice (ED(50)=20mg/kg) without affecting the general locomotor activity. In contrast, fluoxetine and imipramine each required at least four days of repeated dosing to show this activity. The acute activity of OPC-14523 was blocked by pretreatment with the sigma receptor antagonist NE-100 or the selective 5-HT(1A) receptor antagonist WAY-100635. The induction of flat body posture by OPC-14523 was blocked by the selective 5-HT(1A) receptor antagonist NAN-190, and forebrain 5-HT biosynthesis was attenuated by OPC-14523 at behaviorally effective doses. In contrast, OPC-14523, unlike fluoxetine, failed to inhibit 5-HT reuptake at oral doses below 100mg/kg. Thus, the acute antidepressant-like action of OPC-14523 is achieved by the combined stimulation of sigma and 5-HT(1A) receptors without inhibition of 5-HT reuptake in vivo.

Adrenergic beta 2-selective blocker in isoprenaline-enhanced essential tremor.

PubMed

Teräväinen, H; Huttunen, J

1987-01-01

A beta 2-selective adrenergic-receptor-blocking drug, ICI 118.551, 150 mg/day, prevented almost as effectively as the nonselective antagonist propranolol, 240 mg/day, the isoprenaline enhancement of essential tremor amplitude.

Decoy receptors block TRAIL sensitivity at a supracellular level: the role of stromal cells in controlling tumour TRAIL sensitivity.

PubMed

O'Leary, L; van der Sloot, A M; Reis, C R; Deegan, S; Ryan, A E; Dhami, S P S; Murillo, L S; Cool, R H; Correa de Sampaio, P; Thompson, K; Murphy, G; Quax, W J; Serrano, L; Samali, A; Szegezdi, E

2016-03-10

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is a death ligand cytokine known for its cytotoxic activity against malignantly transformed cells. TRAIL induces cell death through binding to death receptors DR4 and DR5. The inhibitory decoy receptors (DcR1 and DcR2) co-expressed with death receptor 4 (DR4)/DR5 on the same cell can block the transmission of the apoptotic signal. Here, we show that DcRs also regulate TRAIL sensitivity at a supracellular level and thus represent a mechanism by which the microenvironment can diminish tumour TRAIL sensitivity. Mathematical modelling and layered or spheroid stroma-extracellular matrix-tumour cultures were used to model the tumour microenvironment. By engineering TRAIL to escape binding by DcRs, we found that DcRs do not only act in a cell-autonomous or cis-regulatory manner, but also exert trans-cellular regulation originating from stromal cells and affect tumour cells, highlighting the potent inhibitory effect of DcRs in the tumour tissue and the necessity of selective targeting of the two death-inducing TRAIL receptors to maximise efficacy.

Involvement of NMDA glutamate receptors in the acquisition and reinstatement of the conditioned place preference induced by MDMA.

PubMed

García-Pardo, Maria P; Escobar-Valero, Carla; Rodríguez-Arias, Marta; Miñarro, Jose; Aguilar, Maria A

2015-08-01

Some 3,4-methylenedioxymethamphetamine (MDMA) users become dependent as a result of chronic consumption. A greater understanding of the neurobiological basis of the rewarding effects of MDMA could contribute to developing effective pharmacotherapies for MDMA-related problems. The present study evaluated the role of N-methyl-D-aspartate (NMDA) glutamate receptors (NMDARs) in the acquisition and reinstatement of conditioned place preference (CPP) induced by MDMA. Adolescent male mice were conditioned with 1 or 10 mg/kg MDMA and pretreated with 5 or 10 mg/kg of the NMDAR antagonist memantine during acquisition of conditioning (experiment 1), or before a reinstatement test (experiment 2). In addition, the effects of memantine on acquisition of chocolate-induced CPP and the effects of memantine and MDMA on a passive avoidance task were evaluated. Memantine did not exert any motivational effects, but blocked the acquisition of MDMA-induced CPP. Moreover, following acquisition and extinction of MDMA-induced CPP, memantine did not induce reinstatement but blocked reinstatement of the CPP induced by priming with MDMA. Memantine did not block the CPP induced by chocolate, and it partially reversed the impairing effects of MDMA on memory. Our results demonstrate that NMDARs are involved in acquisition of the conditioned rewarding effects of MDMA and in priming-induced reinstatement of CPP following extinction. Moreover, they suggest the validity of memantine for the treatment of MDMA abuse.

THE ROLE OF DELTA OPIOID RECEPTORS IN THE ANXIOLYTIC ACTIONS OF BENZODIAZEPINES

PubMed Central

Primeaux, Stefany D.; Wilson, Steven P.; McDonald, Alexander J.; Mascagni, Franco; Wilson, Marlene A.

2007-01-01

The anxiolytic effects of benzodiazepines appear to involve opioid processes in the amygdala. In previous experiments, overexpression of enkephalin in the amygdala enhanced the anxiolytic actions of the benzodiazepine agonist diazepam in the elevated plus maze. The effects of systemically administered diazepam are also blocked by injections of naltrexone into the central nucleus of the amygdala. The current studies investigated the role of delta opioid receptors in the anxiety-related effects of diazepam. Three days following bilateral stereotaxic injections of viral vectors containing cDNA encoding proenkephalin or β-galactosidase (control vector), the delta opioid receptor antagonist naltrindole (10 mg/kg, s.c.) attenuated the enhanced anxiolytic effects of 1–2 mg/kg diazepam in rats overexpressing preproenkephalin in the amygdala. Despite this effect, naltrindole failed to attenuate the anxiolytic action of higher diazepam doses (3 mg/kg) in animals with normal amygdalar enkephalin expression. Similarly, the mu opioid receptor antagonist, β-funaltrexamine (20mg/kg, sc), had no effect on the anxiolytic effect of diazepam alone. These data support a role for delta opioid receptors in the opioid-enhanced anxiolytic effects of diazepam. PMID:17109943

Insect odorant receptors are molecular targets of the insect repellent DEET.

PubMed

Ditzen, Mathias; Pellegrino, Maurizio; Vosshall, Leslie B

2008-03-28

DEET (N,N-diethyl-meta-toluamide) is the world's most widely used topical insect repellent, with broad effectiveness against most insects. Its mechanism of action and molecular target remain unknown. Here, we show that DEET blocks electrophysiological responses of olfactory sensory neurons to attractive odors in Anopheles gambiae and Drosophila melanogaster. DEET inhibits behavioral attraction to food odors in Drosophila, and this inhibition requires the highly conserved olfactory co-receptor OR83b. DEET inhibits odor-evoked currents mediated by the insect odorant receptor complex, comprising a ligand-binding subunit and OR83b. We conclude that DEET masks host odor by inhibiting subsets of heteromeric insect odorant receptors that require the OR83b co-receptor. The identification of candidate molecular targets for the action of DEET may aid in the design of safer and more effective insect repellents.

Drug interactions with neuromuscular blockers.

PubMed

Feldman, S; Karalliedde, L

1996-10-01

Drugs administered to patients undergoing anaesthesia may complicate the use of the neuromuscular blockers that are given to provide good surgical conditions. The various sites of interaction include actions on motor nerve conduction and spinal reflexes, acetylcholine (ACh) synthesis, mobilisation and release, sensitivity of the motor end plate to ACh and the ease of propagation of the motor action potential. In addition, many drugs affect the pharmacokinetics of neuromuscular blockers, especially as most drugs depend to a greater or lesser extent upon renal excretion. The clinically significant interaction between nondepolarisers and depolarisers may be due to blockade of the pre-synaptic nicotinic receptors by the depolarisers, leading to decreased ACh mobilisation and release. Synergism between nondepolarisers probably results from post-synaptic receptor mechanisms. Volatile anaesthetic agents affect the sensitivity of the motor end-plate (post-synaptic receptor blockade) in addition to having effects on pre-synaptic nicotinic function. The effects of nondepolarisers are likely to be potentiated and their action prolonged by large doses of local anaesthetics due to depression of nerve conduction, depression of ACh formation, mobilisation and release, decreases in post-synaptic receptor channel opening times and reductions in muscular contraction. Most antibacterials have effects on pre-synaptic mechanisms. Procainamide and quinidine principally block nicotinic receptor channels. Magnesium has a marked inhibitory effect on ACh release. Calcium antagonists could theoretically interfere with neurotransmitter release and muscle contractility. Phenytoin and lithium decrease ACh release, whilst corticosteroids and furosemide (frusemide) tend to increase the release of the transmitter. Ecothiopate, tacrine, organophosphates, propanidid, metoclopramide and bambuterol depress cholinesterase activity and prolong the duration of the neuromuscular block. The probability of clinically significant interactions increases in patients receiving several drugs with possible effects on neuromuscular transmission and muscle contraction.

Effects of the κ-opioid receptor on the inhibition of 100 Hz electroacupuncture on cocaine-induced conditioned place preference

PubMed Central

Hou, Bingjun

2016-01-01

The administration of 100 Hz electroacupuncture has been demonstrated to suppress cocaine-induced conditioned place preference (CPP) in rats, and there is evidence that the κ-opioid receptor may have a role in cocaine addiction. The present study sought to explore the mechanisms underlying the inhibitory effects of 100 Hz electroacupuncture on cocaine-induced CPP in rats. A rat model of cocaine-induced CPP was used in the present study to investigate the following: i) Naloxone treatment (5 and 10 mg/kg) following 100 Hz electroacupuncture-mediated inhibition on cocaine-induced CPP, revealing that a high dose (10 mg/kg) of naloxone blocked the inhibitory effects of 100 Hz electroacupuncture on cocaine-induced CPP; ii) nor-binaltorphimine (nor-BNI) on 100 Hz electroacupuncture-mediated inhibition on cocaine-induced CPP, which indicated that administration of 10 µg/5 µl and 0.3 µg/1 µl nor-BNI intracerebroventricularly and via the nucleus accumbens, respectively, reversed the inhibitory effects of 100 Hz electroacupuncture on cocaine-induced CPP, and that injection of nor-BNI in different brain areas of rats blocks the inhibitory effects of electroacupuncture on cocaine-induced CPP; and iv) 100 Hz electroacupuncture on the mRNA expression levels of the κ-opioid receptor in the rat nucleus accumbens and amygdala, which established that mRNA expression levels of κ-opioid receptor in the nucleus accumbens were increased with 100 Hz electroacupuncture plus cocaine-induced CPP. Overall, the results of the present study indicated that 100 Hz electroacupuncture was able to suppress cocaine-induced CPP via the κ-opioid receptor in the nucleus accumbens. PMID:27588082

Tachykinins Stimulate a Subset of Mouse Taste Cells

PubMed Central

Grant, Jeff

2012-01-01

The tachykinins substance P (SP) and neurokinin A (NKA) are present in nociceptive sensory fibers expressing transient receptor potential cation channel, subfamily V, member 1 (TRPV1). These fibers are found extensively in and around the taste buds of several species. Tachykinins are released from nociceptive fibers by irritants such as capsaicin, the active compound found in chili peppers commonly associated with the sensation of spiciness. Using real-time Ca2+-imaging on isolated taste cells, it was observed that SP induces Ca2+ -responses in a subset of taste cells at concentrations in the low nanomolar range. These responses were reversibly inhibited by blocking the SP receptor NK-1R. NKA also induced Ca2+-responses in a subset of taste cells, but only at concentrations in the high nanomolar range. These responses were only partially inhibited by blocking the NKA receptor NK-2R, and were also inhibited by blocking NK-1R indicating that NKA is only active in taste cells at concentrations that activate both receptors. In addition, it was determined that tachykinin signaling in taste cells requires Ca2+-release from endoplasmic reticulum stores. RT-PCR analysis further confirmed that mouse taste buds express NK-1R and NK-2R. Using Ca2+-imaging and single cell RT-PCR, it was determined that the majority of tachykinin-responsive taste cells were Type I (Glial-like) and umami-responsive Type II (Receptor) cells. Importantly, stimulating NK-1R had an additive effect on Ca2+ responses evoked by umami stimuli in Type II (Receptor) cells. This data indicates that tachykinin release from nociceptive sensory fibers in and around taste buds may enhance umami and other taste modalities, providing a possible mechanism for the increased palatability of spicy foods. PMID:22363709

Endothelial Barrier Protection by Local Anesthetics: Ropivacaine and Lidocaine Block Tumor Necrosis Factor-α–induced Endothelial Cell Src Activation

PubMed Central

Piegeler, Tobias; Votta-Velis, E. Gina; Bakhshi, Farnaz R.; Mao, Mao; Carnegie, Graeme; Bonini, Marcelo G.; Schwartz, David E.; Borgeat, Alain; Beck-Schimmer, Beatrice; Minshall, Richard D.

2014-01-01

Background Pulmonary endothelial barrier dysfunction mediated in part by Src-kinase activation plays a crucial role in acute inflammatory disease. Proinflammatory cytokines, such as tumor necrosis factor-α (TNFα), activate Src via phosphatidylinositide 3-kinase/Akt-dependent nitric oxide generation, a process initiated by recruitment of phosphatidylinositide 3-kinase regulatory subunit p85 to TNF-receptor-1. Because amide-linked local anesthetics have well-established anti-inflammatory effects, the authors hypothesized that ropivacaine and lidocaine attenuate inflammatory Src signaling by disrupting the phosphatidylinositide 3-kinase–Akt–nitric oxide pathway, thus blocking Src-dependent neutrophil adhesion and endothelial hyperpermeability. Methods Human lung microvascular endothelial cells, incubated with TNFα in the absence or presence of clinically relevant concentrations of ropivacaine and lidocaine, were analyzed by Western blot, probing for phosphorylated/activated Src, endothelial nitric oxide synthase, Akt, intercellular adhesion molecule-1, and caveolin-1. The effect of ropivacaine on TNFα-induced nitric oxide generation, co-immunoprecipitation of TNF-receptor-1 with p85, neutrophil adhesion, and endothelial barrier disruption were assessed. Results Ropivacaine and lidocaine attenuated TNFα-induced Src activation (half-maximal inhibitory concentration [IC50] = 8.611 × 10−10 M for ropivacaine; IC50 = 5.864 × 10−10 M for lidocaine) and endothelial nitric oxide synthase phosphorylation (IC50 = 7.572 × 10−10 M for ropivacaine; IC50 = 6.377 × 10−10 M for lidocaine). Akt activation (n = 7; P = 0.006) and stimulus-dependent binding of TNF-receptor-1 and p85 (n = 6; P = 0.043) were blocked by 1 nM of ropivacaine. TNFα-induced neutrophil adhesion and disruption of endothelial monolayers via Src-dependent intercellular adhesion molecule-1- and caveolin-1-phosphorylation, respectively, were also attenuated. Conclusions Ropivacaine and lidocaine effectively blocked inflammatory TNFα signaling in endothelial cells by attenuating p85 recruitment to TNF-receptor-1. The resultant decrease in Akt, endothelial nitric oxide synthase, and Src phosphorylation reduced neutrophil adhesion and endothelial hyperpermeability. This novel anti-inflammatory “side-effect” of ropivacaine and lidocaine may provide therapeutic benefit in acute inflammatory disease. PMID:24525631

Effects of Cetuximab and Erlotinib on the behaviour of cancer stem cells in head and neck squamous cell carcinoma.

PubMed

Setúbal Destro Rodrigues, Maria Fernanda; Gammon, Luke; Rahman, Muhammad M; Biddle, Adrian; Nunes, Fabio Daumas; Mackenzie, Ian C

2018-03-02

The therapeutic responses of many solid tumours to chemo- and radio-therapies are far from fully effective but therapies targeting malignancy-related cellular changes show promise for further control. In head and neck squamous cell carcinoma, the epidermal growth factor receptor (EGFR) is commonly overexpressed and investigation of agents that block this receptor indicate a limited response when used alone but an ability to enhance the actions of other drugs. The hierarchical stem cell patterns present in tumours generate cellular heterogeneity and this is further complicated by cancer stem cells (CSC) shifting between epithelial (Epi-CSC) and mesenchymal (EMT-CSC) states. To clarify how such heterogeneity influences responses to EGFR blocking, we examined the effects of Cetuximab and Erlotinib on the cell sub-populations in HNSCC cell lines. These agents reduced cell proliferation for all subpopulations but induced little cell death. They did however induce large shifts of cells between the EMT-CSC, Epi-CSC and differentiating cell compartments. Loss of EMT-CSCs reduced cell motility and is expected to reduce invasion and metastasis. EGFR blocking also induced shifts of Epi-CSCs into the differentiating cell compartment which typically has greater sensitivity to chemo/radiation, an effect expected to enhance the overall response of tumour cell populations to adjunctive therapies.

Effects of Cetuximab and Erlotinib on the behaviour of cancer stem cells in head and neck squamous cell carcinoma

PubMed Central

Setúbal Destro Rodrigues, Maria Fernanda; Gammon, Luke; Rahman, Muhammad M.; Biddle, Adrian; Nunes, Fabio Daumas; Mackenzie, Ian C.

2018-01-01

The therapeutic responses of many solid tumours to chemo- and radio-therapies are far from fully effective but therapies targeting malignancy-related cellular changes show promise for further control. In head and neck squamous cell carcinoma, the epidermal growth factor receptor (EGFR) is commonly overexpressed and investigation of agents that block this receptor indicate a limited response when used alone but an ability to enhance the actions of other drugs. The hierarchical stem cell patterns present in tumours generate cellular heterogeneity and this is further complicated by cancer stem cells (CSC) shifting between epithelial (Epi-CSC) and mesenchymal (EMT-CSC) states. To clarify how such heterogeneity influences responses to EGFR blocking, we examined the effects of Cetuximab and Erlotinib on the cell sub-populations in HNSCC cell lines. These agents reduced cell proliferation for all subpopulations but induced little cell death. They did however induce large shifts of cells between the EMT-CSC, Epi-CSC and differentiating cell compartments. Loss of EMT-CSCs reduced cell motility and is expected to reduce invasion and metastasis. EGFR blocking also induced shifts of Epi-CSCs into the differentiating cell compartment which typically has greater sensitivity to chemo/radiation, an effect expected to enhance the overall response of tumour cell populations to adjunctive therapies. PMID:29568372

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

Yagi, Yukihiro; Pharmaceutical Research Center, Meiji Seika Pharma Co., Ltd., 760 Morooka-cho, Kohoku-ku, Yokohama, Kanagawa 222–8567; Nakamura, Yuji

Fingolimod, a sphingosine 1-phosphate (S1P) receptor subtype 1, 3, 4 and 5 modulator, has been used for the treatment of patients with relapsing forms of multiple sclerosis, but atrioventricular conduction block and/or QT-interval prolongation have been reported in some patients after the first dose. In this study, we directly compared the electropharmacological profiles of fingolimod with those of siponimod, a modulator of sphingosine 1-phosphate receptor subtype 1 and 5, using in vivo guinea-pig model and in vitro human ether-a-go-go-related gene (hERG) assay to better understand the onset mechanisms of the clinically observed adverse events. Fingolimod (0.01 and 0.1 mg/kg) ormore » siponimod (0.001 and 0.01 mg/kg) was intravenously infused over 10 min to the halothane-anaesthetized guinea pigs (n = 4), whereas the effects of fingolimod (1 μmol/L) and siponimod (1 μmol/L) on hERG current were examined (n = 3). The high doses of fingolimod and siponimod induced atrioventricular conduction block, whereas the low dose of siponimod prolonged PR interval, which was not observed by that of fingolimod. The high dose of fingolimod prolonged QT interval, which was not observed by either dose of siponimod. Meanwhile, fingolimod significantly inhibited hERG current, which was not observed by siponimod. These results suggest that S1P receptor subtype 1 in the heart could be one of the candidates for fingolimod- and siponimod-induced atrioventricular conduction block since S1P receptor subtype 5 is localized at the brain, and that direct I{sub Kr} inhibition may play a key role in fingolimod-induced QT-interval prolongation. - Highlights: • Fingolimod and siponimod are S1P{sub 1,3,4,5} and S1P{sub 1,5} receptor modulators, respectively. • Fingolimod and siponimod induced AV block in the halothane-anesthetized guinea pigs. • S1P{sub 1} in the hearts may be the target of fingolimod- and siponimod-induced AV block. • Fingolimod directly inhibited hERG current, which was not observed by siponimod. • I{sub Kr} inhibition may play a key role in the fingolimod-induced QT prolongation.« less

Endocannabinoids protect the rat isolated heart against ischaemia

PubMed Central

Lépicier, Philippe; Bouchard, Jean-François; Lagneux, Caroline; Lamontagne, Daniel

2003-01-01

The purpose of this study was to determine whether endocannabinoids can protect the heart against ischaemia and reperfusion. Rat isolated hearts were exposed to low-flow ischaemia (0.5–0.6 ml min−1) and reperfusion. Functional recovery as well as CK and LDH overflow into the coronary effluent were monitored. Infarct size was determined at the end of the experiments. Phosphorylation levels of p38, ERK1/2, and JNK/SAPK kinases were measured by Western blots. None of the untreated hearts recovered from ischaemia during the reperfusion period. Perfusion with either 300 nM palmitoylethanolamide (PEA) or 300 nM 2-arachidonoylglycerol (2-AG), but not anandamide (up to 1 μM), 15 min before and throughout the ischaemic period, improved myocardial recovery and decreased the levels of coronary CK and LDH. PEA and 2-AG also reduced infarct size. The CB2-receptor antagonist, SR144528, blocked completely the cardioprotective effect of both PEA and 2-AG, whereas the CB1-receptor antagonist, SR141716A, blocked partially the effect of 2-AG only. In contrast, both ACEA and JWH015, two selective agonists for CB1- and CB2- receptors, respectively, reduced infarct size at a concentration of 50 nM. PEA enhanced the phosphorylation level of p38 MAP kinase during ischaemia. PEA perfusion doubled the baseline phosphorylation level of ERK1/2, and enhanced its increase upon reperfusion. The cardioprotective effect of PEA was completely blocked by the p38 MAP kinase inhibitor, SB203580, and significantly reduced by the ERK1/2 inhibitor, PD98059, and the PKC inhibitor, chelerythrine. In conclusion, endocannabinoids exert a strong cardioprotective effect in a rat model of ischaemia–reperfusion that is mediated mainly through CB2-receptors, and involves p38, ERK1/2, as well as PKC activation. PMID:12813004

Effect of Prazosin and Naltrexone on Script Induced Alcohol Craving in Veterans with Alcohol Use Disorders with and without Co-occurring PTSD

DTIC Science & Technology

2015-01-01

status, moderate medication response. 15. SUBJECT TERMS Alcohol Drinking, Drinking Behavior, Naltrexone, Prazosin, Adrenergic Agents, Adrenergice ...primates and humans express α1 adrenergic receptors. Given the interplay of the noradrenergic system with craving-related brain systems, blocking α1...Antagonists, Adrenergic alpha-1 receptor antagonists, Adrenergic alpha- antagonists, Antihypertensive agents, Narcotic antagonists, Therapeutic uses

Hypocretin and GABA interact in the pontine reticular formation to increase wakefulness.

PubMed

Brevig, Holly N; Watson, Christopher J; Lydic, Ralph; Baghdoyan, Helen A

2010-10-01

Hypocretin-1/orexin A administered directly into the oral part of rat pontine reticular formation (PnO) causes an increase in wakefulness and extracellular gamma-aminobutyric acid (GABA) levels. The receptors in the PnO that mediate these effects have not been identified. Therefore, this study tested the hypothesis that the increase in wakefulness caused by administration of hypocretin-1 into the PnO occurs via activation of GABAA receptors and hypocretin receptors. Within/between subjects. University of Michigan. Twenty-three adult male Crl:CD*(SD) (Sprague Dawley) rats. Microinjection of hypocretin-1, bicuculline (GABAA receptor antagonist), SB-334867 (hypocretin receptor-1 antagonist), and Ringer solution (vehicle control) into the PnO. Hypocretin-1 caused a significant concentration-dependent increase in wakefulness and decrease in rapid eye movement (REM) sleep and non-REM (NREM) sleep. Coadministration of SB-334867 and hypocretin-1 blocked the hypocretin-1-induced increase in wakefulness and decrease in both the NREM and REM phases of sleep. Coadministration of bicuculline and hypocretin-1 blocked the hypocretin-1-induced increase in wakefulness and decrease in NREM sleep caused by hypocretin-1. The increase in wakefulness caused by administering hypocretin-1 to the PnO is mediated by hypocretin receptors and GABAA receptors in the PnO. These results show for the first time that hypocretinergic and GABAergic transmission in the PnO can interact to promote wakefulness.

Memantine and dizocilpine interactions with antinociceptive or discriminative stimulus effects of morphine in rats after acute or chronic treatment with morphine

PubMed Central

Chen, Yukun; Evola, Marianne

2013-01-01

Rationale Memantine is a N-methyl-d-aspartic acid receptor (NMDAR) channel blocker that binds to dizocilpine sites and appears well tolerated during chronic use. Published studies suggest NMDAR antagonists prevent development of tolerance to effects of morphine by blocking NMDAR hyperactivation. Objectives We sought to compare effects of memantine to those of the more frequently studied dizocilpine and to evaluate memantine as a potential adjunct to modify tolerance to mu-opioid receptor agonists. Methods Sprague–Dawley rats were trained to discriminate morphine (3.2 mg/kg) and saline under fixed ratio 15 schedules of food delivery. Potency and maximal stimulus or rate-altering effects of cumulative doses of morphine were examined 30 min after pretreatment with dizocilpine (0.032–0.1 mg/kg) or memantine (5–10 mg/kg) and after chronic treatment with combinations of dizocilpine or memantine and morphine, 10 mg/kg twice daily, for 6 to 14 days. Effects of dizocilpine or memantine on morphine antinociception were examined in a 55 °C water tail-withdrawal assay with drug treatments parallel to those in discrimination studies. Results Acutely, memantine attenuated while dizocilpine potentiated the stimulus and antinociceptive effects of morphine. Neither chronic dizocilpine nor memantine blocked tolerance to the stimulus effects of morphine. In contrast, combined-treatment with dizocilpine (0.1 mg/kg) blocked tolerance to antinociceptive effects of lower (0.1∼3.2 mg/kg) but not higher doses of morphine, whereas memantine did not block tolerance. Conclusions Memantine and dizocilpine interacted differently with morphine, possibly due to different NMDAR binding profiles. The lack of memantine-induced changes in morphine tolerance suggests memantine may not be a useful adjunct in chronic pain management. PMID:22864944

Mapping of melanin-concentrating hormone receptor 1 B cell epitopes predicts two major binding sites for vitiligo patient autoantibodies.

PubMed

Gavalas, Nikos G; Gottumukkala, Raju V S R K; Gawkrodger, David J; Watson, Philip F; Weetman, Anthony P; Kemp, E Helen

2009-05-01

The melanin-concentrating hormone receptor 1 (MCHR1) has been identified as a B cell autoantigen in vitiligo with antibodies to the receptor detectable in binding and function-blocking assays. Two epitope domains (amino acids 1-138 and 139-298) have been previously identified. In this study, we aimed to further define the epitope specificity of MCHR1 antibodies using phage-display technology and to identify the epitopes recognised by receptor antibodies detected in MCHR1 function-blocking assays. Antibody reactivity to MCHR1 peptides 51-80, 85-98, 154-158 and 254-260 was identified by phage-display and subsequently confirmed in phage ELISA in 2/12, 5/12, 3/12 and 6/12 of vitiligo patients, respectively. The results suggest that major autoantibody epitopes are localised in the 85-98 and 254-260 amino acid regions of MCHR1 with minor epitopes in amino acid sequences 51-80 and 154-158. Antibodies with MCHR1 function-blocking activity were determined to recognise epitope 254-260, this being the first epitope to be reported as a target site for antibodies that block the function of the receptor.

Intracellular angiotensin II directly induces in vitro transcription of TGF-β1, MCP-1 and NHE-3 mRNAs in isolated rat renal cortical nuclei via activation of nuclear AT1 receptors

PubMed Central

Li, Xiao C.; Zhuo, Jia L.

2008-01-01

The present study tested the hypothesis that intracellular angiotensin II (Ang II) directly induces transcriptional effects by stimulating AT1 receptors in the nucleus of rat renal cortical cells. Intact nuclei were freshly isolated from the rat renal cortex and transcriptional responses to Ang II were studied using in vitro RNA transcription assays and semi-quantitative RT-PCR. High power phase contrast micrographs showed that isolated nuclei were encircled by an intact nuclear envelop, stained strongly by the DNA marker DAPI, but not by the membrane or endosomal markers. FITC-labeled Ang II and [125I]-Val5-Ang II binding confirmed the presence of Ang II receptors in the nuclei with a predominance of AT1 receptors. RT-PCR showed that AT1a mRNA expression was 3-fold greater than AT1b receptor mRNAs in these nuclei. In freshly isolated nuclei, Ang II increased in vitro [α-32P]CTP incorporation in a concentration manner, and the effect was confirmed by autoradiography and RNA electrophoresis. Ang II markedly increased in vitro transcription of mRNAs for transforming growth factor-β1 by 143% (p < 0.01), macrophage chemoattractant protein-1 by 89% (p < 0.01), and the sodium and hydrogen exchanger-3 by 110% (p < 0.01). These transcriptional effects of Ang II on the nuclei were completely blocked by the AT1 receptor antagonist losartan (p < 0.01). By contrast, Ang II had no effects on transcription of angiotensinogne and GAPDH mRNAs. Since these transcriptional effects of Ang II in isolated nuclei were induced by Ang II in the absence of cell surface receptor-mediated signaling and completely blocked by losartan, we concluded that Ang II may directly stimulate nuclear AT1a receptors to induce transcriptional responses that are associated with tubular epithelial sodium transport, cellular growth and hypertrophy, and proinflammatory cytokines. PMID:18256274

GABAB Receptor Positive Modulation Decreases Selective Molecular and Behavioral Effects of Cocaine

PubMed Central

Lhuillier, Loic; Mombereau, Cedric; Cryan, John F.; Kaupmann, Klemens

2006-01-01

Exposure to cocaine induces selective behavioral and molecular adaptations. In rodents, acute cocaine induces increased locomotor activity whereas prolonged drug exposure results in behavioral locomotor sensitization, which is thought to be a consequence of drug–induced neuroadaptive changes. Recent attention has been given to compounds activating GABAB receptors as potential anti-addictive therapies. In particular the principle of allosteric positive GABAB receptor modulators is very promising in this respect, as positive modulators lack the sedative and muscle relaxant properties of full GABAB receptor agonists such as baclofen. Here we investigated the effects of systemic application of the GABAB receptor positive modulator GS39783 in animals treated with acute and chronic cocaine administration. Both GS39783 and baclofen dose-dependently attenuated acute cocaine-induced hyperlocomotion. Furthermore, both compounds also efficiently blocked cocaine-induced Fos induction in the striatal complex. In chronic studies GS39783 induced a modest attenuation of cocaine-induced locomotor sensitization. Chronic cocaine induces the accumulation of the transcription factor ΔFosB and up regulates cAMP-response-element-binding-protein (CREB) and dopamine-and-cAMP-regulated-phosphoprotein of 32 kd (DARPP-32). GS39783 blocked the induction/activation of DARPP-32 and CREB in the nucleus accumbens and dorsal striatum and partially inhibited ΔFosB accumulation in the dorsal striatum. In summary our data provide evidence that GS39783 attenuates the acute behavioral effects of cocaine exposure in rodents and in addition prevents the induction of selective long-term adaptive changes in dopaminergic signaling pathways. Further investigation of GABAB receptor positive modulation as a novel therapeutic strategy for the treatment of cocaine dependence and possibly other drugs of abuse is therefore warranted. PMID:16710312

Low doses of dextromethorphan attenuate morphine-induced rewarding via the sigma-1 receptor at ventral tegmental area in rats.

PubMed

Chen, Shiou-Lan; Hsu, Kuei-Ying; Huang, Eagle Yi-Kung; Lu, Ru-Band; Tao, Pao-Luh

2011-09-01

Chronic use of morphine causes rewarding and behavioral sensitization, which may lead to the development of psychological craving. In our previous study, we found that a widely used antitussive dextromethorphan (known as a low affinity NMDA receptor antagonist), at doses of 10-20 mg/kg (i.p.), effectively decreased morphine rewarding in rats. In this study, we further investigated the effects and mechanisms of low doses of DM (μg/kg range) on morphine rewarding and behavioral sensitization. A conditioned place preference test was used to determine the rewarding and a locomotor activity test was used to determine the behavioral sensitization induced by the drug(s) in rats. When a low dose of DM (3 or 10 μg/kg, i.p.) was co-administered with morphine (5 mg/kg, s.c.), the rewarding effect, but not behavioral sensitization, induced by morphine was inhibited. The inhibiting effect of DM could be blocked by systemically administering a sigma-1 receptor antagonist, BD1047 (3 mg/kg, i.p.). When BD1047 (5 nmole/site) was locally given at the VTA, it also blocked the effects of a low dose of DM in inhibiting morphine rewarding. Our findings suggest that the activation of the sigma-1 receptor at the VTA may be involved in the mechanism of low doses of DM in inhibiting the morphine rewarding effect and the possibility of using extremely low doses of DM in treatment of opioid addiction in clinics. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Pregnenolone blocks cannabinoid-induced acute psychotic-like states in mice

PubMed Central

Busquets-Garcia, Arnau; Soria-Gómez, Edgar; Redon, Bastien; Mackenbach, Yarmo; Chaouloff, Francis; Varilh, Marjorie; Ferreira, Guillaume; Piazza, Pier-Vincenzo; Marsicano, Giovanni

2017-01-01

Cannabis-induced acute psychotic-like states (CIAPS) represent a growing health issue, but their underlying neurobiological mechanisms are poorly understood. The use of antipsychotics and benzodiazepines against CIAPS is limited by side-effects and/or by their ability to tackle only certain aspects of psychosis. Thus, safer wide-spectrum treatments are currently needed. Although the blockade of cannabinoid type-1 receptor (CB1) had been suggested as a therapeutical means against CIAPS, the use of orthosteric CB1 receptor full antagonists is strongly limited by undesired side effects and low efficacy. The neurosteroid pregnenolone has been recently shown to act as a potent endogenous allosteric signal-specific inhibitor of CB1 receptors. Thus, we tested in mice the potential therapeutic use of pregnenolone against acute psychotic-like effects of Δ9-tetrahydrocannabinol (THC), the main psychoactive component of cannabis. We found that pregnenolone blocks a wide spectrum of THC-induced endophenotypes typically associated with psychotic-like states, including impairments in cognitive functions, somatosensory gating and social interaction. In order to capture THC-induced positive psychotic-like symptoms (e.g. perceptual delusions), we adapted a behavioral paradigm based on associations between different sensory modalities and selective devaluation, allowing the measurement of mental sensory representations in mice. Acting at hippocampal CB1 receptors, THC impaired the correct processing of mental sensory representations (reality testing) in an antipsychotic- and pregnenolone-sensitive manner. Overall, this work reveals that signal-specific inhibitors mimicking pregnenolone effects can be considered as promising new therapeutic tools to treat CIAPS. PMID:28220044

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.

Leptin Suppresses Mouse Taste Cell Responses to Sweet Compounds

PubMed Central

Noguchi, Kenshi; Shigemura, Noriatsu; Jyotaki, Masafumi; Takahashi, Ichiro; Margolskee, Robert F.

2015-01-01

Leptin is known to selectively suppress neural and behavioral responses to sweet-tasting compounds. However, the molecular basis for the effect of leptin on sweet taste is not known. Here, we report that leptin suppresses sweet taste via leptin receptors (Ob-Rb) and KATP channels expressed selectively in sweet-sensitive taste cells. Ob-Rb was more often expressed in taste cells that expressed T1R3 (a sweet receptor component) than in those that expressed glutamate-aspartate transporter (a marker for Type I taste cells) or GAD67 (a marker for Type III taste cells). Systemically administered leptin suppressed taste cell responses to sweet but not to bitter or sour compounds. This effect was blocked by a leptin antagonist and was absent in leptin receptor–deficient db/db mice and mice with diet-induced obesity. Blocking the KATP channel subunit sulfonylurea receptor 1, which was frequently coexpressed with Ob-Rb in T1R3-expressing taste cells, eliminated the effect of leptin on sweet taste. In contrast, activating the KATP channel with diazoxide mimicked the sweet-suppressing effect of leptin. These results indicate that leptin acts via Ob-Rb and KATP channels that are present in T1R3-expressing taste cells to selectively suppress their responses to sweet compounds. PMID:26116698

Interactions among GYKI-52466, cyclothiazide, and aniracetam at recombinant AMPA and kainate receptors.

PubMed

Johansen, T H; Chaudhary, A; Verdoorn, T A

1995-11-01

We examined the actions of cyclothiazide, aniracetam, and 1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine (GYKI-52466) on recombinant alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) and kainate receptors. Receptors expressed in Xenopus oocytes or human embryonic kidney 293 cells were characterized using voltage and patch-clamp electrophysiology. Aniracetam and cyclothiazide potentiated AMPA receptor currents by slowing or blocking desensitization. Cyclothiazide was more potent at receptors consisting of flip subunits compared with receptors consisting of flop subunits, whereas aniracetam appeared to be more efficacious at flop receptors. The potency of GYKI-52466 did not differ in heteromeric flip or flop containing AMPA receptors, but GYKI-52466 was less potent at homomeric GluRAi and GluRDi receptors. At heteromeric AMPA receptors, 50 microM cyclothiazide increased the IC50 value for GYKI-52466 significantly. The increase was largest in GluRBi/Di receptors where the IC50 value shifted from 21.9 microM (95% confidence interval, 12.0-39.8 microM) to 126 microM (95% confidence interval, 72.4-214 microM) in the presence of cyclothiazide. In contrast, 100 microM GYKI-52466 did not alter the EC50 of cyclothiazide at GluRBi/Di receptors nor did it markedly change the maximal potentiation induced by cyclothiazide. At GluRBi/Di receptors transiently expressed in human embryonic kidney 293 cells, 30 microM GYKI-52466 inhibited the steady state and the peak current evoked by 300 microns L-glutamate to the same extent (34.5 +/- 12% and 27.3 +/- 13.0%, respectively; five experiments), and GYKI-52466 did not alter the apparent rate of desensitization (tau = 15.7 +/- 4.7 and 17.5 +/- 8.3 msec in the absence and presence of GYKI-52466, respectively; five experiments). GYKI-52466 inhibited L-glutamate currents in the presence and absence of 10 microM cyclothiazide, but GYKI-52466 never restored the desensitization that was blocked by cyclothiazide. Furthermore, GYKI-52466 inhibited L-glutamate currents mediated by homomeric Glu6 receptors, which are not potentiated by cyclothiazide. Our data suggest that the effect of cyclothiazide on the affinity of GYKI-52466 for its binding site is allosteric and that the positive modulatory effect of cyclothiazide and the negative modulatory effect of GYKI-52466 result from binding to separate sites on recombinant subunits.

A Combination of Buprenorphine and Naltrexone Blocks Compulsive Cocaine Intake in Rodents Without Producing Dependence

PubMed Central

Wee, Sunmee; Vendruscolo, Leandro F.; Misra, Kaushik K.; Schlosburg, Joel E.; Koob, George F.

2012-01-01

Buprenorphine, a synthetic opioid that acts at both μ and κ opioid receptors, can decrease cocaine use in individuals with opioid addiction. However, the potent agonist action of buprenorphine at μ opioid receptors raises its potential for creating opioid dependence in non–opioid-dependent cocaine abusers. Here, we tested the hypothesis that a combination of buprenorphine and naltrexone (a potent μ opioid antagonist with weaker δ and κ antagonist properties) could block compulsive cocaine self-administration without producing opioid dependence. The effects of buprenorphine and various doses of naltrexone on cocaine self-administration were assessed in rats that self-administered cocaine under conditions of either short access (noncompulsive cocaine seeking) or extended access (compulsive cocaine seeking). Buprenorphine alone reproducibly decreased cocaine self-administration. Although this buprenorphine-alone effect was blocked in a dose-dependent manner by naltrexone in both the short-access and the extended-access groups, the combination of the lowest dose of naltrexone with buprenorphine blocked cocaine self-administration in the extended-access group but not in the short-access group. Rats given this low dose of naltrexone with buprenorphine did not exhibit the physical opioid withdrawal syndrome seen in rats treated with buprenorphine alone, and naltrexone at this dose did not block κ agonist–induced analgesia. The results suggest that the combination of buprenorphine and naltrexone at an appropriate dosage decreases compulsive cocaine self-administration with minimal liability to produce opioid dependence and may be useful as a treatment for cocaine addiction. PMID:22875830

A combination of buprenorphine and naltrexone blocks compulsive cocaine intake in rodents without producing dependence.

PubMed

Wee, Sunmee; Vendruscolo, Leandro F; Misra, Kaushik K; Schlosburg, Joel E; Koob, George F

2012-08-08

Buprenorphine, a synthetic opioid that acts at both μ and κ opioid receptors, can decrease cocaine use in individuals with opioid addiction. However, the potent agonist action of buprenorphine at μ opioid receptors raises its potential for creating opioid dependence in non-opioid-dependent cocaine abusers. Here, we tested the hypothesis that a combination of buprenorphine and naltrexone (a potent μ opioid antagonist with weaker δ and κ antagonist properties) could block compulsive cocaine self-administration without producing opioid dependence. The effects of buprenorphine and various doses of naltrexone on cocaine self-administration were assessed in rats that self-administered cocaine under conditions of either short access (noncompulsive cocaine seeking) or extended access (compulsive cocaine seeking). Buprenorphine alone reproducibly decreased cocaine self-administration. Although this buprenorphine-alone effect was blocked in a dose-dependent manner by naltrexone in both the short-access and the extended-access groups, the combination of the lowest dose of naltrexone with buprenorphine blocked cocaine self-administration in the extended-access group but not in the short-access group. Rats given this low dose of naltrexone with buprenorphine did not exhibit the physical opioid withdrawal syndrome seen in rats treated with buprenorphine alone, and naltrexone at this dose did not block κ agonist-induced analgesia. The results suggest that the combination of buprenorphine and naltrexone at an appropriate dosage decreases compulsive cocaine self-administration with minimal liability to produce opioid dependence and may be useful as a treatment for cocaine addiction.

Aortic remodeling after transverse aortic constriction in mice is attenuated with AT1 receptor blockade.

PubMed

Kuang, Shao-Qing; Geng, Liang; Prakash, Siddharth K; Cao, Jiu-Mei; Guo, Steven; Villamizar, Carlos; Kwartler, Callie S; Peters, Andrew M; Brasier, Allan R; Milewicz, Dianna M

2013-09-01

Although hypertension is the most common risk factor for thoracic aortic diseases, it is not understood how increased pressures on the ascending aorta lead to aortic aneurysms. We investigated the role of angiotensin II type 1 receptor activation in ascending aortic remodeling in response to increased biomechanical forces using a transverse aortic constriction (TAC) mouse model. Two weeks after TAC, the increased biomechanical pressures led to ascending aortic dilatation and thickening of the medial and adventitial layers of the aorta. There was significant adventitial hyperplasia and inflammatory responses in TAC ascending aortas were accompanied by increased adventitial collagen, elevated inflammatory and proliferative markers, and increased cell density attributable to accumulation of myofibroblasts and macrophages. Treatment with losartan significantly blocked TAC-induced vascular inflammation and macrophage accumulation. However, losartan only partially prevented TAC-induced adventitial hyperplasia, collagen accumulation, and ascending aortic dilatation. Increased Tgfb2 expression and phosphorylated-Smad2 staining in the medial layer of TAC ascending aortas were effectively blocked with losartan. In contrast, the increased Tgfb1 expression and adventitial phospho-Smad2 staining were only partially attenuated by losartan. In addition, losartan significantly blocked extracellular signal-regulated kinase activation and reactive oxygen species production in the TAC ascending aorta. Inhibition of the angiotensin II type 1 receptor using losartan significantly attenuated the vascular remodeling associated with TAC but did not completely block the increased transforming growth factor-β1 expression, adventitial Smad2 signaling, and collagen accumulation. These results help to delineate the aortic transforming growth factor-β signaling that is dependent and independent of the angiotensin II type 1 receptor after TAC.

Stimulation of ANP secretion by 2-Cl-IB-MECA through A(3) receptor and CaMKII.

PubMed

Yuan, Kuichang; Bai, Guang Yi; Park, Woo Hyun; Kim, Sung Zoo; Kim, Suhn Hee

2008-12-01

Adenosine is a potent mediator of myocardial protection against hypertrophy via A(1) or A(3) receptors that may be partly related to atrial natriuretic peptide (ANP) release. However, little is known about the possible involvement of the A(3) receptor on ANP release. We studied the effects of the A(3) receptor on atrial functions and its modification in hypertrophied atria. A selective A(3) receptor agonist, 2-chloro-N(6)-(3-iodobenzyl) adenosine-5'-N-methyluronamide (2-CI-IB-MECA), was perfused into isolated, beating rat atria with and without receptor modifiers. 2-CI-IB-MECA dose-dependently increased the ANP secretion, which was blocked by the A(3) receptor antagonist, but the increased atrial contractility and decreased cAMP levels induced by 30muM 2-CI-IB-MECA were not affected. The 100muM 2-(1-hexylnyl)-N-methyladenosine (HEMADO) and N(6)-(3-iodobenzyl) adenosine-5'-N-methyluronamide (IB-MECA), A(3) receptor agonist, also stimulated the ANP secretion without positive inotropy. The potency for the stimulation of ANP secretion was 2-CI-IB-MECA>IB-MECA=HEMADO. The inhibition of the ryanodine receptor or calcium/calmodulin-dependent kinase II (CaMKII) attenuated 2-CI-IB-MECA-induced ANP release, positive inotropy, and translocation of extracellular fluid. However, the inhibition of L-type Ca(2+) channels, sarcoplasmic reticulum Ca(2+)-reuptake, phospholipase C or inositol 1,4,5-triphosphate receptors did not affect these parameters. 2-CI-IB-MECA decreased cAMP level, which was blocked only with an inhibitor of CaMKII or adenylyl cyclase. These results suggest that 2-CI-IB-MECA increases the ANP secretion mainly via A(3) receptor activation and positive inotropy by intracellular Ca(2+) regulation via the ryanodine receptor and CaMKII.

A peptide targeting an interaction interface disrupts the dopamine D1-D2 receptor heteromer to block signaling and function in vitro and in vivo: effective selective antagonism

PubMed Central

Hasbi, Ahmed; Perreault, Melissa L.; Shen, Maurice Y. F.; Zhang, Lucia; To, Ryan; Fan, Theresa; Nguyen, Tuan; Ji, Xiaodong; O'Dowd, Brian F.; George, Susan R.

2014-01-01

Although the dopamine D1-D2 receptor heteromer has emerging physiological relevance and a postulated role in different neuropsychiatric disorders, such as drug addiction, depression, and schizophrenia, there is a need for pharmacological tools that selectively target such receptor complexes in order to analyze their biological and pathophysiological functions. Since no selective antagonists for the D1-D2 heteromer are available, serial deletions and point mutations were used to precisely identify the amino acids involved in an interaction interface between the receptors, residing within the carboxyl tail of the D1 receptor that interacted with the D2 receptor to form the D1-D2 receptor heteromer. It was determined that D1 receptor carboxyl tail residues 404Glu and 405Glu were critical in mediating the interaction with the D2 receptor. Isolated mutation of these residues in the D1 receptor resulted in the loss of agonist activation of the calcium signaling pathway mediated through the D1-D2 receptor heteromer. The physical interaction between the D1 and D2 receptor could be disrupted, as shown by coimmunoprecipitation and BRET analysis, by a small peptide generated from the D1 receptor sequence that contained these amino acids, leading to a switch in G-protein affinities and loss of calcium signaling, resulting in the inhibition of D1-D2 heteromer function. The use of the D1-D2 heteromer-disrupting peptide in vivo revealed a pathophysiological role for the D1-D2 heteromer in the modulation of behavioral despair. This peptide may represent a novel pharmacological tool with potential therapeutic benefits in depression treatment.—Hasbi, A., Perreault, M. L., Shen, M. Y. F., Zhang, L., To, R., Fan, T., Nguyen, T., Ji, X., O'Dowd, B. F., George, S. R. A peptide targeting an interaction interface disrupts the dopamine D1-D2 receptor heteromer to block signaling and function in vitro and in vivo: effective selective antagonism. PMID:25063849

Effects of receptor-selective neurokinin agonists and a neurokinin antagonist on the electrical activity of spinal cord neurones in culture.

PubMed

Wienrich, M; Reuss, K; Harting, J

1989-11-01

1. Rat spinal cord neurones grown in tissue culture were used to examine the electrophysiological effects of the neurokin in (NK)-selective agonists (pGlu6, Pro9) substance P(6-11) (septide; NK1, 10(-6)M) and (pGlu5, MePhe8, MeGly9)SP(1-7) (DiMe-C7; NK3, 10(-6)M). In addition, the effect of the neurokinin antagonist (D-Arg1, D-Pro2, D-Trp7,9, Leu11)SP (10(-5)M) on the neurokinin-evoked responses was investigated. 2. Neurokinin-evoked responses consisted of an increase in neuronal activity with or without long-lasting (mean: 50s) depolarizations of the membrane potential of up to 25mV. The latter also occurred in the presence of tetrodotoxin (10(-7)M) (direct response). 3. In a number of spinal cord neurones (n = 17) only septide induced a membrane depolarization while DiMe-C7 elicited no response. On the other hand, in 2 neurones a response was exclusively evoked by DiMe-C7. 4. The neurokinin antagonist (D-Arg1, D-Pro2, D-Trp7,9, Leu11)SP had no effect of its own but blocked the septide- and DiMe-C7-induced depolarizations. It had no effect on the glutamate (10(-5)M)-evoked depolarization. 5. It is concluded that by the use of neurokinin receptor-selective agonists, subpopulations of spinal cord neurones in primary dissociated cell culture can be differentiated which express the NK1 or the NK3 receptor. Cells expressing only the NK1 receptor outnumber those expressing only the NK3 receptor subtype. Both receptors can be blocked by the neurokinin antagonist (D-Arg1, D-Pro2, D-Trp7,9, Leu11)SP.

Regulation and signaling of human bombesin receptors and their biological effects.

PubMed

Weber, H Christian

2009-02-01

This review will highlight recent advances in the understanding of molecular mechanisms by which mammalian bombesin receptors are regulated and which intracellular signaling pathways have been characterized to mediate agonist-dependent receptor biological effects. Mammalian bombesin receptors have been demonstrated to be involved in a larger array of physiological and pathophysiological conditions than previously reported. Pharmacological experiments in vitro and in vivo as well as utilization of animals genetically deficient of the gastrin-releasing peptide receptor demonstrated roles in memory and fear behavior, lung development and injury, small intestinal cell repair, autocrine tumor growth, and mediating signals for pruritus and penile reflexes. Intracellular signaling studies predominantly of the gastrin-releasing peptide receptor owing to its frequent overexpression in some human malignancies showed that PI3 kinase activation is an important mechanism of cell proliferation. Tumor cell treatment including gastrin-releasing peptide receptor antagonists combined with inhibition of epidermal growth factor receptor resulted in an additive effect on blocking cell proliferation. Novel molecular mechanisms of the orphan bombesin receptor subtype-3 and gastrin-releasing peptide receptor gene regulation have been elucidated. Inhibition of gastrin-releasing peptide receptor signaling in human malignancies represents an attractive target for pharmacological treatment. Novel functions of bombesin related peptides have been identified including processes in the central nervous system, lung and intestinal tract.

Effects of the selective EP4 antagonist, CJ-023,423 on chronic inflammation and bone destruction in rat adjuvant-induced arthritis.

PubMed

Okumura, Takako; Murata, Yoko; Taniguchi, Kana; Murase, Akio; Nii, Aisuke

2008-06-01

Prostaglandin E2 (PGE2) produced by cyclooxygenase (COX) is a potent pro-inflammatory mediator. We have recently discovered CJ-023,423, a highly selective antagonist of EP4 receptors, one of the PGE2 receptors. This agent is suitable for exploring the effects of blocking EP4 receptors following oral administration in rats. In this study, CJ-023,423 was used in rats with adjuvant-induced arthritis (AIA) to investigate the role of the EP4 receptor in chronic inflammation and bone destruction. These effects were compared with those of rofecoxib, a selective COX-2 inhibitor. CJ-023,423 had significant inhibitory effects on paw swelling, inflammatory biomarkers, synovial inflammation and bone destruction in AIA rats. In particular, the inhibitory effect on paw swelling in AIA rats was comparable to that of rofecoxib. These results suggest that PGE2 acting via the EP4 receptor is involved in the development of chronic inflammation and bone destruction, particularly with respect to oedema in AIA rats. This is the first study to confirm the in-vivo effects of EP4 receptor blockade on inflammation and bone destruction in AIA rats with a small-molecule compound.

Assessment of dopamine receptor blockade by neuroleptic drugs in the living human brain

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

Wong, D.F.; Wagner, H.N. Jr.; Coyle, J.

1985-05-01

Positron emission tomography (PET) makes it possible to attempt to relate directly the antipsychotic effect of neuroleptic drugs and their blocking effect on dopamine receptors (D2) in vivo. The authors have examined the ability of haloperidol (HAL) and molindone (MOL) to block the binding of C-11 n-methylspiperone (NMSP) in 6 normal subjects. A dose of 0.05 mg/kg of HAL resulted in a 68% drop in the slope of the caudate/cerebellum (Ca/Cb) vs. time. This slope is related to the rate of specific binding of NMSP to the receptor. A dose response was seen with both drugs. With increasing doses ofmore » HAL from .05 to 0.082 mg/kg, CA/Cb vs. time slope fell from .235 to .156/min. (N=4), progressively. Similarly with increasing doses of MOL of .16-.44 mg/kg slopes decreased from .0335 to .0155/min. (N=4). Similar degrees of post injection Ca/Cb ratio were produced with quantities of MOL and HAL administered in the oral dose ratio of doses 3-5:1 times greater than HAL. This is also the dose ratio at which we found similar dopamine receptor blockade by PET in vivo. A question that arises is why the in vitro affinity of HAL for D2 is 30 times greater than that of MOL in the human brain. The results raise the possibility that MOL metabolites are not only active in blocking D2 but indeed may possibly be more potent than MOL itself. It also helps confirm the site of action of MOL and its in vivo metabolites.« less

Effects of NMDA receptor antagonists on probability discounting depend on the order of probability presentation.

PubMed

Yates, Justin R; Breitenstein, Kerry A; Gunkel, Benjamin T; Hughes, Mallory N; Johnson, Anthony B; Rogers, Katherine K; Shape, Sara M

Risky decision making can be measured using a probability-discounting procedure, in which animals choose between a small, certain reinforcer and a large, uncertain reinforcer. Recent evidence has identified glutamate as a mediator of risky decision making, as blocking the N-methyl-d-aspartate (NMDA) receptor with MK-801 increases preference for a large, uncertain reinforcer. Because the order in which probabilities associated with the large reinforcer can modulate the effects of drugs on choice, the current study determined if NMDA receptor ligands alter probability discounting using ascending and descending schedules. Sixteen rats were trained in a probability-discounting procedure in which the odds against obtaining the large reinforcer increased (n=8) or decreased (n=8) across blocks of trials. Following behavioral training, rats received treatments of the NMDA receptor ligands MK-801 (uncompetitive antagonist; 0, 0.003, 0.01, or 0.03mg/kg), ketamine (uncompetitive antagonist; 0, 1.0, 5.0, or 10.0mg/kg), and ifenprodil (NR2B-selective non-competitive antagonist; 0, 1.0, 3.0, or 10.0mg/kg). Results showed discounting was steeper (indicating increased risk aversion) for rats on an ascending schedule relative to rats on the descending schedule. Furthermore, the effects of MK-801, ketamine, and ifenprodil on discounting were dependent on the schedule used. Specifically, the highest dose of each drug decreased risk taking in rats in the descending schedule, but only MK-801 (0.03mg/kg) increased risk taking in rats on an ascending schedule. These results show that probability presentation order modulates the effects of NMDA receptor ligands on risky decision making. Copyright © 2016 Elsevier Inc. All rights reserved.

The different roles of opioid receptors in the inhibitory effects induced by sacral dorsal root ganglion stimulation on nociceptive and nonnociceptive conditions in cats.

PubMed

Wang, Zhaoxia; Liao, Limin; Deng, Han; Li, Xing; Chen, Guoqing; Liao, Xiwen

2018-06-04

To examine the roles of opioid receptors in the inhibition of nociceptive and nonnociceptive bladder reflexes by sacral dorsal root ganglion (DRG) stimulation in cats. Hook electrodes were placed in the right S1 and S2 DRG of cats. The bladders were infused with physiologic saline or 0.25% acetic acid (AA). Naloxone (0.1, 0.3, and 1 mg/kg), an opioid receptor antagonist, was administered intravenously. S1 or S2 DRG stimulation was applied before and after administering the drug. Multiple cystometrograms were performed to determine the effects of DRG stimulation and opioid receptors on the micturition reflex under nociceptive and non-nociceptive conditions. AA significantly (P < 0.01) reduced bladder capacity (BC). DRG stimulation at threshold (T) and 1.5 T significantly increased BC of the saline control under nociceptive and non-nociceptive conditions. When saline was infused, naloxone (0.1-1 mg/kg) significantly (P < 0.01) reduced BC; however, naloxone did not change BC during AA irritation. During saline infusion, naloxone (0.3 and 1 mg/kg) partly blocked S1 DRG stimulation-induced inhibition but had only a slight effect on S2 DRG stimulation. During AA infusion, naloxone (0.3 and 1 mg/kg) only partially blocked S1 DRG stimulation at T intensity but not during 1.5 T stimulation. However, no doses of naloxone significantly affected S2 DRG stimulation. Opioid receptors play a role in sacral DRG stimulation on non-nociceptive condition but are not involved in the inhibitory effect of stimulation in nociceptive conditions. © 2018 Wiley Periodicals, Inc.

A Role for Sigma Receptors in Stimulant Self Administration and Addiction

PubMed Central

Katz, Jonathan L.; Su, Tsung-Ping; Hiranita, Takato; Hayashi, Teruo; Tanda, Gianluigi; Kopajtic, Theresa; Tsai, Shang-Yi

2011-01-01

Sigma1 receptors (σ1Rs) represent a structurally unique class of intracellular proteins that function as chaperones. σ1Rs translocate from the mitochondria-associated membrane to the cell nucleus or cell membrane, and through protein-protein interactions influence several targets, including ion channels, G-protein-coupled receptors, lipids, and other signaling proteins. Several studies have demonstrated that σR antagonists block stimulant-induced behavioral effects, including ambulatory activity, sensitization, and acute toxicities. Curiously, the effects of stimulants have been blocked by σR antagonists tested under place-conditioning but not self-administration procedures, indicating fundamental differences in the mechanisms underlying these two effects. The self administration of σR agonists has been found in subjects previously trained to self administer cocaine. The reinforcing effects of the σR agonists were blocked by σR antagonists. Additionally, σR agonists were found to increase dopamine concentrations in the nucleus accumbens shell, a brain region considered important for the reinforcing effects of abused drugs. Although the effects of the σR agonist, DTG, on dopamine were obtained at doses that approximated those that maintained self administration behavior those of another agonist, PRE-084 required higher doses. The effects of DTG were antagonized by non-selective or a preferential σ2R antagonist but not by a preferential σ1R antagonist. The effects of PRE-084 on dopamine were insensitive to σR antagonists. The data suggest that the self administration of σR agonists is independent of dopamine and the findings are discussed in light of a hypothesis that cocaine has both intracellular actions mediated by σRs, as well as extracellular actions mediated through conventionally studied mechanisms. The co-activation and potential interactions among these mechanisms, in particular those involving the intracellular chaperone σRs, may lead to the pernicious addictive effects of stimulant drugs. PMID:21904468

A Role for Sigma Receptors in Stimulant Self Administration and Addiction.

PubMed

Katz, Jonathan L; Su, Tsung-Ping; Hiranita, Takato; Hayashi, Teruo; Tanda, Gianluigi; Kopajtic, Theresa; Tsai, Shang-Yi

2011-01-01

Sigma(1) receptors (σ(1)Rs) represent a structurally unique class of intracellular proteins that function as chaperones. σ(1)Rs translocate from the mitochondria-associated membrane to the cell nucleus or cell membrane, and through protein-protein interactions influence several targets, including ion channels, G-protein-coupled receptors, lipids, and other signaling proteins. Several studies have demonstrated that σR antagonists block stimulant-induced behavioral effects, including ambulatory activity, sensitization, and acute toxicities. Curiously, the effects of stimulants have been blocked by σR antagonists tested under place-conditioning but not self-administration procedures, indicating fundamental differences in the mechanisms underlying these two effects. The self administration of σR agonists has been found in subjects previously trained to self administer cocaine. The reinforcing effects of the σR agonists were blocked by σR antagonists. Additionally, σR agonists were found to increase dopamine concentrations in the nucleus accumbens shell, a brain region considered important for the reinforcing effects of abused drugs. Although the effects of the σR agonist, DTG, on dopamine were obtained at doses that approximated those that maintained self administration behavior those of another agonist, PRE-084 required higher doses. The effects of DTG were antagonized by non-selective or a preferential σ(2)R antagonist but not by a preferential σ(1)R antagonist. The effects of PRE-084 on dopamine were insensitive to σR antagonists. The data suggest that the self administration of σR agonists is independent of dopamine and the findings are discussed in light of a hypothesis that cocaine has both intracellular actions mediated by σRs, as well as extracellular actions mediated through conventionally studied mechanisms. The co-activation and potential interactions among these mechanisms, in particular those involving the intracellular chaperone σRs, may lead to the pernicious addictive effects of stimulant drugs.

Neurotransmitter-mediated anxiogenic action of PACAP-38 in rats.

PubMed

Telegdy, G; Adamik, A

2015-03-15

The action of PACAP-38 was studied by measuring the anxiogenic-anxiolytic behavior of rats in an elevated plus maze. PACAP-38 was administered into the lateral brain ventricle and the behavior of the animals was measured 3h later. The possible involvement of transmitters was measured by pretreating the animals with receptor blockers which alone did not influence the task, but in the doses used were effective with other neuropeptides. The receptor antagonist PACAP 6-38 (a PAC 1/VPAC2 receptor antagonist of PACAP-38 receptor), haloperidol (a non-selective dopamine receptor antagonist), phenoxybenzamine (an α1/α2β-adrenergic receptor antagonist), propranolol(a β-adrenergic receptor antagonist), bicuculline (a gamma-aminobutyric acid subunit A receptor antagonist), methysergide (a nonselective 5-HT2 serotonergic receptor antagonist), atropine (a nonselective muscarinic acetylcholine receptor antagonist), naloxone (a nonselective opioid receptor antagonist) and nitro-l-arginine which acts by blocking the enzyme nitric oxide synthase, thereby blocking the nitric oxide synthesis, were tested. The following parameters were measured: the time spent in open arms/the time spent in total entries. PACAP-38 decreased the ratio of time spent in open arms to the time spent in total entries, indicating anxiogenic action. The total number of entries was not altered significantly either by PACAP-38 or by the receptor blockers. The following receptor blockers diminished the action of PACAP-38: PACAP 6-38,haloperidol, methysergide, naloxone and nitro-l-arginine. Pretreatment with atropine, phenoxybenzamine, propranolol and bicuculline did not influence the action of PACAP-38 on the time spent in open arms. The results demonstrate that PACAP-38 administered into the lateral brain ventricle exerted anxiogenic action at 3 h following treatment. Pretreatment of the animals with various receptor blockers indicated that a nonselective dopaminergic receptor antagonist, 5HT2 serotonergic and opioid receptors, nitric oxide and PAC1 receptors are involved in the anxiogenic action induced by PACAP-38. Copyright © 2014 Elsevier B.V. All rights reserved.

ENHANCED 5-HT1A RECEPTOR-DEPENDENT FEEDBACK CONTROL OVER DORSAL RAPHE SEROTONIN NEURONS IN THE SERT KNOCKOUT MOUSE

PubMed Central

Soiza-Reilly, Mariano; Goodfellow, Nathalie M.; Lambe, Evelyn K.; Commons, Kathryn G.

2014-01-01

5-HT1A receptors are widely expressed in the brain and play a critical role in feedback inhibition of serotonin (5-HT) neurons through multiple mechanisms. Yet, it remains poorly understood how these feedback mechanisms, particularly those involving long-range projections, adapt in mood disorders. Here, we examined several aspects of 5-HT1A receptor function in the 5-HT transporter knockout mouse (SERT-KO), a model of vulnerability to stress and mood disorders. We found that in comparison to wild-type (WT) mice, SERT-KO mice had more passive coping in response to acute swim stress and this was accompanied by hypo-activation of medial prefrontal cortex (mPFC) Fos expression. Both of these effects were reversed by systemically blocking 5-HT1A receptors. Ex-vivo electrophysiological experiments showed that 5-HT exerted greater 5-HT1A-mediated inhibitory effects in the mPFC of SERT-KO mice compared to WT. Since 5-HT1A receptors in the mPFC provide a key feedback regulation of the dorsal raphe nucleus (DRN), we used a disinhibition strategy to examined endogenous feedback control of 5-HT neurons. Blocking 5-HT1A receptors disinhibited several fold more 5-HT neurons in the DRN of SERT-KO than in WT mice, revealing the presence of enhanced feedback inhibition of 5-HT neurons in the SERT-KO. Taken together our results indicate that increased stress sensitivity in the SERT-KO is associated with the enhanced capacity of 5-HT1A receptors to inhibit neurons in the mPFC as well as to exert feedback inhibition of DRN 5-HT neurons. PMID:25261781

Vasopressin up-regulates the expression of growth-related immediate-early genes via two distinct EGF receptor transactivation pathways

PubMed Central

Fuentes, Lida Q.; Reyes, Carlos E.; Sarmiento, José M.; Villanueva, Carolina I.; Figueroa, Carlos D.; Navarro, Javier; González, Carlos B.

2008-01-01

Activation of V1a receptor triggers the expression of growth-related immediate-early genes (IEGs), including c-Fos and Egr-1. Here we found that pre-treatment of rat vascular smooth muscle A-10 cell line with the EGF receptor inhibitor AG1478 or the over-expression of an EGFR dominant negative mutant (HEBCD533) blocked the vasopressin-induced expression of IEGs, suggesting that activation of these early genes mediated by V1a receptor is via transactivation of the EGF receptor. Importantly, the inhibition of the metalloproteinases, which catalyzed the shedding of the EGF receptor agonist HB-EGF, selectively blocked the vasopressin-induced expression c-Fos. On the other hand, the inhibition of c-Src selectively blocked the vasopressin-induced expression of Egr-1. Interestingly, in contrast to the expression of c-Fos, the expression of Egr-1 was mediated via the Ras/MEK/MAPK-dependent signalling pathway. Vasopressin-triggered expression of both genes required the release of intracellular calcium, activation of PKC and β-arrestin 2. These findings demonstrated that vasopressin up-regulated the expression of c-Fos and Erg-1 via transactivation of two distinct EGF receptor-dependent signalling pathways. PMID:18571897

Phospholipase C mediates (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI)-, but not lysergic acid diethylamide (LSD)-elicited head bobs in rabbit medial prefrontal cortex.

PubMed

Schindler, Emmanuelle A D; Harvey, John A; Aloyo, Vincent J

2013-01-23

The phenethylamine and indoleamine classes of hallucinogens demonstrate distinct pharmacological properties, although they share a serotonin(2A) (5-HT(2A)) receptor mechanism of action (MOA). The 5-HT(2A) receptor signals through phosphatidylinositol (PI) hydrolysis, which is initiated upon activation of phospholipase C (PLC). The role of PI hydrolysis in the effects of hallucinogens remains unclear. In order to better understand the role of PI hydrolysis in the MOA of hallucinogens, the PLC inhibitor, 1-[6-((17β-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl]-1H-pyrrole-2,5-dione (U73122), was used to study the effects of two hallucinogens, the phenethylamine, (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI), and the indoleamine, lysergic acid diethylamide (LSD). PI hydrolysis was quantified through release of [3H]inositol-4-phosphate from living rabbit frontocortical tissue prisms. Head bobs were counted after hallucinogens were infused into the medial prefrontal cortex (mPFC) of rabbits. Both DOI and LSD stimulated PI hydrolysis in frontocortical tissue through activation of PLC. DOI-stimulated PI hydrolysis was blocked by 5-HT(2A/2C) receptor antagonist, ketanserin, whereas the LSD signal was blocked by 5-HT(2B/2C) receptor antagonist, SB206553. When infused into the mPFC, both DOI- and LSD-elicited head bobs. Pretreatment with U73122 blocked DOI-, but not LSD-elicited head bobs. The two hallucinogens investigated were distinct in their activation of the PI hydrolysis signaling pathway. The serotonergic receptors involved with DOI and LSD signals in frontocortical tissue were different. Furthermore, PLC activation in mPFC was necessary for DOI-elicited head bobs, whereas LSD-elicited head bobs were independent of this pathway. These novel findings urge closer investigation into the intracellular mechanism of action of these unique compounds. Published by Elsevier B.V.

Block of Brain Sodium Channels by Peptide Mimetics of the Isoleucine, Phenylalanine, and Methionine (IFM) Motif from the Inactivation Gate

PubMed Central

Eaholtz, Galen; Colvin, Anita; Leonard, Daniele; Taylor, Charles; Catterall, William A.

1999-01-01

Inactivation of sodium channels is thought to be mediated by an inactivation gate formed by the intracellular loop connecting domains III and IV. A hydrophobic motif containing the amino acid sequence isoleucine, phenylalanine, and methionine (IFM) is required for the inactivation process. Peptides containing the IFM motif, when applied to the cytoplasmic side of these channels, produce two types of block: fast block, which resembles the inactivation process, and slow, use-dependent block stimulated by strong depolarizing pulses. Fast block by the peptide ac-KIFMK-NH2, measured on sodium channels whose inactivation was slowed by the α-scorpion toxin from Leiurus quinquestriatus (LqTx), was reversed with a time constant of 0.9 ms upon repolarization. In contrast, control and LqTx-modified sodium channels were slower to recover from use-dependent block. For fast block, linear peptides of three to six amino acid residues containing the IFM motif and two positive charges were more effective than peptides with one positive charge, whereas uncharged IFM peptides were ineffective. Substitution of the IFM residues in the peptide ac-KIFMK-NH2 with smaller, less hydrophobic residues prevented fast block. The positively charged tripeptide IFM-NH2 did not cause appreciable fast block, but the divalent cation IFM-NH(CH2)2NH2 was as effective as the pentapeptide ac-KIFMK-NH2. The constrained peptide cyclic KIFMK containing two positive charges did not cause fast block. These results indicate that the position of the positive charges is unimportant, but flexibility or conformation of the IFM-containing peptide is important to allow fast block. Slow, use-dependent block was observed with IFM-containing peptides of three to six residues having one or two positive charges, but not with dipeptides or phenylalanine-amide. In contrast to its lack of fast block, cyclic KIFMK was an effective use-dependent blocker. Substitutions of amino acid residues in the tripeptide IFM-NH2 showed that large hydrophobic residues are preferred in all three positions for slow, use-dependent block. However, substitution of the large hydrophobic residue diphenylalanine or the constrained residues phenylglycine or tetrahydroisoquinoline for phe decreased potency, suggesting that this phe residue must be able to enter a restricted hydrophobic pocket during the binding of IFM peptides. Together, the results on fast block and slow, use-dependent block indicate that IFM peptides form two distinct complexes of different stability and structural specificity with receptor site(s) on the sodium channel. It is proposed that fast block represents binding of these peptides to the inactivation gate receptor, while slow, use-dependent block represents deeper binding of the IFM peptides in the pore. PMID:9925825

Subcutaneous, intrathecal and periaqueductal grey administration of asimadoline and ICI-204448 reduces tactile allodynia in the rat.

PubMed

Caram-Salas, Nadia L; Reyes-García, Gerardo; Bartoszyk, Gerd D; Araiza-Saldaña, Claudia I; Ambriz-Tututi, Mónica; Rocha-González, Héctor I; Arreola-Espino, Rosaura; Cruz, Silvia L; Granados-Soto, Vinicio

2007-11-14

The purpose of this study was to assess the possible antiallodynic effect of asimadoline ([N-methyl-N-[1S)-1-phenyl)-2-(13S))-3-hydroxypyrrolidine-1-yl)-ethyl]-2,2-diphenylacetamide HCl]) and ICI-20448 ([2-[3-(1-(3,4-Dichlorophenyl-N-methylacetamido)-2-pyrrolidinoethyl)-phenoxy]acetic acid HCl]), two peripheral selective kappa opioid receptor agonists, after subcutaneous, spinal and periaqueductal grey administration to neuropathic rats. Twelve days after spinal nerve ligation tactile allodynia was observed, along with an increase in kappa opioid receptor mRNA expression in dorsal root ganglion and dorsal horn spinal cord. A non-significant increase in periaqueductal grey was also seen. Subcutaneous (s.c.) administration of asimadoline and ICI-204448 (1-30 mg/kg) dose-dependently reduced tactile allodynia. This effect was partially blocked by s.c., but not intrathecal, naloxone. Moreover, intrathecal administration of asimadoline or ICI-204448 (1-30 mug) reduced tactile allodynia in a dose-dependent manner and this effect was completely blocked by intrathecal naloxone. Microinjection of both kappa opioid receptor agonists (3-30 mug) into periaqueductal grey also produced a naloxone-sensitive antiallodynic effect in rats. Our results indicate that systemic, intrathecal and periaqueductal grey administration of asimadoline and ICI-204448 reduces tactile allodynia. This effect may be a consequence of an increase in kappa opioid receptor mRNA expression in dorsal root ganglion, dorsal horn spinal cord and, to some extent, in periaqueductal grey. Finally, our data suggest that these drugs could be useful to treat neuropathic pain in human beings.

Interacting Cannabinoid and Opioid Receptors in the Nucleus Accumbens Core Control Adolescent Social Play

PubMed Central

Manduca, Antonia; Lassalle, Olivier; Sepers, Marja; Campolongo, Patrizia; Cuomo, Vincenzo; Marsicano, Giovanni; Kieffer, Brigitte; Vanderschuren, Louk J. M. J; Trezza, Viviana; Manzoni, Olivier J. J.

2016-01-01

Social play behavior is a highly rewarding, developmentally important form of social interaction in young mammals. However, its neurobiological underpinnings remain incompletely understood. Previous work has suggested that opioid and endocannabinoid neurotransmission interact in the modulation of social play. Therefore, we combined behavioral, pharmacological, electrophysiological, and genetic approaches to elucidate the role of the endocannabinoid 2-arachidonoylglycerol (2-AG) in social play, and how cannabinoid and opioid neurotransmission interact to control social behavior in adolescent rodents. Systemic administration of the 2-AG hydrolysis inhibitor JZL184 or the opioid receptor agonist morphine increased social play behavior in adolescent rats. These effects were blocked by systemic pretreatment with either CB1 cannabinoid receptor (CB1R) or mu-opioid receptor (MOR) antagonists. The social play-enhancing effects of systemic morphine or JZL184 treatment were also prevented by direct infusion of the CB1R antagonist SR141716 and the MOR antagonist naloxone into the nucleus accumbens core (NAcC). Searching for synaptic correlates of these effects in adolescent NAcC excitatory synapses, we observed that CB1R antagonism blocked the effect of the MOR agonist DAMGO and, conversely, that naloxone reduced the effect of a cannabinoid agonist. These results were recapitulated in mice, and completely abolished in CB1R and MOR knockout mice, suggesting that the functional interaction between CB1R and MOR in the NAcC in the modulation of social behavior is widespread in rodents. The data shed new light on the mechanism by which endocannabinoid lipids and opioid peptides interact to orchestrate rodent socioemotional behaviors. PMID:27899885

75 FR 58401 - Government-Owned Inventions; Availability for Licensing

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-24

..., attention deficit hyperactivity disorder (ADHD), and schizophrenia. Development of selective pharmacological... Diagnosis of Psychiatric Disorders Description of Invention: Current drugs used to treat schizophrenia block dopamine receptors. These drugs can effectively suppress the ``positive'' symptoms of schizophrenia but...

An Antiprogestin, CDB4124, Blocks Progesterone’s Attenuation of the Negative Effects of a Mild Stress on Sexual Behavior

PubMed Central

Uphouse, Lynda; Hiegel, Cindy

2012-01-01

These experiments were designed to test the hypothesis that a progesterone receptor antagonist would block progesterone’s ability to reduce the negative effects of a 5 min restraint on female rat sexual behavior. Ovariectomized Fisher rats were injected with 10 μg estradiol benzoate. Two days later, rats were injected subcutaneously (sc) with the progesterone receptor antagonist, CDB4124 (17 α-acetoxy-21-methoxy-11β-[4-N,N-dimethyaminopheny]-19-norpregna-4,9-dione-3,20-dione) (60 mg/kg), or vehicle (20% DMSO + propylene glycol). One hr later, rats were injected sc with 500 μg progesterone or vehicle (sesame seed oil). Rats were assigned to one of three different treatment conditions: (1) (ECV) estradiol benzoate, CDB4124, sesame seed oil vehicle, (2) (ECP) estradiol benzoate, CDB4124, progesterone, and (3) (EVP) estradiol benzoate, DMSO/propylene glycol vehicle, progesterone. That afternoon sexual behavior was examined before and after a 5 min restraint experience. Before restraint, lordosis behavior was comparable across treatment conditions but only progesterone-treated rats exhibited proceptive behavior. CDB4124 did not block progesterone’s induction of proceptivity. However, after restraint, CDB4124 attenuated the positive effects of progesterone on all sexual behaviors examined. The restraint experience inhibited sexual behavior in rats treated with estradiol benzoate and CDB4124 and in rats treated with estradiol benzoate, CDB4124, and progesterone but not in rats given estradiol benzoate and progesterone without CDB4124. These findings are consistent with the hypothesis that progesterone receptors mediate progesterone’s ability to reduce the negative sexual behavioral effects of a mild stressor. PMID:23153933

An antiprogestin, CDB4124, blocks progesterone's attenuation of the negative effects of a mild stress on sexual behavior.

PubMed

Uphouse, Lynda; Hiegel, Cindy

2013-03-01

These experiments were designed to test the hypothesis that a progesterone receptor antagonist would block progesterone's ability to reduce the negative effects of a 5 min restraint on female rat sexual behavior. Ovariectomized Fischer rats were injected with 10 μg estradiol benzoate. Two days later, rats were injected subcutaneously (sc) with the progesterone receptor antagonist, CDB4124 (17α-acetoxy-21-methoxy-11β-[4-N,N-dimethyaminopheny]-19-norpregna-4,9-dione-3,20-dione) (60 mg/kg), or vehicle (20% DMSO+propylene glycol). One hour later, rats were injected sc with 500 μg progesterone or vehicle (sesame seed oil). Rats were assigned to one of three different treatment conditions: (1) (ECV) estradiol benzoate, CDB4124, sesame seed oil vehicle, (2) (ECP) estradiol benzoate, CDB4124, progesterone, and (3) (EVP) estradiol benzoate, DMSO/propylene glycol vehicle, progesterone. That afternoon sexual behavior was examined before and after a 5 min restraint experience. Before restraint, lordosis behavior was comparable across treatment conditions but only progesterone-treated rats exhibited proceptive behavior. CDB4124 did not block progesterone's induction of proceptivity. However, after restraint, CDB4124 attenuated the positive effects of progesterone on all sexual behaviors examined. The restraint experience inhibited sexual behavior in rats treated with estradiol benzoate and CDB4124 and in rats treated with estradiol benzoate, CDB4124, and progesterone but not in rats given estradiol benzoate and progesterone without CDB4124. These findings are consistent with the hypothesis that progesterone receptors mediate progesterone's ability to reduce the negative sexual behavioral effects of a mild stressor. Copyright © 2012 Elsevier B.V. All rights reserved.

A Novel Non-agonist Peroxisome Proliferator-activated Receptor γ (PPARγ) Ligand UHC1 Blocks PPARγ Phosphorylation by Cyclin-dependent Kinase 5 (CDK5) and Improves Insulin Sensitivity*

PubMed Central

Choi, Sun-Sil; Kim, Eun Sun; Koh, Minseob; Lee, Soo-Jin; Lim, Donghyun; Yang, Yong Ryoul; Jang, Hyun-Jun; Seo, Kyung-ah; Min, Sang-Hyun; Lee, In Hee; Park, Seung Bum; Suh, Pann-Ghill; Choi, Jang Hyun

2014-01-01

Thiazolidinedione class of anti-diabetic drugs which are known as peroxisome proliferator-activated receptor γ (PPARγ) ligands have been used to treat metabolic disorders, but thiazolidinediones can also cause several severe side effects, including congestive heart failure, fluid retention, and weight gain. In this study, we describe a novel synthetic PPARγ ligand UNIST HYUNDAI Compound 1 (UHC1) that binds tightly to PPARγ without the classical agonism and which blocks cyclin-dependent kinase 5 (CDK5)-mediated PPARγ phosphorylation. We modified the non-agonist PPARγ ligand SR1664 chemically to improve its solubility and then developed a novel PPARγ ligand, UHC1. According to our docking simulation, UHC1 occupied the ligand-binding site of PPARγ with a higher docking score than SR1664. In addition, UHC1 more potently blocked CDK5-mediated PPARγ phosphorylation at Ser-273. Surprisingly, UHC1 treatment effectively ameliorated the inflammatory response both in vitro and in high-fat diet-fed mice. Furthermore, UHC1 treatment dramatically improved insulin sensitivity in high-fat diet-fed mice without causing fluid retention and weight gain. Taken together, compared with SR1664, UHC1 exhibited greater beneficial effects on glucose and lipid metabolism by blocking CDK5-mediated PPARγ phosphorylation, and these data indicate that UHC1 could be a novel therapeutic agent for use in type 2 diabetes and related metabolic disorders. PMID:25100724

Block of calcium channels by enkephalin and somatostatin in neuroblastoma-glioma hybrid NG108-15 cells.

PubMed

Tsunoo, A; Yoshii, M; Narahashi, T

1986-12-01

Leucine-enkephalin, methionine-enkephalin, and morphine caused a reversible block of Ca2+ channel currents in neuroblastoma-glioma hybrid cells (NG108-15). The long-lasting (type 2) component of the Ca2+ channel current was blocked by leucine-enkephalin, while the transient (type 1) component was not affected. The enkephalin-induced blocking action was antagonized by naloxone and appears to be mediated by delta-opiate receptors. Two different aspects of the blocking effect were detected, a resting block and a recovery from block during prolonged depolarizing pulses. Recovery from block was more complete, and its time course was more rapid, with depolarization to more positive potentials. The dose dependence of the type 2 channel block at rest indicated a one-to-one binding stoichiometry, with an apparent dissociation constant of 8.8 nM. Somatostatin exerted a similar selective blocking action on the type 2 Ca2+ channel. The time- and voltage-dependent block of type 2 Ca2+ channels may provide a mechanism underlying the enkephalinergic presynaptic inhibition of transmitter release and the somatostatin block of pituitary growth hormone release.

Infusions of allopregnanolone into the hippocampus and amygdala, but not into the nucleus accumbens and medial prefrontal cortex, produce antidepressant effects on the learned helplessness rats.

PubMed

Shirayama, Yukihiko; Muneoka, Katsumasa; Fukumoto, Makoto; Tadokoro, Shigenori; Fukami, Goro; Hashimoto, Kenji; Iyo, Masaomi

2011-10-01

Patients with depression showed a decrease in plasma and cerebrospinal fluid allopregnanolone (ALLO). But antidepressants increased the contents of ALLO in the rat brain. We examined the antidepressant-like effects of infusion of ALLO into the cerebral ventricle, hippocampus, amygdala, nucleus accumbens, or prefrontal cortex of learned helplessness (LH) rats (an animal model of depression). Of these regions, infusions of ALLO into the cerebral ventricle, the CA3 region of hippocampus, or the central region of amygdala exerted antidepressant-like effects. Infusion of ALLO into the hippocampal CA3 region or the central amygdala did not produce memory deficits or locomotor activation in the passive avoidance and open field tests. It is well documented that ALLO exerts its effects through GABA receptors. Therefore, we examined the antagonistic effects of flumazenil (a GABA receptor antagonist) on the antidepressant-like effects of ALLO. Coinfusion of flumazenil with ALLO into the hippocampal CA3 region, but not into the central amygdala, blocked the antidepressant-like effects of ALLO. However, coinfusion of (+)MK801 (an NMDA receptor antagonist), but not cycloheximide (a protein synthesis inhibitor), blocked the antidepressant-like effects of ALLO in the central amygdala. These results suggest that ALLO exerts antidepressant-like effects in the CA3 region of hippocampus through the GABA system and in the central region of amygdala, dependently on the activation of the glutamatergic mechanisms. Copyright © 2010 Wiley-Liss, Inc.

alpha1B-Adrenergic receptor phosphorylation and desensitization induced by transforming growth factor-beta.

PubMed Central

Romero-Avila, M Teresa; Flores-Jasso, C Fabián; García-Sáinz, J Adolfo

2002-01-01

Transforming growth factor-beta (TGF-beta) induced alpha(1B)-adrenergic receptor phosphorylation in Rat-1 fibroblasts stably expressing these adrenoceptors. This effect of TGF-beta was rapid, reaching a maximum within 30 min and decreasing thereafter, and concentration-dependent (EC(50) 0.3 pM). The phosphoinositide 3-kinase inhibitors wortmannin and LY294002, and the protein kinase C inhibitors staurosporine, Ro 318220 and bisindolylmaleimide, blocked the effect of this growth factor. alpha(1B)-Adrenergic receptor phosphorylation was associated with desensitization, as indicated by a reduction in the adrenergic-mediated production of [(3)H]inositol phosphates. Phosphorylation of alpha(1B)-adrenergic receptors by TGF-beta was also observed in Cos-1 cells transfected with the receptor. Co-transfection of the dominant-negative mutant of the regulatory subunit of phosphoinositide 3-kinase (Deltap85) inhibited the phosphorylation of alpha(1B)-adrenergic receptors induced by TGF-beta. Our results indicate that activation of TGF-beta receptors induces alpha(1B)-adrenergic receptor phosphorylation and desensitization. The data suggest that phosphoinositide 3-kinase and protein kinase C play key roles in this effect of TGF-beta. PMID:12234252

alpha1B-Adrenergic receptor phosphorylation and desensitization induced by transforming growth factor-beta.

PubMed

Romero-Avila, M Teresa; Flores-Jasso, C Fabián; García-Sáinz, J Adolfo

2002-12-01

Transforming growth factor-beta (TGF-beta) induced alpha(1B)-adrenergic receptor phosphorylation in Rat-1 fibroblasts stably expressing these adrenoceptors. This effect of TGF-beta was rapid, reaching a maximum within 30 min and decreasing thereafter, and concentration-dependent (EC(50) 0.3 pM). The phosphoinositide 3-kinase inhibitors wortmannin and LY294002, and the protein kinase C inhibitors staurosporine, Ro 318220 and bisindolylmaleimide, blocked the effect of this growth factor. alpha(1B)-Adrenergic receptor phosphorylation was associated with desensitization, as indicated by a reduction in the adrenergic-mediated production of [(3)H]inositol phosphates. Phosphorylation of alpha(1B)-adrenergic receptors by TGF-beta was also observed in Cos-1 cells transfected with the receptor. Co-transfection of the dominant-negative mutant of the regulatory subunit of phosphoinositide 3-kinase (Deltap85) inhibited the phosphorylation of alpha(1B)-adrenergic receptors induced by TGF-beta. Our results indicate that activation of TGF-beta receptors induces alpha(1B)-adrenergic receptor phosphorylation and desensitization. The data suggest that phosphoinositide 3-kinase and protein kinase C play key roles in this effect of TGF-beta.

A selective, non-peptide CRF receptor 1 antagonist prevents sodium lactate-induced acute panic-like responses.

PubMed

Shekhar, Anantha; Johnson, Philip L; Fitz, Stephanie D; Nakazato, Atsuro; Chaki, Shigeyuki; Steckler, Thomas; Schmidt, Mark

2011-04-01

Corticotropin releasing factor (CRF) is implicated in a variety of stress-related disorders such as depression and anxiety, and blocking CRF receptors is a putative strategy for treating such disorders. Using a well-studied animal model of panic, we tested the efficacy of JNJ19567470/CRA5626, a selective, non-peptidergic CRF type 1 receptor (CRF1) antagonist (3, 10 and 40 mg/kg intraperitoneal injection), in preventing the sodium lactate (NaLac)-induced panic-like behavioural and cardiovascular responses. Adult male rats with chronic reduction of GABA levels (by inhibition of GABA synthesis with l-allyglycine, a glutamic acid decarboxylase inhibitor) in the dorsomedial/perifornical hypothalamus are highly anxious and exhibit physiological and behavioural responses to intravenous NaLac infusions similar to patients with panic disorder. These 'panic-prone' rats pre-treated with vehicle injections displayed NaLac-induced increases in autonomic responses (i.e. tachycardia and hypertensive responses), anxiety-like behaviour in the social interaction test, and flight-like increases in locomotor activity. However, systemically injecting such panic-prone rats with the highest dose of CRF1 receptor antagonist prior to NaLac infusions blocked all NaLac-induced behaviour and cardiovascular responses. These data suggest that selective CRF1 receptor antagonists could be a novel target for developing anti-panic drugs that are as effective as benzodiazepines in acute treatment of a panic attack without the deleterious side-effects (e.g. sedation and cognitive impairment) associated with benzodiazepines.

Endogenous GABA and Glutamate Finely Tune the Bursting of Olfactory Bulb External Tufted Cells

PubMed Central

Hayar, Abdallah; Ennis, Matthew

2008-01-01

In rat olfactory bulb slices, external tufted (ET) cells spontaneously generate spike bursts. Although ET cell bursting is intrinsically generated, its strength and precise timing may be regulated by synaptic input. We tested this hypothesis by analyzing whether the burst properties are modulated by activation of ionotropic γ-aminobutyric acid (GABA) and glutamate receptors. Blocking GABAA receptors increased—whereas blocking ionotropic glutamate receptors decreased—the number of spikes/burst without changing the interburst frequency. The GABAA agonist (isoguvacine, 10 μM) completely inhibited bursting or reduced the number of spikes/burst, suggesting a shunting effect. These findings indicate that the properties of ET cell spontaneous bursting are differentially controlled by GABAergic and glutamatergic fast synaptic transmission. We suggest that ET cell excitatory and inhibitory inputs may be encoded as a change in the pattern of spike bursting in ET cells, which together with mitral/tufted cells constitute the output circuit of the olfactory bulb. PMID:17567771

Endogenous GABA and glutamate finely tune the bursting of olfactory bulb external tufted cells.

PubMed

Hayar, Abdallah; Ennis, Matthew

2007-08-01

In rat olfactory bulb slices, external tufted (ET) cells spontaneously generate spike bursts. Although ET cell bursting is intrinsically generated, its strength and precise timing may be regulated by synaptic input. We tested this hypothesis by analyzing whether the burst properties are modulated by activation of ionotropic gamma-aminobutyric acid (GABA) and glutamate receptors. Blocking GABA(A) receptors increased--whereas blocking ionotropic glutamate receptors decreased--the number of spikes/burst without changing the interburst frequency. The GABA(A) agonist (isoguvacine, 10 microM) completely inhibited bursting or reduced the number of spikes/burst, suggesting a shunting effect. These findings indicate that the properties of ET cell spontaneous bursting are differentially controlled by GABAergic and glutamatergic fast synaptic transmission. We suggest that ET cell excitatory and inhibitory inputs may be encoded as a change in the pattern of spike bursting in ET cells, which together with mitral/tufted cells constitute the output circuit of the olfactory bulb.

Bicuculline reverts the neuroprotective effects of meloxicam in an oxygen and glucose deprivation (OGD) model of organotypic hippocampal slice cultures.

PubMed

Landucci, Elisa; Llorente, Irene L; Anuncibay-Soto, Berta; Pellegrini-Giampietro, Domenico E; Fernández-López, Arsenio

2018-06-24

We previously demonstrated that the non-steroidal anti-inflammatory agent meloxicam has neuroprotective effects in an oxygen and glucose deprivation model (OGD) of rat organotypic hippocampal slice cultures. We wondered if GABAergic transmission changed the neuroprotective effects of meloxicam and if meloxicam was able to modulate endoplasmic reticulum stress (ER stress) in this model. Mortality was measured using propidium iodide. Western blot assays were performed to measure levels of cleaved and non-cleaved caspase-3 to quantify apoptosis, while levels of GRP78, GRP94 and phosphorylated eIF2α were used to detect unfolded protein response (UPR). Transcript levels of GRP78, GRP94 and GABAergic receptor α, β, and γ subunits were measured by real-time quantitative polymerase chain reaction (qPCR). In the present study, we show that the presence of meloxicam in a 30 min OGD assay, followed by 24 h of normoxic conditions, presented an antiapoptotic effect. The simultaneous presence of the GABA A receptor antagonist, bicuculline, in combination with meloxicam blocked the neuroprotective effect provided by the latter. However, in light of its effects on caspase 3 and PARP, bicuculline did not seem to promote the apoptotic pathway. Our results also showed that meloxicam modified the unfolded protein response (UPR), as well as the transcriptional response of different genes, including the GABA A receptor, alpha1, beta3 and gamma2 subunits. We concluded that meloxicam has a neuroprotective anti-apoptotic action, is able to enhance the UPR independently of the systemic anti-inflammatory response and its neuroprotective effect can be inhibited by blocking GABA A receptors. Copyright © 2018. Published by Elsevier Ltd.

Oxyntomodulin analogue increases energy expenditure via the glucagon receptor.

PubMed

Scott, R; Minnion, J; Tan, T; Bloom, S R

2018-06-01

The gut hormone oxyntomodulin (OXM) causes weight loss by reducing appetite and increasing energy expenditure. Several analogues are being developed to treat obesity. Exactly how oxyntomodulin works, however, remains controversial. OXM can activate both glucagon and GLP-1 receptors but no specific receptor has been identified. It is thought that the anorectic effect occurs predominantly through GLP-1 receptor activation but, to date, it has not been formally confirmed which receptor is responsible for the increased energy expenditure. We developed OX-SR, a sustained-release OXM analogue. It produces a significant and sustained increase in energy expenditure in rats as measured by indirect calorimetry. We now show that this increase in energy expenditure occurs via activation of the glucagon receptor. Blockade of the GLP-1 receptor with Exendin 9-39 does not block the increase in oxygen consumption caused by OX-SR. However, when activity at the glucagon receptor is lost, there is no increase in energy expenditure. Glucagon receptor activity therefore appears to be essential for OX-SR's effects on energy expenditure. The development of future 'dual agonist' analogues will require careful balancing of GLP-1 and glucagon receptor activities to obtain optimal effects. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Inhibiting core fucosylation attenuates glucose-induced peritoneal fibrosis in rats.

PubMed

Li, Longkai; Shen, Nan; Wang, Nan; Wang, Weidong; Tang, Qingzhu; Du, Xiangning; Carrero, Juan Jesus; Wang, Keping; Deng, Yiyao; Li, Zhitong; Lin, Hongli; Wu, Taihua

2018-06-01

Ultrafiltration failure is a major complication of long-term peritoneal dialysis, resulting in dialysis failure. Peritoneal fibrosis induced by continuous exposure to high glucose dialysate is the major contributor of ultrafiltration failure, for which there is no effective treatment. Overactivation of several signaling pathways, including transforming growth factor-β1 (TGF-β1) and platelet-derived growth factor (PDGF) pathways, contribute to the development of peritoneal fibrosis. Therefore, simultaneously blocking multiple signaling pathways might be a potential novel method of treating peritoneal fibrosis. Previously, we showed that core fucosylation, an important posttranslational modification of the TGF-β1 receptors, can regulate the activation of TGF-β1 signaling in renal interstitial fibrosis. However, it remains unclear whether core fucosylation affects the progression of peritoneal fibrosis. Herein, we show that core fucosylation was enriched in the peritoneal membrane of rats accompanied by peritoneal fibrosis induced by a high glucose dialysate. Blocking core fucosylation dramatically attenuated peritoneal fibrosis in the rat model achieved by simultaneously inactivating the TGF-β1 and PDGF signaling pathways. Next the protective effects of blocking core fucosylation and imatinib (a selective PDGF receptor inhibitor) on peritoneal fibrosis were compared and found to exhibit a greater inhibitory effect over imatinib alone, suggesting that blocking activation of multiple signaling pathways may have superior inhibitory effects on the development of peritoneal fibrosis. Thus, core fucosylation is essential for the development of peritoneal fibrosis by regulating the activation of multiple signaling pathways. This may be a potential novel target for drug development to treat peritoneal fibrosis. Copyright © 2018 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

Activation of D4 dopamine receptor decreases AT1 angiotensin II receptor expression in rat renal proximal tubule cells

PubMed Central

Chen, Ken; Deng, Kun; Wang, Xiaoyan; Wang, Zhen; Zheng, Shuo; Ren, Hongmei; He, Duofen; Han, Yu; Asico, Laureano D.; Jose, Pedro A.; Zeng, Chunyu

2014-01-01

The dopaminergic and renin angiotensin systems interact to regulate blood pressure. Disruption of the D4 dopamine receptor gene in mice produces hypertension that is associated with increased renal AT1 receptor expression. We hypothesize that the D4 receptor can inhibit AT1 receptor expression and function in renal proximal tubules (RPTs) cells from Wistar-Kyoto (WKY) rats but the D4 receptor regulation of AT1 receptor is aberrant in RPT cells from spontaneously hypertensive rats (SHRs). The D4 receptor agonist, PD168077, decreased AT1 receptor protein expression in a time and concentration-dependent manner in WKY cells. By contrast, in SHR cells, PD168077 increased AT1 receptor protein expression. The inhibitory effect of D4 receptor on AT1 receptor expression in WKY cells was blocked by a calcium channel blocker, nicardipine, or calcium-free medium, indicating that calcium is involved in the D4 receptor-mediated signaling pathway. Angiotensin II increased Na+-K+ ATPase activity in WKY cells. Pretreatment with PD168077 decreased the stimulatory effect of angiotensin II on Na+-K+ ATPase activity in WKY cells. In SHR cells, the inhibitory effect of D4 receptor on angiotensin II-mediated stimulation of Na+-K+ ATPase activity was aberrant; pretreatment with PD168077 augmented the stimulatory effect of AT1 receptor on Na+-K+ ATPase activity in SHR cells. This was confirmed in vivo; pre-treatment with PD128077 for one week augmented the anti-hypertensive and natriuretic effect of losartan in SHRs but not in WKY rats. We suggest that an aberrant interaction between D4 and AT1 receptors may play a role in the abnormal regulation of sodium excretion in hypertension. PMID:25368031

Effect of beta-antagonists on isoprenaline-induced secretion of fluid, amylase and protein by the parotid gland of the red kangaroo, Macropus rufus.

PubMed

Beal, A M

2000-02-01

Selective and non-selective beta-adrenoceptor antagonists were used to block the increases in fluid, protein and amylase secretion caused by sympathomimetic stimulation of the parotid gland of red kangaroos during intracarotid infusion of isoprenaline. ICI118551 at antagonist/agonist ratios up to 300:1 caused increasing but incomplete blockade of fluid secretion, and protein/amylase release. Atenolol at antagonist/agonist ratios up to 300:1 was only marginally more potent than ICI118551 at blocking the fluid, protein and amylase responses. Propranolol at antagonist/agonist ratios of 30:1 was as effective at blocking fluid and protein secretion as the highest ratios of either atenolol or ICI118551. Simultaneous administration of atenolol (30:1) with ICI118551 (30:1) was not as potent as propranolol (30:1). Thus, the beta-adrenoceptor/s in the acini of the kangaroo parotid gland appear to have antagonist-binding affinities atypical of those found for eutherian tissues. The data are consistent with the gland possessing either a single anomalous beta-adrenoceptor or functional beta(2)-receptors in addition to the beta(1)-receptors which are characteristic of eutherian salivary glands.

Rapid actions of aldosterone revisited: Receptors in the limelight.

PubMed

Wehling, Martin

2018-02-01

Steroid hormones like aldosterone have been conclusively shown to elicit both late genomic and rapid, nongenomically initiated responses. Aldosterone was among the first for which rapid, clinically relevant effects were even shown in humans. Yet, after over 30 years of research, the nature of receptors involved in rapid actions of aldosterone is still unclear. Such effects may be assigned to the classical, intracellular steroid receptors, in this case mineralocorticoid receptors (MR, class IIa action Mannheim classification). They typically disappear in knockout models and are blocked by MR-antagonists such as spironolactone, as shown for several cellular and physiological, e.g. renal or cardiovascular effects. In contrast, there is also consistent evidence suggesting type IIb effects involving structurally different receptors ("membrane receptors") being insensitive to classic antagonists and persistent in knockout models; IIb effects have lately even been confirmed by atomic force detection of surface receptors which bind aldosterone but not spironolactone. Type IIa and b may coexist in the same cell with IIa often augmenting early IIb effects. So far cloning of IIb receptors was unsuccessful; therefore results on G-protein coupled estrogen receptor 1 (GPER1) being potentially involved in rapid aldosterone action raised considerable interest. Surprisingly, GPER1 does not bind aldosterone. Though under these circumstances GPER1 should not yet be considered as IIb-receptor, it might be an intermediary signaling enhancer of mineralocorticoid action as shown for epithelial growth factor receptors reconciling those results. We still seem to be left without IIb-receptors whose identification would however be highly desirable and essential for clinical translation. Copyright © 2017 Elsevier Ltd. All rights reserved.

PAR-2 receptor-induced effects on human eccrine sweat gland cells.

PubMed

L Bovell, Douglas; Kofler, Barbara; Lang, Roland

2009-01-01

Serine proteases can induce cell signaling by stimulating G-protein-coupled receptors, called proteinase-activated receptors (PAR's) on a variety of epithelial cells. While PAR-2, one such receptor, activates cell signaling in a secretory cell line derived from human sweat glands, there was no information on their presence and effects on intact sweat glands. PAR-2 presence and activation of eccrine sweat glands isolated from human skin samples was investigated using Western blot analysis, immunohistochemistry, electron microscopy (EM) and Ca(2+) imaging. Anti-human PAR-2 antibody demonstrated the presence of these receptors in eccrine sweat glands. EM showed that PAR-2 activation resulted in degranulation of secretory cells. Ca(2+) imaging using PAR-2 activators demonstrated a two phase increase in [Ca(2+)](i) which was dependent on extracellular Ca(2+) for the second phase, and that the response could be blocked by prior incubation with xestospongin, the IP(3) receptor blocker. The results demonstrated that PAR-2 receptors are present in human sweat gland secretory cells and that these receptors are functionally active and can induce changes associated with secretory events in eccrine glands.

Tobacco smoking interferes with GABAA receptor neuroadaptations during prolonged alcohol withdrawal

PubMed Central

Cosgrove, Kelly P.; McKay, Reese; Esterlis, Irina; Kloczynski, Tracy; Perkins, Evgenia; Bois, Frederic; Pittman, Brian; Lancaster, Jack; Glahn, David C.; O’Malley, Stephanie; Carson, Richard E.; Krystal, John H.

2014-01-01

Understanding the effects of tobacco smoking on neuroadaptations in GABAA receptor levels over alcohol withdrawal will provide critical insights for the treatment of comorbid alcohol and nicotine dependence. We conducted parallel studies in human subjects and nonhuman primates to investigate the differential effects of tobacco smoking and nicotine on changes in GABAA receptor availability during acute and prolonged alcohol withdrawal. We report that alcohol withdrawal with or without concurrent tobacco smoking/nicotine consumption resulted in significant and robust elevations in GABAA receptor levels over the first week of withdrawal. Over prolonged withdrawal, GABAA receptors returned to control levels in alcohol-dependent nonsmokers, but alcohol-dependent smokers had significant and sustained elevations in GABAA receptors that were associated with craving for alcohol and cigarettes. In nonhuman primates, GABAA receptor levels normalized by 1 mo of abstinence in both groups—that is, those that consumed alcohol alone or the combination of alcohol and nicotine. These data suggest that constituents in tobacco smoke other than nicotine block the recovery of GABAA receptor systems during sustained alcohol abstinence, contributing to alcohol relapse and the perpetuation of smoking. PMID:25453062

Is topical haloperidol a useful glaucoma treatment?

PubMed Central

Lavin, M. J.; Andrews, V.

1986-01-01

A randomised, double blind, single dose study of topical haloperidol, a dopamine receptor blocking drug, was performed on 20 healthy volunteers. After its administration a modest reduction in intraocular pressure was recorded over the six-hour study period, but the difference was not significant at the p less than 0.05 level. Although dopamine blocking agents are effective in reducing intraocular pressure in experimental animals, topical haloperidol appears unlikely to be clinically useful in the treatment of glaucoma. PMID:3718908

Control of the subthalamic innervation of substantia nigra pars reticulata by D1 and D2 dopamine receptors.

PubMed

Ibañez-Sandoval, Osvaldo; Hernández, Adán; Florán, Benjamin; Galarraga, Elvira; Tapia, Dagoberto; Valdiosera, Rene; Erlij, David; Aceves, Jorge; Bargas, José

2006-03-01

The effects of activating dopaminergic D1 and D2 class receptors of the subthalamic projections that innervate the pars reticulata of the subtantia nigra (SNr) were explored in slices of the rat brain using the whole cell patch-clamp technique. Excitatory postsynaptic currents (EPSCs) that could be blocked by 6-cyano-7-nitroquinoxalene-2,3-dione and D-(-)-2-amino-5-phosphonopentanoic acid were evoked onto reticulata GABAergic projection neurons by local field stimulation inside the subthalamic nucleus in the presence of bicuculline. Bath application of (RS)-2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine hydrochloride (SKF-38393), a dopaminergic D1-class receptor agonist, increased evoked EPSCs by approximately 30% whereas the D2-class receptor agonist, trans-(-)-4aR-4,4a,5,6,7,8,8a,9-octahydro-5-propyl-1H-pyrazolo(3,4-g)quinoline (quinpirole), reduced EPSCs by approximately 25%. These apparently opposing actions were blocked by the specific D1- and D2-class receptor antagonists: R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetra-hydro-1H-3-benzazepinehydrochloride (SCH 23390) and S-(-)-5-amino-sulfonyl-N-[(1-ethyl-2-pyrrolidinyl)-methyl]-2-methoxybenzamide (sulpiride), respectively. Both effects were accompanied by changes in the paired-pulse ratio, indicative of a presynaptic site of action. The presynaptic location of dopamine receptors at the subthalamonigral projections was confirmed by mean-variance analysis. The effects of both SKF-38393 and quinpirole could be observed on terminals contacting the same postsynaptic neuron. Sulpiride and SCH 23390 enhanced and reduced the evoked EPSC, respectively, suggesting a constitutive receptor activation probably arising from endogenous dopamine. These data suggest that dopamine presynaptically modulates the subthalamic projection that targets GABAergic neurons of the SNr. Implications of this modulation for basal ganglia function are discussed.

Suppressing effect of COR659 on alcohol, sucrose, and chocolate self-administration in rats: involvement of the GABAB and cannabinoid CB1 receptors.

PubMed

Maccioni, Paola; Colombo, Giancarlo; Lorrai, Irene; Zaru, Alessandro; Carai, Mauro A M; Gessa, Gian Luigi; Brizzi, Antonella; Mugnaini, Claudia; Corelli, Federico

2017-09-01

COR659 [methyl2-(4-chlorophenylcarboxamido)-4-ethyl-5-methylthiophene-3-carboxylate] is a new, positive allosteric modulator (PAM) of the GABA B receptor. This study evaluated whether COR659 shared with previously tested GABA B PAMs the capacity to reduce alcohol self-administration in rats. Treatment with non-sedative doses of COR659 (2.5, 5, and 10 mg/kg; i.p.) suppressed lever-responding for alcohol (15% v/v) in Sardinian alcohol-preferring (sP) rats under the fixed ratio (FR) 4 (FR4) and progressive ratio (PR) schedules of reinforcement; COR659 was more potent and effective than the reference GABA B PAM, GS39783. Treatment with COR659, but not GS39783, suppressed (a) lever-responding for a sucrose solution (1-3% w/v) in sP rats under the FR4 and PR schedules, (b) lever-responding for a chocolate solution [5% (w/v) Nesquik®] in Wistar rats under the FR10 and PR schedules, and (c) cue-induced reinstatement of chocolate seeking in Wistar rats. Treatment with COR659 was completely ineffective on lever-responding (FR10) for regular food pellets in food-deprived Wistar rats. Pretreatment with the GABA B receptor antagonist, SCH50911, partially blocked COR659-induced reduction of alcohol self-administration, being ineffective on reduction of chocolate self-administration. Pretreatment with the cannabinoid CB 1 receptor antagonist, AM4113, fully blocked COR659-induced reduction of chocolate self-administration, being ineffective on reduction of alcohol self-administration. COR659 might exert its behavioral effects via a composite mechanism: (i) positive allosteric modulation of the GABA B receptor, responsible for a large proportion of reduction of alcohol self-administration; (ii) an action at other receptor system(s), including the cannabinoid CB 1 receptor, through which COR659 affects seeking and consumption of highly palatable foods.

Alzheimer's Therapeutics Targeting Amyloid Beta 1–42 Oligomers I: Abeta 42 Oligomer Binding to Specific Neuronal Receptors Is Displaced by Drug Candidates That Improve Cognitive Deficits

PubMed Central

Izzo, Nicholas J.; Staniszewski, Agnes; To, Lillian; Fa, Mauro; Teich, Andrew F.; Saeed, Faisal; Wostein, Harrison; Walko, Thomas; Vaswani, Anisha; Wardius, Meghan; Syed, Zanobia; Ravenscroft, Jessica; Mozzoni, Kelsie; Silky, Colleen; Rehak, Courtney; Yurko, Raymond; Finn, Patricia; Look, Gary; Rishton, Gilbert; Safferstein, Hank; Miller, Miles; Johanson, Conrad; Stopa, Edward; Windisch, Manfred; Hutter-Paier, Birgit; Shamloo, Mehrdad; Arancio, Ottavio; LeVine, Harry; Catalano, Susan M.

2014-01-01

Synaptic dysfunction and loss caused by age-dependent accumulation of synaptotoxic beta amyloid (Abeta) 1–42 oligomers is proposed to underlie cognitive decline in Alzheimer's disease (AD). Alterations in membrane trafficking induced by Abeta oligomers mediates reduction in neuronal surface receptor expression that is the basis for inhibition of electrophysiological measures of synaptic plasticity and thus learning and memory. We have utilized phenotypic screens in mature, in vitro cultures of rat brain cells to identify small molecules which block or prevent the binding and effects of Abeta oligomers. Synthetic Abeta oligomers bind saturably to a single site on neuronal synapses and induce deficits in membrane trafficking in neuronal cultures with an EC50 that corresponds to its binding affinity. The therapeutic lead compounds we have found are pharmacological antagonists of Abeta oligomers, reducing the binding of Abeta oligomers to neurons in vitro, preventing spine loss in neurons and preventing and treating oligomer-induced deficits in membrane trafficking. These molecules are highly brain penetrant and prevent and restore cognitive deficits in mouse models of Alzheimer's disease. Counter-screening these compounds against a broad panel of potential CNS targets revealed they are highly potent and specific ligands of the sigma-2/PGRMC1 receptor. Brain concentrations of the compounds corresponding to greater than 80% receptor occupancy at the sigma-2/PGRMC1 receptor restore cognitive function in transgenic hAPP Swe/Ldn mice. These studies demonstrate that synthetic and human-derived Abeta oligomers act as pharmacologically-behaved ligands at neuronal receptors - i.e. they exhibit saturable binding to a target, they exert a functional effect related to their binding and their displacement by small molecule antagonists blocks their functional effect. The first-in-class small molecule receptor antagonists described here restore memory to normal in multiple AD models and sustain improvement long-term, representing a novel mechanism of action for disease-modifying Alzheimer's therapeutics. PMID:25390368

Alzheimer's therapeutics targeting amyloid beta 1-42 oligomers I: Abeta 42 oligomer binding to specific neuronal receptors is displaced by drug candidates that improve cognitive deficits.

PubMed

Izzo, Nicholas J; Staniszewski, Agnes; To, Lillian; Fa, Mauro; Teich, Andrew F; Saeed, Faisal; Wostein, Harrison; Walko, Thomas; Vaswani, Anisha; Wardius, Meghan; Syed, Zanobia; Ravenscroft, Jessica; Mozzoni, Kelsie; Silky, Colleen; Rehak, Courtney; Yurko, Raymond; Finn, Patricia; Look, Gary; Rishton, Gilbert; Safferstein, Hank; Miller, Miles; Johanson, Conrad; Stopa, Edward; Windisch, Manfred; Hutter-Paier, Birgit; Shamloo, Mehrdad; Arancio, Ottavio; LeVine, Harry; Catalano, Susan M

2014-01-01

Synaptic dysfunction and loss caused by age-dependent accumulation of synaptotoxic beta amyloid (Abeta) 1-42 oligomers is proposed to underlie cognitive decline in Alzheimer's disease (AD). Alterations in membrane trafficking induced by Abeta oligomers mediates reduction in neuronal surface receptor expression that is the basis for inhibition of electrophysiological measures of synaptic plasticity and thus learning and memory. We have utilized phenotypic screens in mature, in vitro cultures of rat brain cells to identify small molecules which block or prevent the binding and effects of Abeta oligomers. Synthetic Abeta oligomers bind saturably to a single site on neuronal synapses and induce deficits in membrane trafficking in neuronal cultures with an EC50 that corresponds to its binding affinity. The therapeutic lead compounds we have found are pharmacological antagonists of Abeta oligomers, reducing the binding of Abeta oligomers to neurons in vitro, preventing spine loss in neurons and preventing and treating oligomer-induced deficits in membrane trafficking. These molecules are highly brain penetrant and prevent and restore cognitive deficits in mouse models of Alzheimer's disease. Counter-screening these compounds against a broad panel of potential CNS targets revealed they are highly potent and specific ligands of the sigma-2/PGRMC1 receptor. Brain concentrations of the compounds corresponding to greater than 80% receptor occupancy at the sigma-2/PGRMC1 receptor restore cognitive function in transgenic hAPP Swe/Ldn mice. These studies demonstrate that synthetic and human-derived Abeta oligomers act as pharmacologically-behaved ligands at neuronal receptors--i.e. they exhibit saturable binding to a target, they exert a functional effect related to their binding and their displacement by small molecule antagonists blocks their functional effect. The first-in-class small molecule receptor antagonists described here restore memory to normal in multiple AD models and sustain improvement long-term, representing a novel mechanism of action for disease-modifying Alzheimer's therapeutics.

Ethanol modulates the VR-1 variant amiloride-insensitive salt taste receptor. I. Effect on TRC volume and Na+ flux.

PubMed

Lyall, Vijay; Heck, Gerard L; Phan, Tam-Hao T; Mummalaneni, Shobha; Malik, Shahbaz A; Vinnikova, Anna K; DeSimone, John A

2005-06-01

The effect of ethanol on the amiloride- and benzamil (Bz)-insensitive salt taste receptor was investigated by the measurement of intracellular Na(+) activity ([Na(+)](i)) in polarized rat fungiform taste receptor cells (TRCs) using fluorescence imaging and by chorda tympani (CT) taste nerve recordings. CT responses were monitored during lingual stimulation with ethanol solutions containing NaCl or KCl. CT responses were recorded in the presence of Bz (a specific blocker of the epithelial Na(+) channel [ENaC]) or the vanilloid receptor-1 (VR-1) antagonists capsazepine or SB-366791, which also block the Bz-insensitive salt taste receptor, a VR-1 variant. CT responses were recorded at 23 degrees C or 42 degrees C (a temperature at which the VR-1 variant salt taste receptor activity is maximally enhanced). In the absence of permeable cations, ethanol induced a transient decrease in TRC volume, and stimulating the tongue with ethanol solutions without added salt elicited only transient phasic CT responses that were insensitive to elevated temperature or SB-366791. Preshrinking TRCs in vivo with hypertonic mannitol (0.5 M) attenuated the magnitude of the phasic CT response, indicating that in the absence of mineral salts, transient phasic CT responses are related to the ethanol-induced osmotic shrinkage of TRCs. In the presence of mineral salts, ethanol increased the Bz-insensitive apical cation flux in TRCs without a change in cell volume, increased transepithelial electrical resistance across the tongue, and elicited CT responses that were similar to salt responses, consisting of both a transient phasic component and a sustained tonic component. Ethanol increased the Bz-insensitive NaCl CT response. This effect was further enhanced by elevating the temperature from 23 degrees C to 42 degrees C, and was blocked by SB-366791. We conclude that in the presence of mineral salts, ethanol modulates the Bz-insensitive VR-1 variant salt taste receptor.

Melatonin potentiates glycine currents through a PLC/PKC signalling pathway in rat retinal ganglion cells.

PubMed

Zhao, Wen-Jie; Zhang, Min; Miao, Yanying; Yang, Xiong-Li; Wang, Zhongfeng

2010-07-15

In vertebrate retina, melatonin regulates various physiological functions. In this work we investigated the mechanisms underlying melatonin-induced potentiation of glycine currents in rat retinal ganglion cells (RGCs). Immunofluorescence double labelling showed that rat RGCs were solely immunoreactive to melatonin MT(2) receptors. Melatonin potentiated glycine currents of RGCs, which was reversed by the MT(2) receptor antagonist 4-P-PDOT. The melatonin effect was blocked by intracellular dialysis of GDP-beta-S. Either preincubation with pertussis toxin or application of the phosphatidylcholine (PC)-specific phospholipase C (PLC) inhibitor D609, but not the phosphatidylinositol (PI)-PLC inhibitor U73122, blocked the melatonin effect. The protein kinase C (PKC) activator PMA potentiated the glycine currents and in the presence of PMA melatonin failed to cause further potentiation of the currents, whereas application of the PKC inhibitor bisindolylmaleimide IV abolished the melatonin-induced potentiation. The melatonin effect persisted when [Ca(2+)](i) was chelated by BAPTA, and melatonin induced no increase in [Ca(2+)](i). Neither cAMP-PKA nor cGMP-PKG signalling pathways seemed to be involved because 8-Br-cAMP or 8-Br-cGMP failed to cause potentiation of the glycine currents and both the PKA inhibitor H-89 and the PKG inhibitor KT5823 did not block the melatonin-induced potentiation. In consequence, a distinct PC-PLC/PKC signalling pathway, following the activation of G(i/o)-coupled MT(2) receptors, is most likely responsible for the melatonin-induced potentiation of glycine currents of rat RGCs. Furthermore, in rat retinal slices melatonin potentiated light-evoked glycine receptor-mediated inhibitory postsynaptic currents in RGCs. These results suggest that melatonin, being at higher levels at night, may help animals to detect positive or negative contrast in night vision by modulating inhibitory signals largely mediated by glycinergic amacrine cells in the inner retina.

Melatonin potentiates glycine currents through a PLC/PKC signalling pathway in rat retinal ganglion cells

PubMed Central

Zhao, Wen-Jie; Zhang, Min; Miao, Yanying; Yang, Xiong-Li; Wang, Zhongfeng

2010-01-01

In vertebrate retina, melatonin regulates various physiological functions. In this work we investigated the mechanisms underlying melatonin-induced potentiation of glycine currents in rat retinal ganglion cells (RGCs). Immunofluorescence double labelling showed that rat RGCs were solely immunoreactive to melatonin MT2 receptors. Melatonin potentiated glycine currents of RGCs, which was reversed by the MT2 receptor antagonist 4-P-PDOT. The melatonin effect was blocked by intracellular dialysis of GDP-β-S. Either preincubation with pertussis toxin or application of the phosphatidylcholine (PC)-specific phospholipase C (PLC) inhibitor D609, but not the phosphatidylinositol (PI)-PLC inhibitor U73122, blocked the melatonin effect. The protein kinase C (PKC) activator PMA potentiated the glycine currents and in the presence of PMA melatonin failed to cause further potentiation of the currents, whereas application of the PKC inhibitor bisindolylmaleimide IV abolished the melatonin-induced potentiation. The melatonin effect persisted when [Ca2+]i was chelated by BAPTA, and melatonin induced no increase in [Ca2+]i. Neither cAMP-PKA nor cGMP-PKG signalling pathways seemed to be involved because 8-Br-cAMP or 8-Br-cGMP failed to cause potentiation of the glycine currents and both the PKA inhibitor H-89 and the PKG inhibitor KT5823 did not block the melatonin-induced potentiation. In consequence, a distinct PC-PLC/PKC signalling pathway, following the activation of Gi/o-coupled MT2 receptors, is most likely responsible for the melatonin-induced potentiation of glycine currents of rat RGCs. Furthermore, in rat retinal slices melatonin potentiated light-evoked glycine receptor-mediated inhibitory postsynaptic currents in RGCs. These results suggest that melatonin, being at higher levels at night, may help animals to detect positive or negative contrast in night vision by modulating inhibitory signals largely mediated by glycinergic amacrine cells in the inner retina. PMID:20519319

Cyclopeptide Dmt-[D-Lys-p-CF3-Phe-Phe-Asp]NH2, a novel G protein-biased agonist of the mu opioid receptor.

PubMed

Piekielna-Ciesielska, Justyna; Ferrari, Federica; Calo', Girolamo; Janecka, Anna

2018-03-01

Opioid peptides and alkaloid drugs such as morphine, mediate their analgesic effects, but also undesired side effects, mostly through activation of the mu opioid receptor which belongs to the G protein-coupled receptor (GPCR) family. A new important pharmacological concept in the field of GPCRs is biased agonism. Two mu receptor ligands, Dmt-c[D-Lys-Phe-Phe-Asp]NH 2 (C-36) and Dmt-c[D-Lys-Phe-p-CF 3 -Phe-Asp]NH 2 (F-81), were evaluated in terms of their ability to promote or block mu receptor/G protein and mu receptor/β-arrestin interactions. Using the bioluminescence resonance energy transfer (BRET) assay it was shown that C-36 activated both, G protein and β-arrestin pathways. Incorporation of trifluoromethyl group into the aromatic ring of phenylalanine in the sequence of F-81 led to activation of G-protein pathway rather than β-arrestin recruitment. Opioid cyclopeptide F-81 turned out to be a biased G protein mu receptor agonist. Such biased ligands are able to separate the biological actions of an activated receptor and have the potential to become more effective drug candidates with fewer side effects. Copyright © 2017 Elsevier Inc. All rights reserved.

Pharmacological evaluation of the anxiolytic-like effects of EMD 386088, a partial 5-HT6 receptor agonist, in the rat elevated plus-maze and Vogel conflict tests.

PubMed

Jastrzębska-Więsek, Magdalena; Siwek, Agata; Partyka, Anna; Kubacka, Monika; Mogilski, Szczepan; Wasik, Anna; Kołaczkowski, Marcin; Wesołowska, Anna

2014-10-01

The 5-HT6 is one of the most recent additions to the 5-HT receptor family. Its pharmacological profile and anatomical distribution is suggestive of a putative role in mood disorders. Most of preclinical evidence suggests an anxiolytic-like action of 5-HT6 receptor antagonists. Evaluation the anxiolytic-like effects of EMD 386088, a partial 5-HT6receptor agonist, and its putative mechanism of action in rats. EMD 386088, administered intraperitoneally at a dose of 2.5 mg/kg evoked specific anxiolytic-like activity in the automated version of the conflict drinking Vogel and the elevated plus-maze tests visible by increasing all parameters indicating a potential anti-anxiety effect. Its activity was blocked by the selective 5-HT6 receptor antagonist SB 271046, but not by the selective GABAA/benzodiazepine receptor antagonist flumazenil. EMD 386088 did not intensify an anxiolytic-like effect produced by diazepam in the elevated plus-maze test. These findings suggest that EMD 386088, a 5-HT6 receptor agonist, produces anxiolytic-like activity after systemic administration which may result from direct stimulation of 5-HT6 receptors. Copyright © 2014 Elsevier Ltd. All rights reserved.

A TNF receptor loop peptide mimic blocks RANK ligand–induced signaling, bone resorption, and bone loss

PubMed Central

Aoki, Kazuhiro; Saito, Hiroaki; Itzstein, Cecile; Ishiguro, Masaji; Shibata, Tatsuya; Blanque, Roland; Mian, Anower Hussain; Takahashi, Mariko; Suzuki, Yoshifumi; Yoshimatsu, Masako; Yamaguchi, Akira; Deprez, Pierre; Mollat, Patrick; Murali, Ramachandran; Ohya, Keiichi; Horne, William C.; Baron, Roland

2006-01-01

Activating receptor activator of NF-κB (RANK) and TNF receptor (TNFR) promote osteoclast differentiation. A critical ligand contact site on the TNFR is partly conserved in RANK. Surface plasmon resonance studies showed that a peptide (WP9QY) that mimics this TNFR contact site and inhibits TNF-α–induced activity bound to RANK ligand (RANKL). Changing a single residue predicted to play an important role in the interaction reduced the binding significantly. WP9QY, but not the altered control peptide, inhibited the RANKL-induced activation of RANK-dependent signaling in RAW 264.7 cells but had no effect on M-CSF–induced activation of some of the same signaling events. WP9QY but not the control peptide also prevented RANKL-induced bone resorption and osteoclastogenesis, even when TNFRs were absent or blocked. In vivo, where both RANKL and TNF-α promote osteoclastogenesis, osteoclast activity, and bone loss, WP9QY prevented the increased osteoclastogenesis and bone loss induced in mice by ovariectomy or low dietary calcium, in the latter case in both wild-type and TNFR double-knockout mice. These results suggest that a peptide that mimics a TNFR ligand contact site blocks bone resorption by interfering with recruitment and activation of osteoclasts by both RANKL and TNF. PMID:16680194

Regulation of striatal nitric oxide synthesis by local dopamine and glutamate interactions

PubMed Central

Park, Diana J.; West, Anthony R.

2009-01-01

Nitric oxide (NO) is a key neuromodulator of corticostriatal synaptic transmission. We have shown previously that dopamine (DA) D1/5 receptor stimulation facilitates neuronal NO synthase (nNOS) activity in the intact striatum. To study the impact of local manipulations of D1/5 and glutamatergic NMDA receptors on striatal nNOS activity, we combined the techniques of in vivo amperometry and reverse microdialysis. Striatal NO efflux was monitored proximal to the microdialysis probe in urethane anesthetized rats during local infusion of vehicle or drug. NO efflux elicited by systemic administration of SKF-81297 was blocked following intrastriatal infusion of: 1) the D1/5 receptor antagonist SCH-23390, 2) the nNOS inhibitor 7-nitroindazole, 3) the nonspecific ionotropic glutamate receptor antagonist kynurenic acid, and 4) the selective NMDA receptor antagonist 3-phosphonopropyl-piperazine-2-carboxylic acid. Glycine coperfusion did not affect SKF-81297-induced NO efflux. Furthermore, intrastriatal infusion of SKF-81297 potentiated NO efflux evoked during electrical stimulation of the motor cortex. The facilitatory effects of cortical stimulation and SKF-81297 were both blocked by intrastriatal infusion of SCH-23390, indicating that striatal D1/5 receptor activation is necessary for the activation of nNOS by corticostriatal afferents. These studies demonstrate for the first time that reciprocal DA-glutamate interactions play a critical role in stimulating striatal nNOS activity. PMID:19799710

Transforming growth factor-alpha short-circuits downregulation of the epidermal growth factor receptor.

PubMed

Ouyang, X; Gulliford, T; Huang, G; Epstein, R J

1999-04-01

Transforming growth factor-alpha (TGFalpha) is an epidermal growth factor receptor (EGFR) ligand which is distinguished from EGF by its acid-labile structure and potent transforming function. We recently reported that TGFalpha induces less efficient EGFR heterodimerization and downregulation than does EGF (Gulliford et al., 1997, Oncogene, 15:2219-2223). Here we use isoform-specific EGFR and ErbB2 antibodies to show that the duration of EGFR signalling induced by a single TGFalpha exposure is less than that induced by equimolar EGF. The protein trafficking inhibitor brefeldin A (BFA) reduces the duration of EGF signalling to an extent similar to that seen with TGFalpha alone; the effects of TGFalpha and BFA on EGFR degradation are opposite, however, with TGFalpha sparing EGFR from downregulation but BFA accelerating EGF-dependent receptor loss. This suggests that BFA blocks EGFR recycling and thus shortens EGF-dependent receptor signalling, whereas TGFalpha shortens receptor signalling and thus blocks EGFR downregulation. Consistent with this, repeated application of TGFalpha is accompanied by prolonged EGFR expression and signalling, whereas similar application of EGF causes receptor downregulation and signal termination. These findings indicate that constitutive secretion of pH-labile TGFalpha may perpetuate EGFR signalling by permitting early oligomer dissociation and dephosphorylation within acidic endosomes, thereby extinguishing a phosphotyrosine-based downregulation signal and creating an irreversible autocrine growth loop.

Opiate-induced constipation related to activation of small intestine opioid μ2-receptors.

PubMed

Chen, Wency; Chung, Hsien-Hui; Cheng, Juei-Tang

2012-03-28

To investigate the role of opioid μ-receptor subtype in opiate-induced constipation (OIC). The effect of loperamide on intestinal transit was investigated in mice. Ileum strips were isolated from 12-wk-old male BALB/c mice for identification of isometric tension. The ileum strips were precontracted with 1 μmol/L acetylcholine (ACh). Then, decrease in muscle tone (relaxation) was characterized after cumulative administration of 0.1-10 μmol/L loperamide into the organ bath, for a concentration-dependent study. Specific blockers or antagonists were used for pretreatment to compare the changes in loperamide-induced relaxation. In addition to the delay in intestinal transit, loperamide produced a marked relaxation in isolated ileum precontracted with ACh, in a dose-dependent manner. This relaxation was abolished by cyprodime, a selective opioid μ-receptor antagonist, but not modified by naloxonazine at a dose sufficient to block opioid μ-1 receptors. Also, treatment with opioid μ-1 receptor agonist failed to modify the muscle tone. Moreover, the relaxation by loperamide was attenuated by glibenclamide at a dose sufficient to block ATP-sensitive K+ (K(ATP)) channels, and by protein kinase A (PKA) inhibitor, but was enhanced by an inhibitor of phosphodiesterase for cyclic adenosine monophosphate (cAMP). Loperamide induces intestinal relaxation by activation of opioid μ-2 receptors via the cAMP-PKA pathway to open K(ATP) channels, relates to OIC.

Opiate-induced constipation related to activation of small intestine opioid μ2-receptors

PubMed Central

Chen, Wency; Chung, Hsien-Hui; Cheng, Juei-Tang

2012-01-01

AIM: To investigate the role of opioid μ-receptor subtype in opiate-induced constipation (OIC). METHODS: The effect of loperamide on intestinal transit was investigated in mice. Ileum strips were isolated from 12-wk-old male BALB/c mice for identification of isometric tension. The ileum strips were precontracted with 1 μmol/L acetylcholine (ACh). Then, decrease in muscle tone (relaxation) was characterized after cumulative administration of 0.1-10 μmol/L loperamide into the organ bath, for a concentration-dependent study. Specific blockers or antagonists were used for pretreatment to compare the changes in loperamide-induced relaxation. RESULTS: In addition to the delay in intestinal transit, loperamide produced a marked relaxation in isolated ileum precontracted with ACh, in a dose-dependent manner. This relaxation was abolished by cyprodime, a selective opioid μ-receptor antagonist, but not modified by naloxonazine at a dose sufficient to block opioid μ-1 receptors. Also, treatment with opioid μ-1 receptor agonist failed to modify the muscle tone. Moreover, the relaxation by loperamide was attenuated by glibenclamide at a dose sufficient to block ATP-sensitive K+ (KATP) channels, and by protein kinase A (PKA) inhibitor, but was enhanced by an inhibitor of phosphodiesterase for cyclic adenosine monophosphate (cAMP). CONCLUSION: Loperamide induces intestinal relaxation by activation of opioid μ-2 receptors via the cAMP-PKA pathway to open KATP channels, relates to OIC. PMID:22493554

Adenosine A1 receptors modulate high voltage-activated Ca2+ currents and motor pattern generation in the Xenopus embryo

PubMed Central

Brown, Paul; Dale, Nicholas

2000-01-01

Adenosine causes voltage- and non-voltage-dependent inhibition of high voltage-activated (HVA) Ca2+ currents in Xenopus laevis embryo spinal neurons. As this inhibition can be blocked by 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) and mimicked by N6-cyclopentyladenosine (CPA) it appears to be mediated by A1 receptors. Agents active at A2 receptors either were without effect or could be blocked by DPCPX. AMP had no agonist action on these receptors. By using ω-conotoxin GVIA we found that adenosine inhibited an N-type Ca2+ current as well as a further unidentified HVA current that was insensitive to dihydropyridines, ω-agatoxin TK and ω-conotoxin MVIIC. Both types of current were subject to voltage- and non-voltage-dependent inhibition. We used CPA and DPCPX to test whether A1 receptors regulated spinal motor pattern generation in spinalized Xenopus embryos. DPCPX caused a near doubling of, while CPA greatly shortened, the length of swimming episodes. In addition, DPCPX slowed, while CPA greatly speeded up, the rate of run-down of motor activity. Our results demonstrate a novel action of A1 receptors in modulating spinal motor activity. Furthermore they confirm that adenosine is produced continually throughout swimming episodes and acts to cause the eventual termination of activity. PMID:10856119

Hypotensive effects of ghrelin receptor agonists mediated through a novel receptor.

PubMed

Callaghan, Brid; Kosari, Samin; Pustovit, Ruslan V; Sartor, Daniela M; Ferens, Dorota; Ban, Kung; Baell, Jonathan; Nguyen, Trung V; Rivera, Leni R; Brock, James A; Furness, John B

2014-03-01

Some agonists of ghrelin receptors cause rapid decreases in BP. The mechanisms by which they cause hypotension and the pharmacology of the receptors are unknown. The effects of ligands of ghrelin receptors were investigated in rats in vivo, on isolated blood vessels and on cells transfected with the only molecularly defined ghrelin receptor, growth hormone secretagogue receptor 1a (GHSR1a). Three agonists of GHSR1a receptors, ulimorelin, capromorelin and CP464709, caused a rapid decrease in BP in the anaesthetized rat. The effect was not reduced by either of two GHSR1a antagonists, JMV2959 or YIL781, at doses that blocked effects on colorectal motility, in vivo. The rapid hypotension was not mimicked by ghrelin, unacylated ghrelin or the unacylated ghrelin receptor agonist, AZP531. The early hypotension preceded a decrease in sympathetic nerve activity. Early hypotension was not reduced by hexamethonium or by baroreceptor (sino-aortic) denervation. Ulimorelin also relaxed isolated segments of rat mesenteric artery, and, less potently, relaxed aorta segments. The vascular relaxation was not reduced by JMV2959 or YIL781. Ulimorelin, capromorelin and CP464709 activated GHSR1a in transfected HEK293 cells at nanomolar concentrations. JMV2959 and YIL781 both antagonized effects in these cells, with their pA2 values at the GHSR1a receptor being 6.55 and 7.84. Our results indicate a novel vascular receptor or receptors whose activation by ulimorelin, capromorelin and CP464709 lowered BP. This receptor is activated by low MW GHSR1a agonists, but is not activated by ghrelin. © 2013 The British Pharmacological Society.

Partial agonists for α4β2 nicotinic receptors stimulate dopaminergic neuron firing with relatively enhanced maximal effects

PubMed Central

Chen, Ying; Broad, Lisa M; Phillips, Keith G; Zwart, Ruud

2012-01-01

BACKGROUND AND PURPOSE Partial agonists selective for α4β2 nicotinic ACh receptors have been developed for smoking cessation as they induce weak activation of native α4β2* receptors and inhibit effect of nicotine. However, it is unclear whether at brain functions there is an existence of receptor reserve that allows weak receptor activation to induce maximum physiological effects. We assessed the extent of α4β2 partial agonist-induced increase of firing rate in dopaminergic neurons and evaluated the influence of receptor reserve. EXPERIMENTAL APPROACH The relative maximal effects and potencies of six nicotinic agonists were assessed on recombinant human α4β2 and α7 receptors expressed in mammalian cell lines by measuring calcium influx. Agonist-induced increase of the spontaneous firing rate of dopaminergic neurons was recorded using microelectrodes in the ventral tegmental area of rat brain slices. KEY RESULTS All α4β2 partial and full agonists increased the firing rate concentration-dependently. Their sensitivity to subtype-selective antagonists showed predominant activation of native α4β2* receptors. However, partial agonists with relative maximal effects as low as 33% on α4β2 receptors maximally increased the firing rate and induced additional depolarization block of firing, demonstrating that partial activation of receptors caused the maximum increase in firing rate in the presence of a receptor reserve. CONCLUSIONS AND IMPLICATIONS Partial α4β2 agonists induced relatively enhanced effects on the firing rate of dopaminergic neurons, and the effect was mainly attributed to the existence of native α4β2* receptor reserve. The results have implications in the understanding of physiological effects and therapeutic efficacies of α4β2 partial agonists. PMID:21838750

Base modification strategies to modulate immune stimulation by an siRNA.

PubMed

Valenzuela, Rachel Anne P; Suter, Scott R; Ball-Jones, Alexi A; Ibarra-Soza, José M; Zheng, Yuxuan; Beal, Peter A

2015-01-19

Immune stimulation triggered by siRNAs is one of the major challenges in the development of safe RNAi-based therapeutics. Within an immunostimulatory siRNA sequence, this hurdle is commonly addressed by using ribose modifications (e.g., 2'-OMe or 2'-F), which results in decreased cytokine production. However, as immune stimulation by siRNAs is a sequence-dependent phenomenon, recognition of the nucleobases by the trigger receptor(s) is also likely. Here, we use the recently published crystal structures of Toll-like receptor 8 (TLR8) bound to small-molecule agonists to generate computational models for ribonucleotide binding by this immune receptor. Our modeling suggested that modification of either the Watson-Crick or Hoogsteen face of adenosine would disrupt nucleotide/TLR8 interactions. We employed chemical synthesis to alter either the Watson-Crick or Hoogsteen face of adenosine and evaluated the effect of these modifications in an siRNA guide strand by measuring the immunostimulatory and RNA interference properties. For the siRNA guide strand tested, we found that modifying the Watson-Crick face is generally more effective at blocking TNFα production in human peripheral blood mononuclear cells (PBMCs) than modification at the Hoogsteen edge. We also observed that modifications near the 5'-end were more effective at blocking cytokine production than those placed at the 3'-end. This work advances our understanding of how chemical modifications can be used to optimize siRNA performance. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cardiovascular effects of substance P receptor stimulation in the ventrolateral medullary pressor and depressor areas.

PubMed

Urbanski, R W; Murugaian, J; Krieger, A J; Sapru, H N

1989-07-10

The pressor (VLPA) and the depressor (VLDA) areas in the ventrolateral medulla were identified with the microinjection of L-glutamate (1.77 nmol/site) in artificially ventilated urethane-anesthetized male Wistar rats. Bilateral microinjection of a stable substance P (SP) agonist [pGlu5, MePhe8, Sar9]-SP(5-11)], abbreviated as DiMe, into the VLPA (6-600 pmol/site) produced a dose-dependent increase in blood pressure (BP). The effects on heart rate (HR) were variable. Intravenous pretreatment with a ganglionic blocker chlorisondamine (3.0 mg/kg, i.v.), but not with a vasopressin antagonist, blocked these responses. Similar microinjection of DiMe (6-600 pmol/site) into the VLDA produced a dose-dependent decrease in HR but had no effect on BP levels. The DiMe-induced bradycardic response elicited from the VLDA was blocked by i.v. pretreatment with atropine methylbromide (0.5 mg/kg, i.v.). These findings indicate that there are SP receptors localized on sympathoexcitatory neurons in the VLPA and that SP may be an excitatory neurotransmitter in this area. In the VLDA, the SP receptors appear to be localized on a subpopulation of neurons that affect vagal, but not sympathetic, outflow to the heart.

Distinct Fcγ receptors mediate the effect of Serum Amyloid P on neutrophil adhesion and fibrocyte differentiation

PubMed Central

Cox, Nehemiah; Pilling, Darrell; Gomer, Richard H.

2014-01-01

The plasma protein Serum Amyloid P (SAP) reduces neutrophil adhesion, inhibits the differentiation of monocytes into fibroblast-like cells called fibrocytes, and promotes phagocytosis of cell debris by macrophages. Together, these effects of SAP reduce key aspects of inflammation and fibrosis, and SAP injections improve lung function in pulmonary fibrosis patients. SAP functions are mediated in part by Fcγ receptors, but the contribution of each Fcγ receptor is not fully understood. We found that amino acids Q55 and E126 in human SAP affect human fibrocyte differentiation and SAP binding to FcγRI. E126, K130 and Q128 affect neutrophil adhesion and SAP affinity for FcγRIIa. Q128 also affects phagocytosis by macrophages and SAP affinity for FcγRI. All the identified functionally significant amino acids in SAP form a binding site that is distinct from the previously described SAP-FcγRIIa binding site. Blocking FcγRI with an IgG blocking antibody reduces the SAP effect on fibrocyte differentiation, and ligating FcγRIIa with antibodies reduces neutrophil adhesion. Together, these results suggest that SAP binds to FcγRI on monocytes to inhibit fibrocyte differentiation, and binds to FcγRIIa on neutrophils to reduce neutrophil adhesion. PMID:25024390

A novel design of combining the angiotensin converting enzyme (ACE) inhibitor captopril with the angiotensin receptor blocker (ARB) losartan using homo coupling via PEG diacid linker.

PubMed

Hashemzadeh, Mehrnoosh; Park, Shery; Ju, Hee; Movahed, Mohammad R

2013-12-01

Cardiovascular disease is the leading cause of death in American adults. Furthermore, the incidence of congestive heart failure is on the rise as a major cause of hospitalization and mortality in this population. Angiotensin Converting Enzyme (ACE) inhibitors prevent the production of angiotensin II, which has been shown to reduce mortality in patients with congestive heart failure. Angiotensin II receptor blockers (ARB) were developed as a direct inhibitor of angiotensin II. ARBs have been shown to be effective in the treatment of patients with systolic heart failure but do not cause chronic coughing which is a common side effect of ACE inhibitors. In theory, a compound that has the combined effect of an ACE inhibitor and an ARB should be more effective in treating heart failure patients than either agents alone. Therefore, the purpose of this manuscript is to design and discuss the benefits of a new molecule, which combines captopril, an ACE inhibitor, with losartan, an ARB. In this experiment Captopril and Losartan were modified and synthesized separately and combined by homo or mono coupling. This was achieved by taking advantage of PEG (Polyethylene glycol) as a linker. It is expected that this molecule will have the combined modes of action of both ACEs and ARBs. Benefits from combination therapy include; increased efficacy, reduced adverse effects, convenience, compliance, and prolonged duration. Consequently, this combined molecule is expected to block the production of angiotensin II more efficiently and effectively. Although captopril and losartan work in the same system by blocking the effect of angiotensin II they have different action sites and mechanisms some patents are also discussed. Losartan blocks the AT1 receptor which is expressed on the cell surface, while captopril inhibits ACE, preventing production of angiotensin II, which is present in both the plasma and on the cell surface, especially on endothelial and smooth muscle cells.

In vivo effects of CB2 receptor-selective cannabinoids on the vasculature of normal and arthritic rat knee joints

PubMed Central

McDougall, J J; Yu, V; Thomson, J

2007-01-01

Background and purpose: Cannabinoids (CBs) are known to be vasoactive and to regulate tissue inflammation. The present study examined the in vivo vasomotor effects of the CB2 receptor agonists JWH015 and JWH133 in rat knee joints. The effect of acute and chronic joint inflammation on CB2 receptor-mediated responses was also tested. Experimental approach: Blood flow was assessed in rat knee joints by laser Doppler imaging both before and following topical administration of CB2 receptor agonists. Vasoactivity was measured in normal, acute kaolin/carrageenan inflamed and Freund's complete adjuvant chronically inflamed knees. Key results: In normal animals, JWH015 and JWH133 caused a concentration-dependent increase in synovial blood flow which in the case of JWH133 was blocked by the selective CB2 receptor antagonist AM630 as well as the transient receptor potential vanilloid-1 (TRPV1) antagonist SB366791. The vasodilator effect of JWH133 was significantly attenuated in both acute and chronically inflamed knees. Given alone, AM630 had no effect on joint blood flow. Conclusion and implications: In normal joints, the cannabinomimetic JWH133 causes hyperaemia via a CB2 and TRPV1 receptor mechanism. During acute and chronic inflammation, however, this vasodilatatory response is significantly attenuated. PMID:17982474

Opioid receptor involvement in the effect of AgRP- (83-132) on food intake and food selection.

PubMed

Hagan, M M; Rushing, P A; Benoit, S C; Woods, S C; Seeley, R J

2001-03-01

Agouti-related peptide (AgRP) is a receptor antagonist of central nervous system (CNS) melanocortin receptors and appears to have an important role in the control of food intake since exogenous CNS administration in rats and overexpression in mice result in profound hyperphagia and weight gain. Given that AgRP is heavily colocalized with neuropeptide Y (NPY) and that orexigenic effects of NPY depend on activity at opioid receptors, we hypothesized that AgRP's food-intake effects are also mediated by opioid receptors. Subthreshold doses of the opioid receptor antagonist naloxone blocked AgRP-induced intake when given simultaneously but not 24 h after AgRP injection. Opioids not only influence food intake but food selection as well. Hence, we tested AgRP's effect to alter food choice between matched diets with differing dietary fat content. AgRP selectively enhanced intake of the high-fat but not the low-fat diet. Additionally, AgRP selectively increased chow intake in rats given ad libitum access to a 20% sucrose solution and standard rat chow. The current results indicate that AgRP influences not only caloric intake but food selection as well and that the early effects of AgRP depend critically on an interaction with opioid receptors.

Protection by imidazol(ine) drugs and agmatine of glutamate-induced neurotoxicity in cultured cerebellar granule cells through blockade of NMDA receptor

PubMed Central

Olmos, Gabriel; DeGregorio-Rocasolano, Nuria; Regalado, M Paz; Gasull, Teresa; Boronat, M Assumpció; Trullas, Ramón; Villarroel, Alvaro; Lerma, Juan; García-Sevilla, Jesús A

1999-01-01

This study was designed to assess the potential neuroprotective effect of several imidazol(ine) drugs and agmatine on glutamate-induced necrosis and on apoptosis induced by low extracellular K+ in cultured cerebellar granule cells.Exposure (30 min) of energy deprived cells to L-glutamate (1–100 μM) caused a concentration-dependent neurotoxicity, as determined 24 h later by a decrease in the ability of the cells to metabolize 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) into a reduced formazan product. L-glutamate-induced neurotoxicity (EC50=5 μM) was blocked by the specific NMDA receptor antagonist MK-801 (dizocilpine).Imidazol(ine) drugs and agmatine fully prevented neurotoxicity induced by 20 μM (EC100) L-glutamate with the rank order (EC50 in μM): antazoline (13)>cirazoline (44)>LSL 61122 [2-styryl-2-imidazoline] (54)>LSL 60101 [2-(2-benzofuranyl) imidazole] (75)>idazoxan (90)>LSL 60129 [2-(1,4-benzodioxan-6-yl)-4,5-dihydroimidazole] (101)>RX821002 (2-methoxy idazoxan) (106)>agmatine (196). No neuroprotective effect of these drugs was observed in a model of apoptotic neuronal cell death (reduction of extracellular K+) which does not involve stimulation of NMDA receptors.Imidazol(ine) drugs and agmatine fully inhibited [3H]-(+)-MK-801 binding to the phencyclidine site of NMDA receptors in rat brain. The profile of drug potency protecting against L-glutamate neurotoxicity correlated well (r=0.90) with the potency of the same compounds competing against [3H]-(+)-MK-801 binding.In HEK-293 cells transfected to express the NR1-1a and NR2C subunits of the NMDA receptor, antazoline and agmatine produced a voltage- and concentration-dependent block of glutamate-induced currents. Analysis of the voltage dependence of the block was consistent with the presence of a binding site for antazoline located within the NMDA channel pore with an IC50 of 10–12 μM at 0 mV.It is concluded that imidazol(ine) drugs and agmatine are neuroprotective against glutamate-induced necrotic neuronal cell death in vitro and that this effect is mediated through NMDA receptor blockade by interacting with a site located within the NMDA channel pore. PMID:10455281

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

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.

Transmission to interneurons is via slow excitatory synaptic potentials mediated by P2Y(1) receptors during descending inhibition in guinea-pig ileum.

PubMed

Thornton, Peter D J; Gwynne, Rachel M; McMillan, Darren J; Bornstein, Joel C

2013-01-01

The nature of synaptic transmission at functionally distinct synapses in intestinal reflex pathways has not been fully identified. In this study, we investigated whether transmission between interneurons in the descending inhibitory pathway is mediated by a purine acting at P2Y receptors to produce slow excitatory synaptic potentials (EPSPs). Myenteric neurons from guinea-pig ileum in vitro were impaled with intracellular microelectrodes. Responses to distension 15 mm oral to the recording site, in a separately perfused stimulation chamber and to electrical stimulation of local nerve trunks were recorded. A subset of neurons, previously identified as nitric oxide synthase immunoreactive descending interneurons, responded to both stimuli with slow EPSPs that were reversibly abolished by a high concentration of PPADS (30 μM, P2 receptor antagonist). When added to the central chamber of a three chambered organ bath, PPADS concentration-dependently depressed transmission through that chamber of descending inhibitory reflexes, measured as inhibitory junction potentials in the circular muscle of the anal chamber. Reflexes evoked by distension in the central chamber were unaffected. A similar depression of transmission was seen when the specific P2Y(1) receptor antagonist MRS 2179 (10 μM) was in the central chamber. Blocking either nicotinic receptors (hexamethonium 200 μM) or 5-HT(3) receptors (granisetron 1 μM) together with P2 receptors had no greater effect than blocking P2 receptors alone. Slow EPSPs mediated by P2Y(1) receptors, play a primary role in transmission between descending interneurons of the inhibitory reflexes in the guinea-pig ileum. This is the first demonstration for a primary role of excitatory metabotropic receptors in physiological transmission at a functionally identified synapse.

Ionic plasticity and pain: The loss of descending serotonergic fibers after spinal cord injury transforms how GABA affects pain.

PubMed

Huang, Yung-Jen; Grau, James W

2018-05-02

Activation of pain (nociceptive) fibers can sensitize neural circuits within the spinal cord, inducing an increase in excitability (central sensitization) that can foster chronic pain. The development of spinally-mediated central sensitization is regulated by descending fibers and GABAergic interneurons. In adult animals, the co-transporter KCC2 maintains a low intracellular concentration of the anion Cl - . As a result, when the GABA-A receptor is engaged, Cl - flows in the neuron which has a hyperpolarizing (inhibitory) effect. Spinal cord injury (SCI) can down-regulate KCC2 and reverse the flow of Cl - . Under these conditions, engaging the GABA-A receptor can have a depolarizing (excitatory) effect that fosters the development of nociceptive sensitization. The present paper explores how SCI alters GABA function and provides evidence that the loss of descending fibers alters pain transmission to the brain. Prior work has shown that, after SCI, administration of a GABA-A antagonist blocks the development of capsaicin-induced nociceptive sensitization, implying that GABA release plays an essential role. This excitatory effect is linked to serotonergic (5HT) fibers that descend through the dorsolateral funiculus (DLF) and impact spinal function via the 5HT-1A receptor. Supporting this, blocking the 5HT-1A receptor, or lesioning the DLF, emulated the effect of SCI. Conversely, spinal application of a 5HT-1A agonist up-regulated KCC2 and reversed the effect of bicuculline treatment. Finally, lesioning the DLF reversed how a GABA-A antagonist affects a capsaicin-induced aversion in a place conditioning task; in sham operated animals, bicuculline enhanced aversion whereas in DLF-lesioned rats biciculline had an antinociceptive effect. Copyright © 2018 Elsevier Inc. All rights reserved.

Modeling study of mecamylamine block of muscle type acetylcholine receptors.

PubMed

Ostroumov, Konstantin; Shaikhutdinova, Asya; Skorinkin, Andrey

2008-04-01

The blocking action of mecamylamine on different types of nicotinic acetylcholine receptors (nAChRs) has been extensively studied and used as a tool to characterize the nAChRs from different synapses. However, mechanism of mecamylamine action was not fully explored for all types of nAChRs. In the present study, we provide brief description of the mecamylamine action on muscle nAChRs expressed at the frog neuromuscular junction. In this preparation mecamylamine block of nAChRs was accompanied by a use-dependent block relief induced by membrane depolarization combined with the activation of nAChRs by endogenous agonist acetylcholine (ACh). Further, three kinetic models of possible mecamylamine interaction with nAChRs were analyzed including simple open channel block, symmetrical trapping block and asymmetrical trapping block. This analysis suggested that mecamylamine action could be described on the basis of trapping mechanism, when the antagonist remained inside the channel even in the absence of bound agonist. Such receptors with trapped mecamylamine inside were predicted to have a closing rate constant about three times faster than resting one and a fast voltage-dependent unblocking rate constant. Specific experimental conditions and morphological organization of the neuromuscular synapses were considered to simulate time course of the mecamylamine block development. Thus, likewise for the neuronal nAChRs, the trapping mechanism determined the action of mecamylamine on synaptic neuromuscular currents evoked by the endogenous agonist acetylcholine (ACh), however specific morphological organization of the synaptic transmission delayed time development of the currents block.

Muscarinic receptor agonists stimulate human colon cancer cell migration and invasion.

PubMed

Belo, Angelica; Cheng, Kunrong; Chahdi, Ahmed; Shant, Jasleen; Xie, Guofeng; Khurana, Sandeep; Raufman, Jean-Pierre

2011-05-01

Muscarinic receptors (CHRM) are overexpressed in colon cancer. To explore a role for muscarinic receptor signaling in colon cancer metastasis, we used human H508 and HT29 colon cancer cells that coexpress epidermal growth factor (ERBB) and CHRM3 receptors. In a wound closure model, following 8-h incubation of H508 cells with 100 μM ACh we observed a threefold increase in cell migration indistinguishable from the actions of epidermal growth factor (EGF). Atropine blocked the actions of ACh but not of EGF. In SNU-C4 colon cancer cells that express ERBB but not CHRM, EGF caused a threefold increase in migration; ACh had no effect. ACh-induced cell migration was attenuated by chemical inhibitors of ERBB1 activation, by anti-ERBB1 antibody, and by inhibitors of ERK and phosphatidylinositol 3-kinase (PI3K) signaling. Consistent with matrix metalloproteinase-7 (MMP7)-mediated release of an ERBB1 ligand, heparin binding epidermal growth factor-like growth factor (HBEGF), ACh-induced migration was inhibited by an MMP inhibitor and by anti-MMP7 and -HBEGF antibodies. ACh-induced cell migration was blocked by inhibiting RhoA and ROCK, key proteins that interact with the actin cytoskeleton. ACh-induced RhoA activation was attenuated by agents that inhibit ERBB1, ERK, and PI3K activation. Collectively, these findings indicate that ACh-induced cell migration is mediated by MMP7-mediated release of HBEGF, an ERBB ligand that activates ERBB1 and downstream ERK and PI3K signaling. In a cell invasion model, ACh-induced HT29 cell invasion was blocked by atropine. In concert with previous observations, these findings indicate that muscarinic receptor signaling plays a key role in colon cancer cell proliferation, survival, migration, and invasion.

Muscarinic receptor agonists stimulate human colon cancer cell migration and invasion

PubMed Central

Belo, Angelica; Cheng, Kunrong; Chahdi, Ahmed; Shant, Jasleen; Xie, Guofeng; Khurana, Sandeep

2011-01-01

Muscarinic receptors (CHRM) are overexpressed in colon cancer. To explore a role for muscarinic receptor signaling in colon cancer metastasis, we used human H508 and HT29 colon cancer cells that coexpress epidermal growth factor (ERBB) and CHRM3 receptors. In a wound closure model, following 8-h incubation of H508 cells with 100 μM ACh we observed a threefold increase in cell migration indistinguishable from the actions of epidermal growth factor (EGF). Atropine blocked the actions of ACh but not of EGF. In SNU-C4 colon cancer cells that express ERBB but not CHRM, EGF caused a threefold increase in migration; ACh had no effect. ACh-induced cell migration was attenuated by chemical inhibitors of ERBB1 activation, by anti-ERBB1 antibody, and by inhibitors of ERK and phosphatidylinositol 3-kinase (PI3K) signaling. Consistent with matrix metalloproteinase-7 (MMP7)-mediated release of an ERBB1 ligand, heparin binding epidermal growth factor-like growth factor (HBEGF), ACh-induced migration was inhibited by an MMP inhibitor and by anti-MMP7 and -HBEGF antibodies. ACh-induced cell migration was blocked by inhibiting RhoA and ROCK, key proteins that interact with the actin cytoskeleton. ACh-induced RhoA activation was attenuated by agents that inhibit ERBB1, ERK, and PI3K activation. Collectively, these findings indicate that ACh-induced cell migration is mediated by MMP7-mediated release of HBEGF, an ERBB ligand that activates ERBB1 and downstream ERK and PI3K signaling. In a cell invasion model, ACh-induced HT29 cell invasion was blocked by atropine. In concert with previous observations, these findings indicate that muscarinic receptor signaling plays a key role in colon cancer cell proliferation, survival, migration, and invasion. PMID:21273532

A Metabotropic-Like Flux-Independent NMDA Receptor Regulates Ca2+ Exit from Endoplasmic Reticulum and Mitochondrial Membrane Potential in Cultured Astrocytes.

PubMed

Montes de Oca Balderas, Pavel; Aguilera, Penélope

2015-01-01

Astrocytes were long thought to be only structural cells in the CNS; however, their functional properties support their role in information processing and cognition. The ionotropic glutamate N-methyl D-aspartate (NMDA) receptor (NMDAR) is critical for CNS functions, but its expression and function in astrocytes is still a matter of research and debate. Here, we report immunofluorescence (IF) labeling in rat cultured cortical astrocytes (rCCA) of all NMDAR subunits, with phenotypes suggesting their intracellular transport, and their mRNA were detected by qRT-PCR. IF and Western Blot revealed GluN1 full-length synthesis, subunit critical for NMDAR assembly and transport, and its plasma membrane localization. Functionally, we found an iCa2+ rise after NMDA treatment in Fluo-4-AM labeled rCCA, an effect blocked by the NMDAR competitive inhibitors D(-)-2-amino-5-phosphonopentanoic acid (APV) and Kynurenic acid (KYNA) and dependent upon GluN1 expression as evidenced by siRNA knock down. Surprisingly, the iCa2+ rise was not blocked by MK-801, an NMDAR channel blocker, or by extracellular Ca2+ depletion, indicating flux-independent NMDAR function. In contrast, the IP3 receptor (IP3R) inhibitor XestosponginC did block this response, whereas a Ryanodine Receptor inhibitor did so only partially. Furthermore, tyrosine kinase inhibition with genistein enhanced the NMDA elicited iCa2+ rise to levels comparable to those reached by the gliotransmitter ATP, but with different population dynamics. Finally, NMDA depleted the rCCA mitochondrial membrane potential (mΔψ) measured with JC-1. Our results demonstrate that rCCA express NMDAR subunits which assemble into functional receptors that mediate a metabotropic-like, non-canonical, flux-independent iCa2+ increase.

Prevention effect of rare ginsenosides against stress-hormone induced MTOC amplification

PubMed Central

Lee, Jee-Hyun; Cheong, Kyu Jin; Jung, Youn-Sang; Woo, Tae-Gyun; Yoon, Min-Ho; Oh, Ah-Young; Kang, So-Mi; Lee, Chunghui; Sun, Hokeun; Hwang, Jihwan; Song, Gyu-Yong; Park, Bum-Joon

2016-01-01

Stress has been suggested as one of important cause of human cancer without molecular biological evidence. Thus, we test the effect of stress-related hormones on cell viability and mitotic fidelity. Similarly to estrogen, stress hormone cortisol and its relative cortisone increase microtubule organizing center (MTOC) number through elevated expression of γ-tubulin and provide the Taxol resistance to human cancer cell lines. However, these effects are achieved by glucocorticoid hormone receptor (GR) but not by estrogen receptor (ER). Since ginsenosides possess steroid-like structure, we hypothesized that it would block the stress or estrogen-induced MTOC amplification and Taxol resistance. Among tested chemicals, rare ginsenoside, CSH1 (Rg6) shows obvious effect on inhibition of MTOC amplification, γ-tubulin induction and Taxol resistance. Comparing to Fulvestant (FST), ER-α specific inhibitor, this chemical can block the cortisol/cortisone-induced MTOC deregulation as well as ER-α signaling. Our results suggest that stress hormone induced tumorigenesis would be achieved by MTOC amplification, and CSH1 would be useful for prevention of stress-hormone or steroid hormone-induced chromosomal instability. PMID:27147573

Neurokinin B potentiates ATP-activated currents in rat DRG neurons.

PubMed

Wang, M J; Xiong, S H; Li, Z W

2001-12-27

This study aimed to explore whether NKB could modulate the responses mediated by ATP receptor (P2X purinoceptor). Whole-cell patch clamp and repatch experiments were performed on cultured rat DRG neurons. The majority of neurons examined were sensitive both to ATP and to NKB (77.1%, 54/70). NKB preapplied could potentiate ATP-activated currents (I(ATP)) markedly; this effect was concentration-dependent and could be blocked by SR 142801, an NK3 receptor antagonist. Preapplication of 0.001, 0.01, 0.1 and 1.0 microM NKB increased ATP-activated currents by 55.1+/-18.8, 75.2+/-17.4, 84.1+/-18.8 and 81.0+/-21.7%, respectively. The concentration-response curves for ATP with and without preapplication of NKB show that: (1) preapplication of NKB shifted the curve upwards; (2) the maximal amplitude of I(ATP) with NKB preapplication increased by 78.5%, while the threshold value remained unchanged; (3) the EC(50) values of the two curves were very close (44 vs. 42 microM). Intracellular dialysis of H-7 by using repatch clamp technique could block the potentiation of I(ATP) by NKB. It suggests that this potentiating effect was caused by phosphorylation of ATP receptor, which resulted from the activation of G protein coupled NK3 receptor and consequential intracellular signal transduction cascade.

The site of the 5-hydroxytryptamine receptor on the intramural nervous plexus of the guinea-pig isolated ileum

PubMed Central

Brownlee, G.; Johnson, E. S.

1963-01-01

Dose/response measurements were made on the guinea-pig isolated ileum with six agonists, acetylcholine, 5-hydroxytryptamine, nicotine, dimethylphenylpiperazinium, choline phenyl ether and histamine. The dose effects were repeated in the presence of each of twelve antagonists and one anticholinesterase. Acetylcholine and histamine were chosen because of their direct mode of action on smooth muscle, nicotine, dimethylphenylpiperazinium and choline phenyl ether were used as examples of drugs that act at the ganglionic acetylcholine receptor. 5-Hydroxytryptamine was the drug investigated. Hyoscine blocked the contractions caused by acetylcholine, 5-hydroxytryptamine and the ganglion-stimulants but left the responses to histamine unchanged. The anticholinesterase N,N'-diisopropylphosphorodiamidic fluoride (mipafox) potentiated all the agonists except histamine. The strength of potentiation decreased in the order 5-hydroxytryptamine, nicotine, dimethylphenylpiperazinium and choline phenyl ether, and acetylcholine. The local anaesthetic procaine inhibited to the same extent contractions elicited by 5-hydroxytryptamine, nicotine, dimethylphenylpiperazinium and choline phenyl ether. These results showed that 5-hydroxytryptamine, like nicotine, choline phenyl ether and dimethylphenylpiperazinium, mediated its response through the nervous plexus. Of those tested 5-hydroxytryptamine was the only specific antagonist to 5-hydroxytryptamine; lysergic acid derivatives produced spasm and prolonged changes in tone; phenoxybenzamine caused non-specific block. The diverse modes of action of a number of ganglion-blocking agents were selectively used. Thus hexamethonium, pentolinium, and nicotine in its competitive phase, blocked contractions due to nicotine, dimethylphenylpiperazinium and choline phenyl ether and left those due to 5-hydroxytryptamine, acetylcholine and histamine unchanged. The depolarizing ganglion-blocking agents, dimethylphenylpiperazinium and nicotine, inhibited the responses to all the indirectly acting drugs. Furthermore, mecamylamine, a drug with a less well-defined mode of action, partially inhibited contractions due to 5-hydroxytryptamine in a concentration that blocked those due to nicotine, dimethylphenylpiperazinium and choline phenyl ether. Pempidine, known to act like mecamylamine, did not antagonize 5-hydroxytryptamine. It is concluded that 5-hydroxytryptamine activates specific receptors sited at the intramural parasympathetic ganglion cells. PMID:14081661

Soybean-derived Bowman-Birk inhibitor (BBI) blocks HIV entry into macrophages.

PubMed

Ma, Tong-Cui; Le Guo; Zhou, Run-Hong; Wang, Xu; Liu, Jin-Biao; Li, Jie-Liang; Zhou, Yu; Hou, Wei; Ho, Wen-Zhe

2018-01-01

Bowman-Birk inhibitor (BBI) is a soybean-derived protease inhibitor that has anti-inflammation and anti-HIV effect. Here, we further investigated the anti-HIV action of BBI in macrophages, focusing on its effect on viral entry. We found that BBI could significantly block HIV entry into macrophages. Investigation of the mechanism(s) of the BBI action on HIV inhibition showed that BBI down-regulated the expression of CD4 receptor (as much as 80%) and induced the production of the CC chemokines (up to 60 folds at protein level) in macrophages. This inhibitory effect of BBI on HIV entry could be blocked by the neutralization antibodies to CC chemokines. These findings indicate that BBI may have therapeutic potential as a viral entry inhibitor for the prevention and treatment of HIV infection. Copyright © 2017. Published by Elsevier Inc.

Metabotropic glutamate receptor 5 upregulates surface NMDA receptor expression in striatal neurons via CaMKII.

PubMed

Jin, Dao-Zhong; Xue, Bing; Mao, Li-Min; Wang, John Q

2015-10-22

Metabotropic and ionotropic glutamate receptors are closely clustered in postsynaptic membranes and are believed to interact actively with each other to control excitatory synaptic transmission. Metabotropic glutamate receptor 5 (mGluR5), for example, has been well documented to potentiate ionotropic NMDA receptor activity, although underlying mechanisms are poorly understood. In this study, we investigated the role of mGluR5 in regulating trafficking and subcellular distribution of NMDA receptors in adult rat striatal neurons. We found that the mGluR1/5 agonist DHPG concentration-dependently increased NMDA receptor GluN1 and GluN2B subunit expression in the surface membrane. Meanwhile, DHPG reduced GluN1 and GluN2B levels in the intracellular compartment. The effect of DHPG was blocked by an mGluR5 selective antagonist MTEP but not by an mGluR1 selective antagonist 3-MATIDA. Pretreatment with an inhibitor or a specific inhibitory peptide for synapse-enriched Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) also blocked the DHPG-stimulated redistribution of GluN1 and GluN2B. In addition, DHPG enhanced CaMKIIα activity and elevated GluN2B phosphorylation at a CaMKII-sensitive site (serine 1303). These results demonstrate that mGluR5 regulates trafficking of NMDA receptors in striatal neurons. Activation of mGluR5 appears to induce rapid trafficking of GluN1 and GluN2B to surface membranes through a signaling pathway involving CaMKII. Copyright © 2015 Elsevier B.V. All rights reserved.

Targeting striatal metabotropic glutamate receptor type 5 in Parkinson's disease: bridging molecular studies and clinical trials.

PubMed

Vallano, A; Fernandez-Duenas, V; Garcia-Negredo, G; Quijada, M A; Simon, C P; Cuffí, M L; Carbonell, L; Sanchez, S; Arnau, J M; Ciruela, F

2013-12-01

Metabotropic glutamate (mGlu) receptors are G protein-coupled receptors expressed primarily on neurons and glial cells modulating the effects of glutamatergic neurotransmission. The pharmacological manipulation of these receptors has been postulated to be valuable in the management of some neurological disorders. Accordingly, the targeting of mGlu5 receptors as a therapeutic approach for Parkinson's disease (PD) has been proposed, especially to manage the adverse symptoms associated to chronic treatment with classical PD drugs. Thus, the specific pharmacological blocking of mGlu5 receptors constitutes one of the most attractive non-dopaminergic-based strategies for PD management in general and for the L-DOPA-induced dyskinesia (LID) in particular. Overall, we provide here an update of the current state of the art of these mGlu5 receptor-based approaches that are under clinical study as agents devoted to alleviate PD symptoms.

HIV blocking antibodies following immunisation with chimaeric peptides coding a short N-terminal sequence of the CCR5 receptor.

PubMed

Chain, Benjamin M; Noursadeghi, Mahdad; Gardener, Michelle; Tsang, Jhen; Wright, Edward

2008-10-23

The chemokine receptor CCR5 is required for cellular entry by many strains of HIV, and provides a potential target for molecules, including antibodies, designed to block HIV transmission. This study investigates a novel approach to stimulate antibodies to CCR5. Rabbits were immunised with chimaeric peptides which encode a short fragment of the N-terminal sequence of CCR5, as well as an unrelated T cell epitope from Tetanus toxoid. Immunisation with these chimaeric peptides generates a strong antibody response which is highly focused on the N-terminal CCR5 sequence. The antibody to the chimaeric peptide containing an N-terminal methionine also recognises the full length CCR5 receptor on the cell surface, albeit at higher concentrations. Further comparison of binding to intact CCR5 with binding to CCR5 peptide suggest that the receptor specific antibody generated represents a very small fragment of the total anti-peptide antibody. These findings are consistent with the hypothesis that the N-terminal peptide in the context of the intact receptor has a different structure to that of the synthetic peptide. Finally, the antibody was able to block HIV infection of macrophages in vitro. Thus results of this study suggest that N-terminal fragments of CCR5 may provide potential immunogens with which to generate blocking antibodies to this receptor, while avoiding the dangers of including T cell auto-epitopes.

HIV blocking antibodies following immunisation with chimaeric peptides coding a short N-terminal sequence of the CCR5 receptor

PubMed Central

Chain, Benjamin M.; Noursadeghi, Mahdad; Gardener, Michelle; Tsang, Jhen; Wright, Edward

2008-01-01

The chemokine receptor CCR5 is required for cellular entry by many strains of HIV, and provides a potential target for molecules, including antibodies, designed to block HIV transmission. This study investigates a novel approach to stimulate antibodies to CCR5. Rabbits were immunised with chimaeric peptides which encode a short fragment of the N-terminal sequence of CCR5, as well as an unrelated T cell epitope from Tetanus toxoid. Immunisation with these chimaeric peptides generates a strong antibody response which is highly focused on the N-terminal CCR5 sequence. The antibody to the chimaeric peptide containing an N-terminal methionine also recognises the full length CCR5 receptor on the cell surface, albeit at higher concentrations. Further comparison of binding to intact CCR5 with binding to CCR5 peptide suggest that the receptor specific antibody generated represents a very small fragment of the total anti-peptide antibody. These findings are consistent with the hypothesis that the N-terminal peptide in the context of the intact receptor has a different structure to that of the synthetic peptide. Finally, the antibody was able to block HIV infection of macrophages in vitro. Thus results of this study suggest that N-terminal fragments of CCR5 may provide potential immunogens with which to generate blocking antibodies to this receptor, while avoiding the dangers of including T cell auto-epitopes. PMID:18765264

Effects of GABA receptor antagonists on thresholds of P23H rat retinal ganglion cells to electrical stimulation of the retina

NASA Astrophysics Data System (ADS)

Jensen, Ralph J.; Rizzo, Joseph F., III

2011-06-01

An electronic retinal prosthesis may provide useful vision for patients suffering from retinitis pigmentosa (RP). In animal models of RP, the amount of current needed to activate retinal ganglion cells (RGCs) is higher than in normal, healthy retinas. In this study, we sought to reduce the stimulation thresholds of RGCs in a degenerate rat model (P23H-line 1) by blocking GABA receptor mediated inhibition in the retina. We examined the effects of TPMPA, a GABAC receptor antagonist, and SR95531, a GABAA receptor antagonist, on the electrically evoked responses of RGCs to biphasic current pulses delivered to the subretinal surface through a 400 µm diameter electrode. Both TPMPA and SR95531 reduced the stimulation thresholds of ON-center RGCs on average by 15% and 20% respectively. Co-application of the two GABA receptor antagonists had the greatest effect, on average reducing stimulation thresholds by 32%. In addition, co-application of the two GABA receptor antagonists increased the magnitude of the electrically evoked responses on average three-fold. Neither TPMPA nor SR95531, applied alone or in combination, had consistent effects on the stimulation thresholds of OFF-center RGCs. We suggest that the effects of the GABA receptor antagonists on ON-center RGCs may be attributable to blockage of GABA receptors on the axon terminals of ON bipolar cells.

Effect of progesterone-carbachol derivative on perfusion pressure and coronary resistance in isolated rat heart: via activation of the M2 muscarinic receptor.

PubMed

Figueroa-Valverde, Lauro; Diaz-Cedillo, Francisco; Garcia-Cervera, Elodia; Gomez, Eduardo Pool; Lopez-Ramos, Maria

2014-01-01

The present study was designed to investigate the effects of progesterone-carbachol derivative on perfusion pressure and coronary resistance in rats. An additional aim was to identify the molecular mechanisms involved. The Langendorff model was used to measure perfusion pressure and coronary resistance changes in isolated rat heart after progesterone-carbachol derivative alone and after the following compounds; mifepristone (progesterone receptor blocker), yohimbine (α2 adreno-receptor antagonist), ICI 118,551 (selective β2 receptor blocker), atropine (non-selective muscarinic receptor antagonist), methoctramine (antagonist of M2 receptor) and L-NAME (inhibitor of nitric oxide synthase). The results show that progesterone-carbachol derivative [10(-9) mM] significantly decreased perfusion pressure (P=0.005) and coronary resistance (P=0.006) in isolated rat heart. Additionally, the effect of progesterone-carbachol on perfusion pressure [10(-9) to 10(-4) mM] was only blocked in the presence of methoctramine and L-NAME. These data suggest that progesterone derivative exert its effect on perfusion pressure via activation of the M2 muscarinic. In addition, this phenomenon involves stimulation of nitric oxide synthase (NOS).

Effect of memantine on cue-induced alcohol craving in recovering alcohol-dependent patients.

PubMed

Krupitsky, Evgeny M; Neznanova, Olga; Masalov, Dimitry; Burakov, Andrey M; Didenko, Tatyana; Romanova, Tatyana; Tsoy, Marina; Bespalov, Anton; Slavina, Tatyana Y; Grinenko, Alexander A; Petrakis, Ismene L; Pittman, Brian; Gueorguieva, Ralitza; Zvartau, Edwin E; Krystal, John H

2007-03-01

Ethanol blocks N-methyl-d-aspartic acid (NMDA) glutamate receptors. Increased NMDA receptor function may contribute to motivational disturbances that contribute to alcoholism. The authors assessed whether the NMDA receptor antagonist memantine reduces cue-induced alcohol craving and produces ethanol-like subjective effects. Thirty-eight alcohol-dependent inpatients participated in three daylong testing sessions in a randomized order under double-blind conditions. On each test day, subjects received 20 mg of memantine, 40 mg of memantine, or placebo, and subjective responses to treatment were assessed. The level of alcohol craving was assessed before and after exposure to an alcohol cue. Memantine did not stimulate alcohol craving before exposure to an alcohol cue, and it attenuated alcohol cue-induced craving in a dose-related fashion. It produced dose-related ethanol-like effects without adverse cognitive or behavioral effects. These data support further exploration of whether well-tolerated NMDA receptor antagonists might have a role in the treatment of alcoholism.

Roles of neuronal NK1 and NK3 receptors in synaptic transmission during motility reflexes in the guinea-pig ileum

PubMed Central

Johnson, P J; Bornstein, J C; Burcher, E

1998-01-01

The role of NK1 and NK3 receptors in synaptic transmission between myenteric neurons during motility reflexes in the guinea-pig ileum was investigated by recording intracellularly the reflex responses of the circular muscle to distension or compression of the mucosal villi. Experiments were performed in a three-chambered organ bath that enabled drugs to be selectively applied to different sites along the reflex pathways.When applied in the recording chamber, an NK1 receptor antagonist, SR140333 (100 nM), reduced by 40–50% the amplitudes of inhibitory junction potentials (i.j.ps) evoked in the circular muscle by activation of descending reflex pathways. This effect was abolished when synaptic transmission in the stimulus region was blocked with physiological saline containing 0.1 mM Ca2+ plus 10 mM Mg2+, leaving only the component of the descending reflex pathway conducted via long anally directed collaterals of intrinsic sensory neurons.SR140333 (100 nM) had no effect on descending reflex i.j.ps when applied to the stimulus region. Ascending reflexes were also unaffected by SR140333 in the stimulus region or between the stimulus and recording sites.Septide (10 nM), an NK1 receptor agonist, enhanced descending reflexes by 30–60% when in the recording chamber. [Sar9,Met(O2)11]substance P had no effect at 10 nM, but potentiated distension-evoked reflexes at 100 nM.A selective NK3 receptor antagonist, SR142801 (100 nM), when applied to the stimulus region, reduced the amplitude of descending reflex responses to compression by 40%, but had no effect on responses to distension. SR142801 (100 nM) had no effect when applied to other regions of the descending reflex pathways.SR142801 (100 nM) only inhibited ascending reflexes when applied at the recording site. However, after nicotinic transmission in the stimulus region was blocked, SR142801 (100 nM) at this site reduced responses to compression.Contractions of the circular muscle of isolated rings of ileum evoked by low concentrations of septide, but not [Sar9,Met(O2)11]substance P, were potentiated by tetrodotoxin (300 nM).Contractile responses evoked by an NK3 receptor agonist, senktide, were non-competitively inhibited by SR142801. After excitatory neuromuscular transmission was blocked, senktide produced inhibitory responses that were also antagonised by SR142801, but to a lesser extent and in an apparently competitive manner.These results indicate that tachykinins acting via NK1 receptors partly mediate transmission to inhibitory motor neurons. NK3 receptors play a role in transmission from intrinsic sensory neurons and from ascending interneurons to excitatory motor neurons during motility reflexes. PMID:9723948

Carbachol regulates pacemaker activities in cultured interstitial cells of Cajal from the mouse small intestine.

PubMed

So, Keum Young; Kim, Sang Hun; Sohn, Hong Moon; Choi, Soo Jin; Parajuli, Shankar Prasad; Choi, Seok; Yeum, Cheol Ho; Yoon, Pyung Jin; Jun, Jae Yeoul

2009-05-31

We studied the effect of carbachol on pacemaker currents in cultured interstitial cells of Cajal (ICC) from the mouse small intestine by muscarinic stimulation using a whole cell patch clamp technique and Ca2+-imaging. ICC generated periodic pacemaker potentials in the current-clamp mode and generated spontaneous inward pacemaker currents at a holding potential of-70 mV. Exposure to carbachol depolarized the membrane and produced tonic inward pacemaker currents with a decrease in the frequency and amplitude of the pacemaker currents. The effects of carbachol were blocked by 1-dimethyl-4-diphenylacetoxypiperidinium, a muscarinic M(3) receptor antagonist, but not by methotramine, a muscarinic M(2) receptor antagonist. Intracellular GDP-beta-S suppressed the carbachol-induced effects. Carbachol-induced effects were blocked by external Na+-free solution and by flufenamic acid, a non-selective cation channel blocker, and in the presence of thapsigargin, a Ca2+-ATPase inhibitor in the endoplasmic reticulum. However, carbachol still produced tonic inward pacemaker currents with the removal of external Ca2+. In recording of intracellular Ca2+ concentrations using fluo 3-AM dye, carbachol increased intracellular Ca2+ concentrations with increasing of Ca2+ oscillations. These results suggest that carbachol modulates the pacemaker activity of ICC through the activation of non-selective cation channels via muscarinic M(3) receptors by a G-protein dependent intracellular Ca2+ release mechanism.

Vascular Endothelial Growth Factor and Angiopoietin are Required for Prostate Regeneration.

PubMed Central

Wang, Gui-min; Kovalenko, Bruce; Huang, Yili; Moscatelli, David

2007-01-01

BACKGROUND The regulation of the prostate size by androgens may be partly the result of androgen effects on the prostatic vasculature. We examined the effect of changes in androgen levels on the expression of a variety of angiogenic factors in the mouse prostate and determined if vascular endothelial growth factor (VEGF)-A and the angiopoietins are involved in the vascular response to androgens. METHODS Expression of angiogenic factors in prostate was quantitated using real-time PCR at different times after castration and after administration of testosterone to castrated mice. Angiopoietins were localized in prostate by immunohistochemistry and in situ hybridization. The roles of VEGF and the angiopoietins in regeneration of the prostate were examined in mice inoculated with cells expressing soluble VEGF receptor-2 or soluble Tie-2. RESULTS Castration resulted in a decrease in VEGF-A, VEGF-B, VEGF-C, placenta growth factor, FGF-2, and FGF-8 expression after one day. In contrast, VEGF-D mRNA levels increased. No changes in angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), hepatocyte growth factor, VEGF receptor-1, VEGF receptor-2 or tie-2 mRNA levels were observed. Administration of testosterone to castrated mice had the opposite effect on expression of these angiogenic factors. Ang-2 was expressed predominately in prostate epithelial cells whereas Ang-1 was expressed in epithelium and smooth muscle. Inoculation of mice with cells expressing soluble VEGF receptor-2 or Tie-2 blocked the increase in vascular density normally observed after administration of testosterone to castrated mice. The soluble receptors also blocked the increase in prostate weight and proliferation of prostatic epithelial cells. CONCLUSION VEGF-A and angiopoietins are required for the vascular response to androgens and for the ability of the prostate to regenerate in response to androgens. PMID:17221843

Unsurmountable antagonism of brain 5-hydroxytryptamine2 receptors by (+)-lysergic acid diethylamide and bromo-lysergic acid diethylamide.

PubMed

Burris, K D; Sanders-Bush, E

1992-11-01

Lysergic acid diethylamide (LSD) and its structural analogue 2-bromo-lysergic acid diethylamide (BOL) act as unsurmountable antagonists of serotonin-elicited contractions in smooth muscle preparations. Two different models, allosteric and kinetic, have been invoked to explain these findings. The present studies investigate the mechanism of antagonism of brain 5-hydroxytryptamine (5HT)2 receptors, utilizing cells transfected with 5HT2 receptor cDNA cloned from rat brain. A proximal cellular response, phosphoinositide hydrolysis, was examined in order to minimize possible postreceptor effects. Even though LSD behaved as a partial agonist and BOL as a pure antagonist, both drugs blocked the effect of serotonin in an unsurmountable manner, i.e., increasing concentrations of serotonin could not overcome the blocking effect of LSD or BOL. Radioligand binding studies showed that preincubation of membranes with either LSD or BOL reduced the density of [3H]ketanserin binding sites, suggesting that the drugs bind tightly to the 5HT2 receptor and are not displaced during the binding assay. Two additional experiments supported this hypothesis. First, the off-rate of [3H] LSD was slow (20 min), relative to that of [3H]ketanserin (approximately 4 min). Second, when the length of incubation with [3H]ketanserin was increased to 60 min, the LSD-induced decrease in Bmax was essentially eliminated. The possibility that LSD and BOL decrease [3H]ketanserin binding by interacting with an allosteric site was rejected, because neither drug altered the rate of dissociation of [3H]ketanserin. The most parsimonious interpretation of these results is that unsurmountable antagonism reflects prolonged occupancy of the receptor by slowly reversible antagonists.

Activation of muscarinic M3 receptors inhibits large-conductance voltage- and Ca2+-activated K+ channels in rat urinary bladder smooth muscle cells

PubMed Central

Parajuli, Shankar P.

2013-01-01

Large conductance voltage- and Ca2+-activated K+ (BK) channels are key regulators of detrusor smooth muscle (DSM) contraction and relaxation during urine voiding and storage. Here, we explored whether BK channels are regulated by muscarinic receptors (M-Rs) in native freshly isolated rat DSM cells under physiological conditions using the perforated whole cell patch-clamp technique and pharmacological inhibitors. M-R activation with carbachol (1 μM) initially evoked large transient outward BK currents, followed by inhibition of the spontaneous transient outward BK currents (STBKCs) in DSM cells. Carbachol (1 μM) also inhibited the amplitude and frequency of spontaneous transient hyperpolarizations (STHs) and depolarized the DSM cell membrane potential. Selective inhibition of the muscarinic M3 receptors (M3-Rs) with 4-diphenylacetoxy-N-methylpiperidine (4-DAMP; 0.1 μM), but not muscarinic M2 receptors with methoctramine (1 μM), blocked the carbachol inhibitory effects on STBKCs. Furthermore, blocking the inositol 1,4,5-triphosphate (IP3) receptors with xestospongin-C (1 μM) inhibited the carbachol-induced large transient outward BK currents without affecting carbachol inhibitory effects on STBKCs. Upon pharmacological inhibition of all known cellular sources of Ca2+ for BK channel activation, carbachol (1 μM) did not affect the voltage-step-induced steady-state BK currents, suggesting that the muscarinic effects in DSM cells are mediated by mobilization of intracellular Ca2+. In conclusion, our findings provide strong evidence that activation of M3-Rs leads to inhibition of the STBKCs, STHs, and depolarization of DSM cells. Collectively, the data suggest the existence of functional interactions between BK channels and M3-Rs at a cellular level in DSM. PMID:23703523

Strychnine-blocked glycine receptor is removed from synapses by a shift in insertion/degradation equilibrium.

PubMed

Rasmussen, Hanne; Rasmussen, Trine; Triller, Antoine; Vannier, Christian

2002-02-01

The long-term inhibition by strychnine of glycine receptor activity in neurons provokes the receptor's selective intracellular accumulation and disappearance from synapses. This could result either from a disruption of the postsynaptic anchoring of the receptor or from an arrest of its exocytic transport. In this study we combined biochemical and fluorescence microscopy analyses to determine on a short time scale the fate of the strychnine-inactivated glycine receptor. Quantification of the cellular content of receptor showed that the rapid accumulation depends on protein synthesis. Cell surface biotinylation of neurons demonstrated that strychnine did not accelerate the turnover rate of the receptor. Labeling of endosomes indicated that, in strychnine-treated cells, the accumulated receptor is not blocked in the endosomal transport pathway. Taken together, these results indicate that strychnine does not destabilize the postsynaptic receptor but triggers its disappearance from synapses by a nondegradative sequestration of newly synthesized molecules in a nonendocytic compartment. (C)2002 Elsevier Science (USA).

Photoaffinity labelling of the ATP-binding site of the epidermal growth factor-dependent protein kinase.

PubMed

Kudlow, J E; Leung, Y

1984-06-15

Epidermal growth factor (EGF), after binding to its receptor, activates a tyrosine-specific protein kinase which phosphorylates several substrates, including the EGF receptor itself. The effects of a photoaffinity analogue of ATP, 3'-O-(3-[N-(4-azido-2-nitrophenyl)amino]propionyl)adenosine 5'-triphosphate (arylazido-beta-alanyl-ATP) on the EGF-dependent protein kinase in A431 human tumour cell plasma membrane vesicles was investigated. This analogue was capable of inactivating the EGF-receptor kinase in a photodependent manner. Partial inactivation occurred at an analogue concentration of 1 microM and complete inactivation occurred at 10 microM when a 2 min light exposure was used. Arylazido-beta-alanine at 100 microM and ATP at 100 microM were incapable of inactivating the enzyme with 2 min of light exposure. The photodependent inactivation of the enzyme by the analogue could be partially blocked by 20 mM-ATP and more effectively blocked by either 20 mM-adenosine 5'-[beta gamma-imido]triphosphate or 20 mM-guanosine 5'-[beta gamma-imido]triphosphate, indicating nucleotide-binding site specificity. Arylazido-beta-alanyl-[alpha-32P]ATP was capable of labelling membrane proteins in a photodependent manner. Numerous proteins were labelled, the most prominent of which ran with an apparent Mr of 53000 on polyacrylamide-gel electrophoresis. A band of minor intensity was seen of Mr corresponding to the EGF receptor (170000). Immunoprecipitation of affinity-labelled and solubilized membranes with an anti-(EGF receptor) monoclonal antibody demonstrated that the Mr 170000 receptor protein was photoaffinity labelled by the analogue. The Mr 53000 peptide was not specifically bound by the anti-receptor antibody. The affinity labelling of the receptor was not enhanced by EGF, suggesting that EGF stimulation of the kinase activity does not result from changes in the affinity of the kinase for ATP. These studies demonstrate that arylazido-beta-alanyl-ATP interacts with the ATP-binding site of the EGF-receptor kinase with apparent high affinity and that this analogue is an effective photoaffinity label for the kinase. Furthermore, these studies demonstrate that the EGF receptor, identified by using monoclonal antibodies, contains an ATP-binding site, providing further confirmation that the EGF receptor and EGF-dependent protein kinase are domains of the Mr 170000 protein.

Functional autoantibodies targeting G protein-coupled receptors in rheumatic diseases.

PubMed

Cabral-Marques, Otavio; Riemekasten, Gabriela

2017-11-01

G protein-coupled receptors (GPCRs) comprise the largest and most diverse family of integral membrane proteins that participate in different physiological processes such as the regulation of the nervous and immune systems. Besides the endogenous ligands of GPCRs, functional autoantibodies are also able to bind GPCRs to trigger or block intracellular signalling pathways, resulting in agonistic or antagonistic effects, respectively. In this Review, the effects of functional GPCR-targeting autoantibodies on the pathogenesis of autoimmune diseases, including rheumatic diseases, are discussed. Autoantibodies targeting β1 and β2 adrenergic receptors, which are expressed by cardiac and airway smooth muscle cells, respectively, have an important role in the development of asthma and cardiovascular diseases. In addition, high levels of autoantibodies against the muscarinic acetylcholine receptor M3 as well as those targeting endothelin receptor type A and type 1 angiotensin II receptor have several implications in the pathogenesis of rheumatic diseases such as Sjögren syndrome and systemic sclerosis. Expanding the knowledge of the pathophysiological roles of autoantibodies against GPCRs will shed light on the biology of these receptors and open avenues for new therapeutic approaches.

BDNF released during neuropathic pain potentiates NMDA receptors in primary afferent terminals

PubMed Central

Chen, Wenling; Walwyn, Wendy; Ennes, Helena S.; Kim, Hyeyoung; McRoberts, James A.; Marvizón, Juan Carlos G.

2014-01-01

NMDA receptors in primary afferent terminals can contribute to hyperalgesia by increasing neurotransmitter release. In rats and mice, we found that the ability of intrathecal NMDA to induce neurokinin 1 receptor (NK1R) internalization (a measure of substance P release) required a previous injection of BDNF. Selective knock-down of NMDA receptors in primary afferents decreased NMDA-induced NK1R internalization, confirming the presynaptic location of these receptors. The effect of BDNF was mediated by tropomyosin-related kinase B (trkB) receptors and not p75 neurotrophin receptors (p75NTR), because it was not produced by proBDNF and was inhibited by the trkB antagonist ANA-12 but not by the p75NTR inhibitor TAT-Pep5. These effects are probably mediated through the truncated form of the trkB receptor as there is little expression of full-length trkB in dorsal root ganglion (DRG) neurons. Src family kinase inhibitors blocked the effect of BDNF, suggesting that trkB receptors promote the activation of these NMDA receptors by Src family kinase phosphorylation. Western blots of cultured DRG neurons revealed that BDNF increased Tyr1472 phosphorylation of the NR2B subunit of the NMDA receptor, known to have a potentiating effect. Patch-clamp recordings showed that BDNF, but not proBDNF, increased NMDA receptor currents in cultured DRG neurons. NMDA-induced NK1R internalization was also enabled in a neuropathic pain model or by activating dorsal horn microglia with lipopolysaccharide. These effects were decreased by a BDNF scavenger, a trkB receptor antagonist and an Src family kinase inhibitor, indicating that BDNF released by microglia potentiates NMDA receptors in primary afferents during neuropathic pain. PMID:24611998

Effects of a sustained-release naloxone pellet on luteinizing hormone secretion in female rats.

PubMed

Gabriel, S M; Simpkins, J W

1983-11-01

Studies were undertaken to develop a naloxone implant capable of chronically blocking opioid receptors for several weeks in an effort to evaluate the effect of this prolonged narcotic antagonism on luteinizing hormone (LH) secretion in female rats. Antagonism of opiate receptors was achieved with a tablet formulation which contained 75 mg naloxone free base and a high content of the insoluble binding material, Mg stearate. Subcutaneous placement of this implant prevented morphine-induced analgesia for 2 weeks and antagonized the LH suppressory effects of morphine (15 or 30 mg/kg) administration. Thus, this naloxone delivery system is capable of chronically occupying the opioid receptors which mediate morphine's effects on analgesia and LH secretion. Despite this, the naloxone pellet only moderately enhanced the initial rate of increase in LH secretion following ovariectomy (day 1) and was ineffective in further augmenting LH secretion at 3 and 7 days after implantation. In rats which were ovariectomized and implanted immediately with estradiol-containing Silastic capsules, the naloxone pellet was ineffective in altering LH secretion 1, 3 or 7 days later. Thus, while chronic exposure to naloxone persistently antagonizes the pharmacologic actions of morphine, the naloxone pellet only transiently blocked the tonic inhibitory effect of endogenous opioid peptides. The mechanism by which the LH secretory effects of naloxone are lost following chronic exposure to the antagonist are at present unknown, but may involve the activation of compensatory mechanisms which are inhibitory to LH secretion.

Characterization of cocaine-induced block of cardiac sodium channels.

PubMed

Crumb, W J; Clarkson, C W

1990-03-01

Recent evidence suggests that cocaine can produce marked cardiac arrhythmias and sudden death. A possible mechanism for this effect is slowing of impulse conduction due to block of cardiac Na channels. We therefore investigated its effects on Na channels in isolated guinea pig ventricular myocytes using the whole-cell variant of the patch clamp technique. Cocaine (10-50 microM) was found to reduce Na current in a use-dependent manner. The time course for block development and recovery were characterized. At 30 microM cocaine, two phases of block development were defined: a rapid phase (tau = 5.7 +/- 4.9 ms) and a slower phase (tau = 2.3 +/- 0.7 s). Recovery from block at -140 mV was also defined by two phases: (tau f = 136 +/- 61 ms, tau s = 8.5 +/- 1.7 s) (n = 6). To further clarify the molecular mechanisms of cocaine action on cardiac Na channels, we characterized its effects using the guarded receptor model, obtaining estimated Kd values of 328, 19, and 8 microM for channels predominantly in the rested, activated, and inactivated states. These data indicate that cocaine can block cardiac Na channels in a use-dependent manner and provides a possible cellular explanation for its cardiotoxic effects.

Gingerols: a novel class of vanilloid receptor (VR1) agonists

PubMed Central

Dedov, Vadim N; Tran, Van H; Duke, Colin C; Connor, Mark; Christie, MacDonald J; Mandadi, Sravan; Roufogalis, Basil D

2002-01-01

Gingerols, the pungent constituents of ginger, were synthesized and assessed as agonists of the capsaicin-activated VR1 (vanilloid) receptor. [6]-Gingerol and [8]-gingerol evoked capsaicin-like intracellular Ca2+ transients and ion currents in cultured DRG neurones. These effects of gingerols were blocked by capsazepine, the VR1 receptor antagonist. The potency of gingerols increased with increasing size of the side chain and with the overall hydrophobicity in the series. We conclude that gingerols represent a novel class of naturally occurring VR1 receptor agonists that may contribute to the medicinal properties of ginger, which have been known for centuries. The gingerol structure may be used as a template for the development of drugs acting as moderately potent activators of the VR1 receptor. PMID:12411409

Requirement of ERα and basal activities of EGFR and Src kinase in Cd-induced activation of MAPK/ERK pathway in human breast cancer MCF-7 cells.

PubMed

Song, Xiulong; Wei, Zhengxi; Shaikh, Zahir A

2015-08-15

Cadmium (Cd) is a common environmental toxicant and an established carcinogen. Epidemiological studies implicate Cd with human breast cancer. Low micromolar concentrations of Cd promote proliferation of human breast cancer cells in vitro. The growth promotion of breast cancer cells is associated with the activation of MAPK/ERK pathway. This study explores the mechanism of Cd-induced activation of MAPK/ERK pathway. Specifically, the role of cell surface receptors ERα, EGFR, and Src kinase was evaluated in human breast cancer MCF-7 cells treated with 1-3μM Cd. The activation of ERK was studied using a serum response element (SRE) luciferase reporter assay. Receptor phosphorylation was detected by Western blot analyses. Cd treatment increased both the SRE reporter activity and ERK1/2 phosphorylation in a concentration-dependent manner. Cd treatment had no effect on reactive oxygen species (ROS) generation. Also, blocking the entry of Cd into the cells with manganese did not diminish Cd-induced activation of MAPK/ERK. These results suggest that the effect of Cd was likely not caused by intracellular ROS generation, but through interaction with the membrane receptors. While Cd did not appear to activate either EGFR or Src kinase, their inhibition completely blocked the Cd-induced activation of ERK as well as cell proliferation. Similarly, silencing ERα with siRNA or use of ERα antagonist blocked the effects of Cd. Based on these results, it is concluded that not only ERα, but also basal activities of EGFR and Src kinase are essential for Cd-induced signal transduction and activation of MAPK/ERK pathway for breast cancer cell proliferation. Copyright © 2015 Elsevier Inc. All rights reserved.

The selective V1a receptor agonist selepressin (FE 202158) blocks vascular leak in ovine severe sepsis

PubMed Central

Wiśniewska, Halina; Traber, Lillian D.; Lin, ChiiDean; Fan, Juanjuan; Hawkins, Hal K.; Cox, Robert A.; Wiśniewski, Kazimierz; Schteingart, Claudio D.; Landry, Donald W.; Rivière, Pierre J.-M.; Traber, Daniel L.

2014-01-01

Objective To determine if the selective vasopressin type 1a receptor (V1aR) agonist selepressin (FE 202158) is as effective as the mixed V1a/V2 receptor (V1aR/V2R) agonist vasopressor hormone arginine vasopressin (AVP) when used as a titrated first-line vasopressor therapy in an ovine model of Pseudomonas aeruginosa pneumonia-induced severe sepsis. Design Prospective, randomized, controlled laboratory experiment. Setting University animal research facility. Subjects Forty-five chronically instrumented sheep. Interventions Sheep were anesthetized, insufflated with cooled cotton smoke via tracheostomy, and P. aeruginosa were instilled into their airways. They were then placed on assisted ventilation, awakened, and resuscitated with lactated Ringer's solution titrated to maintain hematocrit ± 3% from baseline levels. If, despite fluid management, mean arterial pressure (MAP) fell by > 10 mm Hg from baseline levels, a continuous i.v. infusion of AVP or selepressin was titrated to raise and maintain MAP within 10 mm Hg of baseline. Effects of combination treatment of selepressin with the selective V2R agonist desmopressin were similarly investigated. Measurements and Main Results In septic sheep, MAP fell by ~30 mm Hg, systemic vascular resistance index (SVRI) decreased by ~50%, and ~7 L of fluid were retained over 24 h; this fluid accumulation was partially reduced by AVP and almost completely blocked by selepressin; combined infusion of selepressin and desmopressin increased fluid accumulation to levels similar to AVP treatment. Conclusions Resuscitation with the selective V1aR agonist selepressin blocked vascular leak more effectively than the mixed V1aR/V2R agonist AVP because of its lack of agonist activity at the V2R. PMID:24674922

Activation of the ζ receptor 1 suppresses NMDA responses in rat retinal ganglion cells.

PubMed

Zhang, X-J; Liu, L-L; Jiang, S-X; Zhong, Y-M; Yang, X-L

2011-03-17

The sigma receptor 1 (σR1) has been shown to modulate the activity of several voltage- and ligand-gated channels. Using patch-clamp techniques in rat retinal slice preparations, we demonstrated that activation of σR1 by SKF10047 (SKF) or PRE-084 suppressed N-methyl-D-aspartate (NMDA) receptor-mediated current responses from both ON and OFF type ganglion cells (GCs), dose-dependently, and the effect could be blocked by the σR1 antagonist BD1047 or the σR antagonist haloperidol. The suppression by SKF of NMDA currents was abolished with pre-incubation of the G protein inhibitor GDP-β-S or the Gi/o activator mastoparan. We further explored the intracellular signaling pathway responsible for the SKF-induced suppression of NMDA responses. Application of either cAMP/the PKA inhibitor Rp-cAMP or cGMP/the PKG inhibitor KT5823 did not change the SKF-induced effect, suggesting the involvement of neither cAMP/PKA nor cGMP/PKG pathway. In contrast, suppression of NMDA responses by SKF was abolished by internal infusion of the phosphatidylinostiol-specific phospholipase C (PLC) inhibitor U73122, but not by the phosphatidylcholine-PLC inhibitor D609. SKF-induced suppression of NMDA responses was dependent on intracellular Ca2+ concentration ([Ca2+]i), as evidenced by the fact that the effect was abolished when [Ca2+]i was buffered with 10 mM BAPTA. The SKF effect was blocked by xestospongin-C/heparin, IP3 receptor antagonists, but unchanged by ryanodine/caffeine, ryanodine receptor modulators. Furthermore, application of protein kinase C inhibitors Bis IV and Gö6976 eliminated the SKF effect. These results suggest that the suppression of NMDA responses of rat retinal GCs caused by the activation of σR1 may be mediated by a distinct [Ca2+]i-dependent PLC-PKC pathway. This effect of SKF could help ameliorate malfunction of GCs caused by excessive stimulation of NMDA receptors under pathological conditions. Copyright © 2011 IBRO. Published by Elsevier Ltd. All rights reserved.

Molecular Insights into the Local Anesthetic Receptor within Voltage-Gated Sodium Channels Using Hydroxylated Analogs of Mexiletine

PubMed Central

Desaphy, Jean-François; Dipalma, Antonella; Costanza, Teresa; Carbonara, Roberta; Dinardo, Maria Maddalena; Catalano, Alessia; Carocci, Alessia; Lentini, Giovanni; Franchini, Carlo; Camerino, Diana Conte

2011-01-01

We previously showed that the β-adrenoceptor modulators, clenbuterol and propranolol, directly blocked voltage-gated sodium channels, whereas salbutamol and nadolol did not (Desaphy et al., 2003), suggesting the presence of two hydroxyl groups on the aromatic moiety of the drugs as a molecular requisite for impeding sodium channel block. To verify such an hypothesis, we synthesized five new mexiletine analogs by adding one or two hydroxyl groups to the aryloxy moiety of the sodium channel blocker and tested these compounds on hNav1.4 channels expressed in HEK293 cells. Concentration–response relationships were constructed using 25-ms-long depolarizing pulses at −30 mV applied from an holding potential of −120 mV at 0.1 Hz (tonic block) and 10 Hz (use-dependent block) stimulation frequencies. The half-maximum inhibitory concentrations (IC50) were linearly correlated to drug lipophilicity: the less lipophilic the drug, minor was the block. The same compounds were also tested on F1586C and Y1593C hNav1.4 channel mutants, to gain further information on the molecular interactions of mexiletine with its receptor within the sodium channel pore. In particular, replacement of Phe1586 and Tyr1593 by non-aromatic cysteine residues may help in the understanding of the role of π–π or π–cation interactions in mexiletine binding. Alteration of tonic block suggests that the aryloxy moiety of mexiletine may interact either directly or indirectly with Phe1586 in the closed sodium channel to produce low-affinity binding block, and that this interaction depends on the electrostatic potential of the drug aromatic tail. Alteration of use-dependent block suggests that addition of hydroxyl groups to the aryloxy moiety may modify high-affinity binding of the drug amine terminal to Phe1586 through cooperativity between the two pharmacophores, this effect being mainly related to drug lipophilicity. Mutation of Tyr1593 further impaired such cooperativity. In conclusion, these results confirm our former hypothesis by showing that the presence of hydroxyl groups to the aryloxy moiety of mexiletine greatly reduced sodium channel block, and provide molecular insights into the intimate interaction of local anesthetics with their receptor. PMID:22403541

Regulation of the stimulant actions of neurokinin a and human hemokinin-1 on the human uterus: a comparison with histamine.

PubMed

Pennefather, Jocelyn N; Patak, Eva; Ziccone, Sebastian; Lilley, Alison; Pinto, Francisco M; Page, Nigel M; Story, Margot E; Grover, Sonia; Candenas, M Luz

2006-09-01

Regulation of the contractile effects of tachykinins and histamine on the human uterus was investigated with biopsy sections of the outer myometrial layer. The effects of neurokinin A (NKA) and human hemokinin-1 (hHK-1) in tissues from pregnant but not from nonpregnant women were enhanced by the inhibition of neprilysin. The effects of NKA and eledoisin were blocked by the NK2 receptor antagonist SR 48968 but not by the NK1 receptor antagonist SR 140333 in tissues from both groups of women. Human HK-1 acted as a partial agonist blocked by SR 48968 and, to a lesser extent, by SR 140333; endokinin D was inactive. In tissues from pregnant women, responses to high potassium-containing Krebs solution were 2-3-fold higher than those from nonpregnant women. Mepyramine-sensitive maximal responses to histamine were similarly enhanced. The absolute maximum responses to NKA and its stable NK2 receptor-selective analogue, [Lys5MeLeu9Nle10]NKA(4-10), were increased in pregnancy, but their efficacies relative to potassium responses were decreased. Tachykinin potencies were lower in tissues from pregnant women than in those from nonpregnant women. These data 1) show for the first time that hHK-1 is a uterine stimulant in the human, 2) confirm that the NK2 receptor is predominant in mediating tachykinin actions on the human myometrium, and 3) indicate that mammalian tachykinin effects are tightly regulated during pregnancy in a manner that would negate an inappropriate uterotonic effect. The potencies of these peptides in tissues from nonpregnant women undergoing hysterectomy are consistent with their possible role in menstrual and menopausal disorders.

Cannabidiol Modulates Fear Memory Formation Through Interactions with Serotonergic Transmission in the Mesolimbic System

PubMed Central

Norris, Christopher; Loureiro, Michael; Kramar, Cecilia; Zunder, Jordan; Renard, Justine; Rushlow, Walter; Laviolette, Steven R

2016-01-01

Emerging evidence suggests that the largest phytochemical component of cannabis, cannabidiol (CBD), may possess pharmacotherapeutic properties in the treatment of neuropsychiatric disorders. CBD has been reported to functionally interact with both the mesolimbic dopamine (DA) and serotonergic (5-HT) receptor systems. However, the underlying mechanisms by which CBD may modulate emotional processing are not currently understood. Using a combination of in vivo electrophysiological recording and fear conditioning in rats, the present study aimed to characterize the behavioral, neuroanatomical, and pharmacological effects of CBD within the mesolimbic pathway, and its possible functional interactions with 5-HT and DAergic transmission. Using targeted microinfusions of CBD into the shell region of the mesolimbic nucleus accumbens (NASh), we report that intra-NASh CBD potently blocks the formation of conditioned freezing behaviors. These effects were challenged with DAergic, cannabinoid CB1 receptor, and serotonergic (5-HT1A) transmission blockade, but only 5-HT1A blockade restored associative conditioned freezing behaviors. In vivo intra-ventral tegmental area (VTA) electrophysiological recordings revealed that behaviorally effective doses of intra-NASh CBD elicited a predominant decrease in spontaneous DAergic neuronal frequency and bursting activity. These neuronal effects were reversed by simultaneous blockade of 5-HT1A receptor transmission. Finally, using a functional contralateral disconnection procedure, we demonstrated that the ability of intra-NASh CBD to block the formation of conditioned freezing behaviors was dependent on intra-VTA GABAergic transmission substrates. Our findings demonstrate a novel NAc→VTA circuit responsible for the behavioral and neuronal effects of CBD within the mesolimbic system via functional interactions with serotonergic 5-HT1A receptor signaling. PMID:27296152

Dynamic control of glutamatergic synaptic input in the spinal cord by muscarinic receptor subtypes defined using knockout mice.

PubMed

Chen, Shao-Rui; Chen, Hong; Yuan, Wei-Xiu; Wess, Jürgen; Pan, Hui-Lin

2010-12-24

Activation of muscarinic acetylcholine receptors (mAChRs) in the spinal cord inhibits pain transmission. At least three mAChR subtypes (M(2), M(3), and M(4)) are present in the spinal dorsal horn. However, it is not clear how each mAChR subtype contributes to the regulation of glutamatergic input to dorsal horn neurons. We recorded spontaneous excitatory postsynaptic currents (sEPSCs) from lamina II neurons in spinal cord slices from wild-type (WT) and mAChR subtype knock-out (KO) mice. The mAChR agonist oxotremorine-M increased the frequency of glutamatergic sEPSCs in 68.2% neurons from WT mice and decreased the sEPSC frequency in 21.2% neurons. Oxotremorine-M also increased the sEPSC frequency in ∼50% neurons from M(3)-single KO and M(1)/M(3) double-KO mice. In addition, the M(3) antagonist J104129 did not block the stimulatory effect of oxotremorine-M in the majority of neurons from WT mice. Strikingly, in M(5)-single KO mice, oxotremorine-M increased sEPSCs in only 26.3% neurons, and J104129 abolished this effect. In M(2)/M(4) double-KO mice, but not M(2)- or M(4)-single KO mice, oxotremorine-M inhibited sEPSCs in significantly fewer neurons compared with WT mice, and blocking group II/III metabotropic glutamate receptors abolished this effect. The M(2)/M(4) antagonist himbacine either attenuated the inhibitory effect of oxotremorine-M or potentiated the stimulatory effect of oxotremorine-M in WT mice. Our study demonstrates that activation of the M(2) and M(4) receptor subtypes inhibits synaptic glutamate release to dorsal horn neurons. M(5) is the predominant receptor subtype that potentiates glutamatergic synaptic transmission in the spinal cord.

Dynamic Control of Glutamatergic Synaptic Input in the Spinal Cord by Muscarinic Receptor Subtypes Defined Using Knockout Mice*

PubMed Central

Chen, Shao-Rui; Chen, Hong; Yuan, Wei-Xiu; Wess, Jürgen; Pan, Hui-Lin

2010-01-01

Activation of muscarinic acetylcholine receptors (mAChRs) in the spinal cord inhibits pain transmission. At least three mAChR subtypes (M2, M3, and M4) are present in the spinal dorsal horn. However, it is not clear how each mAChR subtype contributes to the regulation of glutamatergic input to dorsal horn neurons. We recorded spontaneous excitatory postsynaptic currents (sEPSCs) from lamina II neurons in spinal cord slices from wild-type (WT) and mAChR subtype knock-out (KO) mice. The mAChR agonist oxotremorine-M increased the frequency of glutamatergic sEPSCs in 68.2% neurons from WT mice and decreased the sEPSC frequency in 21.2% neurons. Oxotremorine-M also increased the sEPSC frequency in ∼50% neurons from M3-single KO and M1/M3 double-KO mice. In addition, the M3 antagonist J104129 did not block the stimulatory effect of oxotremorine-M in the majority of neurons from WT mice. Strikingly, in M5-single KO mice, oxotremorine-M increased sEPSCs in only 26.3% neurons, and J104129 abolished this effect. In M2/M4 double-KO mice, but not M2- or M4-single KO mice, oxotremorine-M inhibited sEPSCs in significantly fewer neurons compared with WT mice, and blocking group II/III metabotropic glutamate receptors abolished this effect. The M2/M4 antagonist himbacine either attenuated the inhibitory effect of oxotremorine-M or potentiated the stimulatory effect of oxotremorine-M in WT mice. Our study demonstrates that activation of the M2 and M4 receptor subtypes inhibits synaptic glutamate release to dorsal horn neurons. M5 is the predominant receptor subtype that potentiates glutamatergic synaptic transmission in the spinal cord. PMID:20940295

Lactoferrin Levels in Tears are Increased by the Topical Application of Diadenosine Tetraphosphate.

PubMed

Loma, Patricia; Guzman-Aranguez, Ana; Perez de Lara, Maria J; Pintor, Jesus

2016-09-01

This study was undertaken to determine the effect of the topical application of diadenosine tetraphosphate on lactoferrin levels in rabbit tears. Diadenosine tetraphosphate was topically instilled in a single-dose, tear samples were collected by micropipette and lactoferrin was measured by Enzyme-Linked ImmunoSorbent Assay (ELISA). The concentration of lactoferrin in rabbit tears was significantly increased 1 h after diadenosine tetraphosphate application, remaining elevated for 3 h more. This effect was blocked by P2 receptors antagonists. Topical application of diadenosine tetraphosphate stimulates the secretion of lactoferrin in rabbit tears through P2 receptor activation.

Serotonin type-1D receptor stimulation of A-type K(+) channel decreases membrane excitability through the protein kinase A- and B-Raf-dependent p38 MAPK pathways in mouse trigeminal ganglion neurons.

PubMed

Zhao, Xianyang; Zhang, Yuan; Qin, Wenjuan; Cao, Junping; Zhang, Yi; Ni, Jianqiang; Sun, Yangang; Jiang, Xinghong; Tao, Jin

2016-08-01

Although recent studies have implicated serotonin 5-HT1B/D receptors in the nociceptive sensitivity of primary afferent neurons, the underlying molecular and cellular mechanisms remain unclear. In this study, we identified a novel functional role of the 5-HT1D receptor subtype in regulating A-type potassium (K(+)) currents (IA) as well as membrane excitability in small trigeminal ganglion (TG) neurons. We found that the selective activation of 5-HT1D, rather than 5-HT1B, receptors reversibly increased IA, while the sustained delayed rectifier K(+) current was unaffected. The 5-HT1D-mediated IA increase was associated with a depolarizing shift in the voltage dependence of inactivation. Blocking G-protein signaling with pertussis toxin or by intracellular application of a selective antibody raised against Gαo or Gβ abolished the 5-HT1D effect on IA. Inhibition of protein kinase A (PKA), but not of phosphatidylinositol 3-kinase or protein kinase C, abolished the 5-HT1D-mediated IA increase. Analysis of phospho-p38 (p-p38) revealed that activation of 5-HT1D, but not 5-HT1B, receptors significantly activated p38, while p-ERK and p-JNK were unaffected. The p38 MAPK inhibitor SB203580, but not its inactive analogue SB202474, and inhibition of B-Raf blocked the 5-HT1D-mediated IA response. Functionally, we observed a significantly decreased action potential firing rate induced by the 5-HT1D receptors; pretreatment with 4-aminopyridine abolished this effect. Taken together, these results suggest that the activation of 5-HT1D receptors selectively enhanced IA via the Gβγ of the Go-protein, PKA, and the sequential B-Raf-dependent p38 MAPK signaling cascade. This 5-HT1D receptor effect may contribute to neuronal hypoexcitability in small TG neurons. Copyright © 2016 Elsevier Inc. All rights reserved.

Hypotensive effects of ghrelin receptor agonists mediated through a novel receptor

PubMed Central

Callaghan, Brid; Kosari, Samin; Pustovit, Ruslan V; Sartor, Daniela M; Ferens, Dorota; Ban, Kung; Baell, Jonathan; Nguyen, Trung V; Rivera, Leni R; Brock, James A; Furness, John B

2014-01-01

BACKGROUND AND PURPOSE Some agonists of ghrelin receptors cause rapid decreases in BP. The mechanisms by which they cause hypotension and the pharmacology of the receptors are unknown. EXPERIMENTAL APPROACH The effects of ligands of ghrelin receptors were investigated in rats in vivo, on isolated blood vessels and on cells transfected with the only molecularly defined ghrelin receptor, growth hormone secretagogue receptor 1a (GHSR1a). KEY RESULTS Three agonists of GHSR1a receptors, ulimorelin, capromorelin and CP464709, caused a rapid decrease in BP in the anaesthetized rat. The effect was not reduced by either of two GHSR1a antagonists, JMV2959 or YIL781, at doses that blocked effects on colorectal motility, in vivo. The rapid hypotension was not mimicked by ghrelin, unacylated ghrelin or the unacylated ghrelin receptor agonist, AZP531. The early hypotension preceded a decrease in sympathetic nerve activity. Early hypotension was not reduced by hexamethonium or by baroreceptor (sino-aortic) denervation. Ulimorelin also relaxed isolated segments of rat mesenteric artery, and, less potently, relaxed aorta segments. The vascular relaxation was not reduced by JMV2959 or YIL781. Ulimorelin, capromorelin and CP464709 activated GHSR1a in transfected HEK293 cells at nanomolar concentrations. JMV2959 and YIL781 both antagonized effects in these cells, with their pA2 values at the GHSR1a receptor being 6.55 and 7.84. CONCLUSIONS AND IMPLICATIONS Our results indicate a novel vascular receptor or receptors whose activation by ulimorelin, capromorelin and CP464709 lowered BP. This receptor is activated by low MW GHSR1a agonists, but is not activated by ghrelin. PMID:24670149

Inhibition of N-methyl-D-aspartate receptors increases paraoxon-induced apoptosis in cultured neurons

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

Wu Xuan; Tian Feng; Okagaki, Peter

2005-10-01

Organophosphorus (OP) compounds, used as insecticides and chemical warfare agents, are potent neurotoxins. We examined the neurotoxic effect of paraoxon (O,O-diethyl O-p-nitrophenyl phosphate), an organophosphate compound, and the role of NMDA receptors as a mechanism of action in cultured cerebellar granule cells. Paraoxon is neurotoxic to cultured rat cerebellar granule cells in a time- and concentration-dependent manner. Cerebellar granule cells are less sensitive to the neurotoxic effects of paraoxon on day in vitro (DIV) 4 than neurons treated on DIV 8. Surprisingly, the N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801, enhances paraoxon-mediated neurotoxicity suggesting that NMDA receptors may play a protective role.more » Pretreatment with a subtoxic concentration of N-methyl-D-aspartate (NMDA) [100 {mu}M] protects about 40% of the vulnerable neurons that would otherwise die from paraoxon-induced neurotoxicity. Moreover, addition of a neuroprotective concentration of NMDA 3 h after treatment with paraoxon provides the same level of protection. Because paraoxon-mediated neuronal cell death is time-dependent, we hypothesized that apoptosis may be involved. Paraoxon increases apoptosis about 10-fold compared to basal levels. The broad-spectrum caspase inhibitor (Boc-D-FMK) and the caspase-9-specific inhibitor (Z-LEHD-FMK) protect against paraoxon-mediated apoptosis, paraoxon-stimulated caspase-3 activity and neuronal cell death. MK-801 increases, whereas NMDA blocks paraoxon-induced apoptosis and paraoxon-stimulated caspase-3 activity. These results suggest that activation of NMDA receptors protect neurons against paraoxon-induced neurotoxicity by blocking apoptosis initiated by paraoxon.« less

Central N-acetyl aspartylglutamate deficit: a possible pathogenesis of schizophrenia.

PubMed

Tsai, Shih-Jen

2005-09-01

The "glutamate hypothesis" of schizophrenia has emerged from the finding that phencyclidine (PCP) induces psychotic-like behaviors in rodents, possibly by blocking the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor, thereby causing increased glutamate release. N-acetyl aspartylglutamate (NAAG), an endogenous peptide abundant in mammalian nervous systems, is localized in certain brain cells, including cortical and hippocampal pyramidal neurons. NAAG is synthesized from N-acetylaspartate (NAA) and glutamate, and NAA availability may limit the rate of NAAG synthesis. Although NAAG is known to have some neurotransmitter-like functions, NAA does not. NAAG is a highly selective agonist of the type 3 metabotropic glutamate receptor (mGluR3, a presynaptic autoreceptor) and can inhibit glutamate release. In addition, at low levels, NAAG is an NMDA receptor antagonist, and blocking of NMDA receptors may increase glutamate release. Taken together, low central NAAG levels may antagonize the effect of glutamate at NMDA receptors and decrease its agonistic effect on presynaptic mGluR3; both activities could increase glutamate release, similar to the increase demonstrated in the PCP model of schizophrenia. In this report, it is suggested that the central NAAG deficit, possibly through decreased synthesis or increased degradation of NAAG, may play a role in the pathogenesis of schizophrenia. Evidence is presented and discussed from magnetic resonance, postmortem, animal model, schizophrenia treatment, and genetic studies. The central NAAG deficit model of schizophrenia could explain the disease process, from the perspectives of both neurodevelopment and neurodegeneration, and may point to potential treatments for schizophrenia.

p-Coumaric acid activates the GABA-A receptor in vitro and is orally anxiolytic in vivo.

PubMed

Scheepens, Arjan; Bisson, Jean-Francois; Skinner, Margot

2014-02-01

The increasing prevalence and social burden of subclinical anxiety in the western world represents a significant psychosocial and financial cost. Consumers are favouring a more natural and nonpharmacological approach for alleviating the effects of everyday stress and anxiety. The gamma-aminobutyric acid (GABA) receptor is the primary mediator of central inhibitory neurotransmission, and GABA-receptor agonists are well known to convey anxiolytic effects. Using an in vitro screening approach to identify naturally occurring phytochemical GABA agonists, we discovered the plant secondary metabolite p-coumaric acid to have significant GABAergic activity, an effect that could be blocked by co-administration of the specific GABA-receptor antagonist, picrotoxin. Oral administration of p-coumaric acid to rodents induced a significant anxiolytic effect in vivo as measured using the elevated plus paradigm, in line with the effects of oral diazepam. Given that p-coumaric acid is reasonably well absorbed following oral consumption in man and is relatively nontoxic, it may be suitable for the formulation of a safe and effective anxiolytic functional food. Copyright © 2013 John Wiley & Sons, Ltd.

Insulin-Like Growth Factor System in Cancer: Novel Targeted Therapies

PubMed Central

Brahmkhatri, Varsha P.; Prasanna, Chinmayi; Atreya, Hanudatta S.

2015-01-01

Insulin-like growth factors (IGFs) are essential for growth and survival that suppress apoptosis and promote cell cycle progression, angiogenesis, and metastatic activities in various cancers. The IGFs actions are mediated through the IGF-1 receptor that is involved in cell transformation induced by tumour. These effects depend on the bioavailability of IGFs, which is regulated by IGF binding proteins (IGFBPs). We describe here the role of the IGF system in cancer, proposing new strategies targeting this system. We have attempted to expand the general viewpoint on IGF-1R, its inhibitors, potential limitations of IGF-1R, antibodies and tyrosine kinase inhibitors, and IGFBP actions. This review discusses the emerging view that blocking IGF via IGFBP is a better option than blocking IGF receptors. This can lead to the development of novel cancer therapies. PMID:25866791

Prenatal Exposure to Angiotensin II Receptor Blockers and Hemodynamic Effects on the Newborn.

PubMed

Rodríguez-Castaño, MaJosé; Corredera, Araceli; Aleo, Esther; Arruza, Luis

2015-04-01

Angiotensin II receptor blockers (ARBs) are potent antihypertensive agents that block the renin angiotensin aldosterone system (RAS). Their use in pregnancy may cause malformations, oligoanuria, hypotension, and death. Hypotension is observed up to 15% of cases and is described as refractory to volume and inotropic support, although its pathophysiology is unknown. We present a case of prenatal exposure to ARBs in order to characterize the hemodynamic compromise in the newborn, help in decision-making, and guide the therapeutic approach to these patients.

An anxiogenic benzodiazepine receptor ligand induces learned helplessness.

PubMed

Drugan, R C; Maier, S F; Skolnick, P; Paul, S M; Crawley, J N

1985-07-31

Rats treated with the anxiogenic beta-carboline, N-methyl-beta-carboline-3-carboxamide (FG-7142), failed to acquire an escape response 24 h after treatment. Administration of FG-7142 resulted in a behavioral effect equivalent to a session of inescapable tailshock in this paradigm of learned helplessness. Pretreatment of rats with the selective benzodiazepine receptor antagonist Ro15-1788 blocked the development of learned helplessness elicited by FG-7142. These findings suggest that 'anxiety' may be a major factor in the development of learned helplessness.

Differential involvement of dopamine D-1 and D-2 receptors in the circling behaviour induced by apomorphine, SK & F 38393, pergolide and LY 171555 in 6-hydroxydopamine-lesioned rats.

PubMed

Arnt, J; Hyttel, J

1985-01-01

The antagonistic effect of dopamine (DA) D-1 and D-2 antagonists against circling behaviour induced by various DA agonists in 6-OHDA-lesioned rats has been investigated. DA D-1/D-2 selectivity of agonists in vitro was measured by the stimulatory effect on DA-sensitive adenylate cyclase in rat striatal homogenates (D-1), the inhibitory effect on electrically-induced release of 3H-DA in rabbit striatal slices (D-2) and the affinity to 3H-piflutixol (D-1) and 3H-spiroperidol (D-2) binding sites in rat striatal membranes. The contralateral circling behaviour induced by the DA D-1 agonist SK & F 38393 was blocked by the DA D-1 antagonist, SCH 23390, and by the mixed DA D-1/D-2 antagonist cis(Z)-flupentixol, but was not influenced by the DA D-2 antagonists spiroperidol and clebopride. In contrast, circling behaviour induced by the preferential DA D-2 agonists pergolide and LY 171555 was blocked by clebopride, spiroperidol, and cis(Z)-flupentixol, but weakly or not influenced by SCH 23390. Apomorphine-induced circling behaviour was blocked by cis(Z)-flupentixol, partially antagonized by SCH 23390 and clebopride but not inhibited by spiroperidol, although the time-course of circling was changed. Combinations of SCH 23390 with spiroperidol or clebopride in low doses completely blocked the effect of apomorphine. These results indicate that DA D-1 and D-2 receptors mediate circling behaviour through separate mechanisms which can be independently manipulated with respective agonists and antagonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of muscarinic receptor antagonists on cocaine discrimination in wild-type mice and in muscarinic receptor M1, M2, and M4 receptor knockout mice.

PubMed

Joseph, Lauren; Thomsen, Morgane

2017-06-30

Muscarinic M 1 /M 4 receptor stimulation can reduce abuse-related effects of cocaine and may represent avenues for treating cocaine addiction. Muscarinic antagonists can mimic and enhance effects of cocaine, including discriminative stimulus (S D ) effects, but the receptor subtypes mediating those effects are not known. A better understanding of the complex cocaine/muscarinic interactions is needed to evaluate and develop potential muscarinic-based medications. Here, knockout mice lacking M 1 , M 2 , or M 4 receptors (M 1 -/- , M 2 -/- , M 4 -/- ), as well as control wild-type mice and outbred Swiss-Webster mice, were trained to discriminate 10mg/kg cocaine from saline. Muscarinic receptor antagonists with no subtype selectivity (scopolamine), or preferential affinity at the M 1 , M 2 , or M 4 subtype (telenzepine, trihexyphenidyl; methoctramine, AQ-RA 741; tropicamide) were tested alone and in combination with cocaine. In intact animals, antagonists with high affinity at M 1 /M 4 receptors partially substituted for cocaine and increased the S D effect of cocaine, while M 2 -preferring antagonists did not substitute, and reduced the S D effect of cocaine. The cocaine-like effects of scopolamine were absent in M 1 -/- mice. The cocaine S D attenuating effects of methoctramine were absent in M 2 -/- mice and almost absent in M 1 -/- mice. The findings indicate that the cocaine-like S D effects of muscarinic antagonists are primarily mediated through M 1 receptors, with a minor contribution of M 4 receptors. The data also support our previous findings that stimulation of M 1 receptors and M 4 receptors can each attenuate the S D effect of cocaine, and show that this can also be achieved by blocking M 2 autoreceptors, likely via increased acetylcholine release. Copyright © 2017 Elsevier B.V. All rights reserved.

Differential regulation of the cell cycle by alpha1-adrenergic receptor subtypes.

PubMed

Gonzalez-Cabrera, Pedro J; Shi, Ting; Yun, June; McCune, Dan F; Rorabaugh, Boyd R; Perez, Dianne M

2004-11-01

Alpha(1)-Adrenergic receptors have been implicated in growth-promoting pathways. A microarray study of individual alpha(1)-adrenergic receptor subtypes (alpha(1A), alpha(1B), and alpha(1D)) expressed in Rat-1 fibroblasts revealed that epinephrine altered the transcription of several cell cycle regulatory genes in a direction consistent with the alpha(1A)- and alpha(1D)-adrenergic receptors mediating G(1)-S cell cycle arrest and the alpha(1B-)mediating cell-cycle progression. A time course indicated that in alpha(1A) cells, epinephrine stimulated a G(1)-S arrest, which began after 8 h of stimulation and maximized at 16 h, at which point was completely blocked with cycloheximide. The alpha(1B)-adrenergic receptor profile also showed unchecked cell cycle progression, even under low serum conditions and induced foci formation. The G(1)-S arrest induced by alpha(1A)- and alpha(1D)-adrenergic receptors was associated with decreased cyclin-dependent kinase-6 and cyclin E-associated kinase activities and increased expression of the cyclin-dependent kinase inhibitor p27(Kip1), all of which were blocked by prazosin. There were no differences in kinase activities and/or expression of p27(Kip1) in epinephrine alpha(1B)-AR fibroblasts, although the microarray did indicate differences in p27(Kip1) RNA levels. Cell counts proved the antimitotic effect of epinephrine in alpha(1A) and alpha(1D) cells and indicated that alpha(1B)-adrenergic receptor subtype expression was sufficient to cause proliferation of Rat-1 fibroblasts independent of agonist stimulation. Analysis in transfected PC12 cells also confirmed the alpha(1A)- and alpha(1B)-adrenergic receptor effect. The alpha(1B)-subtype native to DDT1-MF2 cells, a smooth muscle cell line, caused progression of the cell cycle. These results indicate that the alpha(1A)- and alpha(1D)-adrenergic receptors mediate G(1)-S cell-cycle arrest, whereas alpha(1B)-adrenergic receptor expression causes a cell cycle progression and may induce transformation in sensitive cell lines.

Gi-coupled γ-aminobutyric acid-B receptors cross-regulate phospholipase C and calcium in airway smooth muscle.

PubMed

Mizuta, Kentaro; Mizuta, Fumiko; Xu, Dingbang; Masaki, Eiji; Panettieri, Reynold A; Emala, Charles W

2011-12-01

γ-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system, and exerts its actions via both ionotropic (GABA(A)) and metabotropic (GABA(B)) receptors. Although the functional expression of GABA(B) receptors coupled to the G(i) protein was reported for airway smooth muscle, the role of GABA(B) receptors in airway responsiveness remains unclear. We investigated whether G(i)-coupled GABA(B) receptors cross-regulate phospholipase C (PLC), an enzyme classically regulated by G(q)-coupled receptors in human airway smooth muscle cells. Both the GABA(B)-selective agonist baclofen and the endogenous ligand GABA significantly increased the synthesis of inositol phosphate, whereas GABA(A) receptor agonists, muscimol, and 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol exerted no effect. The baclofen-induced synthesis of inositol phosphate and transient increases in [Ca(2+)](i) were blocked by CGP35348 and CGP55845 (selective GABA(B) antagonists), pertussis toxin (PTX, which inactivates the G(i) protein), gallein (a G(βγ) signaling inhibitor), U73122 (an inhibitor of PLC-β), and xestospongin C, an inositol 1,4,5-triphosphate receptor blocker. Baclofen also potentiated the bradykinin-induced synthesis of inositol phosphate and transient increases in [Ca(2+)](i), which were blocked by CGP35348 or PTX. Moreover, baclofen potentiated the substance P-induced contraction of airway smooth muscle in isolated guinea pig tracheal rings. In conclusion, the stimulation of GABA(B) receptors in human airway smooth muscle cells rapidly mobilizes intracellular Ca(2+) stores by the synthesis of inositol phosphate via the activation of PLC-β, which is stimulated by G(βγ) protein liberated from G(i) proteins coupled to GABA(B) receptors. Furthermore, crosstalk between GABA(B) receptors and G(q)-coupled receptors potentiates the synthesis of inositol phosphate, transient increases in [Ca(2+)](i), and smooth muscle contraction through G(i) proteins.

Gi-Coupled γ-Aminobutyric Acid–B Receptors Cross-Regulate Phospholipase C and Calcium in Airway Smooth Muscle

PubMed Central

Mizuta, Kentaro; Mizuta, Fumiko; Xu, Dingbang; Masaki, Eiji; Panettieri, Reynold A.

2011-01-01

γ-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system, and exerts its actions via both ionotropic (GABAA) and metabotropic (GABAB) receptors. Although the functional expression of GABAB receptors coupled to the Gi protein was reported for airway smooth muscle, the role of GABAB receptors in airway responsiveness remains unclear. We investigated whether Gi-coupled GABAB receptors cross-regulate phospholipase C (PLC), an enzyme classically regulated by Gq-coupled receptors in human airway smooth muscle cells. Both the GABAB-selective agonist baclofen and the endogenous ligand GABA significantly increased the synthesis of inositol phosphate, whereas GABAA receptor agonists, muscimol, and 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol exerted no effect. The baclofen-induced synthesis of inositol phosphate and transient increases in [Ca2+]i were blocked by CGP35348 and CGP55845 (selective GABAB antagonists), pertussis toxin (PTX, which inactivates the Gi protein), gallein (a Gβγ signaling inhibitor), U73122 (an inhibitor of PLC-β), and xestospongin C, an inositol 1,4,5-triphosphate receptor blocker. Baclofen also potentiated the bradykinin-induced synthesis of inositol phosphate and transient increases in [Ca2+]i, which were blocked by CGP35348 or PTX. Moreover, baclofen potentiated the substance P–induced contraction of airway smooth muscle in isolated guinea pig tracheal rings. In conclusion, the stimulation of GABAB receptors in human airway smooth muscle cells rapidly mobilizes intracellular Ca2+ stores by the synthesis of inositol phosphate via the activation of PLC-β, which is stimulated by Gβγ protein liberated from Gi proteins coupled to GABAB receptors. Furthermore, crosstalk between GABAB receptors and Gq-coupled receptors potentiates the synthesis of inositol phosphate, transient increases in [Ca2+]i, and smooth muscle contraction through Gi proteins. PMID:21719794

5-HT2A receptor activation is necessary for CO2-induced arousal

PubMed Central

Smith, Haleigh R.; MacAskill, Amanda; Richerson, George B.

2015-01-01

Hypercapnia-induced arousal from sleep is an important protective mechanism pertinent to a number of diseases. Most notably among these are the sudden infant death syndrome, obstructive sleep apnea and sudden unexpected death in epilepsy. Serotonin (5-HT) plays a significant role in hypercapnia-induced arousal. The mechanism of 5-HT's role in this protective response is unknown. Here we sought to identify the specific 5-HT receptor subtype(s) involved in this response. Wild-type mice were pretreated with antagonists against 5-HT receptor subtypes, as well as antagonists against adrenergic, cholinergic, histaminergic, dopaminergic, and orexinergic receptors before challenge with inspired CO2 or hypoxia. Antagonists of 5-HT2A receptors dose-dependently blocked CO2-induced arousal. The 5-HT2C receptor antagonist, RS-102221, and the 5-HT1A receptor agonist, 8-OH-DPAT, attenuated but did not completely block CO2-induced arousal. Blockade of non-5-HT receptors did not affect CO2-induced arousal. None of these drugs had any effect on hypoxia-induced arousal. 5-HT2 receptor agonists were given to mice in which 5-HT neurons had been genetically eliminated during embryonic life (Lmx1bf/f/p) and which are known to lack CO2-induced arousal. Application of agonists to 5-HT2A, but not 5-HT2C, receptors, dose-dependently restored CO2-induced arousal in these mice. These data identify the 5-HT2A receptor as an important mediator of CO2-induced arousal and suggest that, while 5-HT neurons can be independently activated to drive CO2-induced arousal, in the absence of 5-HT neurons and endogenous 5-HT, 5-HT receptor activation can act in a permissive fashion to facilitate CO2-induced arousal via another as yet unidentified chemosensor system. PMID:25925320

The contractile effect of anandamide in the guinea-pig small intestine is mediated by prostanoids but not TRPV1 receptors or capsaicin-sensitive nerves.

PubMed

Dékány, András; Benko, Rita; Szombati, Veronika; Bartho, Lorand

2013-05-01

Although exogenous and endogenous cannabinoid receptor agonists have well-documented inhibitory effects on gastrointestinal motility, a TRPV1 receptor-mediated excitatory action of anandamide (arachidonoyl ethanolamide, AEA) in the guinea-pig ileum strip has also been described. We used in vitro capsaicin desensitization for assessing the possible participation of sensory neurons in the contractile effect of anandamide on the guinea-pig whole ileum, as well as autonomic drugs and a cyclooxygenase inhibitor for characterizing this response. Isolated organ experiments were used with isotonic recording. Contractions induced by anandamide (1 or 10 μM) were strongly inhibited by tetrodotoxin, indomethacin or atropine plus a tachykinin NK(1) receptor antagonist, but weakly to moderately reduced by atropine alone and partly diminished by the fatty acid amide hydrolase inhibitor URB 597. Neither capsaicin pre-treatment nor the TRPV1 receptor antagonist BCTC, the ganglionic blocking drug hexamethonium or cannabinoid (CB1 or CB2 ) receptor antagonists, influenced the effect of anandamide. It is concluded that the capsaicin-insensitive, neuronal excitatory effect of anandamide in the intestine is most probably mediated by cyclooxygenase products. Such a mechanism may also play a role at other sites in the mammalian body. © 2012 Nordic Pharmacological Society. Published by Blackwell Publishing Ltd.

Exposure to ethanol on prenatal days 19-20 increases ethanol intake and palatability in the infant rat: involvement of kappa and mu opioid receptors.

PubMed

Díaz-Cenzano, Elena; Gaztañaga, Mirari; Gabriela Chotro, M

2014-09-01

Prenatal exposure to ethanol on gestation Days 19-20, but not 17-18, increases ethanol acceptance in infant rats. This effect seems to be a conditioned response acquired prenatally, mediated by the opioid system, which could be stimulated by ethanol's pharmacological properties (mu-opioid receptors) or by a component of the amniotic fluid from gestation-day 20 (kappa-inducing factor). The latter option was evaluated administering non-ethanol chemosensory stimuli on gestation Days 19-20 and testing postnatal intake and palatability. However, prenatal exposure to anise or vanilla increased neither intake nor palatability of these tastants on postnatal Day 14. In experiment 2, the role of ethanol's pharmacological effect was tested by administering ethanol and selective antagonists of mu and kappa opioid receptors prenatally. Blocking the mu-opioid receptor system completely reversed the effects on intake and palatability, while antagonizing kappa receptors only partially reduced the effects on palatability. This suggests that the pharmacological effect of ethanol on the fetal mu opioid system is the appetitive reinforcer, which induces the prenatally conditioned preference detected in the preweanling period. © 2013 Wiley Periodicals, Inc.

Neurokinin-1 receptor antagonists for chemotherapy-induced nausea and vomiting.

PubMed

Aziz, Fahad

2012-07-01

Chemotherapy can be a life-prolonging treatment for many cancer patients, but it is often associated with profound nausea and vomiting that is so distressing that patients may delay or decline treatment to avoid these side effects. The discovery of several NK1 receptor antagonists is a big revolution to dealt this problem. NK1 receptor antagonists prevent both acute and delayed chemotherapy-induced nausea and vomiting (CINV). These agents act centrally at NK-1 receptors in vomiting centers within the central nervous system to block their activation by substance P released as an unwanted consequence of chemotherapy. By controlling nausea and vomiting, these agents help improve patients' daily living and their ability to complete multiple cycles of chemotherapy. They are effective for both moderately and highly emetogenic chemotherapy regimens. Their use might be associated with increased infection rates; however, additional appraisal of specific data from RCTs is needed.

Prosocial effects of nicotine and ethanol in adolescent rats through partially dissociable neurobehavioral mechanisms

PubMed Central

Trezza, Viviana; Baarendse, Petra J.J.; Vanderschuren, Louk J.M.J.

2009-01-01

The widespread use of tobacco and alcohol among adolescents might be related to the ability of nicotine and ethanol to facilitate social interactions. To investigate the neurobehavioral mechanisms underlying the prosocial effects of nicotine and ethanol, we focused on social play behavior, the most characteristic social activity in adolescent rats. Social play behavior is rewarding, and it is modulated through opioid, cannabinoid and dopaminergic neurotransmission, which are also involved in the reinforcing properties of nicotine and ethanol. We found that nicotine and ethanol increased social play, without affecting locomotion or social exploration. Their effects depended on the level of social activity of the partner, and were comparable in familiar and unfamiliar environments. At doses that increased social play, nicotine and ethanol had no anxiolytic effects in the elevated plus-maze. By contrast, the prototypical anxiolytic drug diazepam reduced social play at doses that reduced anxiety. The effects of nicotine on social play were blocked by the opioid receptor antagonist naloxone, the CB1 cannabinoid receptor antagonist SR141716A, and the dopamine receptor antagonist alpha-flupenthixol. The effects of ethanol were blocked by SR141716A and alpha-flupenthixol, but not by naloxone. Combined administration of subeffective doses of nicotine and ethanol only modestly enhanced social play. These results show that the facilitatory effects of nicotine and ethanol on social play are behaviorally specific and mediated through neurotransmitter systems involved in positive emotions and motivation, through partially dissociable mechanisms. Furthermore, the stimulating effects of nicotine and ethanol on social play behavior are independent of their anxiolytic-like properties. PMID:19657330

Prosocial effects of nicotine and ethanol in adolescent rats through partially dissociable neurobehavioral mechanisms.

PubMed

Trezza, Viviana; Baarendse, Petra J J; Vanderschuren, Louk J M J

2009-11-01

The widespread use of tobacco and alcohol among adolescents might be related to the ability of nicotine and ethanol to facilitate social interactions. To investigate the neurobehavioral mechanisms underlying the prosocial effects of nicotine and ethanol, we focused on social play behavior, the most characteristic social activity in adolescent rats. Social play behavior is rewarding, and it is modulated through opioid, cannabinoid and dopaminergic neurotransmission, which are also involved in the reinforcing properties of nicotine and ethanol. We found that nicotine and ethanol increased social play, without affecting locomotion or social exploration. Their effects depended on the level of social activity of the partner, and were comparable in familiar and unfamiliar environments. At doses that increased social play, nicotine and ethanol had no anxiolytic effects in the elevated plus-maze. By contrast, the prototypical anxiolytic drug diazepam reduced social play at doses that reduced anxiety. The effects of nicotine on social play were blocked by the opioid receptor antagonist naloxone, the CB(1) cannabinoid receptor antagonist SR141716A, and the dopamine receptor antagonist alpha-flupenthixol. The effects of ethanol were blocked by SR141716A and alpha-flupenthixol, but not by naloxone. Combined administration of subeffective doses of nicotine and ethanol only modestly enhanced social play. These results show that the facilitatory effects of nicotine and ethanol on social play are behaviorally specific and mediated through neurotransmitter systems involved in positive emotions and motivation, through partially dissociable mechanisms. Furthermore, the stimulating effects of nicotine and ethanol on social play behavior are independent of their anxiolytic-like properties.

Existence of muscarinic acetylcholine receptor (mAChR) and fibroblast growth factor receptor (FGFR) heteroreceptor complexes and their enhancement of neurite outgrowth in neural hippocampal cultures.

PubMed

Di Liberto, V; Borroto-Escuela, D O; Frinchi, M; Verdi, V; Fuxe, K; Belluardo, N; Mudò, G

2017-02-01

Recently, it was demonstrated that G-protein-coupled receptors (GPCRs) can transactivate tyrosine kinase receptors in absence of their ligands. In this work, driven by the observation that mAChRs and fibroblast growth factor receptors (FGFRs) share signalling pathways and regulation of brain functions, it was decided to explore whether mAChRs activation may transactivate FGFRs and, if so, to characterize the related trophic effects in cultured hippocampal neurons. Oxotremorine-M transactivation of FGFRs and related trophic effects were tested in primary hippocampal neurons. Western blotting and in situ proximity ligation assay (PLA) were used to detect FGFR phosphorylation (pFGFR) levels and M 1 R-FGFR1 heteroreceptor complexes, respectively. Oxotremorine-M, a non-selective mAChRs agonist, was able to transactivate FGFR and this transactivation was blocked by Src inhibitors. Oxotremorine-M treatment produced a significant increase in the primary neurite outgrowth that was blocked by pre-treatment with the pFGFR inhibitor SU5402 and Src inhibitors. This trophic effect was almost similar to that induced by fibroblast growth factor-2 (FGF-2). By using atropine as nonselective mAChRs or pirenzepine as selective antagonist for M 1 receptor (M 1 R) we could show that mAChRs are involved in modulating the pFGFRs. Using PLA, M 1 R-FGFR1 heteroreceptor complexes were identified in the hippocampus and cerebral cortex. The current findings, by showing functional mAChR-FGFR interactions, will contribute to advance the understanding of the mechanisms involved in the actions of cholinergic drugs on neuronal plasticity. Data may help to develop novel therapeutic strategies not only for neurodegenerative diseases but also for depression-induced atrophy of hippocampal neurons. Copyright © 2016 Elsevier B.V. All rights reserved.

Responses to dehydration in the one-humped camel and effects of blocking the renin-angiotensin system.

PubMed

Ali, Mahmoud Alhaj; Adem, Abdu; Chandranath, Irwin S; Benedict, Sheela; Pathan, Javed Y; Nagelkerke, Nicolas; Nyberg, Fred; Lewis, Lynley K; Yandle, Tim G; Nicholls, Gary M; Frampton, Chris M; Kazzam, Elsadig

2012-01-01

Our objectives were to compare the levels of circulating electrolytes, hormones, and renal function during 20 days of dehydration in camels versus the level in non-dehydrated camels and to record the effect of blocking angiotensin II AT1 receptors with losartan during dehydration. Dehydration induced significant increments in serum sodium, creatinine, urea, a substantial fall in body weight, and a doubling in plasma arginine vasopressin (AVP) levels. Plasma aldosterone, however, was unaltered compared with time-matched controls. Losartan significantly enhanced the effect of dehydration to reduce body weight and increase serum levels of creatinine and urea, whilst also impairing the rise in plasma AVP and reducing aldosterone levels. We conclude that dehydration in the camel induces substantial increments in serum sodium, creatinine, urea and AVP levels; that aldosterone levels are altered little by dehydration; that blockade of angiotensin II type 1 receptors enhances the dehydration-induced fall in body weight and increase in serum creatinine and urea levels whilst reducing aldosterone and attenuating the rise in plasma AVP.

Microinjection of urocortin 2 into the dorsal raphe nucleus activates serotonergic neurons and increases extracellular serotonin in the basolateral amygdala.

PubMed

Amat, J; Tamblyn, J P; Paul, E D; Bland, S T; Amat, P; Foster, A C; Watkins, L R; Maier, S F

2004-01-01

The intra dorsal raphe nucleus (DRN) administration of corticotropin releasing hormone (CRF) inhibits serotonergic (5-HT) activity in this structure, an effect blocked by antagonists selective for the type 1 CRF receptor (CRF1). The DRN has a high density of the type 2 receptor (CRF2), and so the present experiments explored the impact of CRF2 activation within the DRN on 5-HT function. The intra-DRN administration of the selective CRF2 agonist urocortin 2 (Ucn 2) dose dependently increased 5-HT efflux in the basolateral amygdala, a projection region of the DRN. Intra-DRN Ucn 2 also increased c-fos expression in labeled 5-HT neurons. Both of these effects of Ucn 2 were completely blocked by intra-DRN antisauvagine-30 (ASV-30), a relatively selective CRF2 antagonist. These data suggest that CRF1 and CRF2 activation within the DRN affect 5-HT neurons in opponent fashion. Implications of these results for understanding the behavioral effects of CRF and other CRF-like ligands are discussed.

Responses to Dehydration in the One-Humped Camel and Effects of Blocking the Renin-Angiotensin System

PubMed Central

Ali, Mahmoud Alhaj; Adem, Abdu; Chandranath, Irwin S.; Benedict, Sheela; Pathan, Javed Y.; Nagelkerke, Nicolas; Nyberg, Fred; Lewis, Lynley K.; Yandle, Tim G.; Nicholls, Gary M.; Frampton, Chris M.; Kazzam, Elsadig

2012-01-01

Our objectives were to compare the levels of circulating electrolytes, hormones, and renal function during 20 days of dehydration in camels versus the level in non-dehydrated camels and to record the effect of blocking angiotensin II AT1 receptors with losartan during dehydration. Dehydration induced significant increments in serum sodium, creatinine, urea, a substantial fall in body weight, and a doubling in plasma arginine vasopressin (AVP) levels. Plasma aldosterone, however, was unaltered compared with time-matched controls. Losartan significantly enhanced the effect of dehydration to reduce body weight and increase serum levels of creatinine and urea, whilst also impairing the rise in plasma AVP and reducing aldosterone levels. We conclude that dehydration in the camel induces substantial increments in serum sodium, creatinine, urea and AVP levels; that aldosterone levels are altered little by dehydration; that blockade of angiotensin II type 1 receptors enhances the dehydration-induced fall in body weight and increase in serum creatinine and urea levels whilst reducing aldosterone and attenuating the rise in plasma AVP. PMID:22624009

Update on the mechanism of action of antiepileptic drugs.

PubMed

Meldrum, B S

1996-01-01

Novel antiepileptic drugs (AEDs) are thought to act on voltage-sensitive ion channels, on inhibitory neurotransmission or on excitatory neurotransmission. Two successful examples of rational AED design that potentiate GABA-mediated inhibition are vigabatrin (VGB) by irreversible inhibition of GABA-transaminase, and tiagabine (TGB) by blocking GABA uptake. Lamotrigine (LTG) prolongs inactivation of voltage-dependent sodium channels. The anticonvulsant action of remacemide (RCM) is probably largely due to blockade of NMDA receptors and prolonged inactivation of sodium channels induced by its desglycinated metabolite. Felbamate (FBM) apparently blocks NMDA receptors, potentiates GABA-mediated responses, blocks L-type calcium channels, and possibly also prolongs sodium channel inactivation. Similarly, topiramate (TPM) has multiple probable sites of action, including sodium channels, GABA receptors, and glutamate (AMPA) receptors. Gabapentin (GBP) apparently has a completely novel type of action, probably involving potentiation of GABA-mediated inhibition and possibly also inactivation of sodium channels. The therapeutic advantages of the novel AEDs are as yet only partially explained by our present understanding of their mechanisms of action.

The Marine Guanidine Alkaloid Crambescidin 816 Induces Calcium Influx and Cytotoxicity in Primary Cultures of Cortical Neurons through Glutamate Receptors.

PubMed

Mendez, Aida G; Juncal, Andrea Boente; Silva, Siguara B L; Thomas, Olivier P; Martín Vázquez, Víctor; Alfonso, Amparo; Vieytes, Mercedes R; Vale, Carmen; Botana, Luís M

2017-07-19

Crambescidin 816 is a guanidine alkaloid produced by the sponge Crambe crambe with known antitumoral activity. While the information describing the effects of this alkaloid in central neurons is scarce, Cramb816 is known to block voltage dependent calcium channels being selective for L-type channels. Moreover, Cramb816 reduced neuronal viability through an unknown mechanism. Here, we aimed to describe the toxic activity of Cramb816 in cortical neurons. Since calcium influx is considered the main mechanism responsible for neuronal cell death, the effects of Cramb816 in the cytosolic calcium concentration of cortical neurons were studied. The alkaloid decreased neuronal viability and induced a dose-dependent increase in cytosolic calcium that was also related to the presence of calcium in the extracellular media. The increase in calcium influx was age dependent, being higher in younger neurons. Moreover, this effect was prevented by glutamate receptor antagonists, which did not fully block the cytotoxic effect of Cramb816 after 24 h of treatment but completely prevented Cramb816 cytotoxicity after 10 min exposure. Therefore, the findings presented herein provide new insights into the cytotoxic effect of Cramb816 in cortical neurons.

Actions of Bupivacaine, a Widely Used Local Anesthetic, on NMDA Receptor Responses

PubMed Central

Paganelli, Meaghan A.

2015-01-01

NMDA receptors mediate excitatory neurotransmission in brain and spinal cord and play a pivotal role in the neurological disease state of chronic pain, which is caused by central sensitization. Bupivacaine is the indicated local anesthetic in caudal, epidural, and spinal anesthesia and is widely used clinically to manage acute and chronic pain. In addition to blocking Na+ channels, bupivacaine affects the activity of many other channels, including NMDA receptors. Importantly, bupivacaine inhibits NMDA receptor-mediated synaptic transmission in the dorsal horn of the spinal cord, an area critically involved in central sensitization. We used recombinant NMDA receptors expressed in HEK293 cells and found that increasing concentrations of bupivacaine decreased channel open probability in GluN2 subunit- and pH-independent manner by increasing the mean duration of closures and decreasing the mean duration of openings. Using kinetic modeling of one-channel currents, we attributed the observed current decrease to two main mechanisms: a voltage-dependent “foot-in-the-door” pore block and an allosteric gating effect. Further, the inhibition was state-independent because it occurred to the same degree whether the drug was applied before or after glutamate stimulation and was mediated by extracellular and intracellular inhibitory sites, via hydrophilic and hydrophobic pathways. These results predict that clinical doses of bupivacaine would decrease the peak and accelerate the decay of synaptic NMDA receptor currents during normal synaptic transmission. These quantitative predictions inform possible applications of bupivacaine as preventative and therapeutic approaches in chronic pain. PMID:25589775

Bitopic Sphingosine 1-Phosphate Receptor 3 (S1P3) Antagonist Rescue from Complete Heart Block: Pharmacological and Genetic Evidence for Direct S1P3 Regulation of Mouse Cardiac Conduction.

PubMed

Sanna, M Germana; Vincent, Kevin P; Repetto, Emanuela; Nguyen, Nhan; Brown, Steven J; Abgaryan, Lusine; Riley, Sean W; Leaf, Nora B; Cahalan, Stuart M; Kiosses, William B; Kohno, Yasushi; Brown, Joan Heller; McCulloch, Andrew D; Rosen, Hugh; Gonzalez-Cabrera, Pedro J

2016-01-01

The molecular pharmacology of the G protein-coupled receptors for sphingosine 1-phosphate (S1P) provides important insight into established and new therapeutic targets. A new, potent bitopic S1P3 antagonist, SPM-354, with in vivo activity, has been used, together with S1P3-knockin and S1P3-knockout mice to define the spatial and functional properties of S1P3 in regulating cardiac conduction. We show that S1P3 is a key direct regulator of cardiac rhythm both in vivo and in isolated perfused hearts. 2-Amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol in vivo and S1P in isolated hearts induced a spectrum of cardiac effects, ranging from sinus bradycardia to complete heart block, as measured by a surface electrocardiogram in anesthetized mice and in volume-conducted Langendorff preparations. The agonist effects on complete heart block are absent in S1P3-knockout mice and are reversed in wild-type mice with SPM-354, as characterized and described here. Homologous knockin of S1P3-mCherry is fully functional pharmacologically and is strongly expressed by immunohistochemistry confocal microscopy in Hyperpolarization Activated Cyclic Nucleotide Gated Potassium Channel 4 (HCN4)-positive atrioventricular node and His-Purkinje fibers, with relative less expression in the HCN4-positive sinoatrial node. In Langendorff studies, at constant pressure, SPM-354 restored sinus rhythm in S1P-induced complete heart block and fully reversed S1P-mediated bradycardia. S1P3 distribution and function in the mouse ventricular cardiac conduction system suggest a direct mechanism for heart block risk that should be further studied in humans. A richer understanding of receptor and ligand usage in the pacemaker cells of the cardiac system is likely to be useful in understanding ventricular conduction in health, disease, and pharmacology. Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.

Adrenomedullin increased the short-circuit current in the pig oviduct through chloride channels via the CGRP receptor: mediation by cAMP and calcium ions but not by nitric oxide.

PubMed

Liao, S B; Cheung, K H; Cheung, M P L; To, Y T; O, W S; Tang, F

2013-10-01

The oviduct serves as a site for the fertilization of the ovum and the transport of the conceptus down to the uterus for implantation. In this study, we investigated the presence of adrenomedullin (ADM) and its receptor component proteins in the pig oviduct. The effect of ADM on oviductal secretion, the specific receptor, and the mechanisms involved were also investigated. The presence of ADM and its receptor component proteins in the pig oviduct were confirmed using immunostaining. Short-circuit current (I(sc)) technique was employed to study chloride ion secretion in the oviductal epithelium. ADM increased I(sc) through cAMP- and calcium-activated chloride channels, and this effect could be inhibited by the CGRP receptor antagonist, hCGRP8-37. In contrast, the nitric oxide synthase inhibitor, L-NG-nitroarginine methyl ester (L-NAME), could not block the effect of ADM on I(sc). In summary, ADM may increase oviductal fluid secretion via chloride secretion independent of the nitric oxide pathway for the transport of sperm and the conceptus.

Activation of kappa opioid receptors in the dorsal raphe have sex dependent effects on social behavior in California mice.

PubMed

Wright, Emily C; Parks, Tiffany V; Alexander, Jonathon O; Supra, Rajesh; Trainor, Brian C

2018-06-06

Kappa opioid receptor activation has been linked to stress and anxiety behavior, thus leading to kappa antagonists being popularized in research as potential anxiolytics. However, while these findings may hold true in standard models, the neuromodulatory effects of social defeat may change the behavioral outcome of kappa opioid receptor activation. Previous research has shown that social defeat can lead to hyperactivity of serotonergic neurons in the dorsal raphe nucleus, and that inhibition of this increase blocks the social deficits caused by defeat. Kappa opioid receptor activation in the dorsal raphe nucleus works to decrease serotonergic activity. We injected the kappa opioid receptor U50,488 directly into the dorsal raphe nucleus of male and female, defeat and control adult California mice. Here we show evidence that U50,488 induces anxiety behavior in control male California mice, but helps relieve it in defeated males. Consistent with previous literature, we find little effect in females adding evidence that there are marked and important sex differences in the kappa opioid system. Copyright © 2018 Elsevier B.V. All rights reserved.

Cannabinoid reward and aversion effects in the posterior ventral tegmental area are mediated through dissociable opiate receptor subtypes and separate amygdalar and accumbal dopamine receptor substrates.

PubMed

Ahmad, Tasha; Laviolette, Steven R

2017-08-01

The ventral tegmental area (VTA) and its projections to the basolateral amygdala (BLA) and nucleus accumbens (NAc) are critical for cannabinoid-related motivational effects. Cannabinoid CB1 receptor (CB1R) transmission modulates VTA dopamine (DA) neuron activity and previous reports demonstrate anatomically segregated effects of CB1R transmission in the VTA. However, the underlying pharmacological and anatomical regions responsible for these effects are currently unknown. The objective of the study is to characterize the motivational effects of localized anterior vs. posterior intra-VTA activation vs. blockade of CB1R transmission and the potential role of intra-BLA and intra-NAc DA transmission in these phenomena. Using a conditioned place preference (CPP) procedure, we administered a CB1 agonist (WIN-55,212-2) or antagonist (AM 251) into the posterior VTA (pVTA) or anterior VTA (aVTA) of rats, combined with intra-BLA or intra-NAc DA receptor blockade and intra-VTA co-administration of selective mu vs. kappa opiate-receptor antagonists. Intra-pVTA CB1R activation produced robust rewarding effects through a mu-opiate receptor mechanism whereas CB1R blockade produced conditioned place aversions (CPA) through a kappa-opiate receptor substrate. In contrast, modulation of aVTA CB1R transmission produced no observable effects. Intra-BLA DA receptor blockade prevented the rewarding effects of pVTA CB1R activation, but had no effects on CB1R blockade-induced aversions. In contrast, intra-NAc DA receptor blockade selectively blocked the aversive effects of pVTA CB1R antagonism. Activation vs. blockade of CB1R transmission in the posterior VTA produces bivalent rewarding or aversive effects through separate mu vs. kappa-opiate receptor substrates. These dissociable effects depend on separate DA receptor transmission substrates in the BLA or NAc, respectively.

Clebopride enhances contractility of the guinea pig stomach by blocking peripheral D2 dopamine receptor and alpha-2 adrenoceptor.

PubMed

Takeda, K; Taniyama, K; Kuno, T; Sano, I; Ishikawa, T; Ohmura, I; Tanaka, C

1991-05-01

The mechanism of action of clebopride on the motility of guinea pig stomach was examined by the receptor binding assay for bovine brain membrane and by measuring gastric contractility and the release of acetylcholine from the stomach. The receptor binding assay revealed that clebopride bound to the D2 dopamine receptor with a high affinity and to the alpha-2 adrenoceptor and 5-HT2 serotonin receptor with relatively lower affinity, and not to D1 dopamine, alpha-1 adrenergic, muscarinic acetylcholine, H1 histamine, or opioid receptor. In strips of the stomach, clebopride at 10(-8) M to 10(-5) M enhanced the electrical transmural stimulation-evoked contraction and the release of acetylcholine. This enhancement was attributed to the blockade of the D2 dopamine receptor and alpha-2 adrenoceptor because: 1) Maximum responses obtained with specific D2 dopamine receptor antagonist, domperidone, and with specific alpha-2 adrenoceptor antagonist, yohimbine, were smaller than that with clebopride, and the sum of the effects of these two specific receptor antagonists is approximately equal to the effect of clebopride. 2) The facilitatory effect of clebopride was partially eliminated by pretreatment of the sample with domperidone or yohimbine, and the facilitatory effect of clebopride was not observed in preparations treated with the combination of domperidone and yohimbine. Clebopride also antagonized the inhibitory effects of dopamine and clonidine on the electrical transmural stimulation-evoked responses. These results indicate that clebopride acts on post ganglionic cholinergic neurons at D2 and alpha-2 receptors in this preparation to enhance enteric nervous system stimulated motility.

Identification of a µ opiate receptor signaling mechanism in human placenta.

PubMed

Mantione, Kirk J; Angert, Robert M; Cadet, Patrick; Kream, Richard M; Stefano, George B

2010-11-01

Previous studies report that genes in the morphine biosynthetic pathway have been found in placental tissue. Prior researchers have shown that kappa opioid receptors are present in human placenta. We determined if a µ opiate receptor was present and which subtype was expressed in human placenta. We also sought to demonstrate a functional µ opiate receptor in human placenta. Polymerase chain reactions as well as DNA sequencing were performed to identify the µ opiate receptor subtypes present in human placenta. The functionality of the receptor was demonstrated by real time amperometric measurements of morphine induced NO release. The µ4 opiate receptor sequence was present as well as the µ1 opioid receptor transcript. The addition of morphine to placental tissue resulted in immediate nitric oxide release and this effect was blocked by naloxone. In the present study, an intact morphine signaling system has been demonstrated in human placenta. Morphine signaling in human placenta probably functions to regulate the immune, vascular, and endocrine functions of this organ via NO.

Vasotocin- and mesotocin-induced increases in short-circuit current across tree frog skin.

PubMed

Takada, Makoto; Fujimaki-Aoba, Kayo; Hokari, Shigeru

2011-02-01

In adult amphibian skin, Na(+) crosses from outside to inside. This Na(+) transport can be measured as the amiloride-blockable short-circuit current (SCC) across the skin. We investigated the effects of arginine vasotocin (AVT) and mesotocin (MT), and those of antagonists of the vasopressin and oxytocin receptors, on the SCC across Hyla japonica skin. (1) Both AVT (100 pmol/L or more) and MT (1 nmol/L or more) increased the SCC. (2) The AVT- and MT-induced increases in SCC recovered with time (downregulation). (3) These AVT/MT-induced effects were blocked by application of OPC-31260 (vasopressin V(2)-receptor antagonist). (4) The OPC-31260 concentration needed to block the AVT-induced response was lower upon post-application (after application of agonist) than upon pre-application (before application of agonist), suggesting the number of receptors may have decreased after AVT application. (5) Upon repeated application of AVT (100 pmol/L), the induced SCC increase did not differ significantly between the 1st and 2nd applications. (6) The time to reach the half-maximum value of the AVT-induced or MT-induced increase in SCC was not significantly different between washout and post-application of OPC-31260, suggesting that post-application of OPC-31260 cleared AVT and MT from their receptors. The effects of AVT, MT, and their antagonists in H. japonica, which is adapted to a terrestrial habitat, are compared with our previously published data on Rana catesbeiana (=Lithobates catesbeianus), which is adapted to a semiaquatic habitat.

Rapid Antidepressant Actions of Scopolamine: Role of Medial Prefrontal Cortex and M1-subtype Muscarinic Acetylcholine Receptors

PubMed Central

Navarria, Andrea; Wohleb, Eric S.; Voleti, Bhavya; Ota, Kristie T.; Dutheil, Sophie; Lepack, Ashley E.; Dwyer, Jason M.; Fuchikami, Manabu; Becker, Astrid; Drago, Filippo; Duman, Ronald S.

2015-01-01

Clinical studies demonstrate that scopolamine, a nonselective muscarinic acetycholine receptor (mAchR) antagonist, produces rapid therapeutic effects in depressed patients, and preclinical studies report that the actions of scopolamine require glutamate receptor activation and the mechanistic target of rapamycin complex 1 (mTORC1) in the medial prefrontal cortex (mPFC). The present study extends these findings to determine the role of the mPFC and specific muscarinic acetylcholine receptor (M-AchR) subtypes in the actions of scopolamine. Administration of scopolamine increases the activity marker Fos in the mPFC, including the infralimbic (IL) and prelimbic (PrL) subregions. Microinfusions of scopolamine into either the IL or PrL produced significant antidepressant responses in the forced swim test, and neuronal silencing of IL or PrL blocked the antidepressant effects of systemic scopolamine. The results also demonstrate that systemic administration of a selective M1-AChR antagonist, VU0255035 produced an antidepressant response and stimulated mTORC1 signaling in the PFC, similar to the actions of scopolamine. Finally, we used a chronic unpredictable stress model as a more rigorous test of rapid antidepressant actions, and found that scopolamine or VU0255035 administration blocked the anhedonic response caused by CUS, an effect that requires chronic administration of typical antidepressants. Taken together, these findings indicate that mPFC is a critical mediator of the behavioral actions of scopolamine, and identify the M1-AChR as a therapeutic target for the development of novel and selective rapid-acting antidepressants. PMID:26102021

The role of NMDA and mGluR5 receptors in calcium mobilization and neurotoxicity of homocysteine in trigeminal and cortical neurons and glial cells.

PubMed

Abushik, Polina A; Niittykoski, Minna; Giniatullina, Raisa; Shakirzyanova, Anastasia; Bart, Genevieve; Fayuk, Dmitriy; Sibarov, Dmitry A; Antonov, Sergei M; Giniatullin, Rashid

2014-04-01

Recent studies suggested contribution of homocysteine (HCY) to neurodegenerative disorders and migraine. However, HCY effect in the nociceptive system is essentially unknown. To explore the mechanism of HCY action, we studied short- and long-term effects of this amino acid on rat peripheral and central neurons. HCY induced intracellular Ca²⁺ transients in cultured trigeminal neurons and satellite glial cells (SGC), which were blocked by the NMDA antagonist AP-5 in neurons, but not in SGCs. In contrast, 3-((2-Methyl-4-thiazolyl)ethynyl)pyridine (MTEP), the metabotropic mGluR5 (metabotropic glutamate receptor 5 subtype) antagonist, preferentially inhibited Ca²⁺ transients in SGCs. Prolonged application of HCY induced apoptotic cell death of both kinds of trigeminal cells. The apoptosis was blocked by AP-5 or by the mGluR5 antagonist MTEP. Likewise, in cortical neurons, HCY-induced cell death was inhibited by AP-5 or MTEP. Imaging with 2',7'-dichlorodihydrofluorescein diacetate or mitochondrial dye Rhodamine-123 as well as thiobarbituric acid reactive substances assay did not reveal involvement of oxidative stress in the action of HCY. Thus, elevation of intracellular Ca²⁺ by HCY in neurons is mediated by NMDA and mGluR5 receptors while SGC are activated through the mGluR5 subtype. Long-term neurotoxic effects in peripheral and central neurons involved both receptor types. Our data suggest glutamatergic mechanisms of HCY-induced sensitization and apoptosis of trigeminal nociceptors. © 2013 International Society for Neurochemistry.

HSV-1 infection of human corneal epithelial cells: receptor-mediated entry and trends of re-infection.

PubMed

Shah, Arpeet; Farooq, Asim V; Tiwari, Vaibhav; Kim, Min-Jung; Shukla, Deepak

2010-11-20

The human cornea is a primary target for herpes simplex virus-1 (HSV-1) infection. The goals of the study were to determine the cellular modalities of HSV-1 entry into human corneal epithelial (HCE) cells. Specific features of the study included identifying major entry receptors, assessing pH dependency, and determining trends of re-infection. A recombinant HSV-1 virus expressing beta-galactosidase was used to ascertain HSV-1 entry into HCE cells. Viral replication within cells was confirmed using a time point plaque assay. Lysosomotropic agents were used to test for pH dependency of entry. Flow cytometry and immunocytochemistry were used to determine expression of three cellular receptors--nectin-1, herpesvirus entry mediator (HVEM), and paired immunoglobulin-like 2 receptor alpha (PILR-a). The necessity of these receptors for viral entry was tested using antibody-blocking. Finally, trends of re-infection were investigated using viral entry assay and flow cytometry post-primary infection. Cultured HCE cells showed high susceptibility to HSV-1 entry and replication. Entry was demonstrated to be pH dependent as blocking vesicular acidification decreased entry. Entry receptors expressed on the cell membrane include nectin-1, HVEM, and PILR-α. Receptor-specific antibodies blocked entry receptors, reduced viral entry and indicated nectin-1 as the primary receptor used for entry. Cells re-infected with HSV-1 showed a decrease in entry, which was correlated to decreased levels of nectin-1 as demonstrated by flow cytometry. HSV-1 is capable of developing an infection in HCE cells using a pH dependent entry process that involves primarily nectin-1 but also the HVEM and PILR-α receptors. Re-infected cells show decreased levels of entry, correlated with a decreased level of nectin-1 receptor expression.

[Impairment of the immune system caused by drugs].

PubMed

Pichler, W J

1987-03-21

The immune response and the ensuing inflammation relies on a complex interaction of cells and mediators. Various drugs can interfere with individual steps of the immune response, and in so doing they often imitate regulatory mechanisms of the immune system itself. The immunosuppressive effect of corticosteroids is based on changes in cell migration, reduced responsiveness of monocytes/macrophages to various stimuli and diminished production of interleukin-2. Cyclosporin A appears to block prolactin binding to prolactin receptors on lymphocytes, thus interfering with the immunostimulatory effect of prolactin. It also appears to have a Calmodulin antagonism and might thus block lymphokine production. Anticoagulants may block delayed type hypersensitivity reactions, since activation of the coagulation cascade is involved in this type of immune reaction. Attempts to use calcium channel blockers as immunosuppressive agents, or to take advantage of the immunoregulatory effects of adrenergic substances/blockers or other neurotransmitters, are of experimental value only.

Identification of ML204, a Novel Potent Antagonist That Selectively Modulates Native TRPC4/C5 Ion Channels*

PubMed Central

Miller, Melissa; Shi, Jie; Zhu, Yingmin; Kustov, Maksym; Tian, Jin-bin; Stevens, Amy; Wu, Meng; Xu, Jia; Long, Shunyou; Yang, Pu; Zholos, Alexander V.; Salovich, James M.; Weaver, C. David; Hopkins, Corey R.; Lindsley, Craig W.; McManus, Owen; Li, Min; Zhu, Michael X.

2011-01-01

Transient receptor potential canonical (TRPC) channels are Ca2+-permeable nonselective cation channels implicated in diverse physiological functions, including smooth muscle contractility and synaptic transmission. However, lack of potent selective pharmacological inhibitors for TRPC channels has limited delineation of the roles of these channels in physiological systems. Here we report the identification and characterization of ML204 as a novel, potent, and selective TRPC4 channel inhibitor. A high throughput fluorescent screen of 305,000 compounds of the Molecular Libraries Small Molecule Repository was performed for inhibitors that blocked intracellular Ca2+ rise in response to stimulation of mouse TRPC4β by μ-opioid receptors. ML204 inhibited TRPC4β-mediated intracellular Ca2+ rise with an IC50 value of 0.96 μm and exhibited 19-fold selectivity against muscarinic receptor-coupled TRPC6 channel activation. In whole-cell patch clamp recordings, ML204 blocked TRPC4β currents activated through either μ-opioid receptor stimulation or intracellular dialysis of guanosine 5′-3-O-(thio)triphosphate (GTPγS), suggesting a direct interaction of ML204 with TRPC4 channels rather than any interference with the signal transduction pathways. Selectivity studies showed no appreciable block by 10–20 μm ML204 of TRPV1, TRPV3, TRPA1, and TRPM8, as well as KCNQ2 and native voltage-gated sodium, potassium, and calcium channels in mouse dorsal root ganglion neurons. In isolated guinea pig ileal myocytes, ML204 blocked muscarinic cation currents activated by bath application of carbachol or intracellular infusion of GTPγS, demonstrating its effectiveness on native TRPC4 currents. Therefore, ML204 represents an excellent novel tool for investigation of TRPC4 channel function and may facilitate the development of therapeutics targeted to TRPC4. PMID:21795696

Receptors involved in the modulation of guinea pig urinary bladder motility by prostaglandin D2

PubMed Central

Guan, Na N; Svennersten, Karl; de Verdier, Petra J; Wiklund, N Peter; Gustafsson, Lars E

2015-01-01

Background and Purpose We have described a urothelium-dependent release of PGD2-like activity which had inhibitory effects on the motility of guinea pig urinary bladder. Here, we have pharmacologically characterized the receptors involved and localized the sites of PGD2 formation and of its receptors. Experimental Approach In the presence of selective DP and TP receptor antagonists alone or combined, PGD2 was applied to urothelium-denuded diclofenac-treated urinary bladder strips mounted in organ baths. Antibodies against PGD2 synthase and DP1 receptors were used with Western blots and for histochemistry. Key Results PGD2 inhibited nerve stimulation -induced contractions in strips of guinea pig urinary bladder with estimated pIC50 of 7.55 ± 0.15 (n = 13), an effect blocked by the DP1 receptor antagonist BW-A868C. After blockade of DP1 receptors, PGD2 enhanced the contractions, an effect abolished by the TP receptor antagonist SQ-29548. Histochemistry revealed strong immunoreactivity for PGD synthase in the urothelium/suburothelium with strongest reaction in the suburothelium. Immunoreactive DP1 receptors were found in the smooth muscle of the bladder wall with a dominant localization to smooth muscle membranes. Conclusions and Implications In guinea pig urinary bladder, the main effect of PGD2 is an inhibitory action via DP1 receptors localized to the smooth muscle, but an excitatory effect via TP receptors can also be evoked. The urothelium with its suburothelium might signal to the smooth muscle which is rich in PGD2 receptors of the DP1 type. The results are important for our understanding of regulation of bladder motility. PMID:25917171

Comparative Effects of Dextromethorphan and Dextrorphan on Nicotine Discrimination in Rats

PubMed Central

Wright, M. Jerry; Vann, Robert E.; Gamage, Thomas F.; Damaj, M. Imad; Wiley, Jenny L.

2007-01-01

While the role of dextrorphan and dextromethorphan as N-methyl-D-aspartate (NMDA) receptor antagonists has received considerable research attention, their effects on nicotinic acetylcholine receptors (nAChR) has been less well characterized. Recent in vitro and in vivo research has suggested that these drugs noncompetitively block α3β4*, α4β2, and α7 nAChR subtypes and antagonize nicotine’s antinociceptive and reinforcing effects. Both drugs were most potent at blocking α3β4* AChR. This study investigated the effects of dextrorphan and dextromethorphan on nicotine’s discriminative stimulus effects. Three groups of rats were trained in a two-lever drug discrimination procedure to discriminate 0.4 mg/kg s.c. nicotine from saline. Nicotine dose-dependently substituted for itself in all three groups. In contrast, when dextrorphan (group 1) or dextromethorphan (group 2) were injected i.p., neither substitution for nor antagonism of nicotine was observed for either drug. Since i.p. administration allows substantial metabolism of dextromethorphan to its parent compound dextrorphan, the two drugs were also tested following s.c. administration (group 3). Discrimination results were similar across both routes of administration, in that neither substitution nor antagonism occurred, however, s.c. administration reduced response rates to a much greater extent than did i.p. administration. Previous work suggests that β2 subunits are crucial for mediation of nicotine’s discriminative stimulus effects and may play a role in its reinforcing effects, albeit other research suggests a role for α3β4* nicotinic receptors in the latter. Our results suggest that α3β4* nicotinic receptors do not play a major role in nicotine’s discriminative stimulus effects. Further, they suggest that the role of cholinergic mediation of the behavioral effects of dextrorphan and dextromethorphan related to the abuse properties of nicotine may be minimal. PMID:17112574

Small molecule inhibitors block Gas6-inducible TAM activation and tumorigenicity.

PubMed

Kimani, Stanley G; Kumar, Sushil; Bansal, Nitu; Singh, Kamalendra; Kholodovych, Vladyslav; Comollo, Thomas; Peng, Youyi; Kotenko, Sergei V; Sarafianos, Stefan G; Bertino, Joseph R; Welsh, William J; Birge, Raymond B

2017-03-08

TAM receptors (Tyro-3, Axl, and Mertk) are a family of three homologous type I receptor tyrosine kinases that are implicated in several human malignancies. Overexpression of TAMs and their major ligand Growth arrest-specific factor 6 (Gas6) is associated with more aggressive staging of cancers, poorer predicted patient survival, acquired drug resistance and metastasis. Here we describe small molecule inhibitors (RU-301 and RU-302) that target the extracellular domain of Axl at the interface of the Ig-1 ectodomain of Axl and the Lg-1 of Gas6. These inhibitors effectively block Gas6-inducible Axl receptor activation with low micromolar IC 50s in cell-based reporter assays, inhibit Gas6-inducible motility in Axl-expressing cell lines, and suppress H1299 lung cancer tumor growth in a mouse xenograft NOD-SCIDγ model. Furthermore, using homology models and biochemical verifications, we show that RU301 and 302 also inhibit Gas6 inducible activation of Mertk and Tyro3 suggesting they can act as pan-TAM inhibitors that block the interface between the TAM Ig1 ectodomain and the Gas6 Lg domain. Together, these observations establish that small molecules that bind to the interface between TAM Ig1 domain and Gas6 Lg1 domain can inhibit TAM activation, and support the further development of small molecule Gas6-TAM interaction inhibitors as a novel class of cancer therapeutics.

ADVERSE EFFECTS OF ANTIANDROGENIC PESTICIDE AND TOXIC SUBSTANCES ON REPRODUCTIVE DEVELOPMENT IN THE MALE

EPA Science Inventory

Anthropogenic endocrine disrupting chemicals (EDCs) or chemical mixtures alter androgen-response tissues via a variety of mechanisms including mimicking or blocking the action of the natural ligand to the androgen receptor (AR), inhibiting steroid hormone synthesis or by acting a...

[Modulation of skeletal muscle contraction by the non-toxic fraction of Buthus occitanus tunetanus venom via the cholinergic receptors].

PubMed

Cheikh, A; Cognard, C; Potreau, D; Bescond, J; Raymond, G; El Ayeb, M; Benkhalifa, R

2007-01-01

Cholinergic receptors have an essential physiological role in the central nervous system because of their implication in higher functions in the neuromuscular junction within the brain and also in the peripheral nervous system by activating nicotinic (nAChRs) or muscarinic (mAChRs) receptors. Moreover, cholinergic receptors could be recognized by animal toxins isolated from snake venoms or alkaloids having animal or vegetal origin. In this context, we aim to find such molecules in a non toxic venom fraction of Buthus occitanus tunetanus scorpion, M1, which could therefore constitute promising medical tool. We present here a physiological study in skeletal muscle cells that regroups data that have been recently published and some new results reinforcing the last ones. The global effect of M1, was firstly studied on isolated nerve-muscle preparation. In cultured myotubes, we have found that the intracellular calcium increase, induced by M1 was blocked when ryanodine or inositol 1,4,5-triphosphate receptors are inhibited. Moreover, we have shown that M1 application on myotubes, induced a membrane depolarization as seen with acetylcholine. The treatment of myotubes with alpha-bungarotoxin blocked in most parts the depolarization amplitude. Thus, these results confirm the presence of at least one component in M1 active in nAChRs.

Fetal human airway smooth muscle cell production of leukocyte chemoattractants is differentially regulated by fluticasone.

PubMed

Pearson, Helen; Britt, Rodney D; Pabelick, Christine M; Prakash, Y S; Amrani, Yassine; Pandya, Hitesh C

2015-12-01

Adult human airway smooth muscle (ASM) produce cytokines involved in recruitment and survival of leukocytes within airway walls. Cytokine generation by adult ASM is glucocorticoid-sensitive. Whether developing lung ASM produces cytokines in a glucocorticoid-sensitive fashion is unknown. Cultured fetal human ASM cells stimulated with TNF-α (0-20 ng/ml) were incubated with TNF-α receptor-blocking antibodies, fluticasone (1 and 100 nm), or vehicle. Supernatants and cells were assayed for the production of CCL5, CXCL10, and CXCL8 mRNA and protein and glucocorticoid receptor phosphorylation. CCL5, CXCL10, and CXCL8 mRNA and protein production by fetal ASM cell was significantly and dose-dependently following TNF-α treatment. Cytokine mRNA and protein production were effectively blocked by TNF-α R1 and R2 receptor neutralizing antibodies but variably inhibited by fluticasone. TNF-α-induced TNF-R1 and R2 receptor mRNA expression was only partially attenuated by fluticasone. Glucocorticoid receptor phosphorylation at serine (Ser) 211 but not at Ser 226 was enhanced by fluticasone. Production of CCL5, CXCL10, and CXCL8 by fetal ASM appears to involve pathways that are both qualitatively and mechanistically distinct to those described for adult ASM. The findings imply developing ASM has potential to recruit leukocyte into airways and, therefore, of relevance to childhood airway diseases.

Interleukin-6 inhibits early differentiation of ATDC5 chondrogenic progenitor cells.

PubMed

Nakajima, Shoko; Naruto, Takuya; Miyamae, Takako; Imagawa, Tomoyuki; Mori, Masaaki; Nishimaki, Shigeru; Yokota, Shumpei

2009-08-01

Interleukin (IL)-6 is a causative agent of systemic juvenile idiopathic arthritis (sJIA), a chronic inflammatory disease complicated with severe growth impairment. Recent trials of anti-IL-6 receptor monoclonal antibody, tocilizumab, indicated that tocilizumab blocks IL-6/IL-6 receptor-mediated inflammation, and induces catch-up growth in children with sJIA. This study evaluates the effects of IL-6 on chondrogenesis by ATDC5 cells, a clonal murine chondrogenic cell line that provides an excellent model for studying endochondral ossification at growth plate. ATDC5 cells were examined for the expression of IL-6 receptor and gp130 by fluorescence-activated cell sorting analysis. Recombinant murine IL-6 was added to ATDC5 cultures to observe cell differentiation, using a quantitative RT-PCR for the chondrogenic differentiation markers type II collagen, aggrecan, and type X collagen. To block IL-6, the anti-mouse IL-6 receptor monoclonal antibody MR16-1 was added. As a result, the cells expressed IL-6 receptor and gp130. The expression of chondrogenic differentiation marker gene was reduced by IL-6, but this was abrogated by MR16-1. We conclude that IL-6 inhibits early chondrogenesis of ATDC5 cells suggesting that IL-6 may affect committed stem cells at a cellular level during chondrogenic differentiation of growth plate chondrocytes, and that IL-6 may be a cellular-level factor in growth impairment in sJIA.

Fetal human airway smooth muscle cell production of leukocyte chemoattractants is differentially regulated by fluticasone

PubMed Central

Pearson, Helen; Britt, Rodney D.; Pabelick, Christine M.; Prakash, Y.S.; Amrani, Yassine; Pandya, Hitesh C.

2016-01-01

Background Adult human airway smooth muscle (ASM) produce cytokines involved in recruitment and survival of leukocytes within airway walls. Cytokine generation by adult ASM is glucocorticoid-sensitive. Whether developing lung ASM produces cytokines in a glucocorticoid-sensitive fashion is unknown. Methods Cultured fetal human ASM cells stimulated with TNF-α (0–20 ng/ml) were incubated with TNF-α receptor-blocking antibodies, fluticasone (1 and 100 nm), or vehicle. Supernatants and cells were assayed for the production of CCL5, CXCL10, and CXCL8 mRNA and protein and glucocorticoid receptor phosphorylation. Results CCL5, CXCL10, and CXCL8 mRNA and protein production by fetal ASM cell was significantly and dose-dependently following TNF-α treatment. Cytokine mRNA and protein production were effectively blocked by TNF-α R1 and R2 receptor neutralizing antibodies but variably inhibited by fluticasone. TNF-α-induced TNF-R1 and R2 receptor mRNA expression was only partially attenuated by fluticasone. Glucocorticoid receptor phosphorylation at serine (Ser) 211 but not at Ser 226 was enhanced by fluticasone. Conclusion Production of CCL5, CXCL10, and CXCL8 by fetal ASM appears to involve pathways that are both qualitatively and mechanistically distinct to those described for adult ASM. The findings imply developing ASM has potential to recruit leukocyte into airways and, therefore, of relevance to childhood airway diseases. PMID:26331770

Tetrahydrocannabinol and endocannabinoids in feeding and appetite.

PubMed

Berry, Elliot M; Mechoulam, Raphael

2002-08-01

The physiological control of appetite and satiety, in which numerous neurotransmitters and neuropeptides play a role, is extremely complex. Here we describe the involvement of endocannabinoids in these processes. These endogenous neuromodulators enhance appetite in animals. The same effect is observed in animals and in humans with the psychotropic plant cannabinoid Delta(9)-tetrahydrocannabinol, which is an approved appetite-enhancing drug. The CB(1) cannabinoid receptor antagonist SR141716A blocks the effects on feeding produced by the endocannabinoids. If administered to mice pups, this antagonist blocks suckling. In obese humans, it causes weight reduction. Very little is known about the physiological and biochemical mechanisms involved in the effects of Delta(9)-tetrahydrocannabinol and the cannabinoids in feeding and appetite.

TRPV1 and PLC Participate in Histamine H4 Receptor-Induced Itch.

PubMed

Jian, Tunyu; Yang, Niuniu; Yang, Yan; Zhu, Chan; Yuan, Xiaolin; Yu, Guang; Wang, Changming; Wang, Zhongli; Shi, Hao; Tang, Min; He, Qian; Lan, Lei; Wu, Guanyi; Tang, Zongxiang

2016-01-01

Histamine H4 receptor has been confirmed to play a role in evoking peripheral pruritus. However, the ionic and intracellular signaling mechanism of activation of H4 receptor on the dorsal root ganglion (DRG) neurons is still unknown. By using cell culture and calcium imaging, we studied the underlying mechanism of activation of H4 receptor on the DRG neuron. Immepip dihydrobromide (immepip)-a histamine H4 receptor special agonist under cutaneous injection-obviously induced itch behavior of mice. Immepip-induced scratching behavior could be blocked by TRPV1 antagonist AMG9810 and PLC pathway inhibitor U73122. Application of immepip (8.3-50 μM) could also induce a dose-dependent increase in intracellular Ca(2+) ([Ca(2+)]i) of DRG neurons. We found that 77.8% of the immepip-sensitized DRG neurons respond to the TRPV1 selective agonist capsaicin. U73122 could inhibit immepip-induced Ca(2+) responses. In addition, immepip-induced [Ca(2+)]i increase could be blocked by ruthenium red, capsazepine, and AMG9810; however it could not be blocked by TRPA1 antagonist HC-030031. These results indicate that TRPV1 but not TRPA1 is the important ion channel to induce the DRG neurons' responses in the downstream signaling pathway of histamine H4 receptor and suggest that TRPV1 may be involved in the mechanism of histamine-induced itch response by H4 receptor activation.

Excitatory and inhibitory effects of opiates in the rat vas deferens: a dual mechanism of opiate action.

PubMed

Jacquet, Y F

1980-10-03

Both natural (-)-morphine and its unnatural enantiomer (+)-morphine exert an excitatory action on electrically stimulated contractions of rat vas deferens. Preexposure to (-)-morphine results in cross-tolerance to the inhibitory action of beta-endorphin. (-)-Naloxone and its stereoisomer (+)-naloxone also exert an excitatory action, but only (-)-naloxone bocks the inhibtory action of beta-endorphin. Thus morphine exerts a dual action on a peripheral organ: one an inhibitory action mediated by the stereospecific endorphin receptor that is blocked stereospecifically by naloxone, the other an excitatory action mediated by a nonstereospecific receptor that is not blocked by naloxone. The opiate abstinence syndrome is seen as due to the unmasking of the excitatory action of opiates when its concomitant inhibitory influence is removed by selective blockade by naloxone or weakened by selective tolerance. The view that the rat vas deferens is devoid of morphine receptors is now seen as arising from a reverse example of morphine's dual action: the masking of the inhibitory action of morphine by its concomitant and more potent excitatory action.

Angiotensin receptor blockers: Focus on cardiac and renal injury.

PubMed

Arumugam, Somasundaram; Sreedhar, Remya; Thandavarayan, Rajarajan A; Karuppagounder, Vengadeshprabhu; Krishnamurthy, Prasanna; Suzuki, Kenji; Nakamura, Masahiko; Watanabe, Kenichi

2016-04-01

Angiotensin II, an important component of renin angiotensin system, is a potent vasopressor and its actions are mostly mediated via angiotensin II type 1 receptor (AT1R) and role of AT2R in counterbalancing the actions of AT1R stimulation are under extensive research. In addition to its physiological actions, angiotensin II plays important roles in the pathogenesis of atherosclerosis, hypertension, left ventricular hypertrophy, and heart failure. The effects of angiotensin II can be blocked by either suppressing its production by blocking angiotensin converting enzyme or by antagonizing its actions on AT1R using angiotensin II receptor blockers (ARBs). Instead of the extensive use of ARBs in the treatment of various cardiovascular diseases, proper selection of a particular ARB is crucial as the clinical condition of individual patient is different and also their economic status would play an essential role in medication compliance. Thus a critical review of the proven and promising actions of ARBs against various pathological conditions will be of great importance for the clinicians as well as for the researchers. Copyright © 2016 Elsevier Inc. All rights reserved.

Suppressive Effects of Bee Venom Acupuncture on Paclitaxel-Induced Neuropathic Pain in Rats: Mediation by Spinal α2-Adrenergic Receptor

PubMed Central

Choi, Jiho; Jeon, Changhoon; Jang, Jo Ung; Quan, Fu Shi; Lee, Kyungjin; Kim, Woojin

2017-01-01

Paclitaxel, a chemotherapy drug for solid tumors, induces peripheral painful neuropathy. Bee venom acupuncture (BVA) has been reported to have potent analgesic effects, which are known to be mediated by activation of spinal α-adrenergic receptor. Here, we investigated the effect of BVA on mechanical hyperalgesia and spinal neuronal hyperexcitation induced by paclitaxel. The role of spinal α-adrenergic receptor subtypes in the analgesic effect of BVA was also observed. Administration of paclitaxel (total 8 mg/kg, intraperitoneal) on four alternate days (days 0, 2, 4, and 6) induced significant mechanical hyperalgesic signs, measured using a von Frey filament. BVA (1 mg/kg, ST36) relieved this mechanical hyperalgesia for at least two hours, and suppressed the hyperexcitation in spinal wide dynamic range neurons evoked by press or pinch stimulation. Both melittin (0.5 mg/kg, ST36) and phospholipase A2 (0.12 mg/kg, ST36) were shown to play an important part in this analgesic effect of the BVA, as they significantly attenuated the pain. Intrathecal pretreatment with the α2-adrenergic receptor antagonist (idazoxan, 50 µg), but not α1-adrenergic receptor antagonist (prazosin, 30 µg), blocked the analgesic effect of BVA. These results suggest that BVA has potent suppressive effects against paclitaxel-induced neuropathic pain, which were mediated by spinal α2-adrenergic receptor. PMID:29088102

Disruption of Chemoreceptor Signaling Arrays by High Levels of CheW, the Receptor-Kinase Coupling Protein

PubMed Central

Cardozo, Marcos J.; Massazza, Diego A.; Parkinson, John S.; Studdert, Claudia A.

2017-01-01

Summary During chemotactic signaling by Escherichia coli, the small cytoplasmic CheW protein couples the histidine kinase CheA to chemoreceptor control. Although essential for assembly and operation of receptor signaling complexes, CheW in stoichiometric excess disrupts chemotactic behavior. To explore the mechanism of the CheW excess effect, we measured the physiological consequences of high cellular levels of wild-type CheW and of several CheW variants with reduced or enhanced binding affinities for receptor molecules. We found that high levels of CheW interfered with trimer assembly, prevented CheA activation, blocked cluster formation, disrupted chemotactic ability, and elevated receptor methylation levels. The severity of these effects paralleled the receptor binding affinities of the CheW variants. Because trimer formation may be an obligate step in the assembly of ternary signaling complexes and higher-order receptor arrays, we suggest that all CheW excess effects stem from disruption of trimer assembly. We propose that the CheW-binding sites in receptor dimers overlap their trimer contact sites and that high levels of CheW saturate the receptor binding sites, preventing trimer assembly. The CheW-trapped receptor dimers seem to be improved substrates for methyltransferase reactions, but cannot activate CheA or assemble into clusters, processes that are essential for chemotactic signaling. PMID:20487303

Ghrelin interacts with neuropeptide Y Y1 and opioid receptors to increase food reward.

PubMed

Skibicka, Karolina P; Shirazi, Rozita H; Hansson, Caroline; Dickson, Suzanne L

2012-03-01

Ghrelin, a stomach-derived hormone, is an orexigenic peptide that was recently shown to potently increase food reward behavior. The neurochemical circuitry that links ghrelin to the mesolimbic system and food reward behavior remains unclear. Here we examined the contribution of neuropeptide Y (NPY) and opioids to ghrelin's effects on food motivation and intake. Both systems have well-established links to the mesolimbic ventral tegmental area (VTA) and reward/motivation control. NPY mediates the effect of ghrelin on food intake via activation of NPY-Y1 receptor (NPY-Y1R); their connection with respect to motivated behavior is unexplored. The role of opioids in any aspect of ghrelin's action on food-oriented behaviors is unknown. Rats were trained in a progressive ratio sucrose-induced operant schedule to measure food reward/motivation behavior. Chow intake was measured immediately after the operant test. In separate experiments, we explored the suppressive effects of a selective NPY-Y1R antagonist or opioid receptor antagonist naltrexone, injected either intracerebroventricularly or intra-VTA, on ghrelin-induced food reward behavior. The ventricular ghrelin-induced increase in sucrose-motivated behavior and chow intake were completely blocked by intracerebroventricular pretreatment with either an NPY-Y1R antagonist or naltrexone. The intra-VTA ghrelin-induced sucrose-motivated behavior was blocked only by intra-VTA naltrexone. In contrast, the intra-VTA ghrelin-stimulated chow intake was attenuated only by intra-VTA NPY-Y1 blockade. Finally, ghrelin infusion was associated with an elevated VTA μ-opioid receptor expression. Thus, we identify central NPY and opioid signaling as the necessary mediators of food intake and reward effects of ghrelin and localize these interactions to the mesolimbic VTA.

Aldosterone increases cardiac vagal tone via G protein-coupled oestrogen receptor activation

PubMed Central

Brailoiu, G Cristina; Benamar, Khalid; Arterburn, Jeffrey B; Gao, Erhe; Rabinowitz, Joseph E; Koch, Walter J; Brailoiu, Eugen

2013-01-01

In addition to acting on mineralocorticoid receptors, aldosterone has been recently shown to activate the G protein-coupled oestrogen receptor (GPER) in vascular cells. In light of the newly identified role for GPER in vagal cardiac control, we examined whether or not aldosterone activates GPER in rat nucleus ambiguus. Aldosterone produced a dose-dependent increase in cytosolic Ca2+ concentration in retrogradely labelled cardiac vagal neurons of nucleus ambiguus; the response was abolished by pretreatment with the GPER antagonist G-36, but was not affected by the mineralocorticoid receptor antagonists, spironolactone and eplerenone. In Ca2+-free saline, the response to aldosterone was insensitive to blockade of the Ca2+ release from lysosomes, while it was reduced by blocking the Ca2+ release via ryanodine receptors and abolished by blocking the IP3 receptors. Aldosterone induced Ca2+ influx via P/Q-type Ca2+ channels, but not via L-type and N-type Ca2+ channels. Aldosterone induced depolarization of cardiac vagal neurons of nucleus ambiguus that was sensitive to antagonism of GPER but not of mineralocorticoid receptor. in vivo studies, using telemetric measurement of heart rate, indicate that microinjection of aldosterone into the nucleus ambiguus produced a dose-dependent bradycardia in conscious, freely moving rats. Aldosterone-induced bradycardia was blocked by the GPER antagonist, but not by the mineralocorticoid receptor antagonists. In summary, we report for the first time that aldosterone decreases heart rate by activating GPER in cardiac vagal neurons of nucleus ambiguus. PMID:23878371

The orphan receptor ALK7 and the Activin receptor ALK4 mediate signaling by Nodal proteins during vertebrate development.

PubMed

Reissmann, E; Jörnvall, H; Blokzijl, A; Andersson, O; Chang, C; Minchiotti, G; Persico, M G; Ibáñez, C F; Brivanlou, A H

2001-08-01

Nodal proteins have crucial roles in mesendoderm formation and left-right patterning during vertebrate development. The molecular mechanisms of signal transduction by Nodal and related ligands, however, are not fully understood. In this paper, we present biochemical and functional evidence that the orphan type I serine/threonine kinase receptor ALK7 acts as a receptor for mouse Nodal and Xenopus Nodal-related 1 (Xnr1). Receptor reconstitution experiments indicate that ALK7 collaborates with ActRIIB to confer responsiveness to Xnr1 and Nodal. Both receptors can independently bind Xnr1. In addition, Cripto, an extracellular protein genetically implicated in Nodal signaling, can independently interact with both Xnr1 and ALK7, and its expression greatly enhances the ability of ALK7 and ActRIIB to respond to Nodal ligands. The Activin receptor ALK4 is also able to mediate Nodal signaling but only in the presence of Cripto, with which it can also interact directly. A constitutively activated form of ALK7 mimics the mesendoderm-inducing activity of Xnr1 in Xenopus embryos, whereas a dominant-negative ALK7 specifically blocks the activities of Nodal and Xnr1 but has little effect on other related ligands. In contrast, a dominant-negative ALK4 blocks all mesoderm-inducing ligands tested, including Nodal, Xnr1, Xnr2, Xnr4, and Activin. In agreement with a role in Nodal signaling, ALK7 mRNA is localized to the ectodermal and organizer regions of Xenopus gastrula embryos and is expressed during early stages of mouse embryonic development. Therefore, our results indicate that both ALK4 and ALK7 can mediate signal transduction by Nodal proteins, although ALK7 appears to be a receptor more specifically dedicated to Nodal signaling.

The orphan receptor ALK7 and the Activin receptor ALK4 mediate signaling by Nodal proteins during vertebrate development

PubMed Central

Reissmann, Eva; Jörnvall, Henrik; Blokzijl, Andries; Andersson, Olov; Chang, Chenbei; Minchiotti, Gabriella; Persico, M. Graziella; Ibáñez, Carlos F.; Brivanlou, Ali H.

2001-01-01

Nodal proteins have crucial roles in mesendoderm formation and left–right patterning during vertebrate development. The molecular mechanisms of signal transduction by Nodal and related ligands, however, are not fully understood. In this paper, we present biochemical and functional evidence that the orphan type I serine/threonine kinase receptor ALK7 acts as a receptor for mouse Nodal and Xenopus Nodal-related 1 (Xnr1). Receptor reconstitution experiments indicate that ALK7 collaborates with ActRIIB to confer responsiveness to Xnr1 and Nodal. Both receptors can independently bind Xnr1. In addition, Cripto, an extracellular protein genetically implicated in Nodal signaling, can independently interact with both Xnr1 and ALK7, and its expression greatly enhances the ability of ALK7 and ActRIIB to respond to Nodal ligands. The Activin receptor ALK4 is also able to mediate Nodal signaling but only in the presence of Cripto, with which it can also interact directly. A constitutively activated form of ALK7 mimics the mesendoderm-inducing activity of Xnr1 in Xenopus embryos, whereas a dominant-negative ALK7 specifically blocks the activities of Nodal and Xnr1 but has little effect on other related ligands. In contrast, a dominant-negative ALK4 blocks all mesoderm-inducing ligands tested, including Nodal, Xnr1, Xnr2, Xnr4, and Activin. In agreement with a role in Nodal signaling, ALK7 mRNA is localized to the ectodermal and organizer regions of Xenopus gastrula embryos and is expressed during early stages of mouse embryonic development. Therefore, our results indicate that both ALK4 and ALK7 can mediate signal transduction by Nodal proteins, although ALK7 appears to be a receptor more specifically dedicated to Nodal signaling. PMID:11485994

Sweet Taste Receptor Expressed in Pancreatic β-Cells Activates the Calcium and Cyclic AMP Signaling Systems and Stimulates Insulin Secretion

PubMed Central

Nakagawa, Yuko; Nagasawa, Masahiro; Yamada, Satoko; Hara, Akemi; Mogami, Hideo; Nikolaev, Viacheslav O.; Lohse, Martin J.; Shigemura, Noriatsu; Ninomiya, Yuzo; Kojima, Itaru

2009-01-01

Background Sweet taste receptor is expressed in the taste buds and enteroendocrine cells acting as a sugar sensor. We investigated the expression and function of the sweet taste receptor in MIN6 cells and mouse islets. Methodology/Principal Findings The expression of the sweet taste receptor was determined by RT–PCR and immunohistochemistry. Changes in cytoplasmic Ca2+ ([Ca2+]c) and cAMP ([cAMP]c) were monitored in MIN6 cells using fura-2 and Epac1-camps. Activation of protein kinase C was monitored by measuring translocation of MARCKS-GFP. Insulin was measured by radioimmunoassay. mRNA for T1R2, T1R3, and gustducin was expressed in MIN6 cells. In these cells, artificial sweeteners such as sucralose, succharin, and acesulfame-K increased insulin secretion and augmented secretion induced by glucose. Sucralose increased biphasic increase in [Ca2+]c. The second sustained phase was blocked by removal of extracellular calcium and addition of nifedipine. An inhibitor of inositol(1, 4, 5)-trisphophate receptor, 2-aminoethoxydiphenyl borate, blocked both phases of [Ca2+]c response. The effect of sucralose on [Ca2+]c was inhibited by gurmarin, an inhibitor of the sweet taste receptor, but not affected by a Gq inhibitor. Sucralose also induced sustained elevation of [cAMP]c, which was only partially inhibited by removal of extracellular calcium and nifedipine. Finally, mouse islets expressed T1R2 and T1R3, and artificial sweeteners stimulated insulin secretion. Conclusions Sweet taste receptor is expressed in β-cells, and activation of this receptor induces insulin secretion by Ca2+ and cAMP-dependent mechanisms. PMID:19352508

Bradykinin-induced growth inhibition of normal rat kidney (NRK) cells is paralleled by a decrease in epidermal-growth-factor receptor expression.

PubMed Central

Van Zoelen, E J; Peters, P H; Afink, G B; Van Genesen, S; De Roos, D G; Van Rotterdam, W; Theuvenet, A P

1994-01-01

Normal rat kidney fibroblasts, grown to density arrest in the presence of epidermal growth factor (EGF), can be induced to undergo phenotypic transformation by treatment with transforming growth factor beta or retinoic acid. Here we show that bradykinin blocks this growth-stimulus-induced loss of density-dependent growth arrest by a specific receptor-mediated mechanism. The effects of bradykinin are specific, and are not mimicked by other phosphoinositide-mobilizing agents such as prostaglandin F2 alpha. Northern-blot analysis and receptor-binding studies demonstrate that bradykinin also inhibits the retinoic acid-induced increase in EGF receptor levels in these cells. These studies provide additional evidence that EGF receptor levels modulate EGF-induced expression of the transformed phenotype in these cells. Images Figure 5 PMID:8135739

Antianxiety effect of cannabis: involvement of central benzodiazepine receptors.

PubMed

Sethi, B B; Trivedi, J K; Kumar, P; Gulati, A; Agarwal, A K; Sethi, N

1986-01-01

The present work, involving clinical, behavioral, and biochemical studies, was undertaken to elucidate the probable mechanism of the observed antianxiety effects of cannabis. The population for the clinical study consisted of 50 male chronic cannabis users who were otherwise healthy and 50 matched controls. When evaluated on Taylor's Manifest Anxiety Scale (TMA), these subjects had low anxiety scores as compared with the controls. To explore the possible interaction of cannabis with the benzodiazepine receptors, behavioral and biochemical studies in mice were devised, involving acute and chronic cannabis administration. Behavioral study revealed that mice under chronic cannabis treatment scored significantly higher on foot shock-induced aggression, but this was significantly blocked by benzodiazepine receptor antagonist. Furthermore, chronic cannabis treatment significantly (p less than 0.001) increased the frequency of licking response periodically punished by shocks. This confirms the antianxiety effect of cannabis, which also appears to be mediated through a benzodiazepine receptor, as it was reduced significantly (p less than 0.001) by a benzodiazepine receptor blocker. Specific 3H-diazepam binding was carried out in frontal cortex to assess both the population and affinity of benzodiazepine receptors. Our results indicate that acute cannabis treatment has no significant effect, whereas chronic cannabis treatment significantly increased 3H-diazepam binding as compared with controls. Scatchard analysis further reveals that increased affinity is responsible for increased binding to these receptors. It is therefore our contention that the antianxiety effect of cannabis is mediated through central benzodiazepine receptors.

Effect of Maternal Electroacupuncture on Perinatal Nicotine Exposure-Induced Lung Phenotype in Offspring.

PubMed

Ji, Bo; Zhao, Guo-Zhen; Sakurai, Reiko; Cao, Yu; Zhang, Zi-Jian; Wang, Dan; Yan, Ming-Na; Rehan, Virender K

2016-08-01

Pregnant women exposed to tobacco smoke predispose the offspring to many adverse consequences including an altered lung development and function. There is no effective therapeutic intervention to block the effects of smoke exposure on the developing lung. Clinical and animal studies demonstrate that acupuncture can modulate a variety of pathophysiological processes, including those involving the respiratory system; however, whether acupuncture affects the lung damage caused by perinatal smoke exposure is not known. To determine the effect of acupuncture on perinatal nicotine exposure on the developing lung, pregnant rat dams were administered (1) saline, (2) nicotine, or (3) nicotine + electroacupuncture (EA). Nicotine was administered (1 mg/kg subcutaneously) once a day and EA was applied to both "Zusanli" (ST 36) points. Both interventions were administered from gestational day 6 to postnatal day 21 (PND21), following which pups were sacrificed. Lungs, blood, and brain were collected to examine markers of lung injury, repair, and hypothalamic pituitary adrenal (HPA) axis. Concomitant EA application blocked nicotine-induced changes in lung morphology, lung peroxisome proliferator-activated receptor γ and wingless-int signaling, two key lung developmental signaling pathways, hypothalamic pituitary adrenal axis (hypothalamic corticotropic releasing hormone and lung glucocorticoid receptor levels), and plasma β-endorphin levels. Electroacupuncture blocks the nicotine-induced changes in lung developmental signaling pathways and the resultant myogenic lung phenotype, known to be present in the affected offspring. We conclude that EA is a promising novel intervention against the smoke exposed lung damage to the developing lung.

The Metabotropic Glutamate 2/3 Receptor Agonist LY379268 Blocked Nicotine-Induced Increases in Nucleus Accumbens Shell Dopamine only in the Presence of a Nicotine-Associated Context in Rats

PubMed Central

D'Souza, Manoranjan S; Liechti, Matthias E; Ramirez-Niño, Ana M; Kuczenski, Ronald; Markou, Athina

2011-01-01

The metabotropic glutamate 2/3 (mGlu2/3) receptor agonist LY379268 ([−]-2-oxa-4-aminobicyclo [3.1.0] hexane-4,6-dicarboxylate) attenuates both nicotine self-administration and cue-induced nicotine seeking in rats. In this study, the effects of LY379268 (1 mg/kg) or saline pretreatment on nicotine-induced increases in nucleus accumbens (NAcc) shell dopamine were evaluated using in vivo microdialysis under different experimental conditions: (i) nicotine (0.4 mg/kg, base) was experimenter-administered subcutaneously to nicotine-naïve rats; (ii) nicotine was experimenter-administered either subcutaneously (0.4 mg/kg) or by a single experimenter-administered infusion (0.06 mg/kg, base) in rats with a history of nicotine self-administration (nicotine experienced) in the absence of a nicotine-associated context (ie, context and cues associated with nicotine self-administration); (iii) nicotine (0.06 mg/kg) was self-administered or experimenter-administered in nicotine-experienced rats in the presence of a nicotine-associated context. In saline-pretreated nicotine-naïve and nicotine-experienced rats, nicotine increased NAcc shell dopamine regardless of the context used for testing. Interestingly, LY379268 pretreatment blocked nicotine-induced increases in NAcc shell dopamine in nicotine-experienced rats only when tested in the presence of a nicotine-associated context. LY379268 did not block nicotine-induced increases in NAcc shell dopamine in nicotine-naïve or -experienced rats tested in the absence of a nicotine-associated context. These intriguing findings suggest that activation of mGlu2/3 receptors negatively modulates the combined effects of nicotine and nicotine-associated contexts/cues on NAcc dopamine. Thus, these data highlight a critical role for mGlu2/3 receptors in context/cue-induced drug-seeking behavior and suggest a neurochemical mechanism by which mGlu2/3 receptor agonists may promote smoking cessation by preventing relapse induced by the combination of nicotine and nicotine-associated contexts and cues. PMID:21654734

Stimulation of sensory neuropeptide release by nociceptin/orphanin FQ leads to hyperaemia in acutely inflamed rat knees

PubMed Central

Zhang, Chunfen; McDougall, Jason J

2006-01-01

The peripheral effect of the ‘opioid-like' peptide nociceptin/orphanin FQ (N/OFQ) on joint blood flow was investigated in acutely inflamed rats. Sensory neuropeptide release from capsaicin-sensitive nerves and the involvement of synovial mast cells and leukocytes on these vasomotor responses were also studied. Blood flow measurements of exposed knee joints were performed in urethane-anaesthetised rats (2 mg kg−1 intraperitoneal) using laser Doppler perfusion imaging. Topical administration of N/OFQ (10−13–10−8 mol) to acutely inflamed joints caused a dose-dependent increase in synovial perfusion with an ED50 of 4.0 × 10−10 mol. This vasodilatatory response was blocked by the selective NOP receptor antagonist [Phe1-(CH2-NH)-Gly2]-Nociceptin(1–13)-NH2 (10−9 mol) (P<0.0001). Co-administration of N/OFQ with the neurokinin-1 (NK1) receptor antagonist [D-Arg1,D-Phe5,D-Trp7,9,Leu11]-Substance P (10−12 mol), the vasoactive intestinal peptide (VIP) receptor antagonist VIP6–28 (10−9 mol) or the calcitonin gene-related peptide (CGRP) receptor antagonist CGRP8–37 (10−9 mol) all blocked the hyperaemic effect of N/OFQ (P<0.0001). Treatment of acutely inflamed knees with capsaicin (8-methyl-N-vanillyl-6-noneamide) to destroy unmyelinated joint afferents also inhibited N/OFQ vasomotor activity. Stabilisation of synovial mast cells with disodium cromoglycate (cromolyn) ameliorated N/OFQ responses, whereas inactivation of circulating leukocytes with the pan-selectin inhibitor fucoidin completely blocked N/OFQ-induced hyperaemia in these joints. These experiments show that in acutely inflamed knee joints, N/OFQ acts on NOP receptors located on synovial mast cells and leukocytes leading to the secondary release of proinflammatory mediators into the joint. These agents subsequently stimulate sensory neuropeptide release from capsaicin-sensitive nerves culminating in vasodilatation and increased articular blood flow. PMID:16783411

Activation of Phosphoinositide Metabolism by Cholinergic Agents.

DTIC Science & Technology

1990-12-16

acid significantly inhibited NE-induced [3H]IP1 production in slices that had been prelabelled with [3H]inositol and baclofen , a specific GABAB...agonist, was as effective as GABA in enhancing the response to NE (Figure 15). Neither GABA nor baclofen significantly blocked the inhibitory effect of...quisqualate, but baclofen reduced the inhibitory effect of arachidonic acid. Effects of NMDA receptor antagonists on phosphoinositide hydrolysis MK-801 is

A Lectin-Like Receptor is Involved in Invasion of Erythrocytes by Plasmodium falciparum

NASA Astrophysics Data System (ADS)

Jungery, M.; Pasvol, G.; Newbold, C. I.; Weatherall, D. J.

1983-02-01

Glycophorin both in solution and inserted into liposomes blocks invasion of erythrocytes by the malaria parasite Plasmodium falciparum. Furthermore, one sugar, N-acetyl-D-glucosamine (GlcNAc), completely blocks invasion of the erythrocyte by this parasite. GlcNAc coupled to bovine serum albumin to prevent the sugar entering infected erythrocytes was at least 100,000 times more effective than GlcNAc alone. Bovine serum albumin coupled to lactose or bovine serum albumin alone had no effect on invasion. These results suggest that the binding of P. falciparum to erythrocytes is lectin-like and is determined by carbohydrates on glycophorin.

Contribution of GABAA, Glycine, and Opioid Receptors to Sacral Neuromodulation of Bladder Overactivity in Cats.

PubMed

Jiang, Xuewen; Fuller, Thomas W; Bandari, Jathin; Bansal, Utsav; Zhang, Zhaocun; Shen, Bing; Wang, Jicheng; Roppolo, James R; de Groat, William C; Tai, Changfeng

2016-12-01

In α-chloralose-anesthetized cats, we examined the role of GABA A , glycine, and opioid receptors in sacral neuromodulation-induced inhibition of bladder overactivity elicited by intravesical infusion of 0.5% acetic acid (AA). AA irritation significantly (P < 0.01) reduced bladder capacity to 59.5 ± 4.8% of saline control. S1 or S2 dorsal root stimulation at threshold intensity for inducing reflex twitching of the anal sphincter or toe significantly (P < 0.01) increased bladder capacity to 105.3 ± 9.0% and 134.8 ± 8.9% of saline control, respectively. Picrotoxin, a GABA A receptor antagonist administered i.v., blocked S1 inhibition at 0.3 mg/kg and blocked S2 inhibition at 1.0 mg/kg. Picrotoxin (0.4 mg, i.t.) did not alter the inhibition induced during S1 or S2 stimulation, but unmasked a significant (P < 0.05) poststimulation inhibition that persisted after termination of stimulation. Naloxone, an opioid receptor antagonist (0.3 mg, i.t.), significantly (P < 0.05) reduced prestimulation bladder capacity and removed the poststimulation inhibition. Strychnine, a glycine receptor antagonist (0.03-0.3 mg/kg, i.v.), significantly (P < 0.05) increased prestimulation bladder capacity but did not reduce sacral S1 or S2 inhibition. After strychnine (0.3 mg/kg, i.v.), picrotoxin (0.3 mg/kg, i.v.) further (P < 0.05) increased prestimulation bladder capacity and completely blocked both S1 and S2 inhibition. These results indicate that supraspinal GABA A receptors play an important role in sacral neuromodulation of bladder overactivity, whereas glycine receptors only play a minor role to facilitate the GABA A inhibitory mechanism. The poststimulation inhibition unmasked by blocking spinal GABA A receptors was mediated by an opioid mechanism. Copyright © 2016 by The American Society for Pharmacology and Experimental Therapeutics.

Synaptic GluN2A and GluN2B Containing NMDA Receptors within the Superficial Dorsal Horn Activated following Primary Afferent Stimulation

PubMed Central

MacDermott, Amy B.

2014-01-01

NMDA receptors are important elements in pain signaling in the spinal cord dorsal horn. They are heterotetramers, typically composed of two GluN1 and two of four GluN2 subunits: GluN2A-2D. Mice lacking some of the GluN2 subunits show deficits in pain transmission yet functional synaptic localization of these receptor subtypes in the dorsal horn has not been fully resolved. In this study, we have investigated the composition of synaptic NMDA receptors expressed in monosynaptic and polysynaptic pathways from peripheral sensory fibers to lamina I neurons in rats. We focused on substance P receptor-expressing (NK1R+) projection neurons, critical for expression of hyperalgesia and allodynia. EAB-318 and (R)-CPP, GluN2A/B antagonists, blocked both monosynaptic and polysynaptic NMDA EPSCs initiated by primary afferent activation by ∼90%. Physiological measurements exploiting the voltage dependence of monosynaptic EPSCs similarly indicated dominant expression of GluN2A/B types of synaptic NMDA receptors. In addition, at synapses between C fibers and NK1R+ neurons, NMDA receptor activation initiated a secondary, depolarizing current. Ifenprodil, a GluN2B antagonist, caused modest suppression of monosynaptic NMDA EPSC amplitudes, but had a widely variable, sometimes powerful, effect on polysynaptic responses following primary afferent stimulation when inhibitory inputs were blocked to mimic neuropathic pain. We conclude that GluN2B subunits are moderately expressed at primary afferent synapses on lamina I NK1R+ neurons, but play more important roles for polysynaptic NMDA EPSCs driven by primary afferents following disinhibition, supporting the view that the analgesic effect of the GluN2B antagonist on neuropathic pain is at least in part, within the spinal cord. PMID:25122884

Antinociceptive actions of honokiol and magnolol on glutamatergic and inflammatory pain

PubMed Central

2009-01-01

The antinociceptive effects of honokiol and magnolol, two major bioactive constituents of the bark of Magnolia officinalis, were investigated on animal paw licking responses and thermal hyperalgesia induced by glutamate receptor agonists including glutamate, N-methyl-D-aspartate (NMDA), and metabotropic glutamate 5 receptor (mGluR5) activator (RS)-2-chloro-5-hydroxyphenylglycine (CHPG), as well as inflammatory mediators such as substance P and prostaglandin E2 (PGE2) in mice. The actions of honokiol and magnolol on glutamate-induced c-Fos expression in the spinal cord dorsal horn were also examined. Our data showed that honokiol and magnolol blocked glutamate-, substance P- and PGE2-induced inflammatory pain with similar potency and efficacy. Consistently, honokiol and magnolol significantly decreased glutamate-induced c-Fos protein expression in superficial (I-II) laminae of the L4-L5 lumbar dorsal horn. However, honokiol was more selective than magnolol for inhibition of NMDA-induced licking behavioral and thermal hyperalgesia. In contrast, magnolol was more potent to block CHPG-mediated thermal hyperalgesia. These results demonstrate that honokiol and magnolol effectively decreased the inflammatory pain. Furthermore, their different potency on inhibition of nociception provoked by NMDA receptor and mGluR5 activation should be considered. PMID:19832997

Toll-like receptor agonists are potent inhibitors of human immunodeficiency virus-type 1 replication in peripheral blood mononuclear cells.

PubMed

Buitendijk, Maarten; Eszterhas, Susan K; Howell, Alexandra L

2014-05-01

Innate immune responses to microbial pathogens are initiated following the binding of ligand to specific pattern recognition receptors. Each pattern recognition receptor, which includes members of the Toll-like receptor (TLR) family, is specific for a particular type of pathogen associated molecular pattern ensuring that the organism can respond rapidly to a wide range of pathogens including bacteria, viruses, and fungi. We studied the extent to which agonists to endosomal TLR could induce anti-HIV-1 activity in peripheral blood mononuclear cells (PBMCs). When agonists to TLR3, TLR7, TLR8 and TLR9 were added prior to infection with HIV-1, they significantly reduced infection of peripheral blood mononuclear cells. Interestingly, agonists to TLR8 and TLR9 were highly effective at blocking HIV replication even when added as late as 48 h or 72 h, respectively, after HIV-1 infection, indicating that the anti-viral effect was durable and long lasting. Analysis of the induction of anti-viral genes after agonist activation of TLR indicated that all of the agonists induced expression of the type I interferons and interferon stimulated genes, although to variable levels that depended on the agonist used. Interestingly, only the agonist to TLR9, ODN2395 DNA, induced expression of type II interferon and the anti-HIV proteins Apobec3G and SAMHD1. By blocking TLR activity using an inhibitor to the MyD88 adaptor protein, we demonstrated that, at least for TLR8 and TLR9, the anti-HIV activity was not entirely mediated by TLR activation, but likely by the activation of additional anti-viral sensors in HIV target cells. These findings suggest that agonists to the endosomal TLR function to induce expression of anti-HIV molecules by both TLR-mediated and non-TLR-mediated mechanisms. Moreover, the non-TLR-mediated mechanisms induced by these agonists could potentially be exploited to block HIV-1 replication in recently HIV-exposed individuals.

Activation of cannabinoid CB1 and CB2 receptors suppresses neuropathic nociception evoked by the chemotherapeutic agent vincristine in rats

PubMed Central

Rahn, E J; Makriyannis, A; Hohmann, A G

2007-01-01

Background and purpose: The ability of cannabinoids to suppress mechanical hypersensitivity (mechanical allodynia) induced by treatment with the chemotherapeutic agent vincristine was evaluated in rats. Sites of action were subsequently identified. Experimental approach: Mechanical hypersensitivity developed over the course of ten daily injections of vincristine relative to groups receiving saline at the same times. Effects of the CB1/CB2 receptor agonist WIN55,212-2, the receptor-inactive enantiomer WIN55,212-3, the CB2-selective agonist (R,S)-AM1241, the opiate agonist morphine and vehicle on chemotherapy-induced neuropathy were evaluated. WIN55,212-2 was administered intrathecally (i.t.) or locally in the hindpaw to identify sites of action. Pharmacological specificity was established using competitive antagonists for CB1 (SR141716) or CB2 receptors (SR144528). Key results: Systemic administration of WIN55,212-2, but not WIN55,212-3, suppressed vincristine-evoked mechanical allodynia. A leftward shift in the dose-response curve was observed following WIN55,212-2 relative to morphine treatment. The CB1 (SR141716) and CB2 (SR144528) antagonists blocked the anti-allodynic effects of WIN55,212-2. (R,S)-AM1241 suppressed vincristine-induced mechanical hypersensitivity through a CB2 mechanism. Both cannabinoid agonists suppressed vincristine-induced mechanical hypersensitivity without inducing catalepsy. Spinal sites of action are implicated in cannabinoid modulation of chemotherapy-induced neuropathy. WIN55,212-2, but not WIN55,212-3, administered i.t. suppressed vincristine-evoked mechanical hypersensitivity at doses that were inactive following local hindpaw administration. Spinal coadministration of both the CB1 and CB2 antagonists blocked the anti-allodynic effects of WIN55,212-2. Conclusions and implications: Cannabinoids suppress the maintenance of vincristine-induced mechanical allodynia through activation of CB1 and CB2 receptors. These anti-allodynic effects are mediated, at least in part, at the level of the spinal cord. PMID:17572696

Selective agonists of somatostatin receptor subtype 1 or 2 injected peripherally induce antihyperalgesic effect in two models of visceral hypersensitivity in mice

PubMed Central

Mulak, Agata; Larauche, Muriel; Biraud, Mandy; Million, Mulugeta; Rivier, Jean; Taché, Yvette

2014-01-01

Somatostatin interacts with 5 G-protein-coupled receptor (sst1–5). Octreotide, a stable sst2≫3≥5 agonist, octreotide, exerts a visceral anti-hyperalgesic effect in experimental and clinical studies. Little is known on the receptor subtypes involved. We investigated the influence of the stable sst1–5 agonist, ODT8-SST and selective receptor subtype peptide agonists (3 or 10 μg/mouse) injected intraperitoneally (ip) on visceral hypersensitivity in mice induced by repeated noxious colorectal distensions (4 sets of 3 CRD, each at 55 mmHg) or corticotropin-releasing factor receptor 1 agonist, cortagine given between 2 sets of graded CRD (15, 30, 45, and 60 mmHg, 3 times each pressure). The mean visceromotor response (VMR) was assessed using a non-invasive manometry method and values were expressed as percentage of the VMR to the 1st set of CRD baseline or to the 60 mmHg CRD, respectively. ODT8-SST (10 μg) and the sst2 agonist, S-346-011 (3 and 10 μg) prevented mechanically-induced visceral hypersensitivity in the 3 sets of CRD, the sst1 agonist (10 μg) blocked only the 2nd set and showed a trend at 3 μg while the sst4 agonist had no effect. The selective sst2 antagonist, S-406-028 blocked the sst2 agonist but not the sst1 agonist effect. The sst1 agonist (3 and 10 μg) prevented cortagine-induced hypersensitivity to CRD at each pressure while the sst2 agonist at 10 μg reduced it. These data indicate that in addition to sst2, the sst1 agonist may provide a novel promising target to alleviate visceral hypersensitivity induced by mechanoreceptor sensitization and more prominently, stress-related visceral nociceptive sensitization. PMID:25451334

Selective agonists of somatostatin receptor subtype 1 or 2 injected peripherally induce antihyperalgesic effect in two models of visceral hypersensitivity in mice.

PubMed

Mulak, Agata; Larauche, Muriel; Biraud, Mandy; Million, Mulugeta; Rivier, Jean; Taché, Yvette

2015-01-01

Somatostatin interacts with five G-protein-coupled receptor (sst1-5). Octreotide, a stable sst2≫3≥5 agonist, exerts a visceral anti-hyperalgesic effect in experimental and clinical studies. Little is known on the receptor subtypes involved. We investigated the influence of the stable sst1-5 agonist, ODT8-SST and selective receptor subtype peptide agonists (3 or 10μg/mouse) injected intraperitoneally (ip) on visceral hypersensitivity in mice induced by repeated noxious colorectal distensions (four sets of three CRD, each at 55mmHg) or corticotropin-releasing factor receptor 1 agonist, cortagine given between two sets of graded CRD (15, 30, 45, and 60mmHg, three times each pressure). The mean visceromotor response (VMR) was assessed using a non-invasive manometry method and values were expressed as percentage of the VMR to the 1st set of CRD baseline or to the 60mmHg CRD, respectively. ODT8-SST (10μg) and the sst2 agonist, S-346-011 (3 and 10μg) prevented mechanically induced visceral hypersensitivity in the three sets of CRD, the sst1 agonist (10μg) blocked only the 2nd set and showed a trend at 3μg while the sst4 agonist had no effect. The selective sst2 antagonist, S-406-028 blocked the sst2 agonist but not the sst1 agonist effect. The sst1 agonist (3 and 10μg) prevented cortagine-induced hypersensitivity to CRD at each pressure while the sst2 agonist at 10μg reduced it. These data indicate that in addition to sst2, the sst1 agonist may provide a novel promising target to alleviate visceral hypersensitivity induced by mechanoreceptor sensitization and more prominently, stress-related visceral nociceptive sensitization. Copyright © 2014 Elsevier Inc. All rights reserved.

Troglitazone stimulates {beta}-arrestin-dependent cardiomyocyte contractility via the angiotensin II type 1{sub A} receptor

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

Tilley, Douglas G., E-mail: douglas.tilley@jefferson.edu; Center for Translational Medicine, Thomas Jefferson University; Nguyen, Anny D.

2010-06-11

Peroxisome proliferator-activated receptor {gamma} (PPAR{gamma}) agonists are commonly used to treat cardiovascular diseases, and are reported to have several effects on cardiovascular function that may be due to PPAR{gamma}-independent signaling events. Select angiotensin receptor blockers (ARBs) interact with and modulate PPAR{gamma} activity, thus we hypothesized that a PPAR{gamma} agonist may exert physiologic effects via the angiotensin II type 1{sub A} receptor (AT1{sub A}R). In AT1{sub A}R-overexpressing HEK 293 cells, both angiotensin II (Ang II) and the PPAR{gamma} agonist troglitazone (Trog) enhanced AT1{sub A}R internalization and recruitment of endogenous {beta}-arrestin1/2 ({beta}arr1/2) to the AT1{sub A}R. A fluorescence assay to measure diacylglycerolmore » (DAG) accumulation showed that although Ang II induced AT1{sub A}R-G{sub q} protein-mediated DAG accumulation, Trog had no impact on DAG generation. Trog-mediated recruitment of {beta}arr1/2 was selective to AT1{sub A}R as the response was prevented by an ARB- and Trog-mediated {beta}arr1/2 recruitment to {beta}1-adrenergic receptor ({beta}1AR) was not observed. In isolated mouse cardiomyocytes, Trog increased both % and rate of cell shortening to a similar extent as Ang II, effects which were blocked with an ARB. Additionally, these effects were found to be {beta}arr2-dependent, as cardiomyocytes isolated from {beta}arr2-KO mice showed blunted contractile responses to Trog. These findings show for the first time that the PPAR{gamma} agonist Trog acts at the AT1{sub A}R to simultaneously block G{sub q} protein activation and induce the recruitment of {beta}arr1/2, which leads to an increase in cardiomyocyte contractility.« less

PPAR-α, a lipid-sensing transcription factor, regulates blood–brain barrier efflux transporter expression

PubMed Central

More, Vijay R; Campos, Christopher R; Evans, Rebecca A; Oliver, Keith D; Chan, Gary NY; Miller, David S

2016-01-01

Lipid sensor peroxisome proliferator-activated receptor alpha (PPAR-α) is the master regulator of lipid metabolism. Dietary release of endogenous free fatty acids, fibrates, and certain persistent environmental pollutants, e.g. perfluoroalkyl fire-fighting foam components, are peroxisome proliferator-activated receptor alpha ligands. Here, we define a role for peroxisome proliferator-activated receptor alpha in regulating the expression of three ATP-driven drug efflux transporters at the rat and mouse blood–brain barriers: P-glycoprotein (Abcb1), breast cancer resistance protein (Bcrp/Abcg2), and multidrug resistance-associated protein 2 (Mrp2/Abcc2). Exposing isolated rat brain capillaries to linoleic acid, clofibrate, or PKAs increased the transport activity and protein expression of the three ABC transporters. These effects were blocked by the PPAR-α antagonist, GW6471. Dosing rats with 20 mg/kg or 200 mg/kg of clofibrate decreased the brain accumulation of the P-glycoprotein substrate, verapamil, by 50% (in situ brain perfusion; effects blocked by GW6471) and increased P-glycoprotein expression and activity in capillaries ex vivo. Fasting C57Bl/6 wild-type mice for 24 h increased both serum lipids and brain capillary P-glycoprotein transport activity. Fasting did not alter P-glycoprotein activity in PPAR-α knockout mice. These results indicate that hyperlipidemia, lipid-lowering fibrates and exposure to certain fire-fighting foam components activate blood–brain barrier peroxisome proliferator-activated receptor alpha, increase drug efflux transporter expression and reduce drug delivery to the brain. PMID:27193034

(+)Lysergic acid diethylamide, but not its nonhallucinogenic congeners, is a potent serotonin 5HT1C receptor agonist

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

Burris, K.D.; Breeding, M.; Sanders-Bush, E.

Activation of central serotonin 5HT2 receptors is believed to be the primary mechanism whereby lysergic acid diethylamide (LSD) and other hallucinogens induce psychoactive effects. This hypothesis is based on extensive radioligand binding and electrophysiological and behavioral studies in laboratory animals. However, the pharmacological profiles of 5HT2 and 5HT1C receptors are similar, making it difficult to distinguish between effects due to activation of one or the other receptor. For this reason, it was of interest to investigate the interaction of LSD with 5HT1C receptors. Agonist-stimulated phosphoinositide hydrolysis in rat choroid plexus was used as a direct measure of 5HT1C receptor activation.more » (+)LSD potently stimulated phosphoinositide hydrolysis in intact choroid plexus and in cultures of choroid plexus epithelial cells, with EC50 values of 9 and 26 nM, respectively. The effect of (+)LSD in both systems was blocked by 5HT receptor antagonists with an order of activity consistent with interaction at 5HT1C receptors. Neither (+)-2-bromo-LSD nor lisuride, two nonhallucinogenic congeners of LSD, were able to stimulate 5HT1C receptors in cultured cells or intact choroid plexus. In contrast, lisuride, like (+)LSD, is a partial agonist at 5HT2 receptors in cerebral cortex slices and in NIH 3T3 cells transfected with 5HT2 receptor cDNA. The present finding that (+)LSD, but not its nonhallucinogenic congeners, is a 5HT1C receptor agonist suggests a possible role for these receptors in mediating the psychoactive effects of LSD.« less

Opiate and N-methyl-D-aspartate receptors in form-deprivation myopia.

PubMed

Fischer, A J; Seltner, R L; Stell, W K

1998-01-01

Pharmacological studies have implicated retinal opiate pathways in the visual regulation of ocular growth. However, the effects of opiate receptor subtype-specific compounds on form-deprivation myopia (FDM) are inconsistent (Seltner et al., 1997), and may be mediated by non-opiate receptors. The purpose of this study was to test whether opiate receptor-inactive (D-) enantiomers elicit the same FDM-suppressing effect as their opiate receptor-active (L-) counterparts. Since some opiates are thought to act at NMDA receptors, we also tested whether NMDA receptor agonists and antagonists influence ocular growth or FDM. We found that both L- and D- enantiomers of morphine-like compounds (dextrorphanol and levorphanol, and D- and L-naloxone) were equally effective in blocking FDM. The NMDA receptor antagonists dextromethorphan, MK801, and AP5 also suppressed FDM. A single toxic dose of NMDA, that destroys many subtypes of amacrine cells (including those that synthesize the opioid peptide enkephalin), induced myopia and ocular enlargement in ungoggled eyes, and eliminated the ability of form-deprivation to enhance ocular growth. The NR-1 subunit of the NMDA receptor was localized to a narrowly stratified, intense stratum at approximately 50% depth in the inner plexiform layer, diffusely throughout the proximal inner plexiform layer, and to many somata in the amacrine and ganglion cell layers. These observations suggest that most effects of opiate receptor ligands on FDM in the chick are mediated by non-opiate receptors, which are likely to include NMDA receptors. NMDA as an excitotoxin transiently enhances ocular growth, but thereafter disables retinal mechanisms that promote emmetropization and FDM. These observations are consistent with a prominent role for pathways utilizing NMDA receptors in FDM and ocular growth-control.

Ionotropic and metabotropic glutamate receptor mediation of glucocorticoid-induced apoptosis in hippocampal cells and the neuroprotective role of synaptic N-methyl-D-aspartate receptors.

PubMed

Lu, J; Goula, D; Sousa, N; Almeida, O F X

2003-01-01

Glutamate receptors have been proposed to mediate the apoptotic actions of glucocorticoids in hippocampal cells. To further analyze the role of glutamate receptors in this process, we pretreated primary hippocampal cells from neonatal (postnatal day 4) rats with antagonists of ionotropic glutamate receptor (iGluR) and metabotropic glutamate receptor (mGluR) antagonists before exposure to the specific glucocorticoid receptor agonist dexamethasone (DEX) at a dose of 1 microM. Dizocilpine (MK801; a general N-methyl-D-aspartic acid [NMDA] receptor antagonist, NMDAR antagonist) and ifenprodil (a specific ligand of the NMDAR 2B subunit, NR2B), were used to block iGluR; (RS)-alpha-ethyl-4-carboxyphenylglycine (E4CPG) and (RS)-alpha-cyclopropyl-4-phosphonophenyl-glycine (CPPG) were employed as I/II (E4CPG) and II/III (CPPG) mGluR antagonists. Blockade of iGluR resulted in a significant attenuation of DEX-induced cell death; the finding that ifenprodil exerted a similar potency to MK801 demonstrates the involvement of NR2B receptors in glucocorticoid-induced cell death. Apoptosis accounted for a significant amount of the cell loss observed, as detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling histochemistry for the in situ labeling of DNA breaks; apoptotic cells were distinguished from necrosis on the basis of morphological criteria, including chromatin condensation, membrane blebbing and presence of apoptotic bodies. Treatment with E4CPG and CPPG completely abolished the apoptotic response to DEX, thus showing the additional contribution of mGluR to the phenomenon. Further, dose-response studies with NMDA revealed that whereas high (10 microM) doses of NMDA themselves elicit cytotoxic responses, low (1-5 microM) concentrations of NMDA can effectively oppose DEX-induced cell death. Interestingly, the neuroprotective actions of low dose NMDA stimulation were abolished when either synaptic or extrasynaptic NMDA receptors were blocked with MK801 in combination with the GABA receptor antagonist bicuculline (synaptic) or ifenprodil (extrasynaptic). In summary, the present data show that both iGluR and mGluR mediate the neurotoxic effects of glucocorticoids on hippocampal cells and that pre-treatment with low doses of NMDA, by acting on synaptic and extrasynaptic receptors, render hippocampal cells less vulnerable to glucocorticoid insults.

Cardiovascular consequences of sympathetic hyperactivity.

PubMed

Leenen, F H

1999-03-01

The sympathetic nervous system plays an integral role in many aspects of cardiovascular homeostasis. However, intermittent or chronic sympathetic hyperactivity can also initiate or accelerate cardiovascular pathology and provoke clinical events in the presence of cardiovascular disease. Both alpha- and beta-receptors mediate these responses. In the case of the heart, alpha- and beta- receptors contribute to ventricular arrhythmias and cardiac hypertrophy. Moreover, cardiac beta2-receptors mediate not only chronotropic and inotropic responses at the postsynaptic level, but also noradrenalin release at the presynaptic level. To block the adverse effects of sympathetic hyperactivity optimally, one would therefore need both alpha- and nonselective beta-receptor blockade. On the other hand, prevention or reversal of sympathetic hyperactivity at the central level appears to be an attractive alternative. Alpha2-agonists such as clonidine and alpha-methyldopa are clearly effective in this regard but are associated with side effects. More recent research indicates that in the central nervous systen (CNS) other classes such as dihydropyridines (eg, nifedipine) or angiotensin II type 1 receptor blockers (eg, losartan) also can decrease elevated sympathetic nerve activity. The therapeutic relevance of these CNS effects and differences between lipophilic and hydrophilic compounds provide intriguing new avenues for research in disorders such as hypertension and congestive heart failure.

Mechanisms of morphine enhancement of spontaneous seizure activity.

PubMed

Saboory, Ehsan; Derchansky, Miron; Ismaili, Mohammed; Jahromi, Shokrollah S; Brull, Richard; Carlen, Peter L; El Beheiry, Hossam

2007-12-01

High-dose opioid therapy can precipitate seizures; however, the mechanism of such a dangerous adverse effect remains poorly understood. The aim of our study was to determine whether the neuroexcitatory activity of high-dose morphine is mediated by selective stimulation of opioid receptors. Mice hippocampi were resected intact and bathed in low magnesium artificial cerebrospinal fluid to induce spontaneous seizure-like events recorded from CA1 neurons. Application of morphine had a biphasic effect on the recorded spontaneous seizure-like events. In a low concentration (10 microM), morphine depressed electrographic seizure activity. Higher morphine concentrations (30 and 100 microM) enhanced seizure activity in an apparent dose-dependent manner. Naloxone, a nonselective opiate antagonist blocked the proconvulsant action of morphine. Selective mu and kappa opiate receptor agonists and antagonists enhanced and suppressed the spontaneous seizure activity, respectively. On the contrary, delta opioid receptor ligands did not have an effect. The proseizure effect of morphine is mediated through selective stimulation of mu and kappa opiate receptors but not the activation of the delta receptor system. The observed dose-dependent mechanism of morphine neuroexcitation underscores careful adjustment and individualized opioid dosing in the clinical setting.

Direct involvement of sigma-1 receptors in the dopamine D1 receptor-mediated effects of cocaine.

PubMed

Navarro, Gemma; Moreno, Estefanía; Aymerich, Marisol; Marcellino, Daniel; McCormick, Peter J; Mallol, Josefa; Cortés, Antoni; Casadó, Vicent; Canela, Enric I; Ortiz, Jordi; Fuxe, Kjell; Lluís, Carmen; Ferré, Sergi; Franco, Rafael

2010-10-26

It is well known that cocaine blocks the dopamine transporter. This mechanism should lead to a general increase in dopaminergic neurotransmission, and yet dopamine D(1) receptors (D(1)Rs) play a more significant role in the behavioral effects of cocaine than the other dopamine receptor subtypes. Cocaine also binds to σ-1 receptors, the physiological role of which is largely unknown. In the present study, D(1)R and σ(1)R were found to heteromerize in transfected cells, where cocaine robustly potentiated D(1)R-mediated adenylyl cyclase activation, induced MAPK activation per se and counteracted MAPK activation induced by D(1)R stimulation in a dopamine transporter-independent and σ(1)R-dependent manner. Some of these effects were also demonstrated in murine striatal slices and were absent in σ(1)R KO mice, providing evidence for the existence of σ(1)R-D(1)R heteromers in the brain. Therefore, these results provide a molecular explanation for which D(1)R plays a more significant role in the behavioral effects of cocaine, through σ(1)R-D(1)R heteromerization, and provide a unique perspective toward understanding the molecular basis of cocaine addiction.

Angiotensin I-converting enzyme inhibitors potentiate bradykinin's inotropic effects independently of blocking its inactivation.

PubMed

Minshall, R D; Erdös, E G; Vogel, S M

1997-08-04

The positive inotropic effects of bradykinin (BK) and 2 analogs resistant to angiotensin I-converting enzyme (ACE) were potentiated on isolated guinea pig atrial preparations by enalaprilat. The stable BK analogs, dextran-BK and [Hyp3-Tyr(Me)8]-BK, were as active as BK. Pretreatment for 5 min with enalaprilat augmented the maximal positive inotropic effect of [Hyp3-Tyr(Me)8]-BK 2.8-fold, from 19% to 53% and that of BK from 28% to 42% over baseline; inotropic responses to dextran-BK (1 microM) were similarly increased. The activity of atrial ACE, a zinc-requiring enzyme, was completely inhibited by 8-hydroxyquinoline-5-sulfonic acid (QSA, 10 mM), which raised the maximal inotropic effect of BK to 39% above baseline. This value rose to 67% when in addition to QSA, 1 microM enalaprilat was added; enalaprilat thus, potentiated the effects of BK independently of enzyme inhibition. The positive inotropic effects to BK and its analogs decline with time in the presence of these agonists. After 10 min of exposure, the response to 1 microM [Hyp3-Tyr(Me)8]-BK decreased to about half, and after 20 min, to 0. Enalaprilat, when present in the tissue bath, prevented the decline in inotropy; even after tachyphylaxis occurred, it reversed this decrease in activity when added. The effects of 1 microM [Hyp3-Tyr(Me)8]-BK, in the absence or presence of enalaprilat, were abolished by the BK B2 receptor antagonist icatibant (0.75 microM). The results indicate that ACE inhibitors, by potentiating the BK effects and blocking BK B2-receptor desensitization, may contribute to the beneficial cardiac effects of BK independently of blocking its inactivation.

P2X1 Receptor Antagonists Inhibit HIV-1 Fusion by Blocking Virus-Coreceptor Interactions

PubMed Central

Giroud, Charline; Marin, Mariana; Hammonds, Jason; Spearman, Paul

2015-01-01

ABSTRACT HIV-1 Env glycoprotein-mediated fusion is initiated upon sequential binding of Env to CD4 and the coreceptor CXCR4 or CCR5. Whereas these interactions are thought to be necessary and sufficient to promote HIV-1 fusion, other host factors can modulate this process. Previous studies reported potent inhibition of HIV-1 fusion by selective P2X1 receptor antagonists, including NF279, and suggested that these receptors play a role in HIV-1 entry. Here we investigated the mechanism of antiviral activity of NF279 and found that this compound does not inhibit HIV-1 fusion by preventing the activation of P2X1 channels but effectively blocks the binding of the virus to CXCR4 or CCR5. The notion of an off-target effect of NF279 on HIV-1 fusion is supported by the lack of detectable expression of P2X1 receptors in cells used in fusion experiments and by the fact that the addition of ATP or the enzymatic depletion of ATP in culture medium does not modulate viral fusion. Importantly, NF279 fails to inhibit HIV-1 fusion with cell lines and primary macrophages when added at an intermediate stage downstream of Env-CD4-coreceptor engagement. Conversely, in the presence of NF279, HIV-1 fusion is arrested downstream of CD4 binding but prior to coreceptor engagement. NF279 also antagonizes the signaling function of CCR5, CXCR4, and another chemokine receptor, as evidenced by the suppression of calcium responses elicited by specific ligands and by recombinant gp120. Collectively, our results demonstrate that NF279 is a dual HIV-1 coreceptor inhibitor that interferes with the functional engagement of CCR5 and CXCR4 by Env. IMPORTANCE Inhibition of P2X receptor activity suppresses HIV-1 fusion and replication, suggesting that P2X signaling is involved in HIV-1 entry. However, mechanistic experiments conducted in this study imply that P2X1 receptor is not expressed in target cells or involved in viral fusion. Instead, we found that inhibition of HIV-1 fusion by a specific P2X1 receptor antagonist, NF279, is due to the blocking of virus interactions with both the CXCR4 and CCR5 coreceptors. The ability of NF279 to abrogate cellular calcium signaling induced by the respective chemokines showed that this compound acts as a dual-coreceptor antagonist. P2X1 receptor antagonists could thus represent a new class of dual-coreceptor inhibitors with a structure and a mechanism of action that are distinct from those of known HIV-1 coreceptor antagonists. PMID:26136569

P2X1 Receptor Antagonists Inhibit HIV-1 Fusion by Blocking Virus-Coreceptor Interactions.

PubMed

Giroud, Charline; Marin, Mariana; Hammonds, Jason; Spearman, Paul; Melikyan, Gregory B

2015-09-01

HIV-1 Env glycoprotein-mediated fusion is initiated upon sequential binding of Env to CD4 and the coreceptor CXCR4 or CCR5. Whereas these interactions are thought to be necessary and sufficient to promote HIV-1 fusion, other host factors can modulate this process. Previous studies reported potent inhibition of HIV-1 fusion by selective P2X1 receptor antagonists, including NF279, and suggested that these receptors play a role in HIV-1 entry. Here we investigated the mechanism of antiviral activity of NF279 and found that this compound does not inhibit HIV-1 fusion by preventing the activation of P2X1 channels but effectively blocks the binding of the virus to CXCR4 or CCR5. The notion of an off-target effect of NF279 on HIV-1 fusion is supported by the lack of detectable expression of P2X1 receptors in cells used in fusion experiments and by the fact that the addition of ATP or the enzymatic depletion of ATP in culture medium does not modulate viral fusion. Importantly, NF279 fails to inhibit HIV-1 fusion with cell lines and primary macrophages when added at an intermediate stage downstream of Env-CD4-coreceptor engagement. Conversely, in the presence of NF279, HIV-1 fusion is arrested downstream of CD4 binding but prior to coreceptor engagement. NF279 also antagonizes the signaling function of CCR5, CXCR4, and another chemokine receptor, as evidenced by the suppression of calcium responses elicited by specific ligands and by recombinant gp120. Collectively, our results demonstrate that NF279 is a dual HIV-1 coreceptor inhibitor that interferes with the functional engagement of CCR5 and CXCR4 by Env. Inhibition of P2X receptor activity suppresses HIV-1 fusion and replication, suggesting that P2X signaling is involved in HIV-1 entry. However, mechanistic experiments conducted in this study imply that P2X1 receptor is not expressed in target cells or involved in viral fusion. Instead, we found that inhibition of HIV-1 fusion by a specific P2X1 receptor antagonist, NF279, is due to the blocking of virus interactions with both the CXCR4 and CCR5 coreceptors. The ability of NF279 to abrogate cellular calcium signaling induced by the respective chemokines showed that this compound acts as a dual-coreceptor antagonist. P2X1 receptor antagonists could thus represent a new class of dual-coreceptor inhibitors with a structure and a mechanism of action that are distinct from those of known HIV-1 coreceptor antagonists. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

The second Lilly Prize Lecture, University of Newcastle, July 1977. beta-Adrenergic receptor blockade in hypertension, past, present and future.

PubMed Central

Prichard, B N

1978-01-01

All beta-adrenoceptor blocking drugs that have been described share the common property of being competitive inhibitors. They differ in their associated properties, the presence or absence of cardioselectivity, membrane stabilizing activity, and partial agonist activity. Recently some beta-adrenoceptor blocking drugs have been reported which also possess alpha-adrenoceptor blocking activity. The associated properties have been used as a basis for classifying beta-adrenoceptor blocking drugs (Fitzgerald, 1969, 1972). The presence or absence of cardioselectivity is most useful for dividing beta-adrenoceptor blocking drugs. The non-selective drugs (Division I) can be further divided according to the presence or absence of intrinsic sympathomimetic activity (ISA) and membrane stabilizing activity (Fitzgerald's groups I-IV). Group I possess both membrane activity and ISA, e.g. alprenolol, oxprenolol, group II just membrane action, e.g. propanolol, group III ISA but no membrane action, e.g. pindolol. Fitzgerald placed pindolol in group I but should be placed in group III as it possesses a high degree of beta-adrenoceptor blocking potency in relation to its membrane activity (Prichard, 1974). Finally drugs in group IV have neither ISA nor membrane action, e.g. sotalol, timolol. The cardioselective drugs (Division II) can be similarly sub-divided into groups I-IV according to the presence or absence of ISA or membrane action (Fitzgerald grouped all these together as group V). Lastly there are new beta-adrenergic receptor blocking drugs which in addition have alpha- adrenergic receptor blocking properties (Division III). PMID:26370

Pretreatment with 5-hydroxymethyl-2-furaldehyde blocks scopolamine-induced learning deficit in contextual and spatial memory in male mice.

PubMed

Lee, Younghwan; Gao, Qingtao; Kim, Eunji; Lee, Younghwa; Park, Se Jin; Lee, Hyung Eun; Jang, Dae Sik; Ryu, Jong Hoon

2015-07-01

5-Hydroxymethyl-2-furaldehyde (5-HMF) is a compound derived from the dehydration of certain sugars. The aim of the present study was to evaluate the effect of 5-HMF on the cognitive impairment induced by scopolamine, a muscarinic receptor antagonist. To measure various cognitive functions, we conducted the step-through passive avoidance task, the Y-maze task and the Morris water maze task. A single administration of 5-HMF (5 or 10mg/kg, p.o.) significantly attenuates scopolamine-induced cognitive impairment in these behavioral tasks without changes in locomotor activity, and the effect of 5-HMF on scopolamine-induced cognitive impairment was significantly reversed by a sub-effective dose of MK-801, an NMDA receptor antagonist. In addition, a single administration of 5-HMF (10mg/kg, p.o.) enhanced the cognitive performance of normal naïve mice in the passive avoidance task. Furthermore, Western blot analysis revealed that the levels of phosphorylated Ca(2+)/calmodulin-dependent protein kinase II-α (CaMKII) and extracellular signal-regulated kinases (ERK) were significantly enhanced by the single administration of 5-HMF in the hippocampal tissues. Taken together, the present study suggests that 5-HMF may block scopolamine-induced learning deficit and enhance cognitive function via the activation of NMDA receptor signaling, including CaMKII and ERK, and would be an effective candidate against cognitive disorders, such as Alzheimer's disease. Copyright © 2015. Published by Elsevier Inc.

What's So Special about FGF19-Unique Effects Reported on Skeletal Muscle Mass and Function.

PubMed

Glass, David J

2017-08-01

In a recent study published in Nature Medicine, Benoit et al. (2017) reported unique effects of FGF19 on mouse skeletal muscle: FGF19 induced skeletal muscle hypertrophy and blocked muscle atrophy, acting via FGF receptors and ßKlotho, while a related FGF21 hormone was ineffective. Copyright © 2017 Elsevier Inc. All rights reserved.

Developmental defects in zebrafish for classification of EGF pathway inhibitors

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

Pruvot, Benoist; Curé, Yoann; Djiotsa, Joachim

2014-01-15

One of the major challenges when testing drug candidates targeted at a specific pathway in whole animals is the discrimination between specific effects and unwanted, off-target effects. Here we used the zebrafish to define several developmental defects caused by impairment of Egf signaling, a major pathway of interest in tumor biology. We inactivated Egf signaling by genetically blocking Egf expression or using specific inhibitors of the Egf receptor function. We show that the combined occurrence of defects in cartilage formation, disturbance of blood flow in the trunk and a decrease of myelin basic protein expression represent good indicators for impairmentmore » of Egf signaling. Finally, we present a classification of known tyrosine kinase inhibitors according to their specificity for the Egf pathway. In conclusion, we show that developmental indicators can help to discriminate between specific effects on the target pathway from off-target effects in molecularly targeted drug screening experiments in whole animal systems. - Highlights: • We analyze the functions of Egf signaling on zebrafish development. • Genetic blocking of Egf expression causes cartilage, myelin and circulatory defects. • Chemical inhibition of Egf receptor function causes similar defects. • Developmental defects can reveal the specificity of Egf pathway inhibitors.« less

Rationale for combination therapy in hypertension management: focus on angiotensin receptor blockers and thiazide diuretics.

PubMed

Nash, David T

2007-04-01

Despite recognition that hypertension is a major risk factor for cardiovascular events and mortality, blood pressure control rates remain low in the US population. Reflecting clinical trial results, hypertension management guidelines assert the clinical benefit of achieving current blood pressure goals and indicate that most patients will require 2 or more drugs to reach goal. Well-designed drug combinations counter hypertension via complementary mechanisms that increase antihypertensive efficacy, potentially with lower rates of adverse events than higher dose monotherapy regimens. Lower adverse event rates, in turn, may contribute to greater adherence with treatment. The combination of a low-dose diuretic with agents that block the effects of the renin-angiotensin system (RAS), such as angiotensin receptor blockers, has been found in numerous clinical trials to be highly effective for lowering blood pressure in patients with uncomplicated as well as high-risk hypertension, with a comparable favorable side effect profile compared with monotherapy. Moreover, agents that block the RAS are associated with a lower risk of new-onset diabetes mellitus than other antihypertensive classes. Complementary combinations of antihypertensive agents provide an efficient and effective approach to hypertension management.

Blocking Mineralocorticoid Receptors Impairs, Blocking Glucocorticoid Receptors Enhances Memory Retrieval in Humans

PubMed Central

Rimmele, Ulrike; Besedovsky, Luciana; Lange, Tanja; Born, Jan

2013-01-01

Memory retrieval is impaired at very low as well as very high cortisol levels, but not at intermediate levels. This inverted-U-shaped relationship between cortisol levels and memory retrieval may originate from different roles of the mineralocorticoid (MR) and glucocorticoid receptor (GR) that bind cortisol with distinctly different affinity. Here, we examined the role of MRs and GRs in human memory retrieval using specific receptor antagonists. In two double-blind within-subject, cross-over designed studies, young healthy men were asked to retrieve emotional and neutral texts and pictures (learnt 3 days earlier) between 0745 and 0915 hours in the morning, either after administration of 400 mg of the MR blocker spironolactone vs placebo (200 mg at 2300 hours and 200 mg at 0400 hours, Study I) or after administration of the GR blocker mifepristone vs placebo (200 mg at 2300 hours, Study II). Blockade of MRs impaired free recall of both texts and pictures particularly for emotional material. In contrast, blockade of GRs resulted in better memory retrieval for pictures, with the effect being more pronounced for neutral than emotional materials. These findings indicate indeed opposing roles of MRs and GRs in memory retrieval, with optimal retrieval at intermediate cortisol levels likely mediated by high MR but concurrently low GR activation. PMID:23303058

Blocking mineralocorticoid receptors impairs, blocking glucocorticoid receptors enhances memory retrieval in humans.

PubMed

Rimmele, Ulrike; Besedovsky, Luciana; Lange, Tanja; Born, Jan

2013-04-01

Memory retrieval is impaired at very low as well as very high cortisol levels, but not at intermediate levels. This inverted-U-shaped relationship between cortisol levels and memory retrieval may originate from different roles of the mineralocorticoid (MR) and glucocorticoid receptor (GR) that bind cortisol with distinctly different affinity. Here, we examined the role of MRs and GRs in human memory retrieval using specific receptor antagonists. In two double-blind within-subject, cross-over designed studies, young healthy men were asked to retrieve emotional and neutral texts and pictures (learnt 3 days earlier) between 0745 and 0915 hours in the morning, either after administration of 400 mg of the MR blocker spironolactone vs placebo (200 mg at 2300 hours and 200 mg at 0400 hours, Study I) or after administration of the GR blocker mifepristone vs placebo (200 mg at 2300 hours, Study II). Blockade of MRs impaired free recall of both texts and pictures particularly for emotional material. In contrast, blockade of GRs resulted in better memory retrieval for pictures, with the effect being more pronounced for neutral than emotional materials. These findings indicate indeed opposing roles of MRs and GRs in memory retrieval, with optimal retrieval at intermediate cortisol levels likely mediated by high MR but concurrently low GR activation.

Escitalopram attenuates β-amyloid-induced tau hyperphosphorylation in primary hippocampal neurons through the 5-HT1A receptor mediated Akt/GSK-3β pathway

PubMed Central

Gong, Wei-Gang; Wu, Di; Tang, Xiang; Li, Xiao-Li; Wu, Fang-Fang; Bai, Feng; Xu, Lin; Zhang, Zhi-Jun

2016-01-01

Tau hyperphosphorylation is an important pathological feature of Alzheimer's disease (AD). To investigate whether escitalopram could inhibit amyloid-β (Aβ)-induced tau hyperphosphorylation and the underlying mechanisms, we treated the rat primary hippocampal neurons with Aβ1-42 and examined the effect of escitalopram on tau hyperphosphorylation. Results showed that escitalopram decreased Aβ1–42-induced tau hyperphosphorylation. In addition, escitalopram activated the Akt/GSK-3β pathway, and the PI3K inhibitor LY294002 blocked the attenuation of tau hyperphosphorylation induced by escitalopram. Moreover, the 5-HT1A receptor agonist 8-OH-DPAT also activated the Akt/GSK-3β pathway and decreased Aβ1-42-induced tau hyperphosphorylation. Furthermore, the 5-HT1A receptor antagonist WAY-100635 blocked the activation of Akt/GSK-3β pathway and the attenuation of tau hyperphosphorylation induced by escitalopram. Finally, escitalopram improved Aβ1–42 induced impairment of neurite outgrowth and spine density, and reversed Aβ1–42 induced reduction of synaptic proteins. Our results demonstrated that escitalopram attenuated Aβ1–42-induced tau hyperphosphorylation in primary hippocampal neurons through the 5-HT1A receptor mediated Akt/GSK-3β pathway. PMID:26950279

Escitalopram attenuates β-amyloid-induced tau hyperphosphorylation in primary hippocampal neurons through the 5-HT1A receptor mediated Akt/GSK-3β pathway.

PubMed

Wang, Yan-Juan; Ren, Qing-Guo; Gong, Wei-Gang; Wu, Di; Tang, Xiang; Li, Xiao-Li; Wu, Fang-Fang; Bai, Feng; Xu, Lin; Zhang, Zhi-Jun

2016-03-22

Tau hyperphosphorylation is an important pathological feature of Alzheimer's disease (AD). To investigate whether escitalopram could inhibit amyloid-β (Aβ)-induced tau hyperphosphorylation and the underlying mechanisms, we treated the rat primary hippocampal neurons with Aβ1-42 and examined the effect of escitalopram on tau hyperphosphorylation. Results showed that escitalopram decreased Aβ1-42-induced tau hyperphosphorylation. In addition, escitalopram activated the Akt/GSK-3β pathway, and the PI3K inhibitor LY294002 blocked the attenuation of tau hyperphosphorylation induced by escitalopram. Moreover, the 5-HT1A receptor agonist 8-OH-DPAT also activated the Akt/GSK-3β pathway and decreased Aβ1-42-induced tau hyperphosphorylation. Furthermore, the 5-HT1A receptor antagonist WAY-100635 blocked the activation of Akt/GSK-3β pathway and the attenuation of tau hyperphosphorylation induced by escitalopram. Finally, escitalopram improved Aβ1-42 induced impairment of neurite outgrowth and spine density, and reversed Aβ1-42 induced reduction of synaptic proteins. Our results demonstrated that escitalopram attenuated Aβ1-42-induced tau hyperphosphorylation in primary hippocampal neurons through the 5-HT1A receptor mediated Akt/GSK-3β pathway.

Desensitization by noradrenaline of responses to stimulation of pre- and postsynaptic adrenoceptors

PubMed Central

Ball, N.; Danks, J.L.; Dorudi, S.; Nasmyth, P.A.

1982-01-01

1 The effect of exposing isolated preparations of rat aortic strip, rat atria and mouse vas deferens to perfusions of Krebs solution containing various concentrations of noradrenaline on their sensitivity to the drug has been determined. 2 The responses evoked by stimulation of postsynaptic adrenoceptors in all the tissues and presynaptic α-adrenoceptors in the mouse vas deferens were diminished by the perfusion of noradrenaline through the organ bath for 30 min. 3 The concentration of noradrenaline required to produce desensitization was higher in the mouse vas deferens than in the other tissues and more was required to desensitize the chronotropic responses than the inotropic responses in rat isolated atria. 4 The inclusion of cocaine (10-5 M) in the bathing solution to block uptake1 increased the sensitivity of most tissues to noradrenaline. With the possible exception of the response to stimulation of presynaptic receptors in the mouse vas deferens, desensitization was somewhat increased in its presence. 5 When uptake2 was blocked by oestradiol (10-5 M), it was not possible to desensitize the contractor responses of the aortic strip and vas deferens to exogenous noradrenaline, nor the inotropic response of the atria to the drug. However, oestradiol failed to block the desensitization of chronotropic responses and responses to stimulation of presynaptic receptors in the vas deferens. 6 Blockade of monoamine oxidase (MAO) with iproniazid (7.2 × 10-4 M) or with pargyline (5 × 10-4 M) did not affect the desensitization process in the aortic strip. 7 Blockade of catechol-O-methyltransferase (COMT) with U-0521 (5.3 × 10-5 M) greatly increased desensitization in the aortic strip and desensitization of inotropic responses in the atria. It had no effect on desensitization of chronotropic responses. Its effect on responses in the mouse vas deferens was not determined. 8 The perfusion of methoxamine at concentrations about 1000 times higher than those of noradrenaline also produced desensitization in the aortic strip. 9 The desensitization of presynaptic receptors in the mouse vas deferens was shown to be specific and that of the responses to postsynaptic receptor stimulation to be non-specific. 10 It is concluded that responses to adrenoceptor stimulation may be desensitized by accumulation of noradrenaline inside the cells bearing the receptors and that the desensitization is caused by noradrenaline itself not by a metabolite. Desensitization may also be caused without accumulation of noradrenaline in uptake2 and for some receptors these may not be alternative mechanisms. PMID:7082904

Buprenorphine and a CRF1 antagonist block the acquisition of opiate withdrawal-induced conditioned place aversion in rats.

PubMed

Stinus, Luis; Cador, Martine; Zorrilla, Eric P; Koob, George F

2005-01-01

Conditioned place aversion in rats has face validity as a measure of the aversive stimulus effects of opiate withdrawal that reflects an important motivational component of opiate dependence. The purpose of the present study was to validate conditioned place aversion as sensitive to medications that will alleviate the aversive stimulus effects of opiate withdrawal in humans, and to extend this model to the exploration of the neuropharmacological basis of the motivational effects of opiate withdrawal. Male Sprague-Dawley rats were implanted with two subcutaneous morphine pellets and 5 days later began place conditioning training following subcutaneous administration of a low dose of naloxone. Animals were subjected to three pairings of a low dose of naloxone (15 microg/kg, s.c.) to one arm of a three-chambered place conditioning apparatus. Buprenorphine administered prior to each pairing dose-dependently blocked the place aversion produced by precipitated opiate withdrawal. A corticotropin-releasing factor-1 (CRF1) receptor antagonist (antalarmin) also reversed the place aversion produced by precipitated opiate withdrawal. Antalarmin did not produce a place preference or place aversion by itself in morphine-dependent rats. No effect was observed with pretreatment of the dopamine partial agonist terguride or the selective serotonin reuptake inhibitor fluoxetine. Also, chronic pretreatment with acamprosate (a glutamate receptor modulator used to prevent relapse in alcohol dependence) did not alter naloxone-induced place aversion. Buprenorphine by itself in dependent rats produced a mild place preference at low doses and a mild place aversion at higher doses. These results suggest that buprenorphine blocks the aversive stimulus effects of precipitated opiate withdrawal in rats and provides some validity for the use of place conditioning as a measure that is sensitive to potential opiate-dependence medications. In addition, these results suggest that CRF1 antagonists can block the aversive stimulus effects of opiate withdrawal and may be potential therapeutic targets for opiate dependence.

Dissociable Effects of the Cannabinoid Receptor Agonists Δ9-Tetrahydrocannabinol and CP55940 on Pain-Stimulated Versus Pain-Depressed Behavior in Rats

PubMed Central

Kwilasz, Andrew J.

2012-01-01

Cannabinoid receptor agonists produce reliable antinociception in most preclinical pain assays but have inconsistent analgesic efficacy in humans. This disparity suggests that conventional preclinical assays of nociception are not sufficient for the prediction of cannabinoid effects related to clinical analgesia. To extend the range of preclinical cannabinoid assessment, this study compared the effects of the marijuana constituent and low-efficacy cannabinoid agonist Δ9-tetrahydrocannabinol (THC) and the high-efficacy synthetic cannabinoid agonist 3-(2-hydroxy-4-(1,1-dimethylheptyl)phenyl)-4-(3-hydroxypropyl)cyclohexanol (CP55940) in assays of pain-stimulated and pain-depressed behavior. Intraperitoneal injection of dilute lactic acid (1.8% in 1 ml/kg) stimulated a stretching response or depressed intracranial self-stimulation (ICSS) in separate groups of male Sprague-Dawley rats. THC (0.1–10 mg/kg) and CP55940 (0.0032–0.32 mg/kg) dose-dependently blocked acid- stimulated stretching but only exacerbated acid-induced depression of ICSS at doses that also decreased control ICSS in the absence of a noxious stimulus. Repeated THC produced tolerance to sedative rate-decreasing effects of THC on control ICSS in the absence of the noxious stimulus but failed to unmask antinociception in the presence of the noxious stimulus. THC and CP55940 also failed to block pain-related depression of feeding in rats, although THC did attenuate satiation-related depression of feeding. In contrast to the effects of the cannabinoid agonists, the clinically effective analgesic and nonsteroidal anti-inflammatory drug ketoprofen (1 mg/kg) blocked acid-stimulated stretching and acid-induced depression of both ICSS and feeding. The poor efficacy of THC and CP55940 to block acute pain-related depression of behavior in rats agrees with the poor efficacy of cannabinoids to treat acute pain in humans. PMID:22892341

Graves' Disease Mechanisms: The Role of Stimulating, Blocking, and Cleavage Region TSH Receptor Antibodies

PubMed Central

Morshed, S. A.; Davies, T. F.

2016-01-01

The immunologic processes involved in Graves' disease (GD) have one unique characteristic – the autoantibodies to the TSH receptor (TSHR) – which have both linear and conformational epitopes. Three types of TSHR antibodies (stimulating, blocking, and cleavage) with different functional capabilities have been described in GD patients, which induce different signaling effects varying from thyroid cell proliferation to thyroid cell death. The establishment of animal models of GD by TSHR antibody transfer or by immunization with TSHR antigen has confirmed its pathogenic role and, therefore, GD is the result of a breakdown in TSHR tolerance. Here we review some of the characteristics of TSHR antibodies with a special emphasis on new developments in our understanding of what were previously called “neutral” antibodies and which we now characterize as autoantibodies to the “cleavage” region of the TSHR ectodomain. PMID:26361259

Rivastigmine improves isolation rearing-induced prepulse inhibition deficits via muscarinic acetylcholine receptors in mice.

PubMed

Higashino, Kosuke; Ago, Yukio; Umeki, Takahiro; Hasebe, Shigeru; Onaka, Yusuke; Hashimoto, Hitoshi; Takuma, Kazuhiro; Matsuda, Toshio

2016-02-01

The acetylcholinesterase inhibitors donepezil, galantamine, and rivastigmine are used for the treatment of Alzheimer's disease. We previously demonstrated that donepezil and galantamine differentially affect isolation rearing-induced prepulse inhibition (PPI) deficits and that this might be due to differential effects on brain muscarinic acetylcholine (mACh) receptor function in mice. We examined the effects of rivastigmine on isolation rearing-induced PPI deficits, brain ACh levels, and mACh receptor function in mice. Acoustic startle responses were measured in a startle chamber. Microdialysis was performed, and the levels of dopamine and ACh in the prefrontal cortex were measured. Rivastigmine (0.3 mg/kg) improved PPI deficits, and this improvement was antagonized by the mACh receptor antagonist telenzepine but not by the nicotinic ACh receptor antagonist mecamylamine. Rivastigmine increased extracellular ACh levels by approximately 2-3-fold, less than the increase produced by galantamine. Rivastigmine enhanced the effect of the mACh receptor agonist N-desmethylclozapine on prefrontal dopamine release, a marker of mACh receptor function, and this increase was blocked by telenzepine. In contrast, galantamine did not affect N-desmethylclozapine-induced dopamine release. Furthermore, rivastigmine did not affect cortical dopamine release induced by the serotonin1A receptor agonist osemozotan, suggesting that the effect of rivastigmine has specificity for mACh receptors. Taken together with our previous finding that marked increases in ACh levels are required for the PPI deficit improvement induced by galantamine, our present results suggest that rivastigmine improves isolation rearing-induced PPI deficits by increasing ACh levels and by concomitantly enhancing mACh receptor function.

Acutely increasing δGABA(A) receptor activity impairs memory and inhibits synaptic plasticity in the hippocampus.

PubMed

Whissell, Paul D; Eng, Dave; Lecker, Irene; Martin, Loren J; Wang, Dian-Shi; Orser, Beverley A

2013-01-01

Extrasynaptic γ-aminobutyric acid type A (GABA(A)) receptors that contain the δ subunit (δGABA(A) receptors) are expressed in several brain regions including the dentate gyrus (DG) and CA1 subfields of the hippocampus. Drugs that increase δGABA(A) receptor activity have been proposed as treatments for a variety of disorders including insomnia, epilepsy and chronic pain. Also, long-term pretreatment with the δGABA(A) receptor-preferring agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP) enhances discrimination memory and increases neurogenesis in the DG. Despite the potential therapeutic benefits of such treatments, the effects of acutely increasing δGABA(A) receptor activity on memory behaviors remain unknown. Here, we studied the effects of THIP (4 mg/kg, i.p.) on memory performance in wild-type (WT) and δGABA(A) receptor null mutant (Gabrd(-/-)) mice. Additionally, the effects of THIP on long-term potentiation (LTP), a molecular correlate of memory, were studied within the DG and CA1 subfields of the hippocampus using electrophysiological recordings of field potentials in hippocampal slices. The results showed that THIP impaired performance in the Morris water maze, contextual fear conditioning and object recognition tasks in WT mice but not Gabrd(-/-) mice. Furthermore, THIP inhibited LTP in hippocampal slices from WT but not Gabrd(-/-) mice, an effect that was blocked by GABA(A) receptor antagonist bicuculline. Thus, acutely increasing δGABA(A) receptor activity impairs memory behaviors and inhibits synaptic plasticity. These results have important implications for the development of therapies aimed at increasing δGABA(A) receptor activity.

Pharmacological profiles of cloned mammalian P2Y-receptor subtypes.

PubMed

von Kügelgen, Ivar

2006-06-01

Membrane-bound P2-receptors mediate the actions of extracellular nucleotides in cell-to-cell signalling. P2X-receptors are ligand-gated ion channels, whereas P2Y-receptors belong to the superfamily of G-protein-coupled receptors (GPCRs). So far, the P2Y family is composed out of 8 human subtypes that have been cloned and functionally defined; species orthologues have been found in many vertebrates. P2Y1-, P2Y2-, P2Y4-, P2Y6-, and P2Y11-receptors all couple to stimulation of phospholipase C. The P2Y11-receptor mediates in addition a stimulation of adenylate cyclase. In contrast, activation of the P2Y12-, P2Y13-, and P2Y14-receptors causes an inhibition of adenylate cyclase activity. The expression of P2Y1-receptors is widespread. The receptor is involved in blood platelet aggregation, vasodilatation and neuromodulation. It is activated by ADP and ADP analogues including 2-methylthio-ADP (2-MeSADP). 2'-Deoxy-N6-methyladenosine-3',5'-bisphosphate (MRS2179) and 2-chloro-N6-methyl-(N)-methanocarba-2'-deoxyadenosine 3',5'-bisphosphate (MRS2279) are potent and selective antagonists. P2Y2 transcripts are abundantly distributed. One important example for its functional role is the control of chloride ion fluxes in airway epithelia. The P2Y2-receptor is activated by UTP and ATP and blocked by suramin. The P2Y2-agonist diquafosol is used for the treatment of the dry eye disease. P2Y4-receptors are expressed in the placenta and in epithelia. The human P2Y4-receptor has a strong preference for UTP as agonist, whereas the rat P2Y4-receptor is activated about equally by UTP and ATP. The P2Y4-receptor is not blocked by suramin. The P2Y6-receptor has a widespread distribution including heart, blood vessels, and brain. The receptor prefers UDP as agonist and is selectively blocked by 1,2-di-(4-isothiocyanatophenyl)ethane (MRS2567). The P2Y11-receptor may play a role in the differentiation of immunocytes. The human P2Y11-receptor is activated by ATP as naturally occurring agonist and it is blocked by suramin and reactive blue 2 (RB2). The P2Y12-receptor plays a crucial role in platelet aggregation as well as in inhibition of neuronal cells. It is activated by ADP and very potently by 2-methylthio-ADP. Nucleotide antagonists including N6-(2-methylthioethyl)-2-(3,3,3-trifluoropropylthio)-beta,gamma-dichloromethylene-ATP (=cangrelor; AR-C69931MX), the nucleoside analogue AZD6140, as well as active metabolites of the thienopyridine compounds clopidogrel and prasugrel block the receptor. These P2Y12-antagonists are used in pharmacotherapy to inhibit platelet aggregation. The P2Y13-receptor is expressed in immunocytes and neuronal cells and is again activated by ADP and 2-methylthio-ADP. The 2-chloro-5-nitro pyridoxal-phosphate analogue 6-(2'-chloro-5'-nitro-azophenyl)-pyridoxal-alpha5-phosphate (MRS2211) is a selective antagonist. mRNA encoding for the human P2Y14-receptor is found in many tissues. However, a physiological role of the receptor has not yet been established. UDP-glucose and related analogues act as agonists; antagonists are not known. Finally, UDP has been reported to act on receptors for cysteinyl leukotrienes as an additional agonist--indicating a dual agonist specificity of these receptors.

Steroids induce acetylcholine receptors on cultured human muscle: Implications for myasthenia gravis

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

Kaplan, I.; Blakely, B.T.; Pavlath, G.K.

1990-10-01

Antibodies to the acetylcholine receptor (AChR), which are diagnostic of the human autoimmune disease myasthenia gravis, block AChR function and increase the rate of AChR degradation leading to impaired neuromuscular transmission. Steroids are frequently used to alleviate symptoms of muscle fatigue and weakness in patients with myasthenia gravis because of their well-documented immunosuppressive effects. The authors show here that the steroid dexamethasone significantly increases total surface AChRs on cultured human muscle exposed to myasthenia gravis sera. The results suggest that the clinical improvement observed in myasthenic patients treated with steroids is due not only to an effect on the immunemore » system but also a direct effect on muscle. They propose that the identification and development of pharmacologic agents that augment receptors and other proteins that are reduced by human genetic or autoimmune disease will have broad therapeutic applications.« less

Memantine block depends on agonist presentation at the NMDA receptor in substantia nigra pars compacta dopamine neurones

PubMed Central

Wild, A.R.; Akyol, E.; Brothwell, S.L.C.; Kimkool, P.; Skepper, J.N.; Gibb, A.J.; Jones, S.

2015-01-01

NMDA glutamate receptors (NMDARs) have critical functional roles in the nervous system but NMDAR over-activity can contribute to neuronal damage. The open channel NMDAR blocker, memantine is used to treat certain neurodegenerative diseases, including Parkinson’s disease (PD) and is well tolerated clinically. We have investigated memantine block of NMDARs in substantia nigra pars compacta (SNc) dopamine neurones, which show severe pathology in PD. Memantine (10 μM) caused robust inhibition of whole-cell (synaptic and extrasynaptic) NMDARs activated by NMDA at a high concentration or a long duration, low concentration. Less memantine block of NMDAR-EPSCs was seen in response to low frequency synaptic stimulation, while responses to high frequency synaptic stimulation were robustly inhibited by memantine; thus memantine inhibition of NMDAR-EPSCs showed frequency-dependence. By contrast, MK-801 (10 μM) inhibition of NMDAR-EPSCs was not significantly different at low versus high frequencies of synaptic stimulation. Using immunohistochemistry, confocal imaging and stereological analysis, NMDA was found to reduce the density of cells expressing tyrosine hydroxylase, a marker of viable dopamine neurones; memantine prevented the NMDA-evoked decrease. In conclusion, memantine blocked NMDAR populations in different subcellular locations in SNc dopamine neurones but the degree of block depended on the intensity of agonist presentation at the NMDAR. This profile may contribute to the beneficial effects of memantine in PD, as glutamatergic activity is reported to increase, and memantine could preferentially reduce over-activity while leaving some physiological signalling intact. PMID:23727219

A Role for σRs in Stimulant Self-administration and Addiction

PubMed Central

Katz, Jonathan L.; Hong, Weimin C.; Hiranita, Takato; Su, Tsung-Ping

2015-01-01

Sigma-1 receptors (σ1Rs) are structurally unique intracellular proteins that function as chaperones. σ1Rs translocate from the mitochondria-associated membrane to other sub-cellular compartments, and can influence a host of targets, including ion channels, G-protein-coupled receptors, lipids, and other signaling proteins. Drugs binding to σRs can induce or block the actions of σRs. Studies indicate that stimulant self-administration induces reinforcing effects of σR agonists, due to dopamine transporter actions. Once established the reinforcing effects of σR agonists are independent of dopaminergic mechanisms traditionally thought to be critical in the reinforcing effects of stimulants. Self-administered doses of σR agonists do not increase dopamine concentrations in the nucleus accumbens shell, a transmitter and brain region considered important for reinforcing effects of abused drugs. However, the self-administration of σR agonists is blocked by σR antagonists. Several effects of stimulants have been blocked by σR antagonists, including reinforcing effects assessed by a place-conditioning procedure. However, the self-administration of stimulants is largely unaffected by σR antagonists, indicating fundamental differences in the mechanisms underlying these two procedures used to assess reinforcing effects. When σR antagonists are administered in combination with dopamine uptake inhibitors an effective and specific blockade of stimulant self-administration is obtained. Actions of stimulant drugs related to their abuse induce unique changes in σR activity and the changes induced potentially create redundant, and once established, independent reinforcement pathways. Concomitant targeting of both dopaminergic pathways and σR proteins produces a selective antagonism of stimulant self-administration, suggesting new avenues for combination chemotherapies to specifically combat stimulant abuse. PMID:26650253

Pertussis toxin-sensitive G-protein mediates the alpha 2-adrenergic receptor inhibition of melatonin release in photoreceptive chick pineal cell cultures

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

Pratt, B.L.; Takahashi, J.S.

The avian pineal gland is a photoreceptive organ that has been shown to contain postjunctional alpha 2-adrenoceptors that inhibit melatonin synthesis and/or release upon receptor activation. Physiological response and (32P)ADP ribosylation experiments were performed to investigate whether pertussis toxin-sensitive guanine nucleotide-binding proteins (G-proteins) were involved in the transduction of the alpha 2-adrenergic signal. For physiological response studies, the effects of pertussis toxin on melatonin release in dissociated cell cultures exposed to norepinephrine were assessed. Pertussis toxin blocked alpha 2-adrenergic receptor-mediated inhibition in a dose-dependent manner. Pertussis toxin-induced blockade appeared to be noncompetitive. One and 10 ng/ml doses of pertussis toxinmore » partially blocked and a 100 ng/ml dose completely blocked norepinephrine-induced inhibition. Pertussis toxin-catalyzed (32P)ADP ribosylation of G-proteins in chick pineal cell membranes was assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography. Membranes were prepared from cells that had been pretreated with 0, 1, 10, or 100 ng/ml pertussis toxin. In the absence of pertussis toxin pretreatment, two major proteins of 40K and 41K mol wt (Mr) were labeled by (32P)NAD. Pertussis toxin pretreatment of pineal cells abolished (32P) radiolabeling of the 40K Mr G-protein in a dose-dependent manner. The norepinephrine-induced inhibition of both cAMP efflux and melatonin release, as assessed by RIA of medium samples collected before membrane preparation, was also blocked in a dose-dependent manner by pertussis toxin. Collectively, these results suggest that a pertussis toxin-sensitive 40K Mr G-protein labeled by (32P)NAD may be functionally associated with alpha 2-adrenergic signal transduction in chick pineal cells.« less

A novel mechanism by which hepatocyte growth factor blocks tubular epithelial to mesenchymal transition.

PubMed

Yang, Junwei; Dai, Chunsun; Liu, Youhua

2005-01-01

Hepatocyte growth factor (HGF) is a potent antifibrotic cytokine that blocks tubular epithelial to mesenchymal transition (EMT) induced by TGF-beta1. However, the underlying mechanism remains largely unknown. This study investigated the signaling events that lead to HGF blockade of the TGF-beta1-initiated EMT. Incubation of human kidney epithelial cells HKC with HGF only marginally affected the expression of TGF-beta1 and its type I and type II receptors, suggesting that disruption of TGF-beta1 signaling likely plays a critical role in mediating HGF inhibition of TGF-beta1 action. However, HGF neither affected TGF-beta1-induced Smad-2 phosphorylation and its subsequent nuclear translocation nor influenced the expression of inhibitory Smad-6 and -7 in tubular epithelial cells. HGF specifically induced the expression of Smad transcriptional co-repressor SnoN but not Ski and TG-interacting factor at both mRNA and protein levels in HKC cells. SnoN physically interacted with activated Smad-2 by forming transcriptionally inactive complex and overrode the profibrotic action of TGF-beta1. In vivo, HGF did not affect Smad-2 activation and its nuclear accumulation in tubular epithelium, but it restored SnoN protein abundance in the fibrotic kidney in obstructive nephropathy. Hence, HGF blocks EMT by antagonizing TGF-beta1's action via upregulating Smad transcriptional co-repressor SnoN expression. These findings not only identify a novel mode of interaction between the signals activated by HGF receptor tyrosine kinase and TGF-beta receptor serine/threonine kinases but also illustrate the feasibility of confining Smad activity as an effective strategy for blocking renal fibrosis.

Fear Potentiated Startle Increases Phospholipase D (PLD) Expression/Activity and PLD-Linked Metabotropic Glutamate Receptor Mediated Post-Tetanic Potentiation in Rat Amygdala

PubMed Central

Krishnan, Balaji; Scott, Michael T.; Pollandt, Sebastian; Schroeder, Bradley; Kurosky, Alexander; Shinnick-Gallagher, Patricia

2016-01-01

Long-term memory (LTM) of fear stores activity dependent modifications that include changes in amygdala signaling. Previously, we identified an enhanced probability of release of glutamate mediated signaling to be important in rat fear potentiated startle (FPS), a well-established translational behavioral measure of fear. Here, we investigated short- and long-term synaptic plasticity in FPS involving metabotropic glutamate receptors (mGluRs) and associated downstream proteomic changes in the thalamic-lateral amygdala pathway (Th-LA). Aldolase A, an inhibitor of phospholipase D (PLD), expression was reduced, concurrent with significantly elevated PLD protein expression. Blocking the PLD-mGluR signaling significantly reduced PLD activity. While transmitter release probability increased in FPS, PLD-mGluR agonist and antagonist actions were occluded. In the unpaired group (UNP), blocking the PLD-mGluR increased while activating the receptor decreased transmitter release probability, consistent with decreased synaptic potentials during tetanic stimulation. FPS Post-tetanic potentiation (PTP) immediately following long-term potentiation (LTP) induction was significantly increased. Blocking PLD-mGluR signaling prevented PTP and reduced cumulative PTP probability but not LTP maintenance in both groups. These effects are similar to those mediated through mGluR7, which is co-immunoprecipitated with PLD in FPS. Lastly, blocking mGluR-PLD in the rat amygdala was sufficient to prevent behavioral expression of fear memory. Thus, our study in the Th-LA pathway provides the first evidence for PLD as an important target of mGluR signaling in amygdala fear-associated memory. Importantly, the PLD-mGluR provides a novel therapeutic target for treating maladaptive fear memories in posttraumatic stress and anxiety disorders. PMID:26748024

Orexin Receptors: Pharmacology and Therapeutic Opportunities

PubMed Central

Scammell, Thomas E.; Winrow, Christopher J.

2011-01-01

Orexin-A and -B (also known as hypocretin-1 and -2) are neuropeptides produced in the lateral hypothalamus that promote many aspects of arousal through the OX1 and OX2 receptors. In fact, they are necessary for normal wakefulness, as loss of the orexin-producing neurons causes narcolepsy in humans and rodents. This has generated considerable interest in developing small-molecule orexin receptor antagonists as a novel therapy for the treatment of insomnia. Orexin antagonists, especially those that block OX2 or both OX1 and OX2 receptors, clearly promote sleep in animals, and clinical results are encouraging: Several compounds are in Phase III trials. As the orexin system mainly promotes arousal, these new compounds will likely improve insomnia without incurring many of the side effects encountered with current medications. PMID:21034217

Orexin receptors: pharmacology and therapeutic opportunities.

PubMed

Scammell, Thomas E; Winrow, Christopher J

2011-01-01

Orexin-A and -B (also known as hypocretin-1 and -2) are neuropeptides produced in the lateral hypothalamus that promote many aspects of arousal through the OX1 and OX2 receptors. In fact, they are necessary for normal wakefulness, as loss of the orexin-producing neurons causes narcolepsy in humans and rodents. This has generated considerable interest in developing small-molecule orexin receptor antagonists as a novel therapy for the treatment of insomnia. Orexin antagonists, especially those that block OX2 or both OX1 and OX2 receptors, clearly promote sleep in animals, and clinical results are encouraging: Several compounds are in Phase III trials. As the orexin system mainly promotes arousal, these new compounds will likely improve insomnia without incurring many of the side effects encountered with current medications.

Assembly of high-affinity insulin receptor agonists and antagonists from peptide building blocks

PubMed Central

Schäffer, Lauge; Brissette, Renee E.; Spetzler, Jane C.; Pillutla, Renuka C.; Østergaard, Søren; Lennick, Michael; Brandt, Jakob; Fletcher, Paul W.; Danielsen, Gillian M.; Hsiao, Ku-Chuan; Andersen, Asser S.; Dedova, Olga; Ribel, Ulla; Hoeg-Jensen, Thomas; Hansen, Per Hertz; Blume, Arthur J.; Markussen, Jan; Goldstein, Neil I.

2003-01-01

Insulin is thought to elicit its effects by crosslinking the two extracellular α-subunits of its receptor, thereby inducing a conformational change in the receptor, which activates the intracellular tyrosine kinase signaling cascade. Previously we identified a series of peptides binding to two discrete hotspots on the insulin receptor. Here we show that covalent linkage of such peptides into homodimers or heterodimers results in insulin agonists or antagonists, depending on how the peptides are linked. An optimized agonist has been shown, both in vitro and in vivo, to have a potency close to that of insulin itself. The ability to construct such peptide derivatives may offer a path for developing agonists or antagonists for treatment of a wide variety of diseases. PMID:12684539

Caveolin-1 regulates chemokine receptor 5-mediated contribution of bone marrow-derived cells to dermal fibrosis

PubMed Central

Lee, Rebecca; Perry, Beth; Heywood, Jonathan; Reese, Charles; Bonner, Michael; Hatfield, Corey M.; Silver, Richard M.; Visconti, Richard P.; Hoffman, Stanley; Tourkina, Elena

2014-01-01

In fibrotic diseases caveolin-1 underexpression in fibroblasts results in collagen overexpression and in monocytes leads to hypermigration. These profibrotic behaviors are blocked by the caveolin-1 scaffolding domain peptide (CSD) which compensates for caveolin-1 deficiency. Monocytes and fibroblasts are related in that monocytes are the progenitors of fibrocytes (CD45+/Collagen I+ cells) that, in turn, are the progenitors of many fibroblasts in fibrotic tissues. In an additional anti-fibrotic activity, CSD blocks monocyte differentiation into fibrocytes. We studied a mouse fibrosis model (Pump Model) involving systemic bleomycin delivery that closely models scleroderma (SSc) in several ways, the most important of which for this study is that fibrosis is observed in the lungs, skin, and internal organs. We show here that dermal thickness is increased 2-fold in the Pump Model and that this effect is almost completely blocked by CSD (p < 0.001). Concomitantly, the subcutaneous fat layer becomes >80% thinner. This effect is also blocked by CSD (p < 0.001). Even in mice receiving vehicle instead of bleomycin, CSD increases the thickness of the fat layer. To study the mechanisms of action of bleomycin and CSD, we examined the accumulation of the chemokine receptor CCR5 and its ligands MIP1α and MIP1β in fibrotic tissue and their roles in monocyte migration. Fibrocytes and other leukocytes expressing CCR5 and its ligands were present at high levels in the fibrotic dermis of SSc patients and Pump Model mice while CSD blocked their accumulation in mouse dermis. Migration toward CCR5 ligands of SSc monocytes and Pump Model bone marrow cells was 3-fold greater than cells from control subjects. This enhanced migration was almost completely blocked by CSD. These results suggest that low monocyte caveolin-1 promotes fibrosis by enhancing the recruitment of fibrocytes and their progenitors into affected tissue. PMID:24966836

Bidirectional modulation of visual plasticity by cholinergic receptor subtypes in the frog optic tectum

PubMed Central

Yu, Chuan-Jiang; Butt, Christopher M.; Debski, Elizabeth A.

2008-01-01

Cholinergic input to the optic tectum is necessary for visual map maintenance. To understand why, we examined the effects of activation of the different cholinergic receptor subtypes in tectal brain slices and determined whether the retinotectal map was affected by manipulations of their activity in vivo. Both α-bungarotoxin sensitive and insensitive nicotinic receptor agonists increased spontaneous postsynaptic currents (sPSCs) in a subpopulation of patch-clamped tectal cells; application of subtype selective receptor antagonists reduced nicotine-induced increases in sPSCs. Activation of α-bungarotoxin insensitive nicotinic receptors also induced substantial inward current in some cells. Muscarinic receptor mediated outward current responses were blocked by the M2-like muscarinic receptor antagonists himbacine or AF-DX 384 and mimicked by application of the M2-like agonist oxotremorine. A less frequently observed muscarinic response involving a change in sPSC frequency appeared to be mediated by M1-like muscarinic receptors. In separate experiments, pharmacological manipulation of cholinergic receptor subtype activation led to changes in the activity-dependent visual map created in the tectum by retinal ganglion cell terminals. Chronic exposure of the tectum to either α-bungarotoxin insensitive, α-bungarotoxin sensitive or M1-like receptor antagonists resulted in map disruption. However, treatment with the M2-like receptor antagonist, AF-DX 384, compressed the map. We conclude that nicotinic or M1-like muscarinic receptors control input to tectal cells while α-bungarotoxin insensitive nicotinic receptors and M2-like muscarinic receptors change tectal cell responses to that input. Blockade of the different cholinergic receptor subtypes can have opposing effects on map topography that are consistent with expected effects on tectal cell activity levels. PMID:12670313

Histamine influences body temperature by acting at H1 and H3 receptors on distinct populations of preoptic neurons

PubMed Central

Lundius, Ebba Gregorsson; Sanchez-Alavez, Manuel; Ghochani, Yasmin; Klaus, Joseph; Tabarean, Iustin V.

2010-01-01

The preoptic area/anterior hypothalamus (PO/AH), a region that contains neurons that control thermoregulation, is the main locus at which histamine affects body temperature. Here we report that histamine reduced the spontaneous firing rate of GABAergic preoptic neurons by activating H3 subtype histamine receptors. This effect involved a decrease in the level of phosphorylation of the extracellular signal-regulated kinase (ERK) and was not dependent on synaptic activity. Furthermore, a population of nonGABAergic neurons was depolarized and their firing rate was enhanced by histamine acting at H1 subtype receptors. In our experiments, activation of the H1R receptors was linked to the PLC pathway and Ca2+ release from intracellular stores. This depolarization persisted in TTX or when fast synaptic potentials were blocked indicating that it represents a postsynaptic effect. Single-cell reverse transcription –PCR analysis revealed expression of H3 receptors in a population of GABAergic neurons while H1 receptors were expressed in nonGABAergic cells. Histamine applied in the median preoptic nucleus induced a robust, long lasting hyperthermia effect that was mimicked by either H1 or H3 histamine receptor subtype specific agonists. Our data indicate that histamine modulates the core body temperature by acting at two distinct populations of preoptic neurons which express H1 and H3 receptor subtypes, respectively. PMID:20335473

Histamine influences body temperature by acting at H1 and H3 receptors on distinct populations of preoptic neurons.

PubMed

Lundius, Ebba Gregorsson; Sanchez-Alavez, Manuel; Ghochani, Yasmin; Klaus, Joseph; Tabarean, Iustin V

2010-03-24

The preoptic area/anterior hypothalamus, a region that contains neurons that control thermoregulation, is the main locus at which histamine affects body temperature. Here we report that histamine reduced the spontaneous firing rate of GABAergic preoptic neurons by activating H3 subtype histamine receptors. This effect involved a decrease in the level of phosphorylation of the extracellular signal-regulated kinase and was not dependent on synaptic activity. Furthermore, a population of non-GABAergic neurons was depolarized, and their firing rate was enhanced by histamine acting at H1 subtype receptors. In our experiments, activation of the H1R receptors was linked to the PLC pathway and Ca(2+) release from intracellular stores. This depolarization persisted in TTX or when fast synaptic potentials were blocked, indicating that it represents a postsynaptic effect. Single-cell reverse transcription-PCR analysis revealed expression of H3 receptors in a population of GABAergic neurons, while H1 receptors were expressed in non-GABAergic cells. Histamine applied in the median preoptic nucleus induced a robust, long-lasting hyperthermia effect that was mimicked by either H1 or H3 histamine receptor subtype-specific agonists. Our data indicate that histamine modulates the core body temperature by acting at two distinct populations of preoptic neurons that express H1 and H3 receptor subtypes, respectively.

Three days after a single exposure to ozone, the mechanism of airway hyperreactivity is dependent on substance P and nerve growth factor.

PubMed

Verhein, Kirsten C; Hazari, Mehdi S; Moulton, Bart C; Jacoby, Isabella W; Jacoby, David B; Fryer, Allison D

2011-02-01

Ozone causes persistent airway hyperreactivity in humans and animals. One day after ozone exposure, airway hyperreactivity is mediated by release of eosinophil major basic protein that inhibits neuronal M(2) muscarinic receptors, resulting in increased acetylcholine release and increased smooth muscle contraction in guinea pigs. Three days after ozone, IL-1β, not eosinophils, mediates ozone-induced airway hyperreactivity, but the mechanism at this time point is largely unknown. IL-1β increases NGF and the tachykinin substance P, both of which are involved in neural plasticity. These experiments were designed to test whether there is a role for NGF and tachykinins in sustained airway hyperreactivity following a single ozone exposure. Guinea pigs were exposed to filtered air or ozone (2 parts per million, 4 h). In anesthetized and vagotomized animals, ozone potentiated vagally mediated airway hyperreactivity 24 h later, an effect that was sustained over 3 days. Pretreatment with antibody to NGF completely prevented ozone-induced airway hyperreactivity 3 days, but not 1 day, after ozone and significantly reduced the number of substance P-positive airway nerve bundles. Three days after ozone, NK(1) and NK(2) receptor antagonists also blocked this sustained hyperreactivity. Although the effect of inhibiting NK(2) receptors was independent of ozone, the NK(1) receptor antagonist selectively blocked vagal hyperreactivity 3 days after ozone. These data confirm mechanisms of ozone-induced airway hyperreactivity change over time and demonstrate 3 days after ozone that there is an NGF-mediated role for substance P, or another NK(1) receptor agonist, that enhances acetylcholine release and was not present 1 day after ozone.

Three days after a single exposure to ozone, the mechanism of airway hyperreactivity is dependent on substance P and nerve growth factor

PubMed Central

Verhein, Kirsten C.; Hazari, Mehdi S.; Moulton, Bart C.; Jacoby, Isabella W.; Jacoby, David B.

2011-01-01

Ozone causes persistent airway hyperreactivity in humans and animals. One day after ozone exposure, airway hyperreactivity is mediated by release of eosinophil major basic protein that inhibits neuronal M2 muscarinic receptors, resulting in increased acetylcholine release and increased smooth muscle contraction in guinea pigs. Three days after ozone, IL-1β, not eosinophils, mediates ozone-induced airway hyperreactivity, but the mechanism at this time point is largely unknown. IL-1β increases NGF and the tachykinin substance P, both of which are involved in neural plasticity. These experiments were designed to test whether there is a role for NGF and tachykinins in sustained airway hyperreactivity following a single ozone exposure. Guinea pigs were exposed to filtered air or ozone (2 parts per million, 4 h). In anesthetized and vagotomized animals, ozone potentiated vagally mediated airway hyperreactivity 24 h later, an effect that was sustained over 3 days. Pretreatment with antibody to NGF completely prevented ozone-induced airway hyperreactivity 3 days, but not 1 day, after ozone and significantly reduced the number of substance P-positive airway nerve bundles. Three days after ozone, NK1 and NK2 receptor antagonists also blocked this sustained hyperreactivity. Although the effect of inhibiting NK2 receptors was independent of ozone, the NK1 receptor antagonist selectively blocked vagal hyperreactivity 3 days after ozone. These data confirm mechanisms of ozone-induced airway hyperreactivity change over time and demonstrate 3 days after ozone that there is an NGF-mediated role for substance P, or another NK1 receptor agonist, that enhances acetylcholine release and was not present 1 day after ozone. PMID:21056958

Different protein kinase C isoenzymes mediate inhibition of cardiac rapidly activating delayed rectifier K+ current by different G-protein coupled receptors.

PubMed

Liu, Xueli; Wang, Yuhong; Zhang, Hua; Shen, Li; Xu, Yanfang

2017-12-01

Elevated angiotensin II (Ang II) and sympathetic activity contributes to a high risk of ventricular arrhythmias in heart disease. The rapidly activating delayed rectifier K + current (I Kr ) carried by the hERG channels plays a critical role in cardiac repolarization, and decreased I Kr is involved in increased cardiac arrhythmogenicity. Stimulation of α 1A -adrenoreceptors or angiotensin II AT 1 receptors is known to inhibit I Kr via PKC. Here, we have identified the PKC isoenzymes mediating the inhibition of I Kr by activation of these two different GPCRs. The whole-cell patch-clamp technique was used to record I Kr in guinea pig cardiomyocytes and HEK293 cells co-transfected with hERG and α 1A -adrenoreceptor or AT 1 receptor genes. A broad spectrum PKC inhibitor Gö6983 (not inhibiting PKCε), a selective cPKC inhibitor Gö6976 and a PKCα-specific inhibitor peptide, blocked the inhibition of I Kr by the α 1A -adrenoreceptor agonist A61603. However, these inhibitors did not affect the reduction of I Kr by activation of AT 1 receptors, whereas the PKCε-selective inhibitor peptide did block the effect. The effects of angiotensin II and the PKCε activator peptide were inhibited in mutant hERG channels in which 17 of the 18 PKC phosphorylation sites were deleted, whereas a deletion of the N-terminus of the hERG channels selectively prevented the inhibition elicited by A61603 and the cPKC activator peptide. Our results indicated that inhibition of I Kr by activation of α 1A -adrenoreceptors or AT 1 receptors were mediated by PKCα and PKCε isoforms respectively, through different molecular mechanisms. © 2017 The British Pharmacological Society.

Virally mediated increased neurotensin 1 receptor in the nucleus accumbens decreases behavioral effects of mesolimbic system activation.

PubMed

Cáceda, Ricardo; Kinkead, Becky; Owens, Michael J; Nemeroff, Charles B

2005-12-14

Dopamine receptor agonist and NMDA receptor antagonist activation of the mesolimbic dopamine system increases locomotion and disrupts prepulse inhibition of the acoustic startle response (PPI), paradigms frequently used to study both the pharmacology of antipsychotic drugs and drugs of abuse. In rats, virally mediated overexpression of the neurotensin 1 (NT1) receptor in the nucleus accumbens antagonized d-amphetamine- and dizocilpine-induced PPI disruption, hyperlocomotion, and D-amphetamine-induced rearing. The NT receptor antagonist SR 142948A [2-[[5-(2,6-dimethoxyphenyl)-1-(4-N-(3-dimethylaminopropyl)-N-methylcarbamoyl)-2-isopropylphenyl)-1H-pyrazole-3-carbonyl]amino] adamantane-2-carboxylic acid, hydrochloride] blocked inhibition of dizocilpine-induced hyperlocomotion mediated by overexpression of the NT1 receptor. Together, these results suggest that increased nucleus accumbens NT neurotransmission, via the NT1 receptor, can decrease the effects of activation of the mesolimbic dopamine system and disruption of the glutamatergic input from limbic cortices, resembling the action of the atypical antipsychotic drug clozapine. In contrast to clozapine, virally mediated overexpression of the NT1 receptor in the nucleus accumbens had prolonged protective effects (up to 4 weeks after viral injection) without perturbing baseline PPI and locomotor behaviors. These data further confirm the NT1 receptor as the receptor mediating the antistimulant- and antipsychotic-like properties of NT and provide rationale for the development of NT1 receptor agonists as novel antipsychotic drugs. In addition, the NT1 receptor vector might be a valuable tool for understanding the mechanism of action of antipsychotic drugs and drugs of abuse and may have potential therapeutic applications.

Glutamate Signaling and Mitochnodrial Dysfunction in Models of Parkinson’s Disease

DTIC Science & Technology

2012-12-01

synaptic response; 3) antagonism of ionotropic glutamate receptors essentially eliminates the response to PPN stimulation, suggesting that nicotinic...systemic administration of drug, significantly lowers mitochondrial oxidant stress. Third, antagonizing glutamatergic NMDA receptors , but not...metabotropic glutamate receptors , diminishes oxidant stress in dopaminergic neurons; stimulating NMDA receptors raises stress levels. Fourth, blocking

Characterization of prejunctional 5-HT receptors mediating inhibition of sympathetic vasopressor responses in the pithed rat.

PubMed Central

Villalón, C. M.; Contreras, J.; Ramírez-San Juan, E.; Castillo, C.; Perusquía, M.; Terrón, J. A.

1995-01-01

1. It has recently been shown that continuous infusions of 5-hydroxytryptamine (5-HT) are able to inhibit, in a dose-dependent manner, the pressor responses induced by preganglionic (T7-T9) sympathetic stimulation in pithed rats pretreated with desipramine (50 micrograms kg-1, i.v.). This inhibitory effect, besides being significantly more pronounced at lower frequencies of stimulation (0.03-I Hz) and devoid of tachyphylaxis, is reversible after interrupting the infusions of 5-HT (up to 5.6 micrograms kg-1 min-1). In the present study we have characterized the pharmacological profile of the receptors mediating the above inhibitory effect of 5-HT. 2. The inhibition induced by 5.6 micrograms kg-1 min-1 of 5-HT on sympathetically-induced pressor responses was not blocked after i.v. treatment with physiological saline (1 ml kg-1), ritanserin (0.1 mg kg-1), MDL 72222 (0.15 mg kg-1) or tropisetron (3 mg kg-1), which did not modify the sympathetically-induced pressor responses per se, but was significantly antagonized by the 5-HT1-like and 5-HT2 receptor antagonist, methysergide (0.3 mg kg-1), which also produced a slight attenuation of the pressor responses to 0.03 and 0.1 Hz per se. 3. Unexpectedly and contrasting with methysergide, the 5-HT1-like and 5-HT2 receptor antagonists, methiothepin (0.01, 0.03 and 0.1 mg kg-1) and metergoline (1 and 3 mg kg-1), apparently failed to block the above 5-HT-induced inhibition. Nevertheless, it is noteworthy that these antagonists also blocked the electrically-induced pressor responses per se, presumably by blockade of vascular alpha 1-adrenoceptors and, indeed, this property might have masked their potential antagonism at the inhibitory 5-HT1-like receptors. 4. Consistent with the above findings, 5-carboxamidotryptamine (5-CT, a potent 5-HT1-like receptor agonist), metergoline and methysergide mimicked the inhibitory action of 5-HT with the following rank order of agonist potency: 5CT > > 5-HT > metergoline > or = methysergide. 5. Taken together, the above results suggest that the inhibitory action of 5-HT on the electrically-induced pressor responses is primarily mediated by an action on inhibitory prejunctional 5-HT1-like receptors leading to a decrease in the sympathetic nerve discharge. Interestingly, 5-HT-induced excitatory mechanisms could be made manifest once the inhibitory action of 5-HT had been antagonized. PMID:8719815

A High Content Drug Screen Identifies Ursolic Acid as an Inhibitor of Amyloid β Protein Interactions with Its Receptor CD36*

PubMed Central

Wilkinson, Kim; Boyd, Justin D.; Glicksman, Marcie; Moore, Kathryn J.; El Khoury, Joseph

2011-01-01

A pathological hallmark of Alzheimer disease (AD) is deposition of amyloid β (Aβ) in the brain. Aβ binds to microglia via a receptor complex that includes CD36 leading to production of proinflammatory cytokines and neurotoxic reactive oxygen species and subsequent neurodegeneration. Interruption of Aβ binding to CD36 is a potential therapeutic strategy for AD. To identify pharmacologic inhibitors of Aβ binding to CD36, we developed a 384-well plate assay for binding of fluorescently labeled Aβ to Chinese hamster ovary cells stably expressing human CD36 (CHO-CD36) and screened an Food and Drug Administration-approved compound library. The assay was optimized based on the cells' tolerance to dimethyl sulfoxide, Aβ concentration, time required for Aβ binding, reproducibility, and signal-to-background ratio. Using this assay, we identified four compounds as potential inhibitors of Aβ binding to CD36. These compounds were ursolic acid, ellipticine, zoxazolamine, and homomoschatoline. Of these compounds, only ursolic acid, a naturally occurring pentacyclic triterpenoid, successfully inhibited binding of Aβ to CHO-CD36 cells in a dose-dependent manner. The ursolic acid effect reached a plateau at ∼20 μm, with a maximal inhibition of 64%. Ursolic acid also blocked binding of Aβ to microglial cells and subsequent ROS production. Our data indicate that cell-based high-content screening of small molecule libraries for their ability to block binding of Aβ to its receptors is a useful tool to identify novel inhibitors of receptors involved in AD pathogenesis. Our data also suggest that ursolic acid is a potential therapeutic agent for AD via its ability to block Aβ-CD36 interactions. PMID:21835916