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Sample records for 5-ht3 receptor activation

  1. Structure-activity relationships of quinoxaline-based 5-HT3A and 5-HT3AB receptor-selective ligands.

    PubMed

    Thompson, Andrew J; Verheij, Mark H P; van Muijlwijk-Koezen, Jacqueline E; Lummis, Sarah C R; Leurs, Rob; de Esch, Iwan J P

    2013-06-01

    Until recently, discriminating between homomeric 5-HT3A and heteromeric 5-HT3AB receptors was only possible with ligands that bind in the receptor pore. This study describes the first series of ligands that can discriminate between these receptor types at the level of the orthosteric binding site. During a recent fragment screen, 2-chloro-3-(4-methylpiperazin-1-yl)quinoxaline (VUF10166) was identified as a ligand that displays an 83-fold difference in [(3)H]granisetron binding affinity between 5-HT3A and 5-HT3AB receptors. Fragment hit exploration, initiated from VUF10166 and 3-(4-methylpiperazin-1-yl)quinoxalin-2-ol, resulted in a series of compounds with higher affinity at either 5-HT3A or 5-HT3AB receptors. These ligands reveal that a single atom is sufficient to change the selectivity profile of a compound. At the extremes of the new compounds were 2-amino-3-(4-methylpiperazin-1-yl)quinoxaline, which showed 11-fold selectivity for the 5-HT3A receptor, and 2-(4-methylpiperazin-1-yl)quinoxaline, which showed an 8.3-fold selectivity for the 5-HT3AB receptor. These compounds represent novel molecular tools for studying 5-HT3 receptor subtypes and could help elucidate their physiological roles.

  2. Impact of intracellular domain flexibility upon properties of activated human 5-HT3 receptors*

    PubMed Central

    Kozuska, J L; Paulsen, I M; Belfield, W J; Martin, I L; Cole, D J; Holt, A; Dunn, S M J

    2014-01-01

    Background and Purpose It has been proposed that arginine residues lining the intracellular portals of the homomeric 5-HT3A receptor cause electrostatic repulsion of cation flow, accounting for a single-channel conductance substantially lower than that of the 5-HT3AB heteromer. However, comparison of receptor homology models for wild-type pentamers suggests that salt bridges in the intracellular domain of the homomer may impart structural rigidity, and we hypothesized that this rigidity could account for the low conductance. Experimental Approach Mutations were introduced into the portal region of the human 5-HT3A homopentamer, such that putative salt bridges were broken by neutralizing anionic partners. Single-channel and whole cell currents were measured in transfected tsA201 cells and in Xenopus oocytes respectively. Computational simulations of protein flexibility facilitated comparison of wild-type and mutant receptors. Key Results Single-channel conductance was increased substantially, often to wild-type heteromeric receptor values, in most 5-HT3A mutants. Conversely, introduction of arginine residues to the portal region of the heteromer, conjecturally creating salt bridges, decreased conductance. Gating kinetics varied significantly between different mutant receptors. EC50 values for whole-cell responses to 5-HT remained largely unchanged, but Hill coefficients for responses to 5-HT were usually significantly smaller in mutants. Computational simulations suggested increased flexibility throughout the protein structure as a consequence of mutations in the intracellular domain. Conclusions and Implications These data support a role for intracellular salt bridges in maintaining the quaternary structure of the 5-HT3 receptor and suggest a role for the intracellular domain in allosteric modulation of cooperativity and agonist efficacy. Linked Article This article is commented on by Vardy and Kenakin, pp. 1614–1616 of volume 171 issue 7. To view this commentary

  3. Subunit rotation models activation of serotonin 5-HT3AB receptors by agonists

    NASA Astrophysics Data System (ADS)

    Maksay, Gábor; Simonyi, Miklós; Bikádi, Zsolt

    2004-10-01

    The N-terminal extracellular regions of heterooligomeric 3AB-type human 5-hydroxytryptamine receptors (5-HT 3ABR) were modelled based on the crystal structure of snail acetylcholine binding protein AChBP. Stepwise rotation of subunit A by 5° was performed between -10° and 15° to mimic agonist binding and receptor activation. Anticlockwise rotation reduced the size of the binding cavity in interface AB and reorganised the network of hydrogen bonds along the interface. AB subunit dimers with different rotations were applied for docking of ligands with different efficacies: 5-HT, m-chlorophenylbiguanide, SR 57227, quinolinyl piperazine and lerisetron derivatives. All ligands were docked into the dimer with -10° rotation representing ligand-free, open binding cavities similarly, without pharmacological discrimination. Their ammonium ions were in hydrogen bonding distance to the backbone carbonyl of W183. Anticlockwise rotation and contraction of the binding cavity led to distinctive docking interactions of agonists with E129 and cation-π interactions of their ammonium ions. Side chains of several further amino acids participating in docking (Y143, Y153, Y234 and E236) are in agreement with the effects of point mutations in the binding loops. Our model postulates that 5-HT binds to W183 in a hydrophobic cleft as well as to E236 in a hydrophilic vestibule. Then it elicits anticlockwise rotation to draw in loop C via π-cation-π interactions of␣its ammonium ion with W183 and Y234. Finally, closure of the binding cavity might end in rebinding of 5-HT to E129 in the hydrophilic vestibule.

  4. Spinal 5-HT(3) receptor activation induces behavioral hypersensitivity via a neuronal-glial-neuronal signaling cascade.

    PubMed

    Gu, Ming; Miyoshi, Kan; Dubner, Ronald; Guo, Wei; Zou, Shiping; Ren, Ke; Noguchi, Koichi; Wei, Feng

    2011-09-07

    Recent studies indicate that the descending serotonin (5-HT) system from the rostral ventromedial medulla (RVM) in the brainstem and the 5-HT(3) receptor subtype in the spinal dorsal horn are involved in enhanced descending pain facilitation after tissue and nerve injury. However, the mechanisms underlying the activation of the 5-HT(3) receptor and its contribution to facilitation of pain remain unclear. In the present study, activation of spinal 5-HT(3) receptor by intrathecal injection of a selective 5-HT(3) receptor agonist, SR57227, induced spinal glial hyperactivity, neuronal hyperexcitability, and pain hypersensitivity in rats. We found that there was neuron-to-microglia signaling via chemokine fractalkine, microglia to astrocyte signaling via the cytokine IL-18, astrocyte to neuronal signaling by IL-1β, and enhanced activation of GluN (NMDA) receptors in the spinal dorsal horn. In addition, exogenous brain-derived neurotrophic factor-induced descending pain facilitation was accompanied by upregulation of CD11b and GFAP expression in the spinal dorsal horn after microinjection in the RVM, and these events were significantly prevented by functional blockade of spinal 5-HT(3) receptors. Enhanced expression of spinal CD11b and GFAP after hindpaw inflammation was also attenuated by molecular depletion of the descending 5-HT system by intra-RVM Tph-2 shRNA interference. Thus, these findings offer new insights into the cellular and molecular mechanisms at the spinal level responsible for descending 5-HT-mediated pain facilitation during the development of persistent pain after tissue and nerve injury. New pain therapies should focus on prime targets of descending facilitation-induced glial involvement, and in particular the blocking of intercellular signaling transduction between neuron and glia.

  5. Spinal 5-HT3 receptor activation induces behavioral hypersensitivity via a neuronal-glial-neuronal signaling cascade

    PubMed Central

    Gu, Ming; Miyoshi, Kan; Dubner, Ronald; Guo, Wei; Zou, Shiping; Ren, Ke; Noguchi, Koichi; Wei, Feng

    2011-01-01

    Recent studies indicate that the descending serotonin (5-HT) system from the rostral ventromedial medulla (RVM) in brainstem and the 5-HT3 receptor subtype in the spinal dorsal horn are involved in enhanced descending pain facilitation after tissue and nerve injury. However, the mechanisms underlying the activation of the 5-HT3 receptor and its contribution to facilitation of pain remain unclear. In the present study, activation of spinal 5-HT3 receptor by intrathecal injection of a selective 5-HT3 receptor agonist SR 57227 induced spinal glial hyperactivity, neuronal hyperexcitability and pain hypersensitivity in rats. We found that there was neuron-to-microglia signaling via chemokine fractalkine, microglia to astrocyte signaling via cytokine IL-18, astrocyte to neuronal signaling by IL-1β, and enhanced activation of GluN (NMDA) receptors in the spinal dorsal horn. In addition, exogenous BDNF-induced descending pain facilitation was accompanied with up-regulation of CD11b and GFAP expression in the spinal dorsal horn after microinjection in the RVM, which were significantly prevented by functional blockade of spinal 5-HT3 receptors. Enhanced expression of spinal CD11b and GFAP after hindpaw inflammation was also attenuated by molecular depletion of the descending 5-HT system by intra-RVM Tph-2 shRNA interference. Thus, these findings offer new insights into the cellular and molecular mechanisms at the spinal level responsible for descending 5-HT-mediated pain facilitation during the development of persistent pain after tissue and nerve injury. New pain therapies should focus on prime targets of descending facilitation-induced glial involvement, and in particular the blocking of intercellular signaling transduction between neuron and glia. PMID:21900561

  6. Effects of repeated daily treatments with a 5-HT3 receptor antagonist on dopamine neurotransmission and functional activity of 5-HT3 receptors within the nucleus accumbens of Wistar rats.

    PubMed

    Liu, Wen; Thielen, Richard J; McBride, William J

    2006-06-01

    A previous study indicated that pretreatment with repeated daily injections of serotonin-3 (5-HT3) receptor antagonists subsequently reduced the effectiveness of the 5-HT3 antagonists to attenuate ethanol intake under 24-h free-choice conditions; one possibility to account for this is that the functional activity of the 5-HT3 receptor may have been altered by prior treatment with the antagonists. The present experiments were conducted to examine the effects of local perfusion of the 5-HT3 agonist 1-(m-chlorophenyl)-biguanide (CPBG) on the extracellular levels of dopamine (DA) in the nucleus accumbens (ACB) and ventral tegmental area (VTA) of adult male Wistar rats that had received repeated daily injections of the 5-HT3 antagonist, MDL 72222 (MDL). In vivo microdialysis was used to test the hypothesis that alterations in 5-HT3 receptor function have occurred with repeated antagonist injections. One group was given daily injections of MDL (1 mg/kg, s.c.) for 10 consecutive days (MDL group), and the other group was administered saline for 10 days (saline group). On the day after the last treatment, rats were implanted with a unilateral guide cannula aimed at either the ACB or VTA. Two days later, the microdialysis probe was inserted into the guide cannula; on the next day, microdialysis experiments were conducted to determine the extracellular levels of DA in the ACB or VTA. Local perfusion of CPBG (17.5, 35, 70 microM) in the ACB significantly stimulated DA release in the saline- and MDL-treated animals. In terms of percent baseline, the CPBG-stimulated DA release was higher in the MDL-treated group than in the saline-treated group in both the ACB and VTA; however, on the basis of the extracellular concentration, there were no significant differences in the ACB between the two groups. Using the no-net-flux microdialysis, it was determine that the basal extracellular concentration of DA in the ACB was approximately 60% lower in the MDL group than saline group; there

  7. Toward Biophysical Probes for the 5-HT3 Receptor: Structure−Activity Relationship Study of Granisetron Derivatives

    PubMed Central

    2010-01-01

    This report describes the synthesis and biological characterization of novel granisetron derivatives that are antagonists of the human serotonin (5-HT3A) receptor. Some of these substituted granisetron derivatives showed low nanomolar binding affinity and allowed the identification of positions on the granisetron core that might be used as attachment points for biophysical tags. A BODIPY fluorophore was appended to one such position and specifically bound to 5-HT3A receptors in mammalian cells. PMID:20146481

  8. Menthol inhibits 5-HT3 receptor-mediated currents.

    PubMed

    Ashoor, Abrar; Nordman, Jacob C; Veltri, Daniel; Yang, Keun-Hang Susan; Shuba, Yaroslav; Al Kury, Lina; Sadek, Bassem; Howarth, Frank C; Shehu, Amarda; Kabbani, Nadine; Oz, Murat

    2013-11-01

    The effects of alcohol monoterpene menthol, a major active ingredient of the peppermint plant, were tested on the function of human 5-hydroxytryptamine type 3 (5-HT3) receptors expressed in Xenopus laevis oocytes. 5-HT (1 μM)-evoked currents recorded by two-electrode voltage-clamp technique were reversibly inhibited by menthol in a concentration-dependent (IC50 = 163 μM) manner. The effects of menthol developed gradually, reaching a steady-state level within 10-15 minutes and did not involve G-proteins, since GTPγS activity remained unaltered and the effect of menthol was not sensitive to pertussis toxin pretreatment. The actions of menthol were not stereoselective as (-), (+), and racemic menthol inhibited 5-HT3 receptor-mediated currents to the same extent. Menthol inhibition was not altered by intracellular 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid injections and transmembrane potential changes. The maximum inhibition observed for menthol was not reversed by increasing concentrations of 5-HT. Furthermore, specific binding of the 5-HT3 antagonist [(3)H]GR65630 was not altered in the presence of menthol (up to 1 mM), indicating that menthol acts as a noncompetitive antagonist of the 5-HT3 receptor. Finally, 5-HT3 receptor-mediated currents in acutely dissociated nodose ganglion neurons were also inhibited by menthol (100 μM). These data demonstrate that menthol, at pharmacologically relevant concentrations, is an allosteric inhibitor of 5-HT3 receptors.

  9. Regulation of central noradrenergic activity by 5-HT(3) receptors located in the locus coeruleus of the rat.

    PubMed

    Ortega, Jorge E; Mendiguren, Aitziber; Pineda, Joseba; Meana, J Javier

    2012-06-01

    A functional interaction between serotonergic and noradrenergic systems has been shown in the locus coeruleus (LC). Noradrenaline (NA) levels in the prefrontal cortex (PFC) are dependent on the firing rate of LC neurons, which is controlled by α(2) adrenoceptors (α2ADR). The aim of the present study was to investigate the role of 5-HT(3) receptors (5HT3R) in the modulation of central noradrenergic activity. We measured extracellular NA concentrations in the LC and PFC by dual-probe microdialysis in awake rats and the firing rate of LC neurons by electrophysiological techniques in vitro. Administration of the 5HT3R agonists SR57227 (1-100 μM) and m-chlorophenylbiguanide (mCPBG, 1-100 μM) into the LC increased NA in this nucleus (E(max) = 675 ± 121% and E(max) = 5575 ± 1371%, respectively) and decreased NA in the PFC (E(max) = -49 ± 6% and E(max) = -25 ± 11%, respectively). Administration of the 5HT3R antagonist Y25130 (50 μM) into LC attenuated SR57227 effect in the LC (E(max) = 323 ± 28%) and PFC (E(max) = -37 ± 7%). The α2ADR antagonist RS79948 (1 μM) blocked the SR57227 effect in the PFC but it did not change the effect in the LC (E(max) = 677 ± 202%). In electrophysiological assays, both mCPBG (1-10 μM) and SR57227 (1-10 μM) reduced the firing rate of about 50% of tested LC neurons (maximal effect = -37 ± 2% and -31 ± 4%, respectively); this effect was partially blocked by Y25130 (50 μM). Administration of RS79948 (1 μM) reversed the inhibition induced by mCPBG. Competition radioligand assays against [(3)H]UK14304 and [(3)H]RX821002 (α2ADR selective drugs) in the rat brain cortex showed a very weak affinity of SR57227 for α2ADR, whereas the affinity of mCPBG for α2ADR was 17-fold higher than that of SR57227 for α2ADR. The present results suggest that 5HT3R stimulate NA release in the LC, which promotes simultaneously a decrease in the firing rate of LC neurons through α2ADR and then a decrease

  10. Kampo Medicine: Evaluation of the Pharmacological Activity of 121 Herbal Drugs on GABAA and 5-HT3A Receptors

    PubMed Central

    Hoffmann, Katrin M.; Herbrechter, Robin; Ziemba, Paul M.; Lepke, Peter; Beltrán, Leopoldo; Hatt, Hanns; Werner, Markus; Gisselmann, Günter

    2016-01-01

    Kampo medicine is a form of Japanese phytotherapy originating from traditional Chinese medicine (TCM). During the last several decades, much attention has been paid to the pharmacological effects of these medical plants and their constituents. However, in many cases, a systematic screening of Kampo remedies to determine pharmacologically relevant targets is still lacking. In this study, a broad screening of Kampo remedies was performed to look for pharmacologically relevant 5-HT3A and GABAA receptor ligands. Several of the Kampo remedies are currently used for symptoms such as nausea, emesis, gastrointestinal motility disorders, anxiety, restlessness, or insomnia. Therefore, the pharmacological effects of 121 herbal drugs from Kampo medicine were analyzed as ethanol tinctures on heterologously expressed 5-HT3A and GABAA receptors, due to the involvement of these receptors in such pathophysiological processes. The tinctures of Lindera aggregata (radix) and Leonurus japonicus (herba) were the most effective inhibitory compounds on the 5-HT3A receptor. Further investigation of known ingredients in these compounds led to the identification of leonurine from Leonurus as a new natural 5-HT3A receptor antagonist. Several potentiating herbs (e.g., Magnolia officinalis (cortex), Syzygium aromaticum (flos), and Panax ginseng (radix)) were also identified for the GABAA receptor, which are all traditionally used for their sedative or anxiolytic effects. A variety of tinctures with antagonistic effects Salvia miltiorrhiza (radix) were also detected. Therefore, this study reveals new insights into the pharmacological action of a broad spectrum of herbal drugs from Kampo, allowing for a better understanding of their physiological effects and clinical applications. PMID:27524967

  11. Design, synthesis and structure-activity relationship of novel quinoxalin-2-carboxamides as 5-HT3 receptor antagonists for the management of depression.

    PubMed

    Mahesh, Radhakrishnan; Devadoss, Thangaraj; Pandey, Dilip Kumar; Bhatt, Shvetank; Yadav, Shushil Kumar

    2010-11-15

    A novel series of quinoxalin-2-carboxamides were designed based on the ligand-based approach, employing a three-point pharmacophore model; it consists of an aromatic residue and a linking carbonyl group and a basic nitrogen. The target new chemical entities were synthesized from the key intermediate, quinoxalin-2-carboxylic acid, by coupling it with various amines in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and 1-hydroxybenzotriazole (HOBt). The obtained compounds' structures were confirmed by spectral data. The target new chemical entities were evaluated for their 5-HT(3) receptor antagonisms in longitudinal muscle myenteric plexus preparation from guinea pig ileum against 5-HT(3) agonist, 2-methyl-5-HT, which was expressed in the form of pA(2) value. All the synthesized compounds showed antagonism towards 5-HT(3) receptor; based on this result, a structure-activity relationship was derived, which reveals that the aromatic residue in 5-HT(3) receptor antagonists may have hydrophobic interaction with 5-HT(3) receptor. Regardless of their antagonistic potentials, all the synthesized molecules were screened for their anti-depressant potentials by using forced swim test in mice model; interestingly none of the tested compounds affect the locomotion of mice in the tested dose levels. Compounds with significant pA(2) values exhibited good anti-depressant-like activity as compared to the vehicle-treated group.

  12. Piperazine analogs of naphthyridine-3-carboxamides and indole-2-carboxamides: novel 5-HT3 receptor antagonists with antidepressant-like activity.

    PubMed

    Dhar, Arghya K; Mahesh, Radhakrishnan; Jindal, Ankur; Bhatt, Shvetank

    2015-01-01

    Series of piperazine analogs of naphthyridine-3-carboxamides and indole-2-carboxamides were designed using a ligand-based approach with consideration of the pharmacophoric requirements for 5-HT3 receptor antagonists. The title carboxamides were synthesized using appropriate synthetic routes. Initially, the 5-HT3 receptor antagonistic activity of all the compounds was determined on isolated guinea pig ileum tissue against the 5-HT3 agonist, 2-methyl-5-hydroxytryptamine, which was denoted in the form of pA2 values. The structure-activity relationship regarding the influence of the aromatic part and basic moiety as features in the 5-HT3 pharmacophore was derived. Among all the compounds screened, the piperazine derivatives of indole-2-carboxamide 13i and naphthyridine-3-carboxamide 8h exhibited prominent 5-HT3 receptor antagonism with pA2 values of 7.5 and 7.3, respectively. Subsequent investigation of the antidepressant activities of selected compounds in the mouse forced swim test (FST) led to the identification of the piperazine analogs of indole-2-carboxamide 13i and naphthyridine-3-carboxamide 8h as the most promising compounds. Both 13i and 8h demonstrated significant reduction in the duration of immobility as compared to the control. Importantly, none of the tested compounds affected the baseline locomotion of mice at the tested dose levels.

  13. Bivalent Ligands for the Serotonin 5-HT3 Receptor

    PubMed Central

    2011-01-01

    The serotonin 5-HT3 receptor is a ligand-gated ion channel, which by virtue of its pentameric architecture, can be considered to be an intriguing example of intrinsically multivalent biological receptors. This paper describes a general design approach to the study of multivalency in this multimeric ion channel. Bivalent ligands for 5-HT3 receptor have been designed by linking an arylpiperazine moiety to probes showing different functional features. Both homobivalent and heterobivalent ligands have shown 5-HT3 receptor affinity in the nanomolar range, providing evidence for the viability of our design approach. Moreover, the high affinity shown by homobivalent ligands suggests that bivalency is a promising approach in 5-HT3 receptor modulation and provides the rational basis for applying the concepts of multivalency to the study of 5-HT3 receptor function. PMID:24900351

  14. Effects of 5-HT2B, 5-HT3 and 5-HT4 receptor antagonists on gastrointestinal motor activity in dogs

    PubMed Central

    Morita, Hiroki; Mochiki, Erito; Takahashi, Nobuyuki; Kawamura, Kiyoshi; Watanabe, Akira; Sutou, Toshinaga; Ogawa, Atsushi; Yanai, Mitsuhiro; Ogata, Kyoichi; Fujii, Takaaki; Ohno, Tetsuro; Tsutsumi, Souichi; Asao, Takayuki; Kuwano, Hiroyuki

    2013-01-01

    AIM: To study the effects of 5-hydroxytryptamine (5-HT) receptor antagonists on normal colonic motor activity in conscious dogs. METHODS: Colonic motor activity was recorded using a strain gauge force transducer in 5 dogs before and after 5-HT2B, 5-HT3 and 5-HT4 receptor antagonist administration. The force transducers were implanted on the serosal surfaces of the gastric antrum, terminal ileum, ileocecal sphincter and colon. Test materials or vehicle alone was administered as an intravenous bolus injection during a quiescent period of the whole colon in the interdigestive state. The effects of these receptor antagonists on normal gastrointestinal motor activity were analyzed. RESULTS: 5-HT2B, 5-HT3 and 5-HT4 receptor antagonists had no contractile effect on the fasting canine terminal ileum. The 5-HT3 and 5-HT4 receptor antagonists inhibited phase III of the interdigestive motor complex of the antrum and significantly inhibited colonic motor activity. In the proximal colon, the inhibitory effect was dose dependent. Dose dependency, however, was not observed in the distal colon. The 5-HT2B receptor antagonist had no contractile effect on normal colonic motor activity. CONCLUSION: The 5-HT3 and 5-HT4 receptor antagonists inhibited normal colonic motor activity. The 5-HT2B receptor antagonist had no contractile effect on normal colonic motor activity. PMID:24151388

  15. [5-HT3 receptor antagonist als analgetics in rheumatic diseases].

    PubMed

    Müller, W; Fiebich, B L; Stratz, T

    2006-10-01

    Various rheumatic diseases like fibromyalgia, systemic inflammatory rheumatic disorders and localized diseases, such as arthritides and activated arthroses, tendinopathies and periarthropathies, as well as trigger points can be improved considerably by treatment with the 5-HT3 receptor antagonist tropisetron. Particularly in the latter group of diseases, local injections have done surprisingly rapid analgesic action. This effect matches that of local anesthetics, but lasts considerably longer and is comparable to local injections of local anesthetics combined with corticosteroids. The action of the 5-HT3 receptor antagonists can be attributed to an antinociceptive effect that occurs at the same time as an antiphlogistic and probably also an immunosuppressive effect. Whereas an inhibited release of substance P from the nociceptors, and possibly some other neurokins as well, seems to be the most likely explanation for the antinociceptive action, the antiphlogistic effect is primarily due to an inhibited formation of various different phlogistic substances; in some conditions, like systemic inflammatory rheumatic diseases, for example, the 5-HT3 receptor antagonists may exert an immunosuppressive effect in addition to this.

  16. Design, synthesis and evaluation of antidepressant activity of novel 2-methoxy 1, 8 naphthyridine 3-carboxamides as 5-HT3 receptor antagonists.

    PubMed

    Mahesh, Radhakrishnan; Dhar, Arghya Kusum; Jindal, Ankur; Bhatt, Shvetank

    2014-05-01

    A series of novel 1,8-naphthyridine-3-carboxamides as 5-HT3 receptor antagonists were synthesized with an intention to explore the antidepressant activity of these compounds. The title carboxamides were designed using ligand-based approach keeping in consideration the structural requirement of the pharmacophore of 5-HT3 receptor antagonists. The compounds were synthesized using appropriate synthetic route from the starting material nicotinamide. 5-HT3 receptor antagonism of all the compounds, which was denoted in the form of pA2 value, was determined in longitudinal muscle myenteric plexus preparation from guinea-pig ileum against 5-HT3 agonist, 2-methyl-5-HT. Compound 8g (2-methoxy-1, 8-naphthyridin-3-yl) (2-methoxy phenyl piperazine-1-yl) methanone was identified as the most active compound, which expressed a pA2 value of 7.67. The antidepressant activity of all the compounds was examined in mice model of forced swim test (FST); importantly, none of the compounds was found to cause any significant changes in the locomotor activity of mice at the tested dose levels. In FST, the compounds with considerably higher pA2 value exhibited promising antidepressant-like activity, whereas compounds with lower pA2 value did not show antidepressant-like activity as compared to the control group.

  17. Downregulated hypothalamic 5-HT3 receptor expression and enhanced 5-HT3 receptor antagonist-mediated improvement in fatigue-like behaviour in cholestatic rats.

    PubMed

    Nguyen, H; Wang, H; le, T; Ho, W; Sharkey, K A; Swain, M G

    2008-03-01

    The serotonin neurotransmitter system, including the 5-HT(3) receptor, has been implicated in the genesis of fatigue in patients with liver disease. Therefore, we examined the possible role of 5-HT(3) receptors in cholestasis-associated fatigue. Rats were either bile duct resected (BDR) or sham resected and studied 10 days postsurgery. A significant decrease in hypothalamic 5-HT(3) receptor expression was detected by immunohistochemistry and Western blot in BDR vs sham rats, coupled with increased hypothalamic serotonin turnover identified by an elevated 5-hydroxyindoleacetic acid (5-HIAA) to 5-HT ratio in BDR vs sham rats. To examine fatigue-like behaviour, an activity meter was used. BDR rats exhibited significantly lower locomotor activity than did sham animals. Subcutaneous injection of the 5-HT(3) receptor antagonist tropisetron (0.1 mg kg(-1)) resulted in significantly increased locomotor activity in BDR rats compared to the activity in saline-treated controls, but was without effect in sham rats. However, a 10-fold higher dose of tropisetron significantly increased locomotor activity in both BDR and sham rats compared to saline-injected controls. These findings indicate that cholestasis in the rat is associated with increased hypothalamic serotonin turnover, decreased hypothalamic 5-HT(3) receptor expression, and enhanced sensitivity to locomotor activation induced by 5-HT(3) receptor antagonism, thereby implicating the 5-HT(3) receptor system in cholestasis associated fatigue.

  18. The serotonin 5-HT3 receptor: a novel neurodevelopmental target.

    PubMed

    Engel, Mareen; Smidt, Marten P; van Hooft, Johannes A

    2013-01-01

    Serotonin (5-hydroxytryptamine, 5-HT), next to being an important neurotransmitter, recently gained attention as a key-regulator of pre- and postnatal development in the mammalian central nervous system (CNS). Several receptors for 5-HT are expressed in the developing brain including a ligand-gated ion channel, the 5-HT3 receptor. Over the past years, evidence has been accumulating that 5-HT3 receptors are involved in the regulation of neurodevelopment by serotonin. Here, we review the spatial and temporal expression patterns of 5-HT3 receptors in the pre- and early postnatal rodent brain and its functional implications. First, 5-HT3 receptors are expressed on GABAergic interneurons in neocortex and limbic structures derived from the caudal ganglionic eminence. Mature inhibitory GABAergic interneurons fine-tune neuronal excitability and thus are crucial for the physiological function of the brain. Second, 5-HT3 receptors are expressed on specific glutamatergic neurons, Cajal-Retzius cells in the cortex and granule cells in the cerebellum, where they regulate morphology, positioning, and connectivity of the local microcircuitry. Taken together, the 5-HT3 receptor emerges as a potential key-regulator of network formation and function in the CNS, which could have a major impact on our understanding of neurodevelopmental disorders in which 5-HT plays a role.

  19. Lamotrigine, an antiepileptic drug, inhibits 5-HT3 receptor currents in NCB-20 neuroblastoma cells

    PubMed Central

    Kim, Ki Jung; Jeun, Seung Hyun

    2017-01-01

    Lamotrigine is an antiepileptic drug widely used to treat epileptic seizures. Using whole-cell voltage clamp recordings in combination with a fast drug application approach, we investigated the effects of lamotrigine on 5-hydroxytryptamine (5-HT)3 receptors in NCB-20 neuroblastoma cells. Co-application of lamotrigine (1~300 µM) resulted in a concentration-dependent reduction in peak amplitude of currents induced by 3 µM of 5-HT for an IC50 value of 28.2±3.6 µM with a Hill coefficient of 1.2±0.1. These peak amplitude decreases were accompanied by the rise slope reduction. In addition, 5-HT3-mediated currents evoked by 1 mM dopamine, a partial 5-HT3 receptor agonist, were inhibited by lamotrigine co-application. The EC50 of 5-HT for 5-HT3 receptor currents were shifted to the right by co-application of lamotrigine without a significant change of maximal effect. Currents activated by 5-HT and lamotrigine co-application in the presence of 1 min pretreatment of lamotrigine were similar to those activated by 5-HT and lamotrigine co-application alone. Moreover, subsequent application of lamotrigine in the presence of 5-HT and 5-hydroxyindole, known to attenuate 5-HT3 receptor desensitization, inhibited 5-HT3 receptor currents in a concentration-dependent manner. The deactivation of 5-HT3 receptor was delayed by washing with an external solution containing lamotrigine. Lamotrigine accelerated the desensitization process of 5-HT3 receptors. There was no voltage-dependency in the inhibitory effects of lamotrigine on the 5-HT3 receptor currents. These results indicate that lamotrigine inhibits 5-HT3-activated currents in a competitive manner by binding to the open state of the channels and blocking channel activation or accelerating receptor desensitization. PMID:28280410

  20. Lamotrigine, an antiepileptic drug, inhibits 5-HT3 receptor currents in NCB-20 neuroblastoma cells.

    PubMed

    Kim, Ki Jung; Jeun, Seung Hyun; Sung, Ki-Wug

    2017-03-01

    Lamotrigine is an antiepileptic drug widely used to treat epileptic seizures. Using whole-cell voltage clamp recordings in combination with a fast drug application approach, we investigated the effects of lamotrigine on 5-hydroxytryptamine (5-HT)3 receptors in NCB-20 neuroblastoma cells. Co-application of lamotrigine (1~300 µM) resulted in a concentration-dependent reduction in peak amplitude of currents induced by 3 µM of 5-HT for an IC50 value of 28.2±3.6 µM with a Hill coefficient of 1.2±0.1. These peak amplitude decreases were accompanied by the rise slope reduction. In addition, 5-HT3-mediated currents evoked by 1 mM dopamine, a partial 5-HT3 receptor agonist, were inhibited by lamotrigine co-application. The EC50 of 5-HT for 5-HT3 receptor currents were shifted to the right by co-application of lamotrigine without a significant change of maximal effect. Currents activated by 5-HT and lamotrigine co-application in the presence of 1 min pretreatment of lamotrigine were similar to those activated by 5-HT and lamotrigine co-application alone. Moreover, subsequent application of lamotrigine in the presence of 5-HT and 5-hydroxyindole, known to attenuate 5-HT3 receptor desensitization, inhibited 5-HT3 receptor currents in a concentration-dependent manner. The deactivation of 5-HT3 receptor was delayed by washing with an external solution containing lamotrigine. Lamotrigine accelerated the desensitization process of 5-HT3 receptors. There was no voltage-dependency in the inhibitory effects of lamotrigine on the 5-HT3 receptor currents. These results indicate that lamotrigine inhibits 5-HT3-activated currents in a competitive manner by binding to the open state of the channels and blocking channel activation or accelerating receptor desensitization.

  1. [Medical economics evaluation of 5-HT3 receptor antagonist drugs].

    PubMed

    Utsunomiya, Junpei; Hirano, Shigeki; Fukui, Aiko; Funabashi, Kazuaki; Deguchi, Yuko; Yamada, Susumu; Naito, Kazuyuki

    2010-10-01

    At Komaki City Hospital, the drug cost in connection with cancer chemotherapy was re-examined as part of improved management along with the introduction of DPC in July 2008. With due attention to the 5-HT3 receptor antagonists, both the change from injections to oral drugs and the change from brand-name drugs to generic drugs were tried between July 2008 and June 2009. After that, in order to examine the economic impact of these changes, we investigated and analyzed the number of medications, the cost of medicine purchased, and the average drug cost per medication of the 5-HT3 receptor antagonists between April 2008 and September 2009. As a result, the cost of 5-HT3 receptor antagonists purchased decreased greatly, and the impact of the improvement was mainly due to the change to oral drugs, and partially to the change to generic drugs. Therefore, from the viewpoint of hospital economic improvement in DPC, it was thought that the change to oral drugs(5-HT3 receptor antagonists)is given top priority.

  2. The Role of 5-HT3 Receptors in Signaling from Taste Buds to Nerves.

    PubMed

    Larson, Eric D; Vandenbeuch, Aurelie; Voigt, Anja; Meyerhof, Wolfgang; Kinnamon, Sue C; Finger, Thomas E

    2015-12-02

    Activation of taste buds triggers the release of several neurotransmitters, including ATP and serotonin (5-hydroxytryptamine; 5-HT). Type III taste cells release 5-HT directly in response to acidic (sour) stimuli and indirectly in response to bitter and sweet tasting stimuli. Although ATP is necessary for activation of nerve fibers for all taste stimuli, the role of 5-HT is unclear. We investigated whether gustatory afferents express functional 5-HT3 receptors and, if so, whether these receptors play a role in transmission of taste information from taste buds to nerves. In mice expressing GFP under the control of the 5-HT(3A) promoter, a subset of cells in the geniculate ganglion and nerve fibers in taste buds are GFP-positive. RT-PCR and in situ hybridization confirmed the presence of 5-HT(3A) mRNA in the geniculate ganglion. Functional studies show that only those geniculate ganglion cells expressing 5-HT3A-driven GFP respond to 10 μM 5-HT and this response is blocked by 1 μM ondansetron, a 5-HT3 antagonist, and mimicked by application of 10 μM m-chlorophenylbiguanide, a 5-HT3 agonist. Pharmacological blockade of 5-HT3 receptors in vivo or genetic deletion of the 5-HT3 receptors reduces taste nerve responses to acids and other taste stimuli compared with controls, but only when urethane was used as the anesthetic. We find that anesthetic levels of pentobarbital reduce taste nerve responses apparently by blocking the 5-HT3 receptors. Our results suggest that 5-HT released from type III cells activates gustatory nerve fibers via 5-HT3 receptors, accounting for a significant proportion of the neural taste response.

  3. In silico investigation into the interactions between murine 5-HT3 receptor and the principle active compounds of ginger (Zingiber officinale).

    PubMed

    Lohning, Anna E; Marx, Wolfgang; Isenring, Liz

    2016-11-01

    Gingerols and shogaols are the primary non-volatile actives within ginger (Zingiber officinale). These compounds have demonstrated in vitro to exert 5-HT3 receptor antagonism which could benefit chemotherapy-induced nausea and vomiting (CINV). The site and mechanism of action by which these compounds interact with the 5-HT3 receptor is not fully understood although research indicates they may bind to a currently unidentified allosteric binding site. Using in silico techniques, such as molecular docking and GRID analysis, we have characterized the recently available murine 5-HT3 receptor by identifying sites of strong interaction with particular functional groups at both the orthogonal (serotonin) site and a proposed allosteric binding site situated at the interface between the transmembrane region and the extracellular domain. These were assessed concurrently with the top-scoring poses of the docked ligands and included key active gingerols, shogaols and dehydroshogaols as well as competitive antagonists (e.g. setron class of pharmacologically active drugs), serotonin and its structural analogues, curcumin and capsaicin, non-competitive antagonists and decoys. Unexpectedly, we found that the ginger compounds and their structural analogs generally outscored other ligands at both sites. Our results correlated well with previous site-directed mutagenesis studies in identifying key binding site residues. We have identified new residues important for binding the ginger compounds. Overall, the results suggest that the ginger compounds and their structural analogues possess a high binding affinity to both sites. Notwithstanding the limitations of such theoretical analyses, these results suggest that the ginger compounds could act both competitively or non-competitively as has been shown for palonosetron and other modulators of CYS loop receptors.

  4. From Chemotherapy-Induced Emesis to Neuroprotection: Therapeutic Opportunities for 5-HT3 Receptor Antagonists.

    PubMed

    Fakhfouri, Gohar; Mousavizadeh, Kazem; Mehr, Sharam Ejtemaei; Dehpour, Ahmad Reza; Zirak, Mohammad Reza; Ghia, Jean-Eric; Rahimian, Reza

    2015-12-01

    5-HT3 receptor antagonists are extensively used as efficacious agents in counteracting chemotherapy-induced emesis. Recent investigations have shed light on other potential effects (analgesic, anxiolytic, and anti-psychotic). Some studies have reported neuroprotective properties for the 5-HT3 receptor antagonists in vitro and in vivo. When administered to Aβ-challenged rat cortical neurons, 5-HT3 receptor antagonists substantially abated apoptosis, elevation of cytosolic Ca(2), glutamate release, reactive oxygen species (ROS) generation, and caspase-3 activity. In addition, in vivo studies show that 5-HT3 receptor antagonists possess, alongside their anti-emetic effects, notable immunomodulatory properties in CNS. We found that pretreatment with tropisetron significantly improved neurological deficits and diminished leukocyte transmigration into the brain, TNF-α level, and brain infarction in a murine model of embolic stroke. Our recent investigation revealed that tropisetron protects against Aβ-induced neurotoxicity in vivo through both 5-HT3 receptor-dependent and -independent pathways. Tropisetron, in vitro, was found to be an efficacious inhibitor of the signaling pathway leading to the activation of pro-inflammatory NF-κB, a transcription factor pivotal to the upregulation of several neuroinflammatory mediators in brain. This mini review summarizes novel evidence concerning effects of 5-HT3 antagonists and their possible mechanisms of action in ameliorating neurodegenerative diseases including Alzheimer, multiple sclerosis, and stroke. Further, we discuss some newly synthesized 5-HT3 receptor antagonists with dual properties of 5-HT3 receptor blockade/alpha-7 nicotinic receptor activator and their potential in management of memory impairment. Since 5-HT3 receptor antagonists possess a large therapeutic window, they can constitute a scaffold for design and synthesis of new neuroprotective medications.

  5. 5-Chloroindole: a potent allosteric modulator of the 5-HT3 receptor

    PubMed Central

    Newman, Amy S; Batis, Nikolaos; Grafton, Gillian; Caputo, Francesca; Brady, Catherine A; Lambert, Jeremy J; Peters, John A; Gordon, John; Brain, Keith L; Powell, Andrew D; Barnes, Nicholas M

    2013-01-01

    Background and Purpose The 5-HT3 receptor is a ligand-gated ion channel that is modulated allosterically by various compounds including colchicine, alcohols and volatile anaesthetics. However the positive allosteric modulators (PAMs) identified to date have low affinity, which hinders investigation because of non-selective effects at pharmacologically active concentrations. The present study identifies 5-chloroindole (Cl-indole) as a potent PAM of the 5-HT3 receptor. Experimental Approach 5-HT3 receptor function was assessed by the increase in intracellular calcium and single-cell electrophysiological recordings in HEK293 cells stably expressing the h5-HT3A receptor and also the mouse native 5-HT3 receptor that increases neuronal contraction of bladder smooth muscle. Key Results Cl-indole (1–100 μM) potentiated agonist (5-HT) and particularly partial agonist [(S)-zacopride, DDP733, RR210, quipazine, dopamine, 2-methyl-5-HT, SR57227A, meta chlorophenyl biguanide] induced h5-HT3A receptor-mediated responses. This effect of Cl-indole was also apparent at the mouse native 5-HT3 receptor. Radioligand-binding studies identified that Cl-indole induced a small (∼twofold) increase in the apparent affinity of 5-HT for the h5-HT3A receptor, whereas there was no effect upon the affinity of the antagonist, tropisetron. Cl-indole was able to reactivate desensitized 5-HT3 receptors. In contrast to its effect on the 5-HT3 receptor, Cl-indole did not alter human nicotinic α7 receptor responses. Conclusions and Implications The present study identifies Cl-indole as a relatively potent and selective PAM of the 5-HT3 receptor; such compounds will aid investigation of the molecular basis for allosteric modulation of the 5-HT3 receptor and may assist the discovery of novel therapeutic drugs targeting this receptor. Linked Articles Recent reviews on allosteric modulation can be found at: Kenakin, T (2013). New concepts in pharmacological efficacy at 7TM receptors: IUPHAR Review 2

  6. Fluvoxamine alleviates seizure activity and downregulates hippocampal GAP-43 expression in pentylenetetrazole-kindled mice: role of 5-HT3 receptors.

    PubMed

    Alhaj, Momen W; Zaitone, Sawsan A; Moustafa, Yasser M

    2015-06-01

    Epilepsy has been documented to lead to many changes in the nervous system including cell loss and mossy fiber sprouting. Neuronal loss and aberrant neuroplastic changes in the dentate gyrus of the hippocampus have been identified in the pentylenetetrazole (PTZ) kindling model. Antiseizure activity of selective serotonin reuptake inhibitors has been reported in several studies. In the current study, the protective effect of fluvoxamine against PTZ-kindling was investigated in terms of seizure scores, neuronal loss, and regulation of hippocampal neuroplasticity. Further, the role of 5-HT3 receptors was determined. Kindling was induced by repeated injections of PTZ (35 mg/kg) thrice weekly, for a total of 13 injections. One hundred male albino mice were allocated into 10 groups: (1) saline, (2) PTZ, (3) diazepam (1 mg/kg)+PTZ, (4-6) fluvoxamine (5, 10 or 20 mg/kg)+PTZ, (7) ondansetron+fluvoxamine (20 mg/kg)+PTZ, (8) ondansetron+PTZ group, (9) ondansetron (2 mg/kg, i.p.)+saline, and (10) fluvoxamine (20 mg/kg)+saline. PTZ-kindled mice showed high seizure activity, hippocampal neuronal loss, and expression of growth-associated phosphoprotein (GAP-43) compared with saline-treated mice. Repeated administration of fluvoxamine (20 mg/kg) in PTZ-kindled mice suppressed seizure scores, protected against hippocampal neuronal loss, and downregulated GAP-43 expression, without producing any signs of the 5-HT syndrome in healthy rats. Importantly, pretreatment with a selective 5-HT3 receptor blocker (ondansetron) attenuated the aforementioned effects of fluvoxamine. In conclusion, the ameliorating effect of fluvoxamine on hippocampal neurons and neuroplasticity in PTZ-kindled mice was, at least in part, dependent on enhancement of hippocampal serotoninergic transmission at 5-HT3 receptors.

  7. The Role of 5-HT3 Receptors in Signaling from Taste Buds to Nerves

    PubMed Central

    Vandenbeuch, Aurelie; Voigt, Anja; Meyerhof, Wolfgang; Kinnamon, Sue C.; Finger, Thomas E.

    2015-01-01

    Activation of taste buds triggers the release of several neurotransmitters, including ATP and serotonin (5-hydroxytryptamine; 5-HT). Type III taste cells release 5-HT directly in response to acidic (sour) stimuli and indirectly in response to bitter and sweet tasting stimuli. Although ATP is necessary for activation of nerve fibers for all taste stimuli, the role of 5-HT is unclear. We investigated whether gustatory afferents express functional 5-HT3 receptors and, if so, whether these receptors play a role in transmission of taste information from taste buds to nerves. In mice expressing GFP under the control of the 5-HT3A promoter, a subset of cells in the geniculate ganglion and nerve fibers in taste buds are GFP-positive. RT-PCR and in situ hybridization confirmed the presence of 5-HT3A mRNA in the geniculate ganglion. Functional studies show that only those geniculate ganglion cells expressing 5-HT3A-driven GFP respond to 10 μm 5-HT and this response is blocked by 1 μm ondansetron, a 5-HT3 antagonist, and mimicked by application of 10 μm m-chlorophenylbiguanide, a 5-HT3 agonist. Pharmacological blockade of 5-HT3 receptors in vivo or genetic deletion of the 5-HT3 receptors reduces taste nerve responses to acids and other taste stimuli compared with controls, but only when urethane was used as the anesthetic. We find that anesthetic levels of pentobarbital reduce taste nerve responses apparently by blocking the 5-HT3 receptors. Our results suggest that 5-HT released from type III cells activates gustatory nerve fibers via 5-HT3 receptors, accounting for a significant proportion of the neural taste response. SIGNIFICANCE STATEMENT Historically, serotonin (5-hydroxytryptamine; 5-HT) has been described as a candidate neurotransmitter in the gustatory system and recent studies show that type III taste receptor cells release 5-HT in response to various taste stimuli. In the present study, we demonstrate that a subset of gustatory sensory neurons express functional

  8. Role of central vagal 5-HT3 receptors in gastrointestinal physiology and pathophysiology

    PubMed Central

    Browning, Kirsteen N.

    2015-01-01

    Vagal neurocircuits are vitally important in the co-ordination and modulation of GI reflexes and homeostatic functions. 5-hydroxytryptamine (5-HT; serotonin) is critically important in the regulation of several of these autonomic gastrointestinal (GI) functions including motility, secretion and visceral sensitivity. While several 5-HT receptors are involved in these physiological responses, the ligand-gated 5-HT3 receptor appears intimately involved in gut-brain signaling, particularly via the afferent (sensory) vagus nerve. 5-HT is released from enterochromaffin cells in response to mechanical or chemical stimulation of the GI tract which leads to activation of 5-HT3 receptors on the terminals of vagal afferents. 5-HT3 receptors are also present on the soma of vagal afferent neurons, including GI vagal afferent neurons, where they can be activated by circulating 5-HT. The central terminals of vagal afferents also exhibit 5-HT3 receptors that function to increase glutamatergic synaptic transmission to second order neurons of the nucleus tractus solitarius within the brainstem. While activation of central brainstem 5-HT3 receptors modulates visceral functions, it is still unclear whether central vagal neurons, i.e., nucleus of the tractus solitarius (NTS) and dorsal motor nucleus of the vagus (DMV) neurons themselves also display functional 5-HT3 receptors. Thus, activation of 5-HT3 receptors may modulate the excitability and activity of gastrointestinal vagal afferents at multiple sites and may be involved in several physiological and pathophysiological conditions, including distention- and chemical-evoked vagal reflexes, nausea, and vomiting, as well as visceral hypersensitivity. PMID:26578870

  9. The Role of 5-HT3 Receptors in Drug Abuse and as a Target for Pharmacotherapy

    PubMed Central

    Engleman, E.A.; Rodd, Z.A.; Bell, R.L.; Murphy, J.M.

    2010-01-01

    Alcohol and drug abuse continue to be a major public health problem in the United States and other industrialized nations. Extensive preclinical research indicates the mesolimbic dopamine (DA) pathway and associated regions mediate the rewarding and reinforcing effects of drugs of abuse and natural rewards, such as food and sex. The serotonergic (5-HT) system, in concert with others neurotransmitter systems, plays a key role in modulating neuronal systems within the mesolimbic pathway. A substantial portion of this modulation is mediated by activity at the 5-HT3 receptor. The 5-HT3 receptor is unique among the 5-HT receptors in that it directly gates an ion channel inducing rapid depolarization that, in turn, causes the release of neurotransmitters and/or peptides. Preclinical findings indicate that antagonism of the 5-HT3 receptor in the ventral tegmental area, nucleus accumbens or amygdala reduces alcohol self-administration and/or alcohol-associated effects. Less is known about the effects of 5-HT3 receptor activity on the self-administration of other drugs of abuse or their associated effects. Clinical findings parallel the preclinical findings such that antagonism of the 5-HT3 receptor reduces alcohol consumption and some of its subjective effects. This review provides an overview of the structure, function, and pharmacology of 5-HT3 receptors, the role of these receptors in regulating DA neurotransmission in mesolimbic brain areas, and discusses data from animal and human studies implicating 5-HT3 receptors as targets for the development of new pharmacological agents to treat addictions. PMID:19128203

  10. The role of 5-HT3 receptors in drug abuse and as a target for pharmacotherapy.

    PubMed

    Engleman, E A; Rodd, Z A; Bell, R L; Murphy, J M

    2008-11-01

    Alcohol and drug abuse continue to be a major public health problem in the United States and other industrialized nations. Extensive preclinical research indicates the mesolimbic dopamine (DA) pathway and associated regions mediate the rewarding and reinforcing effects of drugs of abuse and natural rewards, such as food and sex. The serotonergic (5-HT) system, in concert with others neurotransmitter systems, plays a key role in modulating neuronal systems within the mesolimbic pathway. A substantial portion of this modulation is mediated by activity at the 5-HT3 receptor. The 5-HT3 receptor is unique among the 5-HT receptors in that it directly gates an ion channel inducing rapid depolarization that, in turn, causes the release of neurotransmitters and/or peptides. Preclinical findings indicate that antagonism of the 5-HT3 receptor in the ventral tegmental area, nucleus accumbens or amygdala reduces alcohol self-administration and/or alcohol-associated effects. Less is known about the effects of 5-HT3 receptor activity on the self-administration of other drugs of abuse or their associated effects. Clinical findings parallel the preclinical findings such that antagonism of the 5-HT3 receptor reduces alcohol consumption and some of its subjective effects. This review provides an overview of the structure, function, and pharmacology of 5-HT3 receptors, the role of these receptors in regulating DA neurotransmission in mesolimbic brain areas, and discusses data from animal and human studies implicating 5-HT3 receptors as targets for the development of new pharmacological agents to treat addictions.

  11. The antimalarial drug proguanil is an antagonist at 5-HT3 receptors.

    PubMed

    Lochner, Martin; Thompson, Andrew J

    2014-12-01

    Proguanil is an antimalarial prodrug that is metabolized to 4-chlorophenyl-1-biguanide (CPB) and the active metabolite cycloguanil (CG). These compounds are structurally related to meta-chlorophenyl biguanide (mCPBG), a 5-hydroxytryptamine 3 (5-HT3) receptor agonist. Here we examine the effects of proguanil and its metabolites on the electrophysiology and ligand-binding properties of human 5-HT3A receptors expressed in Xenopus oocytes and human embryonic kidney 293 cells, respectively. 5-HT3 receptor responses were reversibly inhibited by proguanil, with an IC50 of 1.81 μM. Competitive antagonism was shown by a lack of voltage-dependence, Schild plot (Kb = 1.70 μM), and radioligand competition (Ki = 2.61 μM) with the 5-HT3 receptor antagonist [(3)H]granisetron. Kinetic measurements (kon = 4.0 × 10(4) M(-1) s(-1) ; koff = 0.23 s(-1)) were consistent with a simple bimolecular reaction scheme with a Kb of 4.35 μM. The metabolites CG and CPB similarly inhibited 5-HT3 receptors as assessed by IC50 (1.48 and 4.36 μM, respectively), Schild plot (Kb = 2.97 and 11.4 μM), and radioligand competition (Ki = 4.89 and 0.41 μM). At higher concentrations, CPB was a partial agonist (EC50 = 14.1 μM; I/Imax = 0.013). These results demonstrate that proguanil competitively inhibits 5-HT3 receptors, with an IC50 that exceeds whole-blood concentrations following its oral administration. They may therefore be responsible for the occasional gastrointestinal side effects, nausea, and vomiting reported following its use. Clinical development of related compounds should therefore consider effects at 5-HT3 receptors as an early indication of possible unwanted gastrointestinal side effects.

  12. Pathways and Barriers for Ion Translocation through the 5-HT3A Receptor Channel

    PubMed Central

    Di Maio, Danilo; Chandramouli, Balasubramanian; Brancato, Giuseppe

    2015-01-01

    Pentameric ligand gated ion channels (pLGICs) are ionotropic receptors that mediate fast intercellular communications at synaptic level and include either cation selective (e.g., nAChR and 5-HT3) or anion selective (e.g., GlyR, GABAA and GluCl) membrane channels. Among others, 5-HT3 is one of the most studied members, since its first cloning back in 1991, and a large number of studies have successfully pinpointed protein residues critical for its activation and channel gating. In addition, 5-HT3 is also the target of a few pharmacological treatments due to the demonstrated benefits of its modulation in clinical trials. Nonetheless, a detailed molecular analysis of important protein features, such as the origin of its ion selectivity and the rather low conductance as compared to other channel homologues, has been unfeasible until the recent crystallization of the mouse 5-HT3A receptor. Here, we present extended molecular dynamics simulations and free energy calculations of the whole 5-HT3A protein with the aim of better understanding its ion transport properties, such as the pathways for ion permeation into the receptor body and the complex nature of the selectivity filter. Our investigation unravels previously unpredicted structural features of the 5-HT3A receptor, such as the existence of alternative intersubunit pathways for ion translocation at the interface between the extracellular and the transmembrane domains, in addition to the one along the channel main axis. Moreover, our study offers a molecular interpretation of the role played by an arginine triplet located in the intracellular domain on determining the characteristic low conductance of the 5-HT3A receptor, as evidenced in previous experiments. In view of these results, possible implications on other members of the superfamily are suggested. PMID:26465896

  13. Key role of 5-HT3 receptors in the nucleus tractus solitarii in cardiovagal stress reactivity.

    PubMed

    Sévoz-Couche, Caroline; Brouillard, Charly

    2017-03-01

    Serotonin plays a modulatory role in central control of the autonomic nervous system (ANS). The nucleus tractus solitarii (NTS) in the medulla is an area of viscerosomatic integration innervated by both central and peripheral serotonergic fibers. Influences from different origins therefore trigger the release of serotonin into the NTS and exert multiple influences on the ANS. This major influence on the ANS is also mediated by activation of several receptors in the NTS. In particular, the NTS is the central zone with the highest density of serotonin3 (5-HT3) receptors. In this review, we present evidence that 5-HT3 receptors in the NTS play a key role in one of the crucial homeostatic responses to acute and chronic stress: inhibitory modulation of the parasympathetic component of the ANS. The possible functional interactions of 5-HT3 receptors with GABAA and NK1 receptors in the NTS are also discussed.

  14. Intrathecal nefopam-induced antinociception through activation of descending serotonergic projections involving spinal 5-HT7 but not 5-HT3 receptors.

    PubMed

    Lee, Hyung Gon; Kim, Woong Mo; Kim, Joung Min; Bae, Hong-Beom; Choi, Jeong Il

    2015-02-05

    We examined the involvement of spinal 5-HT(5-hydroxytryptamine) receptor 3(5-HT3R) and 7(5-HT7R) as well as the overall role of descending serotonergic projections in the analgesic effects of intrathecal(i.t.) nefopam for two rat models of formalin and paw incision test. I.t. nefopam produced an antinociceptive effect in a dose-dependent manner in both tests. Lesioning the spinal serotonergic projections using i.t. 5,7-dihydroxytryptamine(5,7-DHT) did not influence the intensity of allodynia in the paw incision test, but i.t. 5,7-DHT abolished the effect of nefopam. In the formain test, i.t. 5,7-DHT alone significantly diminished the flinches, but the effect of nefopam was not affected by i.t. 5,7-DHT. Antagonism study showed that i.t. 5-HT7R antagonist, SB269970 significantly blocked the antinociceptive effect of nefopam in both tests, but i.t. 5-HT3R antagonist, ondansetron has no influence on the effect of nefopam. The present study demonstrates that descending spinal serotonergic projections play a vital role in antinociceptive effect of i.t. nefopam in the paw incision test, but indeterminate in the formalin test. In both tests, the antinociceptive effect of i.t. nefopam involves the spinal 5-HT7R, but not 5-HT3R.

  15. Serotonin 5-HT3 receptor-mediated vomiting occurs via the activation of Ca2+/CaMKII-dependent ERK1/2 signaling in the least shrew (Cryptotis parva).

    PubMed

    Zhong, Weixia; Hutchinson, Tarun E; Chebolu, Seetha; Darmani, Nissar A

    2014-01-01

    Stimulation of 5-HT3 receptors (5-HT3Rs) by 2-methylserotonin (2-Me-5-HT), a selective 5-HT3 receptor agonist, can induce vomiting. However, downstream signaling pathways for the induced emesis remain unknown. The 5-HT3R channel has high permeability to extracellular calcium (Ca(2+)) and upon stimulation allows increased Ca(2+) influx. We examined the contribution of Ca(2+)/calmodulin-dependent protein kinase IIα (Ca(2+)/CaMKIIα), interaction of 5-HT3R with calmodulin, and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling to 2-Me-5-HT-induced emesis in the least shrew. Using fluo-4 AM dye, we found that 2-Me-5-HT augments intracellular Ca(2+) levels in brainstem slices and that the selective 5-HT3R antagonist palonosetron, can abolish the induced Ca(2+) signaling. Pre-treatment of shrews with either: i) amlodipine, an antagonist of L-type Ca(2+) channels present on the cell membrane; ii) dantrolene, an inhibitor of ryanodine receptors (RyRs) Ca2+-release channels located on the endoplasmic reticulum (ER); iii) a combination of their less-effective doses; or iv) inhibitors of CaMKII (KN93) and ERK1/2 (PD98059); dose-dependently suppressed emesis caused by 2-Me-5-HT. Administration of 2-Me-5-HT also significantly: i) enhanced the interaction of 5-HT3R with calmodulin in the brainstem as revealed by immunoprecipitation, as well as their colocalization in the area postrema (brainstem) and small intestine by immunohistochemistry; and ii) activated CaMKIIα in brainstem and in isolated enterochromaffin cells of the small intestine as shown by Western blot and immunocytochemistry. These effects were suppressed by palonosetron. 2-Me-5-HT also activated ERK1/2 in brainstem, which was abrogated by palonosetron, KN93, PD98059, amlodipine, dantrolene, or a combination of amlodipine plus dantrolene. However, blockade of ER inositol-1, 4, 5-triphosphate receptors by 2-APB, had no significant effect on the discussed behavioral and biochemical parameters. This study

  16. Serotonin 5-HT3 Receptor-Mediated Vomiting Occurs via the Activation of Ca2+/CaMKII-Dependent ERK1/2 Signaling in the Least Shrew (Cryptotis parva)

    PubMed Central

    Zhong, Weixia; Hutchinson, Tarun E.; Chebolu, Seetha; Darmani, Nissar A.

    2014-01-01

    Stimulation of 5-HT3 receptors (5-HT3Rs) by 2-methylserotonin (2-Me-5-HT), a selective 5-HT3 receptor agonist, can induce vomiting. However, downstream signaling pathways for the induced emesis remain unknown. The 5-HT3R channel has high permeability to extracellular calcium (Ca2+) and upon stimulation allows increased Ca2+ influx. We examined the contribution of Ca2+/calmodulin-dependent protein kinase IIα (Ca2+/CaMKIIα), interaction of 5-HT3R with calmodulin, and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling to 2-Me-5-HT-induced emesis in the least shrew. Using fluo-4 AM dye, we found that 2-Me-5-HT augments intracellular Ca2+ levels in brainstem slices and that the selective 5-HT3R antagonist palonosetron, can abolish the induced Ca2+ signaling. Pre-treatment of shrews with either: i) amlodipine, an antagonist of L-type Ca2+ channels present on the cell membrane; ii) dantrolene, an inhibitor of ryanodine receptors (RyRs) Ca2+-release channels located on the endoplasmic reticulum (ER); iii) a combination of their less-effective doses; or iv) inhibitors of CaMKII (KN93) and ERK1/2 (PD98059); dose-dependently suppressed emesis caused by 2-Me-5-HT. Administration of 2-Me-5-HT also significantly: i) enhanced the interaction of 5-HT3R with calmodulin in the brainstem as revealed by immunoprecipitation, as well as their colocalization in the area postrema (brainstem) and small intestine by immunohistochemistry; and ii) activated CaMKIIα in brainstem and in isolated enterochromaffin cells of the small intestine as shown by Western blot and immunocytochemistry. These effects were suppressed by palonosetron. 2-Me-5-HT also activated ERK1/2 in brainstem, which was abrogated by palonosetron, KN93, PD98059, amlodipine, dantrolene, or a combination of amlodipine plus dantrolene. However, blockade of ER inositol-1, 4, 5-triphosphate receptors by 2-APB, had no significant effect on the discussed behavioral and biochemical parameters. This study demonstrates

  17. Building a 5-HT3A Receptor Expression Map in the Mouse Brain

    PubMed Central

    Koyama, Yoshihisa; Kondo, Makoto; Shimada, Shoichi

    2017-01-01

    Of the many serotonin receptors, the type 3 receptors (5-HT3R) are the only ionotropic ones, playing a key role in fast synaptic transmission and cognitive and emotional brain function through controlled neuronal excitation. To better understand the various functions of 5-HT3Rs, it is very important to know their expression pattern in the central nervous system (CNS). To date, many distributional studies have shown localized 5-HT3R expression in the brain and spinal cord. However, an accurate pattern of 5-HT3R expression in the CNS remains to be elucidated. To investigate the distribution of 5-HT3R in the mouse brain in detail, we performed immunofluorescent staining using 5-HT3AR-GFP transgenic mice. We found strong 5-HT3AR expression in the olfactory bulb, cerebral cortex, hippocampus, and amygdala; and partial expression in the pons, medulla, and spinal cord. Meanwhile, the thalamus, hypothalamus, and midbrain exhibited a few 5-HT3AR-expressing cells, and no expression was detected in the cerebellum. Further, double-immunostaining using neural markers confirmed that 5-HT3AR is expressed in GABAergic interneurons containing somatostatin or calretinin. In the present study, we built a 5-HT3AR expression map in the mouse brain. Our findings make significant contributions in elucidating the novel functions of 5-HT3R in the CNS. PMID:28276429

  18. Is All Radiation-Induced Emesis Ameliorated by 5-HT3 Receptor Antagonists

    DTIC Science & Technology

    1992-01-01

    5 - HT3 receptor antagonists ;~// 9-72 Bernard M.I Rabin 0’) and Gregory L. Kingt2) -) Behavioral Sciences and 2 PhYSzo~o~y Dcpiarlrnvni . Arm,. ii - R...RY Exposing ferrets to gamuma rays or X-rays produces vomiting that can be attenuated by 5 - HT3 receptor antagonists and by subdiaphraqmatic vagotomy...Pretreating ferrets with serotonin type-3 ( 5 - HT3 ) receptor antagonists or performing bilateral subdiaphragmatic vagotomy reliably attenuates the

  19. Interaction of Pyridostigmine with the 5-HT(3) Receptor Antagonist Ondansetron in Guinea Pigs

    DTIC Science & Technology

    1993-05-13

    5 - HT3 RECEPTOR - ANTAGONIST .ONDANSETRON IN GUINEA PIGS BR. Capacio, CE. Byers...apart. REFERENCES 1. Fozard JR. 5 -HT; The Enigma Variations. =JE, 8, 501-506 (December 1987). 2. Watling KJ. 5 - HT3 Receptor Agonists and Antagonists . In... 5 -HT receptor subtype three antagonists (5HT 3 ) such as the compound ondansetron (OND) have been identified as useful in the treatment of

  20. 5-HT3 receptors antagonists reduce serotonin-induced scratching in mice.

    PubMed

    Ostadhadi, Sattar; Kordjazy, Nastaran; Haj-Mirzaian, Arya; Mansouri, Parvin; Dehpour, Ahmad Reza

    2015-06-01

    Serotonin (5-hydroxytryptamine, 5-HT) acts as a pruritogen in humans and animals, but the mechanisms of action through that serotonin induces itch response have not been extensively discovered. In our study, we attempted to investigate the role of 5-HT3 receptors in scratching behavior due to intradermal serotonin injection. Intradermal injection of serotonin (14.1-235 nmol/site) into the nape of the neck of mice was performed to elicit itch. Scratching behavior was evaluated by measuring the number of bouts during 60 min after injection. We evaluated the effect of intraperitoneal pretreatment with ondansetron and tropisetron (0.1, 0.3, and 1 mg/kg) on itch induced by serotonin. Also, intradermal ondansetron and tropisetron at doses 50, 100, and 200 nmol/site were concurrently administrated with serotonin. Serotonin produced a significant enhancement in scratching at dose 141 nmol/site. Concurrent administration of ondansetron (50, 100, and 200 nmol/site) and tropisetron (100 and 200 nmol/site) with serotonin reduced scratching activity compared to the animals that only received serotonin. Also, pretreatment with intraperitoneal ondansetron and tropisetron (0.3 and 1 mg/kg) 30 min before serotonin attenuated the itch response. We showed that the scratching induced by intradermal serotonin is mediated by 5-HT3 receptors subtype. It can be concluded that 5-HT3 may play a role in mediating serotonin-associated itch responses, and we introduce 5-HT3 receptors as possible targets for antipruritic agents.

  1. Comparative receptor mapping of serotoninergic 5-HT3 and 5-HT4 binding sites*

    NASA Astrophysics Data System (ADS)

    López-Rodríguez, María L.; Morcillo, María José; Benhamú, Bellinda; Rosado, María Luisa

    1997-11-01

    The clinical use of currently available drugs acting at the5-HT4 receptor has been hampered by their lack of selectivityover 5-HT3 binding sites. For this reason, there is considerableinterest in the medicinal chemistry of these serotonin receptor subtypes, andsignificant effort has been made towards the discovery of potent and selectiveligands. Computer-aided conformational analysis was used to characterizeserotoninergic 5-HT3 and 5-HT4 receptorrecognition. On the basis of the generally accepted model of the5-HT3 antagonist pharmacophore, we have performed a receptormapping of this receptor binding site, following the active analog approach(AAA) defined by Marshall. The receptor excluded volume was calculated as theunion of the van der Waals density maps of nine active ligands(pKi ≥ 8.9), superimposed in pharmacophoric conformations.Six inactive analogs (pKi < 7.0) were subsequently used todefine the essential volume, which in its turn can be used to define theregions of steric intolerance of the 5-HT3 receptor. Five activeligands (pKi ≥ 9.3) at 5-HT4 receptors wereused to construct an antagonist pharmacophore for this receptor, and todetermine its excluded volume by superimposition of pharmacophoricconformations. The volume defined by the superimposition of five inactive5-HT4 receptor analogs that possess the pharmacophoric elements(pKi ≤ 6.6) did not exceed the excluded volume calculated forthis receptor. In this case, the inactivity may be due to the lack of positiveinteraction of the amino moiety with a hypothetical hydrophobic pocket, whichwould interact with the voluminous substituents of the basic nitrogen ofactive ligands. The difference between the excluded volumes of both receptorshas confirmed that the main difference is indeed in the basic moiety. Thus,the 5-HT3 receptor can only accommodate small substituents inthe position of the nitrogen atom, whereas the 5-HT4 receptorrequires more voluminous groups. Also, the basic nitrogen is located at ca

  2. Expression of 5-HT3 receptors by extrinsic duodenal afferents contribute to intestinal inhibition of gastric emptying.

    PubMed

    Raybould, Helen E; Glatzle, Jorg; Robin, Carla; Meyer, James H; Phan, Thomas; Wong, Helen; Sternini, Catia

    2003-03-01

    Intestinal perfusion with carbohydrates inhibits gastric emptying via vagal and spinal capsaicin-sensitive afferent pathways. The aim of the present study was to determine the role of 1) 5-hydroxytryptamine (5-HT)(3) receptors (5-HT(3)R) in mediating glucose-induced inhibition of gastric emptying and 2) 5-HT(3)R expression in vagal and spinal afferents in innervating the duodenum. In awake rats fitted with gastric and duodenal cannulas, perfusion of the duodenum with glucose (50 and 100 mg) inhibited gastric emptying. Intestinal perfusion of mannitol inhibited gastric emptying only at the highest concentration (990 mosm/kgH(2)O). Pretreatment with the 5-HT(3)R antagonist tropisetron abolished both glucose- and mannitol-induced inhibition of gastric emptying. Retrograde labeling of visceral afferents by injection of dextran-conjugated Texas Red into the duodenal wall was used to identify extrinsic primary afferents. Immunoreactivity for 5-HT(3)R, visualized with an antibody directed to the COOH terminus of the rat 5-HT(3)R, was found in >80% of duodenal vagal and spinal afferents. These results show that duodenal extrinsic afferents express 5-HT(3)R and that the receptor mediates specific glucose-induced inhibition of gastric emptying. These findings support the hypothesis that enterochromaffin cells in the intestinal mucosa release 5-HT in response to glucose, which activates 5-HT(3)R on afferent nerve terminals to evoke reflex changes in gastric motility. The primary glucose sensors of the intestine may be mucosal enterochromaffin cells.

  3. L-type calcium channels contribute to 5-HT3-receptor-evoked CaMKIIα and ERK activation and induction of emesis in the least shrew (Cryptotis parva).

    PubMed

    Hutchinson, Tarun E; Zhong, Weixia; Chebolu, Seetha; Wilson, Sean M; Darmani, Nissar A

    2015-05-15

    Activation of serotonergic 5-HT3 receptors by its selective agonist 2-methyl serotonin (2-Me-5-HT) induces vomiting, which is sensitive to selective antagonists of both 5-HT3 receptors (palonosetron) and L-type calcium channels (LTCC) (amlodipine or nifedipine). Previously we demonstrated that 5-HT3 receptor activation also causes increases in a palonosetron-sensitive manner in: i) intracellular Ca(2+) concentration, ii) attachment of calmodulin (CaM) to 5-HT3 receptor, and iii) phosphorylation of Ca(2+)/calmodulin-dependent protein kinase IIα (CaMKIIα) and extracellular-signal-regulated kinase 1/2 (ERK1/2). Here, we investigate the role of the short-acting LTCC blocker nifedipine on 2-Me-5-HT-evoked intracellular Ca(2+) increase and on downstream intracellular emetic signaling, which have been shown to be coupled with 2-Me-5-HT׳s emetic effects in the least shrew. Using the cell-permeant Ca(2+) indicator fluo-4 AM, here we present evidence for the contribution of Ca(2+) influx through LTCCs (sensitive to nifedipine) in 2-Me-5-HT (1µM) -evoked rise in cytosolic Ca(2+) levels in least shrew brainstem slices. Nifedipine pretreatment (10mg/kg, s.c.) also suppressed 2-Me-5-HT-evoked interaction of 5-HT3 receptors with CaM as well as phosphorylation of CaMKIIα and ERK1/2 in the least shrew brainstem, and 5-HT3 receptors -CaM colocalization in jejunum of the small intestine. In vitro exposure of isolated enterochromaffin cells of the small intestine to 2-Me-5-HT (1µM) caused CaMKIIα phosphorylation, which was also abrogated by nifedipine pretreatment (0.1µM). In addition, pretreatment with the CaMKII inhibitor KN62 (10mg/kg, i.p.) suppressed emesis and also the activation of CaMKIIα, and ERK in brainstem caused by 2-Me-5-HT (5mg/kg, i.p.). This study provides further mechanistic explanation for our published findings that nifedipine can dose-dependently protect shrews from 2-Me-5-HT-induced vomiting.

  4. 2-Amino-6-chloro-3,4-dihydroquinazoline: A novel 5-HT3 receptor antagonist with antidepressant character.

    PubMed

    Dukat, Małgorzata; Alix, Katie; Worsham, Jessica; Khatri, Shailesh; Schulte, Marvin K

    2013-11-01

    2-Amino-6-chloro-3,4-dihydroquinazoline HCl (A6CDQ, 4) binds at 5-HT3 serotonin receptors and displays antidepressant-like action in the mouse tail suspension test (TST). Empirically, 4 was demonstrated to be a 5-HT3 receptor antagonist (two-electrode voltage clamp recordings using frog oocytes; IC50=0.26μM), and one that should readily penetrate the blood-brain barrier (logP=1.86). 5-HT3 receptor antagonists represent a potential approach to the development of new antidepressants, and 4 is an example of a structurally novel 5-HT3 receptor antagonist that is active in a preclinical antidepressant model (i.e., the mouse TST).

  5. 5-HT3a Receptors Modulate Hippocampal Gamma Oscillations by Regulating Synchrony of Parvalbumin-Positive Interneurons.

    PubMed

    Huang, Ying; Yoon, Kristopher; Ko, Ho; Jiao, Song; Ito, Wataru; Wu, Jian-Young; Yung, Wing-Ho; Lu, Bai; Morozov, Alexei

    2016-02-01

    Gamma-frequency oscillatory activity plays an important role in information integration across brain areas. Disruption in gamma oscillations is implicated in cognitive impairments in psychiatric disorders, and 5-HT3 receptors (5-HT3Rs) are suggested as therapeutic targets for cognitive dysfunction in psychiatric disorders. Using a 5-HT3aR-EGFP transgenic mouse line and inducing gamma oscillations by carbachol in hippocampal slices, we show that activation of 5-HT3aRs, which are exclusively expressed in cholecystokinin (CCK)-containing interneurons, selectively suppressed and desynchronized firings in these interneurons by enhancing spike-frequency accommodation in a small conductance potassium (SK)-channel-dependent manner. Parvalbumin-positive interneurons therefore received diminished inhibitory input leading to increased but desynchronized firings of PV cells. As a consequence, the firing of pyramidal neurons was desynchronized and gamma oscillations were impaired. These effects were independent of 5-HT3aR-mediated CCK release. Our results therefore revealed an important role of 5-HT3aRs in gamma oscillations and identified a novel crosstalk among different types of interneurons for regulation of network oscillations. The functional link between 5-HT3aR and gamma oscillations may have implications for understanding the cognitive impairments in psychiatric disorders.

  6. The binding characteristics and orientation of a novel radioligand with distinct properties at 5-HT3A and 5-HT3AB receptors

    PubMed Central

    Thompson, Andrew J.; Verheij, Mark H.P.; Verbeek, Joost; Windhorst, Albert D.; de Esch, Iwan J.P.; Lummis, Sarah C.R.

    2014-01-01

    VUF10166 (2-chloro-3-(4-methyl piperazin-1-yl)quinoxaline) is a ligand that binds with high affinity to 5-HT3 receptors. Here we synthesise [3H]VUF10166 and characterise its binding properties at 5-HT3A and 5-HT3AB receptors. At 5-HT3A receptors [3H]VUF10166 displayed saturable binding with a Kd of 0.18 nM. Kinetic measurements gave monophasic association (6.25 × 107 M−1 min−1) and dissociation (0.01 min−1) rates that yielded a similar Kd value (0.16 nM). At 5-HT3AB receptors two association (6.15 × 10−7, 7.23 M−1 min−1) and dissociation (0.024, 0.162 min−1) rates were seen, yielding Kd values (0.38 nM and 22 nM) that were consistent with values obtained in saturation (Kd = 0.74 nM) and competition (Ki = 37 nM) binding experiments respectively. At both receptor types, specific binding was inhibited by classical 5-HT3 receptor-selective orthosteric ligands (5-HT, allosetron, d-tubocurarine, granisetron, mCPBG, MDL72222, quipazine), but not by non-competitive antagonists (bilobalide, ginkgolide B, picrotoxin) or competitive ligands of other Cys-loop receptors (ACh, bicuculline, glycine, gabazine). To explore VUF10166 ligand–receptor interactions we used in silico modelling and docking, and tested the predictions using site directed mutagenesis. The data suggest that VUF10166 adopts a similar orientation to 5-HT3 receptor agonists bound in AChBP (varenicline) and 5HTBP (5-HT) crystal structures. PMID:25174552

  7. Unraveling mechanisms underlying partial agonism in 5-HT3A receptors.

    PubMed

    Corradi, Jeremías; Bouzat, Cecilia

    2014-12-10

    Partial agonists have emerged as attractive therapeutic molecules. 2-Me-5HT and tryptamine have been defined as partial agonists of 5-HT3 receptors on the basis of macroscopic measurements. Because several mechanisms may limit maximal responses, we took advantage of the high-conductance form of the mouse serotonin type 3A (5-HT3A) receptor to understand their molecular actions. Individual 5-HT-bound receptors activate in long episodes of high open probability, consisting of groups of openings in quick succession. The activation pattern is similar for 2-Me-5HT only at very low concentrations since profound channel blockade takes place within the activating concentration range. In contrast, activation episodes are significantly briefer in the presence of tryptamine. Generation of a full activation scheme reveals that the fully occupied receptor overcomes transitions to closed preopen states (primed states) before opening. Reduced priming explains the partial agonism of tryptamine. In contrast, 2-Me-5HT is not a genuine partial agonist since priming is not dramatically affected and its low apparent efficacy is mainly due to channel blockade. The analysis also shows that the first priming step is the rate-limiting step and partial agonists require an increased number of priming steps for activation. Molecular docking suggests that interactions are similar for 5-HT and 2-Me-5HT but slightly different for tryptamine. Our study contributes to understanding 5-HT3A receptor activation, extends the novel concept of partial agonism within the Cys-loop family, reveals novel aspects of partial agonism, and unmasks molecular actions of classically defined partial agonists. Unraveling mechanisms underlying partial responses has implications in the design of therapeutic compounds.

  8. Involvement of 5-HT3 receptors in the action of vortioxetine in rat brain: Focus on glutamatergic and GABAergic neurotransmission.

    PubMed

    Riga, Maurizio S; Sánchez, Connie; Celada, Pau; Artigas, Francesc

    2016-09-01

    The antidepressant vortioxetine is a 5-HT3-R, 5-HT7-R and 5-HT1D-R antagonist, 5-HT1B-R partial agonist, 5-HT1A-R agonist, and serotonin (5-HT) transporter (SERT) inhibitor. Vortioxetine occupies all targets at high therapeutic doses and only SERT and 5-HT3-R at low doses. Vortioxetine increases extracellular monoamine concentrations in rat forebrain more than selective serotonin reuptake inhibitors (SSRI) and shows pro-cognitive activity in preclinical models. Given its high affinity for 5-HT3-R (Ki = 3.7 nM), selectively expressed in GABA interneurons, we hypothesized that vortioxetine may disinhibit glutamatergic and monoaminergic neurotransmission following 5-HT3-R blockade. Here we assessed vortioxetine effect on pyramidal neuron activity and extracellular 5-HT concentration using in vivo extracellular recordings of rat medial prefrontal cortex (mPFC) pyramidal neurons and microdialysis in mPFC and ventral hippocampus (vHPC). Vortioxetine, but not escitalopram, increased pyramidal neuron discharge in mPFC. This effect was prevented by SR57227A (5-HT3-R agonist) and was mimicked by ondansetron (5-HT3-R antagonist) and by escitalopram/ondansetron combinations. In microdialysis experiments, ondansetron augmented the 5-HT-enhancing effect of escitalopram in mPFC and vHPC. Local ondansetron in vHPC augmented escitalopram effect, indicating the participation of intrinsic mechanisms. Since 5-HT neurons express GABAB receptors, we examined their putative involvement in controlling 5-HT release after 5-HT3-R blockade. Co-perfusion of baclofen (but not muscimol) reversed the increased 5-HT levels produced by vortioxetine and escitalopram/ondansetron combinations in vHPC. The present results suggest that vortioxetine increases glutamatergic and serotonergic neurotransmission in rat forebrain by blocking 5-HT3 receptors in GABA interneurons.

  9. Partial Agonism of 5-HT3 Receptors: A Novel Approach to the Symptomatic Treatment of IBS-D

    PubMed Central

    2012-01-01

    Irritable bowel syndrome (IBS) is a functional bowel disorder characterized by abdominal pain, discomfort, and altered bowel habits, which have a significant impact on quality of life for approximately 10–20% of the population. IBS can be divided into three main types IBS-D (diarrhea predominant), IBS-C (constipation predominant), and mixed or alternating IBS. 5-HT3 receptor antagonism has proved to be an efficacious treatment option for IBS-D. For example, alosetron displays efficacy in the treatment of multiple symptoms, including abdominal pain, discomfort, urgency, stool frequency and consistency. However, significant constipation occurred in approximately 25% of patients, leading to withdrawal of up to 10% of patients in clinical trials. Targeting compounds with partial agonist activity at the 5-HT3 receptor represents a mechanistic departure from the classic 5-HT3 receptor antagonist approach and should result in agents that are applicable to a broader array of IBS patient populations. Attenuation of the activity of the ion channel without completely abolishing its function may control or normalize bowel function without leading to a total block associated with severe constipation. We have identified a new class of selective, orally active 5-HT3 receptor ligands with high 5-HT3 receptor affinity and low partial agonist activity currently in preclinical development that should offer a significant advantage over existing therapies. PMID:23342199

  10. Immunohistochemical characterization of 5-HT(3A) receptors in the Syrian hamster forebrain.

    PubMed

    Carrillo, Maria; Ricci, Lesley A; Schwartzer, Jared J; Melloni, Richard H

    2010-05-06

    The Syrian hamster (Mesocricetus auratus) has been extensively used as an animal model to investigate neuronal networks underlying various behaviors where 5-HT(3A) receptors have been found to play a critical role. To date, however, there is no comprehensive description of the distribution of 5-HT(3A) receptors in the Syrian hamster brain. The current study examined the localization of 5-HT(3A) receptors across the neuraxis of the Syrian hamster forebrain using immunohistochemistry. Overall, 5-HT(3A) receptors were widely and heterogeneously distributed across the neuraxis of the Syrian hamster brain. Notably, the most intense 5-HT(3A) immunolabeling patterns were observed in the cerebral cortex and amygdala. In addition, high variability in receptor density and expression patterns (i.e., perikarya, fibers and/or neuropilar puncta) was observed within the majority of brain areas examined, indicating that the role this receptor has in the modulation of a particular neural function differs depending on brain region. In some regions (i.e., nucleus accumbens) differences in the immunolabeling pattern between rostral, medial and caudal portions were also observed, suggesting functional heterogeneity of this receptor within a single brain region. Together, these results and the localization of this receptor to brain areas involved in the regulation of sexual behavior, aggression, circadian rhythm, drug abuse and anxiety implicate 5-HT(3A) receptors in the modulation of various behaviors and neural functions in the Syrian hamster. Further, these results underscore the importance of evaluating 5-HT(3A) receptors as a pharmacological target for the treatment of various psychopathological disorders.

  11. The interaction of trichloroethanol with murine recombinant 5-HT3 receptors.

    PubMed Central

    Downie, D L; Hope, A G; Belelli, D; Lambert, J J; Peters, J A; Bentley, K R; Steward, L J; Chen, C Y; Barnes, N M

    1995-01-01

    1. The effects of ethanol, chloral hydrate and trichloroethanol upon the 5-HT3 receptor have been investigated by use of electrophysiological techniques applied to recombinant 5-HT3 receptor subunits (5-HT3R-A or 5-HT3R-As) expressed in Xenopus laevis oocytes. Additionally, the influence of trichloroethanol upon the specific binding of [3H]-granisetron to membrane preparations of HEK 293 cells stably transfected with the murine 5-HT3R-As subunit and 5-HT3 receptors endogenous to NG 108-15 cell membranes was assessed. 2. Ethanol (30-300 mM), chloral hydrate (1-30 mM) and trichloroethanol (0.3-10 mM), produced a reversible, concentration-dependent, enhancement of 5-HT-mediated currents recorded from oocytes expressing either the 5-HT3R-A, or the 5-HT3R-As subunit. 3. Trichloroethanol (5 mM) produced a parallel leftward shift of the 5-HT concentration-response curve, reducing the EC50 for 5-HT from 1 +/- 0.04 microM (n = 4) to 0.5 +/- 0.01 microM (n = 4) for oocytes expressing the 5-HT3R-A. A similar shift, from 2.1 +/- 0.05 microM (n = 11) to 1.3 +/- 0.1 microM (n = 4), was observed in oocytes expressing the 5-HT3R-As subunit. Trichloroethanol (5 mM) had little or no effect upon the maximum current produced by 5-HT for either recombinant receptor. 4. Trichloroethanol (5 mM) similarly reduced the EC50 for 2-methyl-5-HT from 13 +/- 0.4 microM (n = 4) to 4.6 +/- 0.2 microM (n = 4) and from 15 +/- 2 microM (n = 4) to 5 +/- 0.4 microM (n = 4) for oocytes expressing the 5-HT3R-A and 5-HT3R-As subunit respectively. Additionally, trichloroethanol (5 mM) produced a clear enhancement of the maximal current to 2-methyl-5-HT (expressed as a percentage of the maximal current to 5-HT) from 63 +/- 0.7% (n = 4) to 101 +/- 1.6% (n = 4) and from 9 +/- 0.2% (n = 4) to 74 +/- 2% (n = 4) for oocytes expressing the 5-HT3R-A and 5-HT3R-As subunit respectively. 5. Trichloroethanol (2.5 mM) had no effect upon the Kd, or Bmax, of specific [3H]-granisetron binding to membrane homogenates of NG

  12. Molecular properties of psychopharmacological drugs determining non-competitive inhibition of 5-HT3A receptors.

    PubMed

    Kornhuber, Johannes; Terfloth, Lothar; Bleich, Stefan; Wiltfang, Jens; Rupprecht, Rainer

    2009-06-01

    We developed a structure-property-activity relationship (SPAR)-model for psychopharmacological drugs acting as non-competitive 5-HT(3A) receptor antagonists by using a decision-tree learner provided by the RapidMiner machine learning tool. A single molecular descriptor, namely the molecular dipole moment per molecular weight (mu/MW), predicts whether or not a substance non-competitively antagonizes 5-HT-induced Na(+) currents. A low mu/MW is compatible with drug-cumulation in apolar lipid rafts. This study confirms that size-intensive descriptors allow the development of compact SPAR models.

  13. Quantitation of 5HT3 receptors in forebrain of serotonin transporter deficient mice.

    PubMed

    Mössner, R; Schmitt, A; Hennig, T; Benninghoff, J; Gerlach, M; Riederer, P; Deckert, J; Lesch, K P

    2004-01-01

    Mice deficient in the serotonin transporter (5HTT) display highly elevated extracellular 5HT levels. 5HT exerts ist effects via at least fourteen different cloned 5HT receptors located pre- and postsynaptically. In contrast to the other 5HT receptors, the 5HT3 receptor is a ionotropic receptor with ligand-gated cation channel function. Since G-protein-coupled 5HT receptors show extensive adaptive changes in 5HTT-deficient mice, we investigated whether 5HT3 receptors are also altered in these mice. Using quantitative autoradiography, we found that 5HT3 receptors are upregulated in frontal cortex (+46%), parietal cortex (+42%), and in stratum oriens of the CA3 region of the hippocampus (+18%) of 5HTT knockout mice. Changes in 5HT3 receptor mRNA expression, as determined by quantitative in situ hybridisation, were less pronounced. The adaptive changes of 5HT3 receptor expression constitute a part of the complex regulatory pattern of 5HT receptors in 5HTT knockout mice.

  14. Method for individualized evaluation of antiemetic effect induced by 5-HT3 receptor antagonist.

    PubMed

    Nakamura, Hironori; Yokoyama, Haruko; Yoshimoto, Koichi; Nakajima, Akihiro; Okuyama, Kiyoshi; Iwase, Osamu; Yamada, Yasuhiko

    2013-01-01

    5-HT3 receptor antagonists are widely used for prevention of chemotherapy-induced nausea and vomiting, though their antiemetic effects vary among patients. We investigated a method for evaluation of antiemetic effects in individual patients. We used the 5-HT3 receptor occupancy of serotonin for our evaluation, which was estimated based on the plasma concentration of granisetron and concentration of serotonin near the 5-HT3 receptor in the small intestine, obtained by measuring the urinary concentrations of granisetron and 5-hydroxyindoleacetic acid (5-HIAA)/creatinine (Cre). The mean cumulative percent for urinary excretion of granisetron at 24 h after administration and coefficient of variation were 16.19 ± 6.30% and 38.91%, respectively. The time course of urinary concentration of 5-HIAA/Cre also varied among the patients. The value for 5-HT3 receptor occupancy of serotonin without granisetron was higher than that prior to administration (blank), thus most treated patients had the possibility of induced emesis. In contrast, that with granisetron was lower than the blank value, indicating that those treated patients would not develop emesis. Furthermore, the estimated 5-HT3 receptor occupancy of serotonin in the small intestine and actual individual patient condition corresponded well, showing the validity of our method. Our results suggest that it is possible to evaluate individual antiemetic effects by estimating the 5-HT3 receptor occupancy of serotonin in the small intestine based on plasma concentrations of granisetron and serotonin near the 5-HT3 receptor in the small intestine using noninvasive urine samples. This method of individual evaluation is considered to be useful and effective.

  15. Serotonin enhances urinary bladder nociceptive processing via a 5-HT3 receptor mechanism.

    PubMed

    Hall, Jason D; DeWitte, Cary; Ness, Timothy J; Robbins, Meredith T

    2015-09-14

    Serotonin from the descending pain modulatory pathway is critical to nociceptive processing. Its effects on pain modulation may either be inhibitory or facilitatory, depending on the type of pain and which receptors are involved. Little is known about the role of serotonergic systems in bladder nociceptive processing. These studies examined the effect of systemic administration of the serotonin precursor, 5-hydroxytryptophan (5-HTP), on normal bladder and somatic sensation in rats. ELISA was used to quantify peripheral and central changes in serotonin and its major metabolite following 5-HTP administration, and the potential role of the 5-HT3 receptor on changes in bladder sensation elicited by 5-HTP was investigated. 5-HTP produced bladder hypersensitivity and somatic analgesia. The pro-nociceptive effect of 5-HTP was attenuated by intrathecal, but not systemic, ondansetron. Peripheral increases in serotonin, its metabolism and rate of turnover were detectable within 30min of 5-HTP administration. Significant enhancement of serotonin metabolism was observed centrally. These findings suggest that 5-HTP increases serotonin, which may then affect descending facilitatory systems to produce bladder hypersensitivity via activation of spinal 5-HT3 receptors.

  16. Open probability of homomeric murine 5-HT3A serotonin receptors depends on subunit occupancy

    PubMed Central

    Mott, David D; Erreger, Kevin; Banke, Tue G; Traynelis, Stephen F

    2001-01-01

    The time course of macroscopic current responses of homomeric murine serotonin 5-HT3A receptors was studied in whole cells and excised membrane patches under voltage clamp in response to rapid application of serotonin. Serotonin activated whole cell currents with an EC50 value for the peak response of 2 μm and a Hill slope of 3.0 (n = 12), suggesting that the binding of at least three agonist molecules is required to open the channel. Homomeric 5-HT3A receptors in excised membrane patches had a slow activation time course (mean ±s.e.m. 10-90 % rise time 12.5 ± 1.6 ms; n = 9 patches) for 100 μm serotonin. The apparent activation rate was estimated by fitting an exponential function to the rising phase of responses to supramaximal serotonin to be 136 s−1. The 5-HT3A receptor response to 100 μm serotonin in outside-out patches (n = 19) and whole cells (n = 41) desensitized with a variable rate that accelerated throughout the experiment. The time course for desensitization was described by two exponential components (for patches τslow 1006 ± 139 ms, amplitude 31 % τfast 176 ± 25 ms, amplitude 69 %). Deactivation of the response following serotonin removal from excised membrane patches (n = 8) and whole cells (n = 29) was described by a dual exponential time course with time constants similar to those for desensitization (for patches τslow 838 ± 217 ms, 55 % amplitude; τfast 213 ± 44 ms, 45 % amplitude). In most patches (6 of 8), the deactivation time course in response to a brief 1-5 ms pulse of serotonin was similar to or slower than desensitization. This suggests that the continued presence of agonist can induce desensitization with a similar or more rapid time course than agonist unbinding. The difference between the time course for deactivation and desensitization was voltage independent over the range -100 to -40 mV in patches (n = 4) and -100 to +50 mV in whole cells (n = 4), suggesting desensitization of these receptors in the presence of

  17. The Structure of the Mouse Serotonin 5-HT3 Receptor in Lipid Vesicles.

    PubMed

    Kudryashev, Mikhail; Castaño-Díez, Daniel; Deluz, Cédric; Hassaine, Gherici; Grasso, Luigino; Graf-Meyer, Alexandra; Vogel, Horst; Stahlberg, Henning

    2016-01-05

    The function of membrane proteins is best understood if their structure in the lipid membrane is known. Here, we determined the structure of the mouse serotonin 5-HT3 receptor inserted in lipid bilayers to a resolution of 12 Å without stabilizing antibodies by cryo electron tomography and subtomogram averaging. The reconstruction reveals protein secondary structure elements in the transmembrane region, the extracellular pore, and the transmembrane channel pathway, showing an overall similarity to the available X-ray model of the truncated 5-HT3 receptor determined in the presence of a stabilizing nanobody. Structural analysis of the 5-HT3 receptor embedded in a lipid bilayer allowed the position of the membrane to be determined. Interactions between the densely packed receptors in lipids were visualized, revealing that the interactions were maintained by the short horizontal helices. In combination with methodological improvements, our approach enables the structural analysis of membrane proteins in response to voltage and ligand gating.

  18. Seizure susceptibility alteration through 5-HT(3) receptor: modulation by nitric oxide.

    PubMed

    Gholipour, Taha; Ghasemi, Mehdi; Riazi, Kiarash; Ghaffarpour, Majid; Dehpour, Ahmad Reza

    2010-01-01

    There is some evidence that epileptic seizures could be induced or increased by 5-hydroxytryptamine (5-HT) attenuation, while augmentation of serotonin functions within the brain (e.g. by SSRIs) has been reported to be anticonvulsant. This study was performed to determine the effect of selective 5-HT(3) channel/receptor antagonist granisetron and agonist SR57227 hydrochloride on the pentylenetetrazole (PTZ)-induced seizure threshold in mice. The possible interaction of this effect with nitrergic system was also examined using the nitric oxide (NO) synthase inhibitor N(G)-nitro-l-arginine methyl ester (l-NAME) and the NO precursor l-arginine. SR57227 (10mg/kg, i.p.) significantly increased the seizure threshold compared to control group, while high dose granisetron (10mg/kg, i.p.) proved proconvulsant. Co-administration of sub-effective doses of the 5-HT(3) agonist with l-NAME (5 and 60mg/kg, i.p., respectively) exerted a significant anticonvulsive effect, while sub-effective doses of granisetron (3mg/kg) was observed to have a proconvulsive action with the addition of l-arginine (75mg/kg, i.p.). Our data demonstrate that enhancement of 5-HT(3) receptor function results in as anticonvulsant effect in the PTZ-induced seizure model, and that selective antagonism at the 5-HT(3) receptor yields proconvulsive effects. Furthermore, the NO system may play a role in 5-HT(3) receptor function.

  19. The muscarinic antagonists scopolamine and atropine are competitive antagonists at 5-HT3 receptors.

    PubMed

    Lochner, Martin; Thompson, Andrew J

    2016-09-01

    Scopolamine is a high affinity muscarinic antagonist that is used for the prevention of post-operative nausea and vomiting. 5-HT3 receptor antagonists are used for the same purpose and are structurally related to scopolamine. To examine whether 5-HT3 receptors are affected by scopolamine we examined the effects of this drug on the electrophysiological and ligand binding properties of 5-HT3A receptors expressed in Xenopus oocytes and HEK293 cells, respectively. 5-HT3 receptor-responses were reversibly inhibited by scopolamine with an IC50 of 2.09 μM. Competitive antagonism was shown by Schild plot (pA2 = 5.02) and by competition with the 5-HT3 receptor antagonists [(3)H]granisetron (Ki = 6.76 μM) and G-FL (Ki = 4.90 μM). The related molecule, atropine, similarly inhibited 5-HT evoked responses in oocytes with an IC50 of 1.74 μM, and competed with G-FL with a Ki of 7.94 μM. The reverse experiment revealed that granisetron also competitively bound to muscarinic receptors (Ki = 6.5 μM). In behavioural studies scopolamine is used to block muscarinic receptors and induce a cognitive deficit, and centrally administered concentrations can exceed the IC50 values found here. It is therefore possible that 5-HT3 receptors are also inhibited. Studies that utilise higher concentrations of scopolamine should be mindful of these potential off-target effects.

  20. Synthesis and characterization of photoaffinity probes that target the 5-HT3 receptor.

    PubMed

    Jack, Thomas; Ruepp, Marc-David; Thompson, Andrew J; Mühlemann, Oliver; Lochner, Martin

    2014-01-01

    The 5-HT3 receptor is one of several ion channels responsible for the transmission of nerve impulses in the peripheral and central nervous systems. Until now, it has been difficult to characterize transmembrane receptors with classical structural biology approaches like X-ray crystallography. The use of photoaffinity probes is an alternative approach to identify regions in the protein where small molecules bind. To this end, we present two photoaffinity probes based on granisetron, a well known antagonist of the 5-HT3 receptor. These new probes show nanomolar binding affinity for the orthosteric binding site. In addition, we investigated their reactivity using irradiation experiments.

  1. Anti-depressant-like activity of a novel serotonin type-3 (5-HT3) receptor antagonist in rodent models of depression.

    PubMed

    Gupta, Deepali; Devadoss, Thangaraj; Bhatt, Shvetank; Gautam, Baldev; Jindal, Ankur; Pandey, Dilip; Mahesh, Radhakrishnan

    2011-08-01

    N-Cyclohexyl-3-methoxyquinoxalin-2-carboxamide (QCM-13), a novel 5-HT3 antagonist identified from a series of compounds with higher pA2 (7.6) and good log P (2.91) value was screened in rodent models of depression such as forced swim test (FST), tail suspension test (TST), interaction studies with standard anti-depressants and confirmatory studies such as reversal of parthenolide induced depression and reserpine induced hypothermia. In FST (2 and 4 mg/kg) and TST (2 and 4 mg/kg), QCM-13 significantly reduced the duration of immobility in mice without affecting the base line locomotion. QCM-13 (2 and 4 mg/kg) was also found to have significant interaction with standard anti-depressants (fluoxetine and bupropion in FST and TST respectively). Further, reversal of parthenolide induced depression in mice and reserpine induced hypothermia in rat models indicate the serotonergic influence of QCM-13 for anti-depressant potential.

  2. Molecular dynamics simulation of the structure and dynamics of 5-HT3 serotonin receptor

    NASA Astrophysics Data System (ADS)

    Antonov, M. Yu.; Popinako, A. V.; Prokopiev, G. A.

    2016-10-01

    In this work, we investigated structure, dynamics and ion transportation in transmembrane domain of the 5-HT3 serotonin receptor. High-resolution (0.35 nm) structure of the 5-HT3 receptor in complex with stabilizing nanobodies was determined by protein crystallography in 2014 (Protein data bank (PDB) code 4PIR). Transmembrane domain of the structure was prepared in complex with explicit membrane environment (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC)) and solvent (TIP3P water model). Molecular dynamics protocols for simulation and stabilization of the transmembrane domain of the 5-HT3 receptor model were developed and 60 ns simulation of the structure was conducted in order to explore structural parameters of the system. We estimated the mean force profile for Na+ ions using umbrella sampling method.

  3. 5-HT3 receptors as important mediators of nausea and vomiting due to chemotherapy.

    PubMed

    Navari, Rudolph M

    2015-10-01

    Chemotherapy-induced nausea and vomiting (CINV) is associated with a significant deterioration in quality of life. The emetogenicity of the chemotherapeutic agents, repeated chemotherapy cycles, and patient risk factors significantly influence CINV. The use of a combination of a 5-hydroxytryptamine-3 (5-HT3) receptor antagonist, dexamethasone, and a neurokinin-1 (NK-1) receptor antagonist has significantly improved the control of acute and delayed emesis in single-day chemotherapy. The first generation 5-HT3 receptor antagonists have been very effective in the control of chemotherapy induced emesis in the first 24 h postchemotherapy (acute emesis), but have not been as effective against delayed emesis (24-120 h postchemotherapy). Palonosetron, a second generation 5-HT3 receptor antagonist with a different half-life, a different binding capacity, and a different mechanism of action than the first generation 5-HT3 receptor antagonists appears to be the most effective agent in its class. Despite the control of emesis, nausea has not been well controlled by current agents. Olanzapine, a FDA approved antipsychotic that blocks multiple neurotransmitters: dopamine at D1, D2, D3, D4 brain receptors, serotonin at 5-HT2a, 5-HT2c, 5-HT3, 5-HT6 receptors, catecholamines at alpha1 adrenergic receptors, acetylcholine at muscarinic receptors, and histamine at H1 receptors, has emerged in recent trials as an effective preventative agent for chemotherapy-induced emesis and nausea, as well as a very effective agent for the treatment of breakthrough emesis and nausea. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.

  4. Palonosetron-5-HT3 Receptor Interactions As Shown by a Binding Protein Cocrystal Structure.

    PubMed

    Price, Kerry L; Lillestol, Reidun K; Ulens, Chris; Lummis, Sarah C R

    2016-12-21

    Palonosetron is a potent 5-HT3 receptor antagonist and an effective therapeutic agent against emesis. Here we identify the molecular determinants of compound recognition in the receptor binding site by obtaining a high resolution structure of palonosetron bound to an engineered acetylcholine binding protein that mimics the 5-HT3 receptor binding site, termed 5-HTBP, and by examining the potency of palonosetron in a range of 5-HT3 receptors with mutated binding site residues. The structural data indicate that palonosetron forms a tight and effective wedge in the binding pocket, made possible by its rigid tricyclic ring structure and its interactions with binding site residues; it adopts a binding pose that is distinct from the related antiemetics granisetron and tropisetron. The functional data show many residues previously shown to interact with agonists and antagonists in the binding site are important for palonosetron binding, and indicate those of particular importance are W183 (a cation-π interaction and a hydrogen bond) and Y153 (a hydrogen bond). This information, and the availability of the structure of palonosetron bound to 5-HTBP, should aid the development of novel and more efficacious drugs that act via 5-HT3 receptors.

  5. Serotonin (5-HT3) receptor antagonists for the reduction of symptoms of low anterior resection syndrome

    PubMed Central

    Itagaki, Ryohei; Koda, Keiji; Yamazaki, Masato; Shuto, Kiyohiko; Kosugi, Chihiro; Hirano, Atsushi; Arimitsu, Hidehito; Shiragami, Risa; Yoshimura, Yukino; Suzuki, Masato

    2014-01-01

    Purpose Serotonin (5-hydroxytryptamine [5-HT])3 receptor antagonists are effective for the treatment of diarrhea-predominant irritable bowel syndrome (IBS-D), in which exaggerated intestinal/colonic hypermotility is often observed. Recent studies have suggested that the motility disorder, especially spastic hypermotility, seen in the neorectum following sphincter-preserving operations for rectal cancer may be the basis of the postoperative defecatory malfunction seen in these patients. We investigated the efficacy of 5-HT3 receptor antagonists in patients suffering from severe low anterior resection syndrome. Patients and methods A total of 25 male patients with complaints of uncontrollable urgency or fecal incontinence following sphincter-preserving operations were enrolled in this study. Defecatory status, assessed on the basis of incontinence score (0–20), urgency grade (0–3), and number of toilet visits per day, was evaluated using a questionnaire before and 1 month after the administration of the 5-HT3 antagonist ramosetron. Results All the parameters assessed improved significantly after taking ramosetron for 1 month. The effect was more prominent in cases whose anastomotic line was lower, ie, inside the anal canal. Defecatory function was better in patients who commenced ramosetron therapy within 6 months postoperatively, as compared to those who were not prescribed ramosetron for more than 7 months postoperatively. Conclusion These results suggest that 5-HT3 antagonists are effective for the treatment of low anterior resection syndrome, as in diarrhea-predominant irritable bowel syndrome. The improvement in symptoms is not merely time dependent, but it is related to treatment with 5-HT3 antagonists. PMID:24648748

  6. Synergistic antiemetic interactions between serotonergic 5-HT3 and tachykininergic NK1-receptor antagonists in the least shrew (Cryptotis parva).

    PubMed

    Darmani, Nissar A; Chebolu, Seetha; Amos, Barry; Alkam, Tursun

    2011-10-01

    Significant electrophysiological and biochemical findings suggest that receptor cross-talk occurs between serotonergic 5-HT(3)- and tachykininergic NK(1)-receptors in which co-activation of either receptor by ineffective doses of their corresponding agonists (serotonin (5-HT) or substance P (SP), respectively) potentiates the activity of the other receptor to produce a response. In contrast, selective blockade of any one of these receptors attenuates the increase in abdominal vagal afferent activity caused by either 5-HT or SP. This interaction has important implications in chemotherapy-induced nausea and vomiting (CINV) since 5-HT(3)- and NK(1)-receptor antagonists are the major classes of antiemetics used in cancer patients receiving chemotherapy. The purpose of this study was to demonstrate whether the discussed interaction produces effects at the behavioral level in a vomit-competent species, the least shrew. Our results demonstrate that pretreatment with either a 5-HT(3) (tropisetron)- or an NK(1) (CP99,994)-receptor specific antagonist, attenuates vomiting caused by a selective agonist (2-methyl 5-HT or GR73632, respectively) of both emetic receptors. In addition, relative to each antagonist alone, their combined doses were 4-20 times more potent against vomiting caused by each emetogen. Moreover, combined sub-maximal doses of the agonists 2-methyl 5-HT and GR73632, produced 8-12 times greater number of vomits relative to each emetogen tested alone. However, due to large variability in vomiting caused by the combination doses, the differences failed to attain significance. The antiemetic dose-response curves of tropisetron against both emetogens were U-shaped probably because larger doses of this antagonist behave as a partial agonist. The data demonstrate that 5-HT(3)- and NK(1)-receptors cross-talk to produce vomiting, and that synergistic antiemetic effects occur when both corresponding antagonists are concurrently used against emesis caused by each

  7. The 5-HT3 receptor is essential for exercise-induced hippocampal neurogenesis and antidepressant effects.

    PubMed

    Kondo, M; Nakamura, Y; Ishida, Y; Shimada, S

    2015-11-01

    Exercise has a variety of beneficial effects on brain structure and function, such as hippocampal neurogenesis, mood and memory. Previous studies have shown that exercise enhances hippocampal neurogenesis, induces antidepressant effects and improves learning behavior. Brain serotonin (5-hydroxytryptamine, 5-HT) levels increase following exercise, and the 5-HT system has been suggested to have an important role in these exercise-induced neuronal effects. However, the precise mechanism remains unclear. In this study, analysis of the 5-HT type 3A receptor subunit-deficient (htr3a(-/-)) mice revealed that lack of the 5-HT type 3 (5-HT3) receptor resulted in loss of exercise-induced hippocampal neurogenesis and antidepressant effects, but not of learning enhancement. Furthermore, stimulation of the 5-HT3 receptor promoted neurogenesis. These findings demonstrate that the 5-HT3 receptor is the critical target of 5-HT action in the brain following exercise, and is indispensable for hippocampal neurogenesis and antidepressant effects induced by exercise. This is the first report of a pivotal 5-HT receptor subtype that has a fundamental role in exercise-induced morphological changes and psychological effects.

  8. 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

  9. 5-HT3 receptor influences the washing phenotype and visual organization in obsessive-compulsive disorder supporting 5-HT3 receptor antagonists as novel treatment option.

    PubMed

    Lennertz, Leonhard; Wagner, Michael; Grabe, Hans Jörgen; Franke, Petra E; Guttenthaler, Vera; Rampacher, Friederike; Schulze-Rauschenbach, Svenja; Vogeley, Andrea; Benninghoff, Jens; Ruhrmann, Stephan; Pukrop, Ralf; Klosterkötter, Joachim; Falkai, Peter; Maier, Wolfgang; Mössner, Rainald

    2014-01-01

    A role of the HTR3A-E genes in obsessive-compulsive disorder (OCD) can be expected based on promising effects of 5-HT3 receptor antagonists as adjunctive treatment of OCD. We therefore genotyped six common coding or promoter variants within the HTR3A-E genes in a case-control-sample consisting of N=236 OCD patients and N=310 control subjects and in N=58 parent-child-trios. Given the heterogeneous OCD phenotype, we also investigated OCD symptom dimensions and cognitive endophenotypes in subsamples. OCD patients scoring high for the washing subtype were significantly more likely to carry the c.256G-allele of the HTR3E variant rs7627615 (p=0.0001) as compared to OCD patients low for this symptom dimension. Visual organization was impaired in OCD patients and unaffected relatives as compared to healthy control subjects and carriers of the HTR3E c.256G/c.256G-genotype performed significantly worse (p=0.007). The case-control analyses revealed a nominal significant association of the HTR3D variant rs1000592 (p.H52R) with OCD (p=0.029) which was also evident after combination of the case-control and the trio-results (p=0.024). In male subjects, the variant rs6766410 (p.N163K) located in the HTR3C was significantly associated with OCD (p=0.007). The association findings of the HTR3C and the HTR3E remained significant after correction for the number of variants investigated. These findings indicate a role of common variants of the HTR3A-E genes in OCD and OCD-related phenotypes and further support the use of 5-HT3 receptor antagonists as novel treatment options. The HTR3E gene is a novel candidate gene impacting on the individual expression of OC symptoms and OCD-related cognitive dysfunction.

  10. Theoretical evaluation of antiemetic effects of 5-HT3 receptor antagonists for prevention of vomiting induced by cisplatin.

    PubMed

    Nakamura, Hironori; Yokoyama, Haruko; Takayanagi, Risa; Yoshimoto, Koichi; Nakajima, Akihiro; Okuyama, Kiyoshi; Iwase, Osamu; Yamada, Yasuhiko

    2015-03-01

    5-HT(3) receptor antagonists are widely used as antiemetic agents in clinical setting, of which palonosetron, with a long elimination half life (t(1/2)), has recently become available. It is important to evaluate the concentration of serotonin when investigating the antiemetic effects of 5-HT(3) receptor antagonists, as those effects are not based solely on the t(1/2) value. We theoretically evaluated the antiemetic effects of three 5-HT(3) receptor antagonists (granisetron, azasetron, palonosetron) on cisplatin-induced nausea and vomiting by estimating the time course of the 5-HT(3) receptor occupancy of serotonin. We estimated the 5-HT(3) receptor occupancy of serotonin in the small intestine, based on the time course of plasma concentration of each 5-HT(3) receptor antagonist and the time course of concentration of serotonin near the 5-HT(3) receptor in the small intestine after administration of cisplatin. The antiemetic effect of each 5-HT(3) receptor antagonist was evaluated based on the normal level of 5-HT(3) receptor occupancy of serotonin. Our results suggest that an adequate antiemetic effect will be provided when a dose of 75 mg/m(2) of cisplatin is given to patients along with any single administration of granisetron, azasetron, or palonosetron at a usual dose. On the other hand, the 5-HT(3) receptor occupancy of serotonin was found to be significantly lower than normal for several days after administration of palonosetron, as compared to granisetron and azasetron, indicating that constipation may be induced. Our results show that granisetron, azasetron, and palonosetron each have an adequate antiemetic effect after administration of 75 mg/m(2) of cisplatin.

  11. Influence of sodium substitutes on 5-HT-mediated effects at mouse 5-HT3 receptors

    PubMed Central

    Barann, M; Schmidt, K; Göthert, M; Urban, B W; Bönisch, H

    2004-01-01

    The influence of sodium ion substitutes on the 5-hydroxytryptamine (5-HT)-induced flux of the organic cation [14C]guanidinium through the ion channel of the mouse 5-HT3 receptor and on the competition of 5-HT with the selective 5-HT3 receptor antagonist [3H]GR 65630 was studied, unless stated otherwise, in mouse neuroblastoma N1E-115 cells. Under physiological conditions (135 mM sodium), 5-HT induced a concentration-dependent [14C]guanidinium influx with an EC50 (1.3 μM) similar to that in electrophysiological studies. The stepwise replacement of sodium by increasing concentrations of the organic cation hydroxyethyl trimethylammonium (choline) concentration dependently caused both a rightward shift of the 5-HT concentration–response curve and an increase in the maximum effect of 5-HT. Complete replacement of sodium resulted in a 34-fold lower potency of 5-HT and an almost two times higher maximal response. A low potency of 5-HT in choline buffer was also observed in other 5-HT3 receptor-expressing rodent cell lines (NG 108-15 or NCB 20). Replacement of Na+ by Li+ left the potency and maximal effects of 5-HT almost unchanged. Replacement by tris (hydroxymethyl) methylamine (Tris), tetramethylammonium (TMA) or N-methyl-D-glucamine (NMDG) caused an increase in maximal response to 5-HT similar to that caused by choline. The potency of 5-HT was only slightly reduced by Tris, to a high degree decreased by TMA (comparable to the decrease by choline), but not influenced by NMDG. The potency of 5-HT in inhibiting [3H]GR65630 binding to intact cells was 35-fold lower when sodium was completely replaced by choline, but remained unchanged after replacement by NMDG. The results are compatible with the suggestion that choline competes with 5-HT for the 5-HT3 receptor; the increase in maximal response may be partly due to a choline-mediated delay of the 5-HT-induced desensitization. For studies of 5-HT-evoked [14C]guanidinium flux through 5-HT3 receptor channels, NMDG appears

  12. [Cost-effectiveness analysis of 5-HT3 receptor antagonist drugs in cancer chemotherapy].

    PubMed

    Ishimaru, Hiromasa; Takayama, Shinji; Shiokawa, Mitsuru; Inoue, Tadao

    2008-04-01

    Recently, ambulatory treatment centers (ATC) are markedly increasingboth in number and scale. It is therefore important to consolidate an efficient therapeutic system. A decrease in both treatment time and waitingtime leads to not only the improvement of the quality of life (QOL) for patients but also the efficient use of personnel and running costs for medical institutions by reducingthe bed occupation rate. In ATC, 5-HT3 receptor antagonists are extensively used for high emetic risk patients. However, their high cost and prolonged treatment causes one of the problems in improvingthe efficiency of the therapeutic system when they are administered by intravenous infusion. Amongthe 4 types of 5-HT3 receptor antagonists (injections) currently available in Japan, azasetron is the only drugthat is not designated as a powerful drug and that can be administered by bolus intravenous infusion. In this study, we investigated azasetron and granisetron from the standpoint of pharmacoeconomics with a simulation model using the results of clinical studies in Japan. Accordingto the results of cost-effectiveness analysis, therapeutic and time costs per patient for azasetron 10 mgand granisetron 2 mg (calculated in consideration of both medical institutions and patients) was 8,219 and 10,193 yen, respectively. This gap was attributable to the time loss due to the difference in administration methods. The result suggests that this time loss is more significant not only for patients but also for medical staff than the loss attributable to the drugcost. Furthermore, the bolus intravenous infusion of azasetron is considered superior to the non-bolus intravenous infusion of granisetron from a pharmacoeconomic standpoint. It is desirable to choose the appropriate administration method of 5-HT3 receptor antagonists in various chemotherapy regimens for the purpose of reducingthe treatment time and promotingthe efficiency of the therapeutic system at ATCs.

  13. Inhibition of temporomandibular joint input to medullary dorsal horn neurons by 5HT3 receptor antagonist in female rats

    PubMed Central

    Okamoto, Keiichiro; Katagiri, Ayano; Rahman, Mostafeezur; Thompson, Randall; Bereiter, David A.

    2015-01-01

    Repeated forced swim (FS) conditioning enhances nociceptive responses to temporomandibular joint (TMJ) stimulation in male and female rats. The basis for FS-induced TMJ hyperalgesia remains unclear. To test the hypothesis that serotonin 3 receptor (5HT3R) mechanisms contribute to enhanced TMJ nociception after FS, ovariectomized female rats were treated with estradiol and subjected to FS for three days. On day 4, rats were anesthetized with isoflurane and TMJ-responsive neurons were recorded from superficial and deep laminae at the trigeminal subnucleus caudalis/upper cervical (Vc/C1–2) region and electromyographic (EMG) activity was recorded from the masseter muscle. Only Vc/C1–2 neurons activated by intra-TMJ injections of ATP were included for further analysis. Although neurons in both superficial and deep laminae were activated by ATP, only neurons in deep laminae displayed enhanced responses after FS. Local application of the 5HT3R antagonist, ondansetron (OND), at the Vc/C1–2 region reduced the ATP-evoked responses of neurons in superficial and deep laminae and reduced the EMG response in both sham and FS rats. OND also decreased the spontaneous firing rate of neurons in deep laminae and reduced the high threshold convergent cutaneous receptive field area of neurons in superficial and deep laminae in both sham and FS rats. These results revealed that central application of a 5HT3R antagonist, had widespread effects on the properties of TMJ-responsive neurons at the Vc/C1–2 region and on jaw muscle reflexes under sham and FS conditions. It is concluded that 5HT3R does not play a unique role in mediating stress-induced hyperalgesia related to TMJ nociception. PMID:25913635

  14. Inhibition of temporomandibular joint input to medullary dorsal horn neurons by 5HT3 receptor antagonist in female rats.

    PubMed

    Okamoto, K; Katagiri, A; Rahman, M; Thompson, R; Bereiter, D A

    2015-07-23

    Repeated forced swim (FS) conditioning enhances nociceptive responses to temporomandibular joint (TMJ) stimulation in female rats. The basis for FS-induced TMJ hyperalgesia remains unclear. To test the hypothesis that serotonin 3 receptor (5HT3R) mechanisms contribute to enhanced TMJ nociception after FS, ovariectomized female rats were treated with estradiol and subjected to FS for three days. On day 4, rats were anesthetized with isoflurane and TMJ-responsive neurons were recorded from superficial and deep laminae at the trigeminal subnucleus caudalis/upper cervical (Vc/C1-2) region and electromyographic (EMG) activity was recorded from the masseter muscle. Only Vc/C1-2 neurons activated by intra-TMJ injections of ATP were included for further analysis. Although neurons in both superficial and deep laminae were activated by ATP, only neurons in deep laminae displayed enhanced responses after FS. Local application of the 5HT3R antagonist, ondansetron (OND), at the Vc/C1-2 region reduced the ATP-evoked responses of neurons in superficial and deep laminae and reduced the EMG response in both sham and FS rats. OND also decreased the spontaneous firing rate of neurons in deep laminae and reduced the high-threshold convergent cutaneous receptive field area of neurons in superficial and deep laminae in both sham and FS rats. These results revealed that central application of a 5HT3R antagonist, had widespread effects on the properties of TMJ-responsive neurons at the Vc/C1-2 region and on jaw muscle reflexes under sham and FS conditions. It is concluded that 5HT3R does not play a unique role in mediating stress-induced hyperalgesia related to TMJ nociception.

  15. The rapid recovery of 5-HT cell firing induced by the antidepressant vortioxetine involves 5-HT(3) receptor antagonism.

    PubMed

    Bétry, Cécile; Pehrson, Alan L; Etiévant, Adeline; Ebert, Bjarke; Sánchez, Connie; Haddjeri, Nasser

    2013-06-01

    The therapeutic effect of current antidepressant drugs appears after several weeks of treatment and a significant number of patients do not respond to treatment. Here, we report the effects of the multi-modal antidepressant vortioxetine (Lu AA21004), a 5-HT(3) and 5-HT(7) receptor antagonist, 5-HT(1B) receptor partial agonist, 5-HT(1A) receptor agonist and 5-HT transporter (SERT) inhibitor, on rat 5-HT neurotransmission. Using in vivo electrophysiological recordings in the dorsal raphe nucleus of anaesthetized rats, we assessed the acute and subchronic effects of vortioxetine and/or the selective 5-HT(3) receptor agonist, SR57227 or the selective 5-HT(1A) receptor agonist flesinoxan, on 5-HT neuronal firing activity. Using ex-vivo autoradiography, we correlated SERT occupancy and presumed 5-HT firing activity. The selective serotonin reuptake inhibitor, fluoxetine, was used as comparator. Importantly, the recovery of 5-HT neuronal firing was achieved after 1 d with vortioxetine and 14 d with fluoxetine. SR57227 delayed this recovery. In contrast, vortioxetine failed to alter the reducing action of 3 d treatment of flesinoxan. Acute dosing of vortioxetine inhibited neuronal firing activity more potently than fluoxetine. SR57227 prevented the suppressant effect of vortioxetine, but not of fluoxetine. In contrast, flesinoxan failed to modify the suppressant effect of vortioxetine acutely administered. Differently to fluoxetine, vortioxetine suppressed neuronal firing without saturating occupancy at the SERT. Vortioxetine produced a markedly faster recovery of 5-HT neuronal firing than fluoxetine. This is at least partly due to 5-HT(3) receptor antagonism of vortioxetine in association with its reduced SERT occupancy.

  16. Inhibitory effects of dextrorotatory morphinans on the human 5-HT(3A) receptor expressed in Xenopus oocytes: Involvement of the N-terminal domain of the 5-HT(3A) receptor.

    PubMed

    Lee, Byung-Hwan; Hwang, Sung-Hee; Choi, Sun-Hye; Shin, Tae-Joon; Kang, Jiyeon; Kim, Hyun-Joong; Kim, Hyoung-Chun; Lee, Joon-Hee; Nah, Seung-Yeol

    2012-07-05

    We previously developed a series of dextromethorphan (DM, 3-methoxy-17-methylmorphinan) analogs modified at positions 3 and 17 of the morphinan ring system. Recent reports have shown that DM attenuates abdominal pain caused by irritable bowel syndrome, and multidrug regimens that include DM prevent nausea/vomiting following cancer surgery. However, little is known regarding the molecular mechanisms underlying the beneficial effects of DM. Here, we investigated the effects of DM, 3 of its analogs (AM, 3-allyloxy-17-methoxymorphian; CM, 3-cyclopropyl-17-methoxymorphinan; and DF, 3-methyl-17-methylmorphinan), and 1 of its metabolites (HM, 3-methoxymorphinan) on the activity of the human 5-HT(3A) receptor channel expressed in Xenopus laevis oocytes, using the 2-microelectrode voltage clamp technique. We found that intra-oocyte injection of human 5-HT(3A) receptor cRNAs elicited an inward current (I(5-HT)) in the presence of 5-HT. Cotreatment with AM, CM, DF, DM, or HM inhibited I(5-HT) in a dose-dependent, voltage-independent, and reversible manner. The IC(50) values for AM, CM, DF, DM, and HM were 24.5±1.4, 21.5±4.2, 132.6±35.8, 181.3±23.5, and 191.3±31.5μM, respectively. The IC(50) values of AM and CM were 7-fold lower than that of DM, and mechanistic analysis revealed that DM, DF, HM, AM, and CM were competitive inhibitors of I(5-HT). Point mutations of Arg241 in the N-terminal, but not amino acids in the pore region, to other amino acid residues attenuated or abolished DM- and DM-analog-induced inhibition of I(5-HT). Together, these results demonstrated that dextrorotatory morphinans might regulate 5-HT(3A) receptor channel activity via interaction with its N-terminal domain.

  17. 2-(4-substituted piperazin-1-yl)-1,8-naphthyridine-3-carboxylic acids: novel 5-HT3 receptor antagonists with anxiolytic-like activity in rodent behavioral models.

    PubMed

    Mahesh, Radhakrishnan; Dhar, Arghya Kusum; Jindal, Ankur; Bhatt, Shvetank

    2013-10-01

    The aim of this study was to investigate the anxiolytic potential of a series of novel carboxylic acid based 1,8 naphthyridines as 5-HT3 receptor antagonists. The pA2 values of all the compounds were determined against agonist 2-methyl-5-hydroxytryptamine in longitudinal muscle myenteric plexus preparations from guinea pig ileum. Compounds with higher pA2 values, particularly those greater than ondansetron, a standard 5-HT3 receptor antagonist, and optimal log P values were screened in mice by using behavioral tests such as a light-dark (L/D) aversion test, elevated plus maze (EPM) test, and an open field test (OFT). In the L/D test, compounds 7a, 7b, 7d, 7e, and 7i (2 mg/kg body mass, intraperitoneal) significantly (P < 0.05) increased the latency time to leave the light compartment, total time spent in the light compartment, and the number of transitions between the light and dark compartments. Compounds 7a, 7d, 7f, 7h, and 7i (2 mg/kg, i.p.) significantly (P < 0.05) increased the time spent in the open arms and the number of entries into the open arms in the EPM test. In addition, compounds 7a, 7d, 7e, 7f, and 7h (2 mg/kg, i.p.) significantly (P < 0.05) increased the ambulation scores and the frequency of rearing in the OFT.

  18. Discovery of a novel allosteric modulator of 5-HT3 receptors: inhibition and potentiation of Cys-loop receptor signaling through a conserved transmembrane intersubunit site.

    PubMed

    Trattnig, Sarah M; Harpsøe, Kasper; Thygesen, Sarah B; Rahr, Louise M; Ahring, Philip K; Balle, Thomas; Jensen, Anders A

    2012-07-20

    The ligand-gated ion channels in the Cys-loop receptor superfamily mediate the effects of neurotransmitters acetylcholine, serotonin, GABA, and glycine. Cys-loop receptor signaling is susceptible to modulation by ligands acting through numerous allosteric sites. Here we report the discovery of a novel class of negative allosteric modulators of the 5-HT(3) receptors (5-HT(3)Rs). PU02 (6-[(1-naphthylmethyl)thio]-9H-purine) is a potent and selective antagonist displaying IC(50) values of ~1 μM at 5-HT(3)Rs and substantially lower activities at other Cys-loop receptors. In an elaborate mutagenesis study of the 5-HT(3)A receptor guided by a homology model, PU02 is demonstrated to act through a transmembrane intersubunit site situated in the upper three helical turns of TM2 and TM3 in the (+)-subunit and TM1 and TM2 in the (-)-subunit. The Ser(248), Leu(288), Ile(290), Thr(294), and Gly(306) residues are identified as important molecular determinants of PU02 activity with minor contributions from Ser(292) and Val(310), and we propose that the naphthalene group of PU02 docks into the hydrophobic cavity formed by these. Interestingly, specific mutations of Ser(248), Thr(294), and Gly(306) convert PU02 into a complex modulator, potentiating and inhibiting 5-HT-evoked signaling through these mutants at low and high concentrations, respectively. The PU02 binding site in the 5-HT(3)R corresponds to allosteric sites in anionic Cys-loop receptors, which emphasizes the uniform nature of the molecular events underlying signaling through the receptors. Moreover, the dramatic changes in the functional properties of PU02 induced by subtle changes in its binding site bear witness to the delicate structural discrimination between allosteric inhibition and potentiation of Cys-loop receptors.

  19. Functional evidence for the rapid desensitization of 5-HT(3) receptors on vagal afferents mediating the Bezold-Jarisch reflex

    NASA Technical Reports Server (NTRS)

    Whalen, E. J.; Johnson, A. K.; Lewis, S. J.

    2000-01-01

    The aim of this study was to determine whether 5-hydroxytryptamine (5-HT)(3) receptors on cardiopulmonary afferents mediating the Bezold-Jarisch reflex (BJR) desensitize upon repeated exposure to selective agonists. BJR-mediated falls in heart rate, diastolic arterial blood pressure and cardiac output elicited by the 5-HT(3)-receptor agonists, phenylbiguanide (100 microg/kg, i.v.) or 2-methyl-5-HT (100 microg/kg, i.v.), progressively diminished upon repeated injection in conscious rats. The BJR responses elicited by 5-HT (40 microg/kg, i.v.) were markedly reduced in rats which had received the above injections of phenylbiguanide or 2-methyl-5-HT whereas the BJR responses elicited by L-S-nitrosocysteine (10 micromol/kg, i.v.) were similar before and after the injections of the 5-HT(3) receptor agonists. These findings suggest that tachyphylaxis to 5-HT(3) receptor agonists may be due to the desensitization of 5-HT(3) receptors on cardiopulmonary afferents rather than the impairment of the central or peripheral processing of the BJR.

  20. Comparative Pharmacology and Guide to the Use of the Serotonin 5-HT3 Receptor Antagonists for Postoperative Nausea and Vomiting.

    PubMed

    Kovac, Anthony L

    2016-12-01

    Since the introduction of the serotonin 5-hydroxy tryptamine 3 (5-HT3) receptor antagonists in the early 1990s, the incidence of postoperative nausea and vomiting (PONV) and post-discharge nausea and vomiting (PDNV) has decreased, yet continues to be a problem for the surgical patient. The clinical application of the 5-HT3 receptor antagonists has helped define the approach and role of these antiemetics in the prevention and treatment of PONV and PDNV. Pharmacological and clinical differences exist among these medications resulting in corresponding differences in effectiveness, safety, optimal dosage, time of administration, and use as combination and rescue antiemetic therapy. The clinical application of the 5-HT3 receptor antagonist antiemetics has improved the prevention and treatment of PONV and PDNV. The most recent consensus guidelines for PONV published in 2014 outline the use of these antiemetics. The 5-HT3 receptor antagonists play an important role to help prevent PONV and PDNV in perioperative care pathways such as Enhanced Recovery After Surgery (ERAS). Comparisons and guidelines for use of the 5-HT3 receptor antagonists in relation to the risk for PONV and PDNV are reviewed.

  1. [Effect of the 5-HT3 receptor antagonist granisetron on estramustine phosphate sodium (Estracyt)-induced emesis in ferrets].

    PubMed

    Higashioka, Masaya; Yamaguchi, Emi; Takatori, Shingo; Tanaka, Mitsushi; Kyoi, Takashi

    2010-07-01

    Estracyt(R) is an antimitotic drug used for the treatment of prostate cancer, and its most common adverse effects are nausea and vomiting. In this study, we investigated the effect of a 5-HT3 receptor antagonist, granisetron, on emesis induced in ferrets by estramustine phosphate sodium (EMP), the active ingredient of Estracyt. To clarify the mechanism of action of EMP-induced emesis, we also investigated the effect of EMP on the release of serotonin (5-HT) in the isolated rat ileum. EMP (3 mg/kg, per os) induced 75.3+/-10.2 retching episodes and 7.5+/-1.3 vomiting episodes during a 2-h observation period. The latency to the first emetic response was 58.0+/-13.5 min. Granisetron (0.1 mg/kg, per os) administered 1 h before the administration of EMP reduced the number of EMP-induced retching and vomiting episodes to 1.3+/-1.3 and 1.0+/-1.0, respectively, and prolonged the latency by a factor of almost two. EMP (10-5 and 10-4 M) increased 5-HT release from isolated rat ileum, and 10 -7 M granisetron almost completely inhibited the increase induced by 10-4 M EMP. These results suggest that EMP induces nausea and vomiting via 5-HT release from the ileum, and that 5-HT3 receptor antagonists may be useful to prevent gastrointestinal adverse effects that occur during treatment with Estracyt.

  2. The 5-HT3 receptor antagonist, ondansetron, blocks the development and expression of ethanol-induced locomotor sensitization in mice.

    PubMed

    Umathe, Sudhir N; Bhutada, Pravinkumar S; Raut, Vivek S; Jain, Nishant S; Mundhada, Yogita R

    2009-02-01

    Manipulation of the serotonergic system has been shown to alter ethanol sensitization. Ondansetron is a 5-HT3 receptor antagonist, reported to attenuate cocaine and methamphetamine-induced behavioral sensitization, but no reports are available on its role in ethanol-induced behavioral sensitization. Therefore, an attempt has been made to assess this issue by using an earlier used animal model of ethanol-induced locomotor sensitization. Results indicated that ondansetron (0.25-1.0 mg/kg, subcutaneously) given before the challenge dose of ethanol (2.4 g/kg, intraperitoneally) injection, significantly and dose dependently attenuated the expression of sensitization. In addition, ondansetron (1.0 mg/kg, subcutaneously) given before ethanol injection on days 1, 4, 7, and 10 significantly blocked the development (days 1, 4, 7, and 10), and expression (day 15) of sensitization to the locomotor stimulant effect of ethanol injection. Ondansetron had no effect per se on locomotor activity and did not affect blood ethanol levels. Therefore, the results raise the possibility that ondansetron blocked the development and expression of ethanol-induced locomotor sensitization by acting on 5-HT3 receptors.

  3. Superagonist, Full Agonist, Partial Agonist, and Antagonist Actions of Arylguanidines at 5-Hydroxytryptamine-3 (5-HT3) Subunit A Receptors.

    PubMed

    Alix, Katie; Khatri, Shailesh; Mosier, Philip D; Casterlow, Samantha; Yan, Dong; Nyce, Heather L; White, Michael M; Schulte, Marvin K; Dukat, Małgorzata

    2016-11-16

    Introduction of minor variations to the substitution pattern of arylguanidine 5-hydroxytryptamine-3 (5-HT3) receptor ligands resulted in a broad spectrum of functionally-active ligands from antagonist to superagonist. For example, (i) introduction of an additional Cl-substituent(s) to our lead full agonist N-(3-chlorophenyl)guanidine (mCPG, 2; efficacy % = 106) yielded superagonists 7-9 (efficacy % = 186, 139, and 129, respectively), (ii) a positional isomer of 2, p-Cl analog 11, displayed partial agonist actions (efficacy % = 12), and (iii) replacing the halogen atom at the meta or para position with an electron donating OCH3 group or a stronger electron withdrawing (i.e., CF3) group resulted in antagonists 13-16. We posit based on combined mutagenesis, crystallographic, and computational analyses that for the 5-HT3 receptor, the arylguanidines that are better able to simultaneously engage the primary and complementary subunits, thus keeping them in close proximity, have greater agonist character while those that are deficient in this ability are antagonists.

  4. A 5-HT3 receptor antagonist potentiates the behavioral, neurochemical and electrophysiological actions of an SSRI antidepressant.

    PubMed

    Bétry, C; Overstreet, D; Haddjeri, N; Pehrson, A L; Bundgaard, C; Sanchez, C; Mørk, A

    2015-04-01

    More effective treatments for major depression are needed. We studied if the selective 5-HT3 receptor antagonist ondansetron can potentiate the antidepressant potential of the selective serotonin (5-HT) reuptake inhibitor (SSRI) paroxetine using behavioral, neurochemical and electrophysiological methods. Flinders Sensitive Line (FSL) rats, treated with ondansetron, and/or a sub-effective dose of paroxetine, were assessed in the forced swim test. The effects of an acute intravenous administration of each compound alone and in combination were evaluated with respect to 5-HT neuronal firing rate in the dorsal raphe nucleus (DRN). Effects of s.c. administration of the compounds alone and in combination on extracellular levels of 5-HT were assessed in the ventral hippocampus of freely moving rats by microdialysis. The results showed that ondansetron enhanced the antidepressant activity of paroxetine in the forced swim test. It partially prevented the suppressant effect of paroxetine on DRN 5-HT neuronal firing and enhanced the paroxetine-induced increase of hippocampal extracellular 5-HT release. These findings indicate that 5-HT3 receptor blockade potentiates the antidepressant effects of SSRIs. Since both paroxetine and ondansetron are used clinically, it might be possible to validate this augmentation strategy in depressed patients.

  5. Impact of 5-HT3 receptor antagonists on chemotherapy-induced nausea and vomiting: a retrospective cohort study

    PubMed Central

    2012-01-01

    Background 1st generation 5-hydroxytryptamine receptor antagonists (5-HT3 RAs), and palonosetron, a 2nd generation 5-HT3 RA, are indicated for the prevention of chemotherapy (CT)-induced nausea and vomiting (CINV) associated with moderately (MEC) and highly emetogenic CT agents (HEC). This study explores the impact of step therapy policies requiring use of an older 5-HT3 RA before palonosetron on risk of CINV associated with hospital or emergency department (ED) admissions. Methods Patients who received cyclophosphamide post breast cancer (BC) surgery or who were diagnosed with lung cancer on carboplatin (LC-carboplatin) or cisplatin (LC-cisplatin) were selected from PharMetrics’ (IMS LifeLink) claims dataset (2005-2008). Patients were followed for 6 months from initial CT administration for CINV events identified through ICD-9-CM codes. Patients were grouped into those initiated with older, generic 5-HT3 RAs (ondansetron, granisetron, and dolasetron) and those initiated and maintained on palonosetron throughout study follow-up. CINV events and CINV days were analyzed using multivariate regressions controlling for demographic and clinical variables. Results Eligible patients numbered 3,606 in BC, 4,497 in LC-carboplatin and 1,154 in LC-cisplatin cohorts, with 52%, 40%, and 34% in the palonosetron group, respectively. There was no significant difference between the two 5-HT3 RA groups in age or Charlson Comorbidity Index among the two MEC cohorts (BC and LC-carboplatin). Among the LC-cisplatin cohort, palonosetron users were older with more males than the older 5-HT3 RA group (age: 60.1 vs. 61.3; males, 66.9% vs. 56.9%). Compared to the older 5-HT3 RAs, the palonosetron groups incurred 22%-51% fewer 5-HT3 RA pharmacy claims, had fewer patients with CINV events (3.5% vs. 5.5% in BC, 9.5% vs. 12.8% in LC-carboplatin, 16.4% vs. 21.7% in LC-cisplatin), and had lower risk for CINV events (odds ratios 0.62, 0.71, or 0.71, respectively; p < 0.05). The BC and LC

  6. Spinal 5-HT3 receptors mediate descending facilitation and contribute to behavioral hypersensitivity via a reciprocal neuron-glial signaling cascade

    PubMed Central

    2014-01-01

    Background It has been recently recognized that the descending serotonin (5-HT) system from the rostral ventromedial medulla (RVM) in the brainstem and the 5-HT3 receptor subtype in the spinal dorsal horn are involved in enhanced descending pain facilitation after tissue and nerve injury. However, the mechanisms underlying the activation of the 5-HT3 receptor and its contribution to facilitation of pain remain unclear. Results In the present study, activation of spinal 5-HT3 receptors by intrathecal injection of a selective 5-HT3 receptor agonist SR 57227 induced spinal glial hyperactivity, neuronal hyperexcitability and pain hypersensitivity in rats. We found that there was neuron-to-microglia signaling via the chemokine fractalkine, microglia to astrocyte signaling via cytokine IL-18, astrocyte to neuronal signaling by IL-1β, and enhanced activation of NMDA receptors in the spinal dorsal horn. Glial hyperactivation in spinal dorsal horn after hindpaw inflammation was also attenuated by molecular depletion of the descending 5-HT system by intra-RVM Tph-2 shRNA interference. Conclusions These findings offer new insights into the cellular and molecular mechanisms at the spinal level responsible for descending 5-HT-mediated pain facilitation during the development of persistent pain after tissue and nerve injury. New pain therapies should focus on prime targets of descending facilitation-induced glial involvement, and in particular the blocking of intercellular signaling transduction between neurons and glia. PMID:24913307

  7. Effects of iodoproxyfan, a potent and selective histamine H3 receptor antagonist, on alpha 2 and 5-HT3 receptors.

    PubMed

    Schlicker, E; Pertz, H; Bitschnau, H; Purand, K; Kathmann, M; Elz, S; Schunack, W

    1995-07-01

    We determined the affinity and/or potency of the novel H3 receptor antagonist iodoproxyfan at alpha 2 and 5-HT3 receptors. Iodoproxyfan and rauwolscine (a reference alpha 2 ligand) (i) monophasically displaced 3H-rauwolscine binding to rat brain cortex membranes (pKi 6.79 and 8.59); (ii) facilitated the electrically evoked tritium overflow from superfused mouse brain cortex slices preincubated with 3H-noradrenaline (pEC50 6.46 and 7.91) and (iii) produced rightward shifts of the concentration-response curve (CRC) of (unlabelled) noradrenaline for its inhibitory effect on the evoked overflow (pA2 6.65 and 7.88). In the guinea-pig ileum, iodoproxyfan 6.3 mumol/l failed to evoke a contraction by itself but depressed the maximum of the CRC of 5-hydroxytryptamine (pD'2 5.24). Tropisetron (a reference 5-HT3 antagonist) produced rightward shifts of the CRC of 5-hydroxytryptamine (pA2 7.84). In conclusion, the affinity/potency of iodoproxyfan at H3 receptors (range 8.3-9.7 [1]) exceeds that at alpha 2 receptors by at least 1.5 log units and that at 5-HT3 receptors by at least 3 log units.

  8. MDL72222, a serotonin 5-HT3 receptor antagonist, blocks MDMA's ability to establish a conditioned place preference.

    PubMed

    Bilsky, E J; Reid, L D

    1991-06-01

    Methylenedioxymethamphetamine (MDMA) has previously been shown to produce a positive conditioned place preference (CPP) among rats. Here the effects of doses of a specific 5-HT3 antagonist, MDL72222, on MDMA's ability to produce a CPP were assessed. A dose of MDL72222 (0.03 mg/kg) blocked the establishment of a MDMA CPP. These results support the suggestions that compounds affecting the 5-HT3 receptor may be of particular interest in studying the pharmacology of self-administered drugs.

  9. P2X3 receptors induced inflammatory nociception modulated by TRPA1, 5-HT3 and 5-HT1A receptors.

    PubMed

    Krimon, Suzy; Araldi, Dionéia; do Prado, Filipe César; Tambeli, Cláudia Herrera; Oliveira-Fusaro, Maria Cláudia G; Parada, Carlos Amílcar

    2013-11-01

    It has been described that endogenous ATP via activation of P2X3 and P2X2/3 receptors contributes to inflammatory nociception in different models, including the formalin injected in subcutaneous tissue of the rat's hind paw. In this study, we have evaluated whether TRPA1, 5-HT3 and 5-HT1A receptors, whose activation is essential to formalin-induced inflammatory nociception, are involved in the nociception induced by activation of P2X3 receptors on subcutaneous tissue of the rat's hind paw. We have also evaluated whether the activation of P2X3 receptors increases the susceptibility of primary afferent neurons to formalin action modulated by activation of TRPA1, 5-HT3 or 5-HT1A receptors. Nociceptive response intensity was measured by observing the rat's behavior and considering the number of times the animal reflexively raised its hind paw (flinches) in 60min. Local subcutaneous administration of the selective TRPA1, 5-HT3 or 5-HT1A receptor antagonists HC 030031, tropisetron and WAY 100,135, respectively, prevented the nociceptive responses induced by the administration in the same site of the non-selective P2X3 receptor agonist αβmeATP. Administration of the selective P2X3 and P2X2/3 receptor antagonist A-317491 or pretreatment with oligonucleotides antisense against P2X3 receptor prevented the formalin-induced behavioral nociceptive responses during the first and second phases. Also, the co-administration of a subthreshold dose of αβmeATP with a subthreshold dose of formalin induced nociceptive behavior, which was prevented by local administration of tropisetron, HC 030031 or WAY 100, 135. These findings have demonstrated that the activation of P2X3 receptors induces inflammatory nociception modulated by TRPA1, 5-HT3 and 5-HT1A receptors. Also, they suggest that inflammatory nociception is modulated by the release of endogenous ATP and P2X3 receptor activation, which in turn, increases primary afferent nociceptor susceptibility to the action of inflammatory

  10. Blockade of 5-Ht3 receptors in the septal area increases Fos expression in selected brain areas.

    PubMed

    Urzedo-Rodrigues, Lilia S; Ferreira, Hilda S; Santana, Rejane Conceição; Luz, Carla Patrícia; Perrone, Camila F; Fregoneze, Josmara B

    2014-04-01

    Serotonin is widely distributed throughout the brain and is involved in a multiplicity of visceral, cognitive and behavioral responses. It has been previously shown that injections of different doses of ondansetron, a 5-HT3 receptor antagonist, into the medial septum/vertical limb of the diagonal band complex (MS/vDB) induce a hypertensive response in rats. On the other hand, administration of m-CPBG, a 5-HT3 agonist, into the MS/vDB inhibits the increase of blood pressure during restraint stress. However, it is unclear which neuronal circuitry is involved in these responses. The present study investigated Fos immunoreactive nuclei (Fos-IR) in different brain areas following the blockade of 5-HT3 receptors located in the MS/vDB in sham and in sinoaortic denervated (SAD) rats. Ondansetron injection into the MS/vDB increases Fos-IR in different brain areas including the limbic system (central amygdala and ventral part of the bed nucleus of the stria terminalis), hypothalamus (medial parvocellular parts of the paraventricular nucleus, anterodorsal preoptic area, dorsomedial hypothalamic nucleus), mesencephalon (ventrolateral periaqueductal gray region) and rhombencephalon (lateral parabrachial nucleus) in sham rats. Barodenervation results in higher Fos expression at the parvocellular and magnocellular part of the paraventricular nucleus, the lateral parabrachial nucleus, the central nucleus of amygdala, the locus coeruleus, the medial part of the nucleus of the solitary tract, the rostral ventrolateral medulla and the caudal ventrolateral medulla following 5-HT3receptor blockade in the MS/vDB. Based on the present results and previous data showing a hypertensive response to ondansetron injected into the MS/vDB, it is reasonable to suggest that 5-HT3receptors in the MS/vDB exert an inhibitory drive that may oscillate as a functional regulatory part of the complex central neuronal network participating in the control of blood pressure.

  11. Emesis and Defecations Induced by the 5-Hydroxytryptamine (5-HT3) Receptor Anatagonist Zacopride in the Ferret

    DTIC Science & Technology

    1990-02-16

    and Defecations Induced by the 5 -Hydroxytryptamine ( 5 -HT 3) Receptor Antagonist Zacopride in the Ferret1 GREGORY L. KING Department of Physiology...benzamides and 5 -hydroxytryptamine ( 5 - Zacopride (4-amino-N-[ 1-azabicyclo(2.2.2)oct-3-yl]- 5 -chloro- HT:i) receptor antagonists are effective...prompted development of 5 - the dose-response properties of zacop -ide-induced emesis and HT, receptor antagonist antiemetics with limited gastric

  12. Investigation of 5-HT3 receptor-triggered serotonin release from guinea-pig isolated colonic mucosa: a role of PYY-containing endocrine cell.

    PubMed

    Kojima, Shu-Ichi; Kojima, Ken; Fujita, Tomoe

    2017-03-15

    The effect of a 5-HT3 receptor-selective agonist SR57227A was investigated on the outflow of 5-hydroxytryptamine (5-HT) from isolated muscle layer-free mucosal preparations of guinea-pig colon. The mucosal preparations were incubated in vitro and the outflow of 5-HT from these preparations was determined by high-performance liquid chromatography with electrochemical detection. SR57227A (100μM) produced a tetrodotoxin-resistant and sustained increase in the outflow of 5-HT from the mucosal preparations. The SR57227A-evoked sustained 5-HT outflow was completely inhibited by the 5-HT3 receptor antagonist ramosetron (1μM). The neuropeptide Y1 receptor antagonist BIBO3304 (100nM) partially inhibited the SR57227A-evoked sustained 5-HT outflow, but the Y2 receptor antagonist BIIE0246 (1μM) or the glucagon-like peptide-1 (GLP-1) receptor antagonist exendin-(9-39) (1μM), showed a minimal effect on the SR57227A-evoked sustained 5-HT outflow. In the presence of BIBO3304 (100nM) and exendin-(9-39) (1μM), SR57227A (100μM) failed to produce a sustained increase in the outflow of 5-HT. The Y1 receptor agonist [Leu(31), Pro(34)]-neuropeptide Y (10nM), but not GLP-1-(7-36) amide (100nM), produced a sustained increase in the outflow of 5-HT. We found that 5-HT3 receptor-triggered 5-HT release from guinea-pig colonic mucosa is mediated by the activation of 5-HT3 receptors located at endocrine cells (enterochromaffin cells and peptide YY (PYY)-containing endocrine cells). The activation of both Y1 and GLP-1 receptors appears to be required for the maintenance of 5-HT3 receptor-triggered 5-HT release. It is therefore considered that 5-HT3 receptors located at colonic mucosa play a crucial role in paracrine signaling between enterochromaffin cells and PYY-containing endocrine cells.

  13. 5-Hydroxytryptamine (5-HT) Cellular Sequestration during Chronic Exposure Delays 5-HT3 Receptor Resensitization due to Its Subsequent Release*

    PubMed Central

    Hothersall, J. Daniel; Alexander, Amy; Samson, Andrew J.; Moffat, Christopher; Bollan, Karen A.; Connolly, Christopher N.

    2014-01-01

    The serotonergic synapse is dynamically regulated by serotonin (5-hydroxytryptamine (5-HT)) with elevated levels leading to the down-regulation of the serotonin transporter and a variety of 5-HT receptors, including the 5-HT type-3 (5-HT3) receptors. We report that recombinantly expressed 5-HT3 receptor binding sites are reduced by chronic exposure to 5-HT (IC50 of 154.0 ± 45.7 μm, t½ = 28.6 min). This is confirmed for 5-HT3 receptor-induced contractions in the guinea pig ileum, which are down-regulated after chronic, but not acute, exposure to 5-HT. The loss of receptor function does not involve endocytosis, and surface receptor levels are unaltered. The rate and extent of down-regulation is potentiated by serotonin transporter function (IC50 of 2.3 ± 1.0 μm, t½ = 3.4 min). Interestingly, the level of 5-HT uptake correlates with the extent of down-regulation. Using TX-114 extraction, we find that accumulated 5-HT remains soluble and not membrane-bound. This cytoplasmically sequestered 5-HT is readily releasable from both COS-7 cells and the guinea pig ileum. Moreover, the 5-HT level released is sufficient to prevent recovery from receptor desensitization in the guinea pig ileum. Together, these findings suggest the existence of a novel mechanism of down-regulation where the chronic release of sequestered 5-HT prolongs receptor desensitization. PMID:25281748

  14. Dynamic Expression of Serotonin Receptor 5-HT3A in Developing Sensory Innervation of the Lower Urinary Tract

    PubMed Central

    Ritter, K. Elaine; Southard-Smith, E. Michelle

    2017-01-01

    Sensory afferent signaling is required for normal function of the lower urinary tract (LUT). Despite the wide prevalence of bladder dysfunction and pelvic pain syndromes, few effective treatment options are available. Serotonin receptor 5-HT3A is a known mediator of visceral afferent signaling and has been implicated in bladder function. However, basic expression patterns for this gene and others among developing bladder sensory afferents that could be used to inform regenerative efforts aimed at treating deficiencies in pelvic innervation are lacking. To gain greater insight into the molecular characteristics of bladder sensory innervation, we conducted a thorough characterization of Htr3a expression in developing and adult bladder-projecting lumbosacral dorsal root ganglia (DRG) neurons. Using a transgenic Htr3a-EGFP reporter mouse line, we identified 5-HT3A expression at 10 days post coitus (dpc) in neural crest derivatives and in 12 dpc lumbosacral DRG. Using immunohistochemical co-localization we observed Htr3a-EGFP expression in developing lumbosacral DRG that partially coincides with neuropeptides CGRP and Substance P and capsaicin receptor TRPV1. A majority of Htr3a-EGFP+ DRG neurons also express a marker of myelinated Aδ neurons, NF200. There was no co-localization of 5-HT3A with the TRPV4 receptor. We employed retrograde tracing in adult Htr3a-EGFP mice to quantify the contribution of 5-HT3A+ DRG neurons to bladder afferent innervation. We found that 5-HT3A is expressed in a substantial proportion of retrograde traced DRG neurons in both rostral (L1, L2) and caudal (L6, S1) axial levels that supply bladder innervation. Most bladder-projecting Htr3a-EGFP+ neurons that co-express CGRP, Substance P, or TRPV1 are found in L1, L2 DRG, whereas Htr3a-EGFP+, NF200+ bladder-projecting neurons are from the L6, S1 axial levels. Our findings contribute much needed information regarding the development of LUT innervation and highlight the 5-HT3A serotonin receptor as

  15. Mode of action of peppermint oil and (-)-menthol with respect to 5-HT3 receptor subtypes: binding studies, cation uptake by receptor channels and contraction of isolated rat ileum.

    PubMed

    Heimes, Katharina; Hauk, Florian; Verspohl, Eugen J

    2011-05-01

    Peppermint oil (Mentha × piperita L. (Lamiaceae) has been shown to exert potent antiemetic properties, but its mode of action has not yet been elucidated. Among its active constituents (-)-menthol is the most important. Three different in vitro models were used to investigate the effects on 5-HT(3) receptors (serotonin receptor subtype): [(14)C]guanidinium influx into N1E-115 cells which express 5-HT(3) receptors, isotonic contractions of the isolated rat ileum and equilibrium competition binding studies using a radioactively labelled 5-HT(3) receptor antagonist ([(3)H]GR65630) (3-(5-methyl-1H-imidazol-4-yl)-1-(1-methyl-1H-indol-3-yl)-1-propanone). Both peppermint oil and (-)-menthol inhibited [(14)C]guanidinium influx through 5-HT(3) receptor channels as well as contractions of the ileum induced by serotonin. Neither the peppermint oil nor (-)-menthol, however, was able to displace [(3)H]GR65630 from 5-HT(3) binding sites. It may be concluded that peppermint oil and (-)-menthol exert their antiemetic effect at least partly by acting on the 5-HT(3) receptor ion-channel complex, probably by binding to a modulatory site distinct from the serotonin binding site.

  16. The antiemetic 5-HT3 receptor antagonist Palonosetron inhibits substance P-mediated responses in vitro and in vivo.

    PubMed

    Rojas, Camilo; Li, Ying; Zhang, Jie; Stathis, Marigo; Alt, Jesse; Thomas, Ajit G; Cantoreggi, Sergio; Sebastiani, Silvia; Pietra, Claudio; Slusher, Barbara S

    2010-11-01

    Palonosetron is the only 5-HT(3) receptor antagonist approved for the treatment of delayed chemotherapy-induced nausea and vomiting (CINV) in moderately emetogenic chemotherapy. Accumulating evidence suggests that substance P (SP), the endogenous ligand acting preferentially on neurokinin-1 (NK-1) receptors, not serotonin (5-HT), is the dominant mediator of delayed emesis. However, palonosetron does not bind to the NK-1 receptor. Recent data have revealed cross-talk between the NK-1 and 5HT(3) receptor signaling pathways; we postulated that if palonosetron differentially inhibited NK-1/5-HT(3) cross-talk, it could help explain its efficacy profile in delayed emesis. Consequently, we evaluated the effect of palonosetron, granisetron, and ondansetron on SP-induced responses in vitro and in vivo. NG108-15 cells were preincubated with palonosetron, granisetron, or ondansetron; antagonists were removed and the effect on serotonin enhancement of SP-induced calcium release was measured. In the absence of antagonist, serotonin enhanced SP-induced calcium-ion release. After preincubation with palonosetron, but not ondansetron or granisetron, the serotonin enhancement of the SP response was inhibited. Rats were treated with cisplatin and either palonosetron, granisetron, or ondansetron. At various times after dosing, single neuronal recordings from nodose ganglia were collected after stimulation with SP; nodose ganglia neuronal responses to SP were enhanced when the animals were pretreated with cisplatin. Palonosetron, but not ondansetron or granisetron, dose-dependently inhibited the cisplatin-induced SP enhancement. The results are consistent with previous data showing that palonosetron exhibits distinct pharmacology versus the older 5-HT(3) receptor antagonists and provide a rationale for the efficacy observed with palonosetron in delayed CINV in the clinic.

  17. Antiemetic effects of YM060, a potent and selective serotonin (5HT)3-receptor antagonist, in ferrets and dogs.

    PubMed

    Kamato, T; Miyata, K; Ito, H; Yuki, H; Yamano, M; Honda, K

    1991-11-01

    YM060, (R)-5-[(1-methyl-3-indolyl)carbonyl]-4,5,6,7-tetrahydro-1H-benzimidazole hydrochloride, is a new serotonin (5HT)3-receptor antagonist. We examined the effects of YM060 on chemotherapeutic agent-, apomorphine- and copper sulfate-induced emesis. Intravenous YM060 potently prevented cisplatin (10 mg/kg, i.v.)-induced emesis with ED50 values of 0.06 (0.05-0.07) micrograms/kg, i.v. in ferrets. Based on the ED50 values, YM060 was 300, 20 and 100 times more potent than ondansetron, granisetron and the S-isomer of YM060, respectively. The relative potencies of these drugs described above were similar to those in the previously reported 5HT3-receptor antagonism. YM060 given orally also potently inhibited cisplatin (10 mg/kg, i.p.)- and cyclophosphamide (200 mg/kg, i.p.)-induced emesis in ferrets with ED50 values of 0.1 (0.09-0.11) and 0.02 (0.16-0.27) micrograms/kg, p.o., respectively. All tested 5HT3-receptor antagonists including YM060 failed to prevent apomorphine (0.1 mg/kg, s.c.)-induced emesis in dogs and copper sulfate (1%, 10 ml, p.o.)-induced emesis in ferrets. Our data indicate that YM060 is a highly potent inhibitor of chemotherapeutic agent-induced emesis and that the antiemetic effect of YM060 may be depend on 5HT3-receptor antagonism.

  18. QoL evaluation of olanzapine for chemotherapy-induced nausea and vomiting comparing with 5-HT3 receptor antagonist.

    PubMed

    Liu, J; Tan, L; Zhang, H; Li, H; Liu, X; Yan, Z; Chen, J; Yang, H; Zhang, D

    2015-05-01

    This study evaluated the efficacy of olanzapine in preventing chemotherapy-induced nausea and vomiting (CINV) and improving the quality of life (QoL) of patients with cancer during chemotherapy. Two hundred twenty-nine patients with cancer who received chemotherapy from January 2008 to August 2008 were enrolled, and they were randomised to receive olanzapine or a 5-HT3 receptor antagonist. The patients completed a CINV questionnaire once daily on days 1-5 and a QoL questionnaire on days 0 and 6. The complete response (CR) rates for nausea (76.85% versus 46.2%) and vomiting (84.3% versus 67.6%) were significantly higher in the olanzapine group than in the 5-HT3 receptor antagonist group for delayed CINV but not for acute CINV. The CR rates for nausea (76.85% versus 44.44%) and vomiting (85.95% versus 67.59%) were also significantly higher in the olanzapine group for the 5 days post-chemotherapy. After chemotherapy, global health status, emotional functioning, and insomnia were improved in the olanzapine group but worsened in the 5-HT3 receptor antagonist group, whereas cognitive functioning and appetite loss were unchanged. Moreover, olanzapine significantly improved global health status, emotional functioning, social functioning, fatigue, nausea/vomiting, insomnia, and appetite loss. Olanzapine improved the QoL of patients with cancer during chemotherapy, in part by reducing the incidence of delayed CINV.

  19. Blockade of peripheral 5HT3 receptor attenuates the formalin-induced nocifensive behavior in persistent temporomandibular joint inflammation of rat.

    PubMed

    Okamoto, Keiichiro; Imbe, Hiroki; Tashiro, Akimasa; Kumabe, Shunji; Senba, Emiko

    2004-09-02

    The role of peripheral 5HT3 receptors in the orofacial nocifensive behavior induced by the injection of formalin into masseter muscle was evaluated. The behavioral activities evoked by the formalin injection exhibited a biphasic response in the rats with or without temporomandibular joint (TMJ) inflammation (CFA group or non-CFA group). The orofacial nocifensive behavioral activity was enhanced after TMJ inflammation. Systemic administration of tropisetron, 5HT3 receptor antagonist, reduced the nocifensive behavioral activities in the late phase of orofacial formalin test in CFA group, but not in non-CFA group. Local administration of tropisetron into the masseter muscle in CFA group, but not in non-CFA group also attenuated the behavioral activities in the late phase. Unexpectedly, low dose of local tropisetron reduced the nocifensive behavioral activities in the early phase of orofacial formalin test in CFA group. These data suggest that induction of TMJ inflammation causes the elevation of the orofacial nocifensive behavioral activities evoked by formalin injection into masseter muscle, and that peripheral 5HT3 receptors may play a critical role in nociception and the transmission of orofacial pain.

  20. On the role of brain 5-HT7 receptor in the mechanism of hypothermia: comparison with hypothermia mediated via 5-HT1A and 5-HT3 receptor.

    PubMed

    Naumenko, Vladimir S; Kondaurova, Elena M; Popova, Nina K

    2011-12-01

    Intracerebroventricular administration of selective agonist of serotonin 5-HT(7) receptor LP44 (4-[2-(methylthio)phenyl]-N-(1,2,3,4-tetrahydro-1-naphthalenyl)-1-pyperasinehexanamide hydrochloride; 10.3, 20.5 or 41.0 nmol) produced considerable hypothermic response in CBA/Lac mice. LP44-induced (20.5 nmol) hypothermia was significantly attenuated by the selective 5-HT(7) receptor antagonist SB 269970 (16.1 fmol, i.c.v.) pretreatment. At the same time, intraperitoneal administration of LP44 in a wide range of doses 1.0, 2.0 or 10.0 mg/kg (2.0, 4.0, 20.0 μmol/kg) did not cause considerable hypothermic response. These findings indicate the implication of central, rather than peripheral 5-HT(7) receptors in the regulation of hypothermia. The comparison of LP44-induced (20.5 nmol) hypothermic reaction in eight inbred mouse strains (DBA/2J, CBA/Lac, C57BL/6, BALB/c, ICR, AKR/J, C3H and Asn) was performed and a significant effect of genotype was found. In the same eight mouse strains, functional activity of 5-HT(1A) and 5-HT(3) receptors was studied. The comparison of hypothermic responses produced by 5-HT(7) receptor agonist LP44 (20.5 nmol, i.c.v.) and 5-HT(1A) receptor agonist 8-OH-DPAT 1.0 mg/kg, i.p. (3.0 μmol/kg), 5-HT(3) receptor agonist m-CPBG (40.0 nmol, i.c.v.) did not reveal considerable interstrain correlations between 5-HT(7) and 5-HT(1A) or 5-HT(3) receptor-induced hypothermia. The selective 5-HT(7) receptor antagonist SB 269970 (16.1 fmol, i.c.v.) failed to attenuate the hypothermic effect of 8-OH-DPAT 1.0 mg/kg, i.p. (3.0 μmol/kg) and m-CPBG (40.0 nmol, i.c.v.) indicating that the brain 5-HT(7) receptor is not involved in the hypothermic effects of 8-OH-DPAT or m-CPBG. The obtained results suggest that the central 5-HT(7) receptor plays an essential role in the mediation of thermoregulation independent of 5-HT(1A) and 5-HT(3) receptors.

  1. Wood creosote prevents CRF-induced motility via 5-HT3 receptors in proximal and 5-HT4 receptors in distal colon in rats.

    PubMed

    Ataka, Koji; Kuge, Tomoo; Fujino, Kazunori; Takahashi, Toku; Fujimiya, Mineko

    2007-05-30

    Wood creosote has been used as an herbal medicine against acute diarrhea caused by food poisoning and has an inhibitory effect on colonic motility and enterotoxin-induced ion secretion. Since no previous studies have examined the effects of wood creosote on stress-induced alteration of colonic motility, we examined the effects on the colonic motility altered by intracerebroventricular (i.c.v.) injection of corticotropin-releasing factor (CRF), which is a key mediator in responses to stress. We recorded motor activity in proximal and distal colon of unrestrained conscious rats via two manometory catheters. The frequencies of phase III-like contraction and the % motor indices in both proximal and distal colon were measured. At the same time the number of fecal pellets excreted was counted. I.c.v. injection of CRF increased the motor activity in both proximal and distal colon, and these effects were completely antagonized by i.c.v. injection of a selective CRF type 1 antagonist but not by a CRF type 2 antagonist. Changes in colonic motility induced by CRF were reversed by intravenously administered wood creosote. Intraluminal administration of the 5-HT(3) receptor antagonist granisetron, or the 5-HT(4) receptor antagonist SB 204070 blocked the increase in colonic motility induced by i.c.v. injection of CRF. Wood creosote prevented the increase in colonic motility induced by the 5-HT(3) receptor agonist SR57227A in the proximal colon, while it prevented the increase in colonic motility induced by the 5-HT(4) receptor agonist RS67506 in the distal colon. These results indicate that wood creosote prevents the increase in colonic motility induced by CRF via 5-HT(3) receptors in the proximal colon, and via 5-HT(4) receptors in the distal colon, suggesting that wood creosote might be useful to treat stress-induced diarrhea.

  2. Synthesis and Pharmacological Evaluation of [(11)C]Granisetron and [(18)F]Fluoropalonosetron as PET Probes for 5-HT3 Receptor Imaging.

    PubMed

    Mu, Linjing; Müller Herde, Adrienne; Rüefli, Pascal M; Sladojevich, Filippo; Milicevic Sephton, Selena; Krämer, Stefanie D; Thompson, Andrew J; Schibli, Roger; Ametamey, Simon M; Lochner, Martin

    2016-11-16

    Serotonin-gated ionotropic 5-HT3 receptors are the major pharmacological targets for antiemetic compounds. Furthermore, they have become a focus for the treatment of irritable bowel syndrome (IBS) and there is some evidence that pharmacological modulation of 5-HT3 receptors might alleviate symptoms of other neurological disorders. Highly selective, high-affinity antagonists, such as granisetron (Kytril) and palonosetron (Aloxi), belong to a family of drugs (the "setrons") that are well established for clinical use. To enable us to better understand the actions of these drugs in vivo, we report the synthesis of 8-fluoropalonosetron (15) that has a binding affinity (Ki = 0.26 ± 0.05 nM) similar to the parent drug (Ki = 0.21 ± 0.03 nM). We radiolabeled 15 by nucleophilic (18)F-fluorination of an unsymmetrical diaryliodonium palonosetron precursor and achieved the radiosynthesis of 1-(methyl-(11)C)-N-granisetron ([(11)C]2) through N-alkylation with [(11)C]CH3I, respectively. Both compounds [(18)F]15 (chemical and radiochemical purity >95%, specific activity 41 GBq/μmol) and [(11)C]2 (chemical and radiochemical purity ≥99%, specific activity 170 GBq/μmol) were evaluated for their utility as positron emission tomography (PET) probes. Using mouse and rat brain slices, in vitro autoradiography with both [(18)F]15 and [(11)C]2 revealed a heterogeneous and displaceable binding in cortical and hippocampal regions that are known to express 5-HT3 receptors at significant levels. Subsequent PET experiments suggested that [(18)F]15 and [(11)C]2 are of limited utility for the PET imaging of brain 5-HT3 receptors in vivo.

  3. Discovery of new anti-depressants from structurally novel 5-HT3 receptor antagonists: design, synthesis and pharmacological evaluation of 3-ethoxyquinoxalin-2-carboxamides.

    PubMed

    Mahesh, Radhakrishnan; Devadoss, Thangaraj; Pandey, Dilip Kumar; Bhatt, Shvetank

    2011-02-15

    A novel series of 3-ethoxyquinoxalin-2-carboxamides were designed as per the pharmacophoric requirements of 5-HT(3) receptor antagonist using ligand-based approach. The desired carboxamides were synthesized from the key intermediate, 3-ethoxyquinoxalin-2-carboxylic acid by coupling with appropriate amines in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and 1-hydroxybenzotriazole (HOBt). The 5-HT(3) receptor antagonism was evaluated in longitudinal muscle myenteric plexus preparation from guinea pig ileum against 5-HT(3) agonist, 2-methy-5-HT, which was expressed in the form of pA(2) values. Compound 6h (3-ethoxyquinoxalin-2-yl)(4-methylpiperazin-1-yl)methanone was found to be the most active compound, which expressed a pA(2) value of 7.7. In forced swim test, the compounds with higher pA(2) value exhibited good anti-depressant-like activity and compounds with lower pA(2) value failed to show activity as compared to the vehicle-treated group.

  4. The effects of the 5-HT3 receptor antagonist tropisetron on cocaine-induced conditioned taste aversions.

    PubMed

    Briscione, Maria A; Serafine, Katherine M; Merluzzi, Andrew P; Rice, Kenner C; Riley, Anthony L

    2013-04-01

    Although cocaine readily induces taste aversions, little is known about the mechanisms underlying this effect. Recent work has shown that cocaine's actions on serotonin (5-HT) may be involved. To address this possibility, the present experiments examined a role of the specific 5-HT receptor, 5-HT3, in this effect given that it is implicated in a variety of behavioral effects of cocaine. This series of investigations first assessed the aversive effects of the 5-HT3 receptor antagonist tropisetron alone (Experiment 1). Specifically, in Experiment 1 male Sprague-Dawley rats were given repeated pairings of a novel saccharin solution and tropisetron (0, 0.056, 0.18 and 0.56mg/kg). Following this, a non-aversion-inducing dose of tropisetron (0.18mg/kg) was assessed for its ability to block aversions induced by a range of doses of cocaine (Experiment 2). Specifically, in Experiment 2 animals were given access to a novel saccharin solution and then injected with tropisetron (0 or 0.18mg/kg) followed by an injection of various doses of cocaine (0, 10, 18 and 32mg/kg). Cocaine induced dose-dependent taste aversions that were not blocked by tropisetron, suggesting that cocaine's aversive effects are not mediated by 5-HT, at least at this specific receptor subtype. At the intermediate dose of cocaine, aversions appeared to be potentiated, suggesting 5-HT3 may play a limiting role in cocaine's aversive effects. These data are discussed in the context of previous examinations of the roles of serotonin, dopamine, and norepinephrine in cocaine-induced aversions.

  5. Noncompetitive Inhibition of 5-HT3 Receptors by Citral, Linalool, and Eucalyptol Revealed by Nonlinear Mixed-Effects Modeling.

    PubMed

    Jarvis, Gavin E; Barbosa, Roseli; Thompson, Andrew J

    2016-03-01

    Citral, eucalyptol, and linalool are widely used as flavorings, fragrances, and cosmetics. Here, we examined their effects on electrophysiological and binding properties of human 5-HT3 receptors expressed in Xenopus oocytes and human embryonic kidney 293 cells, respectively. Data were analyzed using nonlinear mixed-effects modeling to account for random variance in the peak current response between oocytes. The oils caused an insurmountable inhibition of 5-HT-evoked currents (citral IC50 = 120 µM; eucalyptol = 258 µM; linalool = 141 µM) and did not compete with fluorescently labeled granisetron, suggesting a noncompetitive mechanism of action. Inhibition was not use-dependent but required a 30-second preapplication. Compound washout caused a slow (∼180 seconds) but complete recovery. Coapplication of the oils with bilobalide or diltiazem indicated they did not bind at the same locations as these channel blockers. Homology modeling and ligand docking predicted binding to a transmembrane cavity at the interface of adjacent subunits. Liquid chromatography coupled to mass spectrometry showed that an essential oil extracted from Lippia alba contained 75.9% citral. This inhibited expressed 5-HT3 receptors (IC50 = 45 µg ml(-1)) and smooth muscle contractions in rat trachea (IC50 = 200 µg ml(-1)) and guinea pig ileum (IC50 = 20 µg ml(-1)), providing a possible mechanistic explanation for why this oil has been used to treat gastrointestinal and respiratory ailments. These results demonstrate that citral, eucalyptol, and linalool inhibit 5-HT3 receptors, and their binding to a conserved cavity suggests a valuable target for novel allosteric modulators.

  6. Role of the 5HT3 Receptor in Alcohol Drinking and Aggression Using A Transgenic Mouse Model

    DTIC Science & Technology

    2005-09-01

    F(1,35) = 33.85, P < 0.0005] and N5 generations [F(1,35) = 6.33, P < 0.017]. Interactions of background and transgene presence were found for N1 [F... interaction was found for the N5 generation as well [F(2,51) = 4.55, P < 0.15]. Figure 2. Contextual conditioning is influenced by 5-HT3 receptor...2,51) = 164.56, P < 0.0005] and transgene presence [F(1,51) = 51.66, P < 0.0005] were found, as was an interaction between background and transgene

  7. Contrasting effects of 5-HT3 receptor stimulation of the nucleus accumbens or ventral tegmentum on food intake in the rat.

    PubMed

    Pratt, Wayne E; Lin, Peagan; Pierce-Messick, Zachary; Ilesanmi, Adeolu O; Clissold, Kara A

    2017-04-14

    Although serotonin (5-HT) signaling is known to regulate food intake and energy homeostasis, the roles of the 5-HT3 receptor in feeding processes have been elusive. 5-HT3 receptors are found throughout mesolimbic circuitry that promote feeding not only in response to hunger, but also to the palatable and rewarding properties of food. These experiments examined if stimulation or blockade of the 5-HT3 receptor of the nucleus accumbens (NAcc) or ventral tegmentum affected food intake in the rat in response to hunger or the presence of a palatable diet. Rats (N=6-9/group) received bilateral injections of the 5-HT3 agonist m-chlorophenylbiguanide hydrochloride (mCPBG; at 0.0, 10.0, or 20.0μg/0.5μl/side) or the 5-HT3 antagonist ondansetron hydrochloride (at 0.0, 1.0, 2.0, or 5.0μg/0.5μl/side) into either the NAcc or the ventral tegmentum. NAcc 5-HT3 receptor stimulation significantly increased 2-h food intake in food-deprived animals offered rat chow and in a separate group of unrestricted rats offered a sweetened fat diet. In contrast to the feeding increase seen with NAcc treatments, stimulation of 5-HT3 receptors of the ventral tegmentum significantly reduced food and water intake in food-restricted animals; reductions of intake in non-restricted rats offered the palatable diet did not approach significance. Blockade of the 5-HT3 receptor had no effect on feeding in either brain region. These data support a functional role for serotonergic signaling in the mesolimbic pathway on motivated behavior, and demonstrate that 5-HT3 receptors differentially modulate food consumption in a region-dependent manner.

  8. A molecular dynamics approach to receptor mapping: application to the 5HT3 and beta 2-adrenergic receptors.

    PubMed

    Gouldson, P R; Winn, P J; Reynolds, C A

    1995-09-29

    A molecular dynamics-based approach to receptor mapping is proposed, based on the method of Rizzi (Rizzi, J. P.; et al. J. Med. Chem. 1990, 33, 2721). In Rizzi's method, the interaction energy between a series of drug molecules and probe atoms (which mimic functional groups on the receptor, such as hydrogen bond donors) was calculated. These interactions were calculated on a three-dimensional grid within a molecular mechanics parameters, were placed at these minima. The distances between the dummy atom sites were monitored during molecular dynamics simulations and plotted as distance distribution functions. Important distances within the receptor became apparent, as drugs with a common mode of binding share similar peaks in the distance distribution functions. In the case of specific 5HT3 ligands, the important donor--acceptor distance within the receptor has a range of ca. 7.9--8.9 A. In the case of specific beta 2-adrenergic ligands, the important donor--acceptor distances within the receptor lie between ca. 7--9 A and between 8 and 10 A. These distances distribution functions were used to assess three different models of the beta 2-adrenergic G-protein-coupled receptor. The comparison of the distance distribution functions for the simulation with the actual donor--acceptor distances in the receptor models suggested that two of the three receptor models were much more consistent with the receptor-mapping studies. These receptor-mapping studies gave support for the use of rhodopsin, rather than the bacteriorhodopsin template, for modeling G-protein-coupled receptors but also sounded a warning that agreement with binding data from site-directed mutagenesis experiments does not necessarily validate a receptor model.

  9. Spinal 5-HT3 receptor mediates nociceptive effect on central neuropathic pain; possible therapeutic role for tropisetron

    PubMed Central

    Nasirinezhad, Farinaz; Hosseini, Marjan; Karami, Zohre; Yousefifard, Mahmoud; Janzadeh, Autosa

    2016-01-01

    Objectives To test the analgesic effect of 5-HT-3 receptor antagonist, tropisetron, in a clip compression injury model of spinal cord pain in rats. Methods Four weeks post compression of the spinal cord at lumbar level, tropisetron was administered intrathecally at 100 μg and 150 μg dosages. Behavioral tests were assessed before administration. Fifteen minutes after injection, behavioral tests were repeated. Randall-Sellitto and plantar test was used for mechanical and thermal hyperalgesia, respectively. Mechanical and cold allodynia were evaluated by Von Frey filament and acetone droplets, respectively. The analgesic effect of tropisetron was compared with intrathecal administration of salicylate. Locomotor score was evaluated by Basso, Beattie and Bresnahan (BBB) test every week after spinal cord injury. Results Intrathecal administration of tropisetron, decreased hyperalgesia and mechanical allodynia, but not cold allodynia were observed after compression of the spinal cord. Conclusion Blockade of 5-HT-3 receptors by tropisetron at the spinal level induces an antinociceptive effect on chronic central neuropathic pain and suggests that this compound may have potential clinical utility for the management of central neuropathic pain, particularly in patients with hyperalgesia and tactile allodynia. PMID:26338446

  10. Spatial orientation of the antagonist granisetron in the ligand-binding site of the 5-HT3 receptor.

    PubMed

    Yan, Dong; White, Michael M

    2005-08-01

    The serotonin type 3 receptor (5-HT(3)R) is a member of the cys-loop ligand-gated ion channel (LGIC) superfamily. Like almost all membrane proteins, high-resolution structural data are unavailable for this class of receptors. We have taken advantage of the high degree of homology between LGICs and the acetylcholine binding protein (AChBP) from the freshwater snail Lymnea stagnalis, for which high-resolution structural data are available, to create a structural model for the extracellular (i.e., ligand-binding) domain of the 5-HT(3)R and to perform a series of ligand docking experiments to delineate the architecture of the ligand-binding site. Structural models were created using homology modeling with the AChBP as a template. Docking of the antagonist granisetron was carried out using a Lamarckian genetic algorithm to produce models of ligand-receptor complexes. Two energetically similar conformations of granisetron in the binding site were obtained from the docking simulations. In one model, the indazole ring of granisetron is near Trp90 and the tropane ring is near Arg92; in the other, the orientation is reversed. We used double-mutant cycle analysis to determine which of the two orientations is consistent with experimental data and found that the data are consistent with the model in which the indazole ring of granisetron interacts with Arg92 and the tropane ring interacts with Trp90. The combination of molecular modeling with double-mutant cycle analysis offers a powerful approach for the delineation of the architecture of the ligand-binding site.

  11. Investigation of 5-HT3A receptor gene expression in peripheral blood mononuclear cells of individuals who had been exposed to air pollution.

    PubMed

    Ahangari, Ghasem; Amirabad, Leila Mohammadi; Mozafari, Sona; Majeidi, Ali; Deilami, Gholamreza Derkhshan

    2013-12-01

    The role of air pollution in exacerbation of allergic symptoms is well known. Several studies have shown the effect of air pollution on serotonergic system. The changes in serotonergic system could trigger several allergic symptoms. 5-HT(3A) is among serotonin receptors on the peripheral Blood Mononuclear Cells (PBMCs) as well as other cells. In the present study we compared the 5-HT(3A) gene expression in PBMCs of the asthmatic patients as well as individuals who had been exposed to the air pollution. Normal individuals were also included in the study as control for comparison of 5-HT(3A) gene expression. Following the synthesis of the cDNA using mRNA extracted from PBMCs the level of 5- HT(3A) gene expression was measured using real-time PCR. The results showed t a significant increase in the relative expression level of 5-HT(3A) receptor in PBMCs from asthmatic patients and individuals exposed to the air pollutants compared to normal controls. Our result indicates that significant increase in 5-HT(3A) receptor may contribute to the pathogenesis as well as allergic symptoms which resulted from air pollution.

  12. Synthesis and biochemical evaluation of tritium-labeled 1-methyl-N-(8-methyl-8-azabicyclo(3. 2. 1)oct-3-yl)-1H-indazole-3-carboxa mide, a useful radioligand for 5HT3 receptors

    SciTech Connect

    Robertson, D.W.; Bloomquist, W.; Cohen, M.L.; Reid, L.R.; Schenck, K.; Wong, D.T. )

    1990-12-01

    The advent of potent, highly selective 5HT3 receptor antagonists has stimulated considerable interest in 5HT3 receptor mediated physiology and pharmacology. To permit detailed biochemical studies regarding interaction of the indazole class of serotonin (5HT) antagonists with 5HT3 receptors in multiple tissues, we synthesized 1-methyl-N-(8-methyl-8-azabicyclo(3.2.1)oct-3-yl)-1H-indazole- 3-carboxamide (LY278584, compound 9) in high specific activity, tritium-labeled form. This radioligand was selected as a synthetic target because of its potency as a 5HT3-receptor antagonist, its selectivity for this receptor viz a viz other 5HT-receptor subtypes, and the ability to readily incorporate three tritia via the indazole N-CH3 substituent. Alkylation of N-(8-methyl-8-azabicyclo(3.2.1)oct-3-yl)-1H-indazole-3-carboxamide (8) with sodium hydride and tritium-labeled iodomethane, followed by HPLC purification, resulted in (3H)-9 with a radiochemical purity of 99% and a specific activity of 80.5 Ci/mmol. This radioligand bound with high affinity to a single class of saturable recognition sites in membranes isolated from cerebral cortex of rat brain. The Kd was 0.69 nM and the Bmax was 16.9 fmol/mg of protein. The specific binding was excellent, and accounted for 83-93% of total binding at concentrations of 2 nM or less. The potencies of known 5HT3-receptor antagonists as inhibitors of (3H)-9 binding correlated well with their pharmacological receptor affinities as antagonists of 5HT-induced decreases in heart rate and contraction of guinea pig ileum, suggesting the central recognition site for this radioligand may be extremely similar to or identical with peripheral 5HT3 receptors.

  13. 5HT3 receptor antagonist (ondansetron) reverses depressive behavior evoked by chronic unpredictable stress in mice: modulation of hypothalamic-pituitary-adrenocortical and brain serotonergic system.

    PubMed

    Gupta, Deepali; Radhakrishnan, Mahesh; Kurhe, Yeshwant

    2014-09-01

    Chronic stress is one of the major causes of depression, associated with behavioral and biochemical impairments. 5HT3 receptor antagonists (such as ondansetron) have shown alleviation of depressive symptomology in preclinical and in few clinical studies. However, their effects in chronic stress-induced depressive behavior and the underlying mechanism(s) are yet to be known. In the present study, the effects of a 5HT3 receptor antagonist, ondansetron were evaluated in chronic unpredictable stress (CUS)-evoked depressive behavior. In addition, the possible mechanism was determined by measuring plasma corticosterone (CORT) as a marker of hypothalamic-pituitary-adrenocortical (HPA)-axis activity and serotonin levels in the discrete brain regions. Mice were subjected to a battery of unpredictable stressors for 28 days. Ondansetron (0.05, 0.1 and 1mg/kg, p.o.) and fluoxetine (10mg/kg, p.o.) were administered during the last 14 days (day 15-28th) of CUS testing paradigm. The results showed that the 4-week CUS produced significant depressive behavior in mice, which included increased despair effects in forced swim test (FST) and reward-related deficits in sucrose preference test. Biochemical assays demonstrated a significant increase in percentage of plasma CORT and decrease in percentage of serotonin levels in the discrete brain regions of CUS mice. Chronic ondansetron treatment, similar to that of positive control fluoxetine, significantly reversed despair effects in FST and reward-related deficits in sucrose preference test. In addition, ondansetron and fluoxetine treatments significantly increased percentage of serotonin levels in the measured brain regions and attenuated HPA-axis hyperactivity, as evidenced by low percentage of plasma CORT levels in CUS mice. These findings indicate the potential role of ondansetron (a 5HT3 receptor antagonist) in reversing CUS-induced depressive behavior, which is possibly mediated by its modulating effects on the HPA-axis and

  14. Contribution of Hippocampal 5-HT3 Receptors in Hippocampal Autophagy and Extinction of Conditioned Fear Responses after a Single Prolonged Stress Exposure in Rats.

    PubMed

    Wu, Zhong-Min; Yang, Li-Hua; Cui, Rong; Ni, Gui-Lian; Wu, Feng-Tian; Liang, Yong

    2017-05-01

    One of the hypotheses about the pathogenesis of posttraumatic stress disorder (PTSD) is the dysfunction of serotonin (5-HT) neurotransmission. While certain 5-HT receptor subtypes are likely critical for the symptoms of PTSD, few studies have examined the role of 5-HT3 receptor in the development of PTSD, even though 5-HT3 receptor is critical for contextual fear extinction and anxiety-like behavior. Therefore, we hypothesized that stimulation of 5-HT3 receptor in the dorsal hippocampus (DH) could prevent hippocampal autophagy and the development of PTSD-like behavior in animals. To this end, we infused SR57227, selective 5-HT3 agonist, into the DH after a single prolonged stress (SPS) treatment in rats. Three weeks later, we evaluated the effects of this pharmacological treatment on anxiety-related behaviors and extinction of contextual fear memory. We also accessed hippocampal autophagy and the expression of 5-HT3A subunit, Beclin-1, LC3-I, and LC3-II in the DH. We found that SPS treatment did not alter anxiety-related behaviors but prolonged the extinction of contextual fear memory, and such a behavioral phenomenon was correlated with increased hippocampal autophagy, decreased 5-HT3A expression, and increased expression of Beclin-1 and LC3-II/LC3-I ratio in the DH. Furthermore, intraDH infusions of SR57227 dose-dependently promoted the extinction of contextual fear memory, prevented hippocampal autophagy, and decreased expression of Beclin-1 and LC3-II/LC3-I ratio in the DH. These results indicated that 5-HT3 receptor in the hippocampus may play a critical role in the pathogenesis of hippocampal autophagy, and is likely involved in the pathophysiology of PTSD.

  15. Antidepressant and anti-anxiety like effects of 4i (N-(3-chloro-2-methylphenyl) quinoxalin-2-carboxamide), a novel 5-HT3 receptor antagonist in acute and chronic neurobehavioral rodent models.

    PubMed

    Gupta, Deepali; Radhakrishnan, Mahesh; Thangaraj, Devadoss; Kurhe, Yeshwant

    2014-07-15

    Depression and anxiety are the most debilitating mood disorders with poor therapeutic recovery rates. In the last decades, 5-HT3 receptor antagonists have been identified as potential agents for mood disorders. The current investigation focuses on evaluating the, antidepressant and anti-anxiety like effects of a novel 5-HT3 antagonist, 4i (N-(3-chloro-2-methylphenyl) quinoxalin-2-carboxamide). Preliminary, in vitro 5-HT3 receptor binding affinity was performed in isolated longitudinal muscle-myenteric plexus from the guinea pig ileum. Consequently, neurobehavioral effects of 4i in acute and chronic rodent models were evaluated. In addition, involvement of serotonergic system in the postulated effects of the compound was analyzed by in vivo assay. in vitro, 4i demonstrated high 5-HT3 receptor antagonistic activity (pA2, 7.6). in vivo acute study, 4i exhibited decreased duration of immobility in forced swim and tail suspension tests, and increased exploratory parameters as number and duration of nose-poking in hole board test and latency and time spent in aversive brightly illuminated light chamber in light-dark model. Moreover, in chronic model of depression, i.e., olfactory bulbectomy with behavioral deficits, 4i reversed depressive anhedonia in sucrose preference test and anxious hyperactive behavior in open field test in rats. Furthermore, synergistic effect of 4i with fluoxetine (a selective serotonin reuptake inhibitor) and inhibitory effect of 1-(m-chlorophenyl)-biguanide (a 5-HT3 receptor agonist) revealed serotonergic modulation by 4i mediated 5-HT3 receptor antagonism, which was further confirmed by potentiation of 5-hydroxytryptophan (a serotonin synthesis precursor) induced head twitch response. These findings suggest the potential antidepressant and anti-anxiety like effects of 4i, which may be related to the modulation of serotonergic system.

  16. Differential effects of a short-term high-fat diet in an animal model of depression in rats treated with the 5-HT3 receptor antagonist, ondansetron, the 5-HT3 receptor agonist, 2-methyl-5-HT, and the SSRI, fluoxetine.

    PubMed

    Sumaya, Isabel C; Bailey, Dee; Catlett, Susan L

    2016-05-01

    Investigation into the effects of a high-fat diet on depression in the context of 5-HT3 receptor function is important given 5-HT3 antagonism may represent a novel candidate for drug discovery. To more fully understand the relationship between the 5-HT3 receptor system, depression, and high-fat intake, our main interest was to study the short-term effects of a high-fat diet on the 5-HT3 receptor antagonist, ondansetron, and the 5-HT3 receptor agonist, 2-methyl-5-HT, as well as the SSRI, fluoxetine, in an animal model of depression. Male Sprague Dawley rats were fed either a standard diet (11% fat) or a high-fat diet (32.5% fat) for seven days then treated with either fluoxetine (10mg/kg, ip), ondansetron (1mg/kg, ip), 2-methyl-5-HT (3mg/kg, ip), fluoxetine+ondansetron or, 2-methyl-5-HT+ondansetron prior to the Forced Swim Test. In the standard diet group, treatment with the 5HT3 receptor agonist, 2-methyl-5-HT, served to significantly decrease time of immobility as compared to controls thus showing anti-depressive-like effects. Treatment with the 5-HT3 receptor antagonist, ondansetron, served to enhance the anti-depressive like effects of the SSRI, fluoxetine, as treatment with both the SSRI and 5-HT3 receptor antagonist dramatically decreased immobility. Importantly, in the high-fat diet groups, a week of high-fat intake served to: 1) counteract the anti-depressive-like effect of the SSRI, fluoxetine, 2) reverse the anti-depressive-like effect of the 5HT3 receptor agonist, 2-methyl-5-HT and 3) provide protection against the depressive-like effects induced by the Forced Swim Test as rats fed a high-fat diet displayed the lowest amounts of immobility. In the aggregate, these data suggest that both SSRIs and the 5HT3 receptor system are affected by short-term high-fat intake and that a short-term high-fat diet protects against depressive-like effects in an animal model of depression.

  17. Changes in characteristics of the specific binding of [3H]LY-278584, a 5-HT3-receptor antagonist, on differentiated NG108-15 cells.

    PubMed

    Matsushima, Kayoko; Imanishi, Takashi; Asano, Hajime; Funakami, Yoshinori; Wada, Tetsuyuki; Ichida, Seiji

    2010-01-01

    We have reported previously that the concentration of intracellular Ca2+ evoked by serotonin (5-HT) was significantly augmented in differentiated NG108-15 (NG) cells treated with dibutyryl cAMP and the enhanced response occurred via 5-HT3 receptors. We investigated changes in the characteristics for specific binding of [(3)H]LY-278584 (a specific antagonist of the 5-HT3 receptor) on membranes from differentiated NG cells. The results indicated that the K(d) and B(max) values for the specific binding to differentiated NG cells were significantly smaller and larger, respectively, than those for undifferentiated NG cells. The binding was significantly inhibited by 10 nM tropisetron, a specific 5-HT3-receptor antagonist, but not by any other types of 5-HT-receptor antagonists. These results suggested that the enhanced response by 5-HT in differentiated NG cells was due to both qualitative and quantitative changes in the 5-HT3 receptor.

  18. Roles of serotonin 5-HT3 receptor in the formation of dendrites and axons in the rat cerebral cortex: an in vitro study.

    PubMed

    Hayashi, Takahiro; Ohtani, Akiko; Onuki, Fumiaki; Natsume, Masaki; Li, Fei; Satou, Tomomi; Yoshikawa, Masaaki; Senzaki, Kouji; Shiga, Takashi

    2010-01-01

    The serotonin type 3 (5-HT(3)) receptor is an only ligand-gated ion channel among 14 serotonin receptors. Here, we examined the roles of the 5-HT(3) receptor in the formation of dendrites and axons, using a dissociation culture of embryonic rat cerebral cortex. Cortical neurons at embryonic day 16 were cultured for 4 days in the presence of a selective 5-HT(3) receptor agonist with or without an antagonist. Neurons were then immunostained by antibodies against microtubule-associated protein 2 (MAP2) and glutamic acid decarboxylase (GAD) 65. All cells expressed MAP2, whereas only limited number of cells expressed GAD65. From the immunoreactivity and the cell shape, we tentatively divided neurons into 3 types; GAD-positive multipolar, GAD-positive bipolar/tripolar and GAD-negative neurons. The total length of axons and dendrites, the number of primary dendrites and the dendritic branching of GAD-negative neurons were decreased by the agonist (10 or 100nM), most of which were reversed by the concomitant treatment of the antagonist. In contrast, no or little effect was observed on the formation of dendrites and axons of GAD-positive multipolar neurons, and the neurite formation of GAD-positive bipolar/tripolar neurons. The present study revealed differential roles of the 5-HT(3) receptor in the formation of dendrites and axons of subtypes of cortical neurons.

  19. Modes and nodes explain the mechanism of action of vortioxetine, a multimodal agent (MMA): blocking 5HT3 receptors enhances release of serotonin, norepinephrine, and acetylcholine.

    PubMed

    Stahl, Stephen M

    2015-10-01

    Vortioxetine is an antidepressant with multiple pharmacologic modes of action at targets where serotonin neurons connect with other neurons. 5HT3 receptor antagonism is one of these actions, and this leads to increased release of norepinephrine (NE), acetylcholine (ACh), and serotonin (5HT) within various brain circuits.

  20. Role of 5-HT3 receptors in basal and K(+)-evoked dopamine release from rat olfactory tubercle and striatal slices.

    PubMed Central

    Zazpe, A; Artaiz, I; Del Río, J

    1994-01-01

    1. The present study was aimed at examining the role of 5-HT3 receptors in basal and depolarization-evoked dopamine release from rat olfactory tubercle and striatal slices. [3H]-dopamine ([3H]-DA) release was measured in both brain regions and endogenous dopamine release from striatal slices was also studied. 2. The selective 5-HT3 receptor agonist 2-methyl-5-HT (0.5-10 microM) produced a concentration-dependent increase in [3H]-DA efflux evoked by K+ (20 mM) from slices of rat olfactory tubercle. 1-Phenylbiguanide (PBG) and 5-HT also increased K(+)-evoked [3H]-DA efflux. 3. 5-HT (1-100 microM) increased in a concentration-dependent manner basal [3H]-DA release from olfactory tubercle and striatal slices as well as endogenous DA release from striatal slices. The selective 5-HT3 receptor agonists 2-methyl-5-HT and 1-phenylbiguanide were weaker releasing agents. In all cases, the release was Ca2+ independent and tetrodotoxin insensitive. 4. 5-HT3 receptor antagonists such as ondansetron, granisetron and tropisetron (0.2 microM) significantly blocked the enhanced K(+)-evoked [3H]-DA efflux from rat olfactory tubercle slices induced by 2-methyl-5HT. A ten fold higher concentration of the 5-HT2 receptor antagonist ketanserin was ineffective. 5. Much higher concentrations, up to 50 microM, of the same 5-HT3 receptor antagonists did not block the increase in basal [3H]-DA release from striatal or olfactory tubercle slices induced by 5-HT or the release of endogenous DA induced by 5-HT from striatal slices.2+ off PMID:7858893

  1. Local-anesthetic like inhibition of the cardiac sodium channel Nav1.5 α-subunit by 5-HT3 receptor antagonists.

    PubMed

    Van't Klooster, Mariet P; Foadi, Nilufar; Hage, Axel; Stoetzer, Carsten; Wegner, Florian; Eberhardt, Mirjam; Leffler, Andreas

    2016-10-15

    5-hydroxytryptamine 3 receptor (5-HT3 receptor) antagonists are administered for prevention and therapy of nausea and vomiting. Although regarded as safe therapeutics, they can also provoke arrhythmias by prolonging the QRS interval. However, the mechanisms mediating this cardiotoxicity are poorly understood. Here we investigated effects of 5-HT3 receptor antagonists on the cardiac Na(+) channel Nav1.5. We explored the interaction of dolasetron, tropisetron, granisetron and ondansetron on the human α-subunit Nav1.5 heterologously expressed in HEK293 cells. Sodium currents were explored by means of whole-cell patch clamp recordings. All four substances inhibited the Nav1.5 in a concentration and state-dependent manner. Dolasetron displayed the lowest blocking efficacy, and tropisetron was the most potent blocker with a half maximum blocking concentration of 18µM for tonic block of inactivated channels. Tropisetron was also the most potent use-dependent inhibitor, and it also induced a strong open -channel block. Both tonic and use-dependent block by tropisetron were abbreviated on the local-anesthetic insensitive mutant Nav1.5-F1760A. Co-administration of tropisetron and the local anesthetic bupivacaine or the hypnotic propofol augmented inhibition of Nav1.5. Our data demonstrate that 5-HT3 receptor antagonists induce a local-anesthetic like inhibition of Nav1.5, and that they display different blocking efficacies. Reports on a relevant cardiotoxicity of dolasetron as opposed to other 5-HT3 receptor antagonists do not seem to correlate with a block of Nav1.5. As inhibition of Nav1.5 was enhanced by propofol and bupivacaine however, it is possible that a combined administration of Na(+) channel blockers and 5-HT3 receptor antagonists can provoke arrhythmias.

  2. [The effects of selective 5HT3 receptor blockade on physiological markers of abdominal pain in awake dogs].

    PubMed

    Panteleev, S S; Busygina, I I; Liubashina, O A

    2013-04-01

    In awake dogs, the visceromotor and cardioautonomic responses to the rectal balloon distension were studied before and after intravenous administration of a selective 5HT3 receptor antagonist granisetron. It was shown that balloon distension level up to 60 mmHg caused neither noticeable muscle responses nor substantial changes in heart rate. In turn, distending pressures of 80 mmHg and higher induced vigorous abdominal muscle contractions and tachycardia that were graded with increasing intensities of stimulation. Thus, the rectal stimulation with pressures 80 mmHg and more produced the changes in visceromotor and cardiovascular indices which could be considered as suitable indicators of visceral nociception in conscious animals. Based on monitoring of these physiological markers in a model of abdominal pain the dose-dependent antinociceptive effect of granisetron in awake dogs has been demonstrated for the first time. It was determined that granisetron in doses of 0.25, 0.5 or 1.0 mg/kg induced correspondingly 33.6 +/- 9.2, 58.0+/- 8.6 [see text] 76.7 +/- 5.5 % decrease in visceromotor response of dogs to nociceptive visceral stimulation. The effect occurred immediately after the drug administration and was lasting more than 90 min. In turn, the dose-dependent suppression of the rectal distension-induced tachycardia was less prominent and only observed during the initial period of granisetron action. The described model of abdominal pain in awake dogs might be useful for preclinical screening of new pharmacological substances, whereas the obtained data could contribute to the development of more efficient analgesics aimed in patients with irritable bowel syndrome.

  3. Antidepressant Potential of 5-HT3 Receptor Antagonist, N-n- propyl-3-ethoxyquinoxaline-2-carboxamide (6n).

    PubMed

    Mahesh, R; Bhatt, S; Devadoss, T; Jindal, Ak; Gautam, Bk; Pandey, Dk

    2012-10-01

    The present study was designed to evaluate the antidepressant potential of 5-HT3 receptor antagonist N-n-propyl-3-ethoxyquinoxaline-2-carboxamide (6n). The compound '6n' with optimum log P and pA 2 value identified from a series of compounds synthesized in our laboratory was subjected to forced Swim Test (FST) (1, 2, and 4 mg/kg, i.p) and Tail Suspension Test (TST) (1, 2, and 4 mg/kg, i.p.). The compound '6n' significantly reduced the duration of immobility in mice without affecting the baseline locomotion. Moreover, '6n' (2 mg/kg, i.p.) potentiated the 5-hydroxytryptophan (5-HTP)-induced head twitch responses in mice and '6n' at tested dose (1 and 2 mg/kg, i.p.) reversed the reserpine-induced hypothermia in rats. In interaction studies of '6n' with various standard drugs/ligands using FST, '6n' (1 mg/kg, i.p.) potentiated the antidepressant effect of venlafaxine (4 and 8 mg/kg, i.p.) and fluoxetine (10 and 20 mg/kg, i.p.). Additionally, '6n' (1 and 2 mg/kg, i.p.) influenced the effect of harmane (5 mg/ kg, i.p.) as well as reversed the effect of parthenolide (1 mg/kg, i.p.) by reducing the duration of immobility in FST. Furthermore, '6n' (1 mg/kg, i.p.) potentiated the effect of bupropion (10 and 20 mg/kg, i.p.) in TST. Chronic '6n' (1 and 2 mg/kg, i.p.) treatment attenuated the behavioral abnormalities in olfactory bulbectomized rats. In conclusion, these various findings reiterated the antidepressant-like effects of '6n' in behavioral models of depression.

  4. Antidepressant Potential of 5-HT3 Receptor Antagonist, N-n- propyl-3-ethoxyquinoxaline-2-carboxamide (6n)

    PubMed Central

    Mahesh, R; Bhatt, S; Devadoss, T; Jindal, AK; Gautam, BK; Pandey, DK

    2012-01-01

    The present study was designed to evaluate the antidepressant potential of 5-HT3 receptor antagonist N-n-propyl-3-ethoxyquinoxaline-2-carboxamide (6n). The compound ‘6n’ with optimum log P and pA2 value identified from a series of compounds synthesized in our laboratory was subjected to forced Swim Test (FST) (1, 2, and 4 mg/kg, i.p) and Tail Suspension Test (TST) (1, 2, and 4 mg/kg, i.p.). The compound ‘6n’ significantly reduced the duration of immobility in mice without affecting the baseline locomotion. Moreover, ‘6n’ (2 mg/kg, i.p.) potentiated the 5-hydroxytryptophan (5-HTP)-induced head twitch responses in mice and ‘6n’ at tested dose (1 and 2 mg/kg, i.p.) reversed the reserpine-induced hypothermia in rats. In interaction studies of ‘6n’ with various standard drugs/ligands using FST, ‘6n’ (1 mg/kg, i.p.) potentiated the antidepressant effect of venlafaxine (4 and 8 mg/kg, i.p.) and fluoxetine (10 and 20 mg/kg, i.p.). Additionally, ‘6n’ (1 and 2 mg/kg, i.p.) influenced the effect of harmane (5 mg/ kg, i.p.) as well as reversed the effect of parthenolide (1 mg/kg, i.p.) by reducing the duration of immobility in FST. Furthermore, ‘6n’ (1 mg/kg, i.p.) potentiated the effect of bupropion (10 and 20 mg/kg, i.p.) in TST. Chronic ‘6n’ (1 and 2 mg/kg, i.p.) treatment attenuated the behavioral abnormalities in olfactory bulbectomized rats. In conclusion, these various findings reiterated the antidepressant-like effects of ‘6n’ in behavioral models of depression. PMID:23493308

  5. The role of second-generation 5-HT3 receptor antagonists in managing chemotherapy-induced nausea and vomiting in hematological malignancies.

    PubMed

    Schwartzberg, Lee S; Jacobs, Peter; Matsouka, Panagiota; Azevedo, Wellington; Pinto, Antonio

    2012-07-01

    Compared with solid tumor patients, those with hematological malignancies are at particular risk of chemotherapy-induced nausea and vomiting (CINV) because of their young age, exposure to highly-emetogenic induction, consolidation and salvage regimens, the high-dose conditioning regimens used before stem cell transplantation (SCT), and the heavy psychological burden of such treatments. In the absence of prophylaxis, around 75% of patients undergoing SCT experience delayed CINV. With first-generation 5-HT(3) receptor antagonists, only about 20% are completely protected from nausea and vomiting, and this frequent and debilitating adverse event has not been fully addressed. In contrast to solid tumors, there are no internationally agreed guidelines for the prevention and treatment of CINV in hematological malignancies. Work on a consensus is urgently required. The second-generation 5-HT(3) antagonist palonosetron is highly effective in preventing CINV in patients with solid tumors. The extended half-life of this agent and its mechanisms of action including allosteric binding, positive cooperativity and 5-HT(3) receptor internalization, may make it particularly effective in controlling delayed CINV. Although controlled comparisons against first-generation 5HT(3) agents have not yet been conducted in the setting of SCT, available evidence suggests that palonosetron may prove beneficial in preventing CINV in high risk patients with hematological malignancies.

  6. Dopamine neurotransmission is involved in the attenuating effects of 5-HT3 receptor antagonist MDL 72222 on acute methamphetamine-induced locomotor hyperactivity in mice.

    PubMed

    Yoo, Ji-Hoon; Nam, Yun-Sun; Lee, Seok-Yong; Jang, Choon-Gon

    2008-01-01

    We have previously shown that 5-HT3 receptors are involved in the development and expression of methamphetamine (MAP)-induced locomotor sensitization in mice. In the present study, we further examined whether the dopaminergic system is involved in the attenuating effects of MDL 72222, a 5-HT3 receptor antagonist, on acute MAP-induced locomotor hyperactivity. For this, we examined alterations of dopamine (DA) in the form of D1 receptor, D2 receptor, and dopamine transporter (DAT) binding labeled with [3H]SCH23390 for D1, [3H]raclopride for D2, and [3H]mazindol for DAT binding in the mouse brains with acute MAP exposure or pretreatment of MDL 72222 with MAP. No significant differences were detected in the D1 receptor, D2 receptor, or DAT binding between any of the groups studied. Interestingly, we found increased DA levels in the striatum following acute MAP exposure; these increased levels were reversed by pretreatment with MDL 72222, but did not affect 5-HT levels in the dorsal raphe. Overall, our results suggest that dopamine neurotransmission plays an important role in the attenuating effects of 5-HT3 receptor antagonist MDL 72222 on acute MAP-induced locomotor hyperactivity in mice.

  7. Cation-pi interactions in ligand recognition by serotonergic (5-HT3A) and nicotinic acetylcholine receptors: the anomalous binding properties of nicotine.

    PubMed

    Beene, Darren L; Brandt, Gabriel S; Zhong, Wenge; Zacharias, Niki M; Lester, Henry A; Dougherty, Dennis A

    2002-08-13

    A series of tryptophan analogues has been introduced into the binding site regions of two ion channels, the ligand-gated nicotinic acetylcholine and serotonin 5-HT(3A) receptors, using unnatural amino acid mutagenesis and heterologous expression in Xenopus oocytes. A cation-pi interaction between serotonin and Trp183 of the serotonin channel 5-HT(3A)R is identified for the first time, precisely locating the ligand-binding site of this receptor. The energetic contribution of the observed cation-pi interaction between a tryptophan and the primary ammonium ion of serotonin is estimated to be approximately 4 kcal/mol, while the comparable interaction with the quaternary ammonium of acetylcholine is approximately 2 kcal/mol. The binding mode of nicotine to the nicotinic receptor of mouse muscle is examined by the same technique and found to differ significantly from that of the natural agonist, acetylcholine.

  8. Synergistic effect between prelimbic 5-HT3 and CB1 receptors on memory consolidation deficit in adult male Sprague-Dawley rats: An isobologram analysis.

    PubMed

    Ahmadi-Mahmoodabadi, N; Nasehi, M; Emam Ghoreishi, M; Zarrindast, M-R

    2016-03-11

    The serotonergic system has often been defined as a neuromodulator system, and is specifically involved in learning and memory via its various receptors. Serotonin is involved in many of the same processes affected by cannabinoids. The present study investigated the influence of bilateral post-training intra-prelimbic (PL) administrations of serotonergic 5-hydroxytryptamine type-3 (5-HT3) receptor agents on arachidonylcyclopropylamide (ACPA) (cannabinoid CB1 receptor agonist)-induced amnesia, using the step-through inhibitory avoidance (IA) task to assess memory in adult male Sprague-Dawley rats. The results indicated that sole intra-PL microinjection of ACPA (0.1 and 0.5 μg/rat) and 5-HT3 serotonin receptor agonist (m-Chlorophenylbiguanide hydrochloride, m-CPBG; 0.001, 0.01 and 0.1 μg/rat) impaired, whereas Y-25130 (a selective 5-HT3 serotonin receptor antagonist; 0.001 and 0.01 and 0.1 μg/rat) did not alter IA memory consolidation, by itself. Moreover, intra-PL administration of subthreshold dose of m-CPBG (0.0005 μg/rat) potentiated, while Y-25130 (0. 1 μg/rat) restored ACPA-induced memory consolidation deficit. The isobologram analysis showed that there is a synergistic effect between ACPA and m-CPBG on memory consolidation deficit. These findings suggest that 5-HT3 receptor mechanism(s), at least partly, play(s) a role in modulating the effect of ACPA on memory consolidation in the PL area.

  9. Regulation of the 5-HT3A receptor-mediated current by alkyl 4-hydroxybenzoates isolated from the seeds of Nelumbo nucifera.

    PubMed

    Youn, Ui Joung; Lee, Jun-Ho; Lee, Yoo Jin; Nam, Joo Won; Bae, Hyunsu; Seo, Eun-Kyoung

    2010-09-01

    Four known alkyl 4-hydroxybenzoates, i.e., methyl 4-hydroxybenzoate (1), ethyl 4-hydroxybenzoate (2), propyl 4-hydroxybenzoate (3), and butyl 4-hydroxybenzoate (4), were isolated from the seeds of Nelumbo nucifera Gaertner (Nymphaeaceae) for the first time. The structures of the isolates were identified by 1D- and 2D-NMR spectroscopy and comparison with published values. The compounds were evaluated for their effects on the 5-HT-stimulated inward current (I(5-HT)) mediated by the human 5-HT(3)A receptors expressed in Xenopus oocytes. Compounds 1 and 2 enhanced the I(5-HT), but 4 reduced it. These results indicate that 4 is an inhibitor of the 5-HT(3)A receptors expressed in Xenopus oocytes.

  10. The effects of varenicline on sensory gating and exploratory behavior with pretreatment with nicotinic or 5-HT3A receptor antagonists.

    PubMed

    Kucinski, Aaron; Wersinger, Scott; Stachowiak, Ewa K; Becker, Chani; Lippiello, Pat; Bencherif, Merouane; Stachowiak, Michal K

    2015-02-01

    Individuals with schizophrenia smoke at high frequency relative to the general population. Despite the harmful effects of cigarette smoking, smoking among schizophrenic patients improves cognitive impairments not addressed or worsened by common neuroleptics. Varenicline, a nonselective neuronal nicotinic receptor (NNR) agonist and full agonist of 5-HT3A receptors, helps reduce smoking among schizophrenic patients. To determine whether varenicline also improves a cognitive symptom of schizophrenia, namely, impaired sensory gating, a transgenic mouse with schizophrenia, th-fgfr1(tk-), was used. Varenicline dose-dependently increased prepulse inhibition (PPI) of the startle response, a measure of sensory gating, in th-fgfr1(tk-) mice and normalized PPI deficits relative to nontransgenic controls. With the highest dose (10 mg/kg), however, there was a robust elevation of PPI and startle response, as well as reduced exploratory behavior in the open field and elevated plus maze. Pretreatment with the nonspecific NNR antagonist mecamylamine attenuated the exaggerated PPI response and, similar to the 5-HT3A receptor antagonist ondansetron, it prevented the reduction in exploratory behavior. Collectively, these results indicate that varenicline at low-to-moderate doses may be beneficial against impaired sensory gating in schizophrenia; however, higher doses may induce anxiogenic effects, which can be prevented with antagonists of NNRs or 5-HT3A receptors.

  11. Design, synthesis, and pharmacological evaluation of novel 2-(4-substituted piperazin-1-yl)1, 8 naphthyridine 3-carboxylic acids as 5-HT3 receptor antagonists for the management of depression.

    PubMed

    Dhar, Arghya K; Mahesh, Radhakrishnan; Jindal, Ankur; Devadoss, Thangaraj; Bhatt, Shvetank

    2014-12-01

    1, 8-naphthyridine-3-carboxylic acid analogs were synthesized and found to possess potential 5-HT3 receptor antagonism as well as antidepressant-like activity. Initially, 5-HT3 receptor antagonism of all the compounds was determined in the form of pA2 value against agonist 2-methyl 5-HT in longitudinal muscle-myenteric plexus preparation from guinea-pig ileum. Among all the compounds tested, compound 7a demonstrated most promising pA2 value of 7.6. Subsequently, all the compounds were evaluated for antidepressant activity using forced swim test and tail suspension test in mice. Compounds 7a, 7d, 7f, 7h, and 7i exhibited significant (p < 0.05) antidepressant-like activity as compound to vehicle-treated group. Importantly, none of the tested compound affected locomotor activity of mice at tested dose levels.

  12. Antidepressant-like effect of novel 5-HT3 receptor antagonist N-n-butyl-3-ethoxyquinoxalin-2-carboxamide (6p): An approach using rodent behavioral antidepressant tests

    PubMed Central

    Bhatt, Shvetank; Mahesh, Radhakrishnan; Devadoss, Thangaraj; Jindal, Ankur Kumar

    2013-01-01

    Objective: The present study was designed to investigate the antidepressant potential of N-n-butyl-3-ethoxyquinoxalin-2-carboxamide (6p), a novel 5-HT3 receptor antagonist in rodent behavioral models of depression. Materials and Methods: The compound 6p was examined in various behavioral models like forced swim test (FST), tail suspension test (TST), mechanistic models [5-hydroxytryptophan (5-HTP)-induced head twitch and reserpine-induced hypothermia (RIH)], and in chronic surgery model-olfactory bulbectomy in rats. Results: Compound 6p (1, 2, and 4 mg/kg, i.p.) exhibited antidepressant-like effect in FST and TST after acute treatment without having an effect on baseline locomotor activity. Moreover, 6p (2 mg/kg, i.p.), potentiated the 5-HTP–induced head twitch responses in mice and inhibited the RIH in rats. Chronic treatment (14 days) with 6p (1 and 2 mg/kg, p.o.) and paroxetine (10 mg/kg, p.o.) in rats significantly reversed the behavioral anomalies induced by bilateral olfactory bulbectomy using open field exploration. Conclusion: The preliminary studies reveal that compound 6p exhibits antidepressant-like effect in behavioral rodent models of depression. PMID:24014909

  13. A nanocomposite material formed by benzofulvene polymer nanoparticles loaded with a potent 5-HT3 receptor antagonist (CR3124)

    NASA Astrophysics Data System (ADS)

    Cappelli, Andrea; Galeazzi, Simone; Zanardi, Iacopo; Travagli, Valter; Anzini, Maurizio; Mendichi, Raniero; Petralito, Stefania; Memoli, Adriana; Paccagnini, Eugenio; Peris, Walter; Giordani, Antonio; Makovec, Francesco; Fresta, Massimo; Vomero, Salvatore

    2010-03-01

    Poly- BF3a, a new hydrophobic polymer obtained by spontaneous polymerization of 1-methylene-3-phenyl-1 H-indene, was found to give nanoparticles characterized by favorable shape and dimensions. Poly- BF3a nanoparticles were loaded with CR3124, a potent 5HT3 antagonist, as a drug model by desolvation methods either in the absence or in the presence of polyethylene glycol (PEG1000) as a wetting agent. The SEM studies showed that the introduction of CR3124 into the preparation led to a variable degree of aggregation-cementation, which afforded a sort of nanocomposite material. In the absence of PEG1000, the drug molecule was found to stay in the amorphous state (DSC studies) when its percentage is not higher than 10% by weight. In vitro release experiments showed that the formation and stability of the dispersion as well as the drug release were remarkably affected by the presence of PEG1000, demonstrating its beneficial effect to the nanoparticle morphology and disaggregation.

  14. Safety of serotonin (5-HT3) receptor antagonists in patients undergoing surgery and chemotherapy: protocol for a systematic review and network meta-analysis

    PubMed Central

    2013-01-01

    Background Serotonin (5-HT3) receptor antagonists are a class of antiemetic medications often used to prevent nausea and vomiting among patients undergoing chemotherapy, radiotherapy or surgery. However, recent studies suggest that these agents might be associated with increased cardiac harm. To examine this further, we are proposing to conduct a systematic review and network meta-analysis on the comparative safety of 5-HT3 receptor antagonists among patients undergoing chemotherapy or surgery. Methods/Design Studies reporting one or more safety outcomes of interest for 5-HT3 receptor antagonists compared with each other, placebo, and/or other anti-emetic agents (for example, benzamides, phenothiazines, butyrophenones, antihistamines, and anticholinergics) among children and adult patients undergoing surgery or chemotherapy will be included. Our primary outcome of interest is arrhythmia. Our secondary outcomes include cardiac death, QT prolongation, PR prolongation, all-cause mortality, nausea, and vomiting. We will include experimental studies, quasi-experimental studies (namely controlled before-after and interrupted time series), and observational studies (namely cohort studies). We will not limit inclusion by publication status, time period, duration of follow-up or language of dissemination. Electronic databases (for example, MEDLINE, EMBASE) will be searched from inception onwards. These main searches will be supplemented by searching for difficult to locate and unpublished studies, such as dissertations, and governmental reports. The eligibility criteria will be pilot-tested and subsequently used to screen the literature search results by two reviewers in duplicate. A similar process will be followed for full-text screening, data abstraction, and risk of bias/methodological quality appraisal. The Cochrane Risk of Bias tool will be used to appraise experimental and quasi-experimental studies, and cohort studies will be assessed using the Newcastle Ottawa

  15. Dual role of serotonin in the pathogenesis of indomethacin-induced small intestinal ulceration: pro-ulcerogenic action via 5-HT3 receptors and anti-ulcerogenic action via 5-HT4 receptors.

    PubMed

    Kato, Shinichi; Matsuda, Narumi; Matsumoto, Kenjiro; Wada, Mai; Onimaru, Naoki; Yasuda, Masashi; Amagase, Kikuko; Horie, Syunji; Takeuchi, Koji

    2012-09-01

    Serotonin (5-HT) exerts multiple physiological functions not only in the central and peripheral nervous systems but also in the gastrointestinal tract, and these multiple functions are accounted for by a variety of 5-HT receptor subtypes. We investigated the role of 5-HT in the pathogenesis of indomethacin-induced intestinal lesions in mice, in relation to 5-HT receptor subtypes. A single oral administration of indomethacin (10 mg/kg) provoked damage in the small intestine of mice 24 h later, and this response was prevented by pretreatment with p-chlorophenylalanine (a 5-HT synthesis inhibitor). The administration of 5-HT3 receptor antagonists, such as ondansetron and ramosetron, dose-dependently reduced the severity of the intestinal lesions, whereas a high dose of GR113808 (a 5-HT4 receptor antagonist) significantly aggravated these lesions. In contrast, NAN-190 (a 5-HT1 receptor antagonist), ketanserin (a 5-HT2 receptor antagonist), and SB269970 (a 5-HT7 receptor antagonist) had no effect on these lesions. Mosapride (a 5-HT4 receptor agonist) significantly reduced the severity of indomethacin-induced intestinal lesions, and this protective effect was totally prevented by either GR113808 or methyllycaconitine (an α7-nicotinic acetylcholine receptor antagonist). Indomethacin increased the activity of myeloperoxidase and the expression of inducible nitric oxide synthase, inflammatory cytokines, and chemokines in the small intestine; these responses were significantly attenuated by ondansetron and mosapride. These findings suggest that endogenous 5-HT exerts a dual role in the pathogenesis of indomethacin-induced intestinal lesions: pro-ulcerogenic action via 5-HT3 receptors and anti-ulcerogenic action via 5-HT4 receptors, and the latter effect via 5-HT4 receptors may be mediated by activation of α7-nicotinic acetylcholine receptors.

  16. 5-HT3 and 5-HT4 receptor-mediated facilitation of the emptying phase of the peristaltic reflex in the marmoset isolated ileum.

    PubMed Central

    Tuladhar, B. R.; Costall, B.; Naylor, R. J.

    1996-01-01

    .83 +/- 0.36 respectively in the presence of GR 113808 (30 nM). 6. In the presence of a high concentration of (10 microM) 5-methoxytryptamine the subsequent addition of 2-methyl-5-HT (3-10 microM) but not 5-methoxytryptamine (10 microM) facilitated peristalsis; the effect of 3 microM 2-methyl-5-HT was significantly decreased by 2 microM ondansetron. 7. It is concluded that the facilitation of the peristaltic reflex in the marmoset intestine induced by 5-HT at submicromolar concentrations involves a 5-HT4 receptor stimulation with an additional 5-HT3 receptor activation at higher concentrations. PMID:8732276

  17. Ondansetron, a 5HT3 receptor antagonist reverses depression and anxiety-like behavior in streptozotocin-induced diabetic mice: possible implication of serotonergic system.

    PubMed

    Gupta, Deepali; Radhakrishnan, Mahesh; Kurhe, Yeshwant

    2014-12-05

    Increased prevalence and high comorbidity of depression-like mood disorders and diabetes have prompted investigation of new targets and potential contributing agents. There is considerable evidence supporting the inconsistent clinical efficacy and persistent undesirable effects of existing antidepressant therapy for depression associated with diabetes. Therefore, the present study was aimed at investigating the effect of ondansetron, a selective 5HT3 receptor antagonist in attenuating depression and anxiety-like behavior comorbid with diabetes. Experimentally, Swiss albino mice were rendered diabetic by a single intraperitoneal (i.p.) injection of streptozotocin (STZ, 200 mg/kg). After 8 weeks, diabetic mice received a single dose of vehicle/ondansetron (0.5 and 1 mg/kg, p.o.)/fluoxetine (the positive control, 10 mg/kg p.o.) for 28 days. Thereafter, behavioral studies were conducted to test depression-like behavior using forced swim test (FST) and anxiety-like deficits using hole-board and light-dark tests, followed by biochemical estimation of serotonin content in discrete brain regions. The results demonstrated that, STZ-induced diabetic mice exhibited increased duration of immobility and decreased swimming behavior in FST, reduced exploratory behavior during hole-board test and increased aversion to brightly illuminated light area in light-dark test as compared to non-diabetic mice, while ondansetron (similar to fluoxetine) treatment significantly reversed the same. Biochemical assay revealed that ondansetron administration attenuated diabetes-induced neurochemical impairment of serotonin function, indicated by elevated serotonin levels in discrete brain regions of diabetic mice. Collectively, the data indicate that ondansetron may reverse depression and anxiety-like behavioral deficits associated with diabetes in mice and modulation of serotonergic activity may be a key mechanism of the compound.

  18. Vortioxetine dose-dependently reverses 5-HT depletion-induced deficits in spatial working and object recognition memory: a potential role for 5-HT1A receptor agonism and 5-HT3 receptor antagonism.

    PubMed

    du Jardin, Kristian Gaarn; Jensen, Jesper Bornø; Sanchez, Connie; Pehrson, Alan L

    2014-01-01

    We previously reported that the investigational multimodal antidepressant, vortioxetine, reversed 5-HT depletion-induced memory deficits while escitalopram and duloxetine did not. The present report studied the effects of vortioxetine and the potential impact of its 5-HT1A receptor agonist and 5-HT3 receptor antagonist properties on 5-HT depletion-induced memory deficits. Recognition and spatial working memory were assessed in the object recognition (OR) and Y-maze spontaneous alternation (SA) tests, respectively. 5-HT depletion was induced in female Long-Evans rats using 4-cholro-DL-phenylalanine methyl ester HCl (PCPA) and receptor occupancies were determined by ex vivo autoradiography. Rats were acutely dosed with vortioxetine, ondansetron (5-HT3 receptor antagonist) or flesinoxan (5-HT1A receptor agonist). The effects of chronic vortioxetine administration on 5-HT depletion-induced memory deficits were also assessed. 5-HT depletion reliably impaired memory performance in both the tests. Vortioxetine reversed PCPA-induced memory deficits dose-dependently with a minimal effective dose (MED) ≤0.1mg/kg (∼80% 5-HT3 receptor occupancy; OR) and ≤3.0mg/kg (5-HT1A, 5-HT1B, 5-HT3 receptor occupancy: ∼15%, 60%, 95%) in SA. Ondansetron exhibited a MED ≤3.0μg/kg (∼25% 5-HT3 receptor occupancy; OR), but was inactive in the SA test. Flesinoxan had a MED ≤1.0mg/kg (∼25% 5-HT1A receptor occupancy; SA); only 1.0mg/kg ameliorated deficits in the NOR. Chronic p.o. vortioxetine administration significantly improved memory performance in OR and occupied 95%, 66%, and 9.5% of 5-HT3, 5-HT1B, and 5-HT1A receptors, respectively. Vortioxetine's effects on SA performance may involve 5-HT1A receptor agonism, but not 5-HT3 receptor antagonism, whereas the effects on OR performance may involve 5-HT3 receptor antagonism and 5-HT1A receptor agonism.

  19. Bidirectional amygdaloid control of neuropathic hypersensitivity mediated by descending serotonergic pathways acting on spinal 5-HT3 and 5-HT1A receptors.

    PubMed

    Sagalajev, B; Bourbia, N; Beloushko, E; Wei, H; Pertovaara, A

    2015-04-01

    Amygdala is involved in processing of primary emotions and particularly its central nucleus (CeA) also in pain control. Here we studied mechanisms mediating the descending control of mechanical hypersensitivity by the CeA in rats with a peripheral neuropathy in the left hind limb. For drug administrations, the animals had a guide cannula in the right CeA and an intrathecal catheter or another guide cannula in the medullary raphe. Hypersensitivity was tested with monofilaments. Glutamate administration in the CeA produced a bidirectional effect on hypersensitivity that varied from an increase at a low-dose (9μg) to a reduction at high doses (30-100μg). The increase but not the reduction of hypersensitivity was prevented by blocking the amygdaloid NMDA receptor with a dose of MK-801 that alone had no effects. The glutamate-induced increase in hypersensitivity was reversed by blocking the spinal 5-HT3 receptor with ondansetron, whereas the reduction in hypersensitivity was reversed by blocking the spinal 5-HT1A receptor with WAY-100635. Both the increase and decrease of hypersensitivity induced by amygdaloid glutamate treatment were reversed by medullary administration of a 5-HT1A agonist, 8-OH-DPAT, that presumably produced autoinhibition of serotonergic cell bodies in the medullary raphe. The results indicate that depending on the dose, glutamate in the CeA has a descending facilitatory or inhibitory effect on neuropathic pain hypersensitivity. Serotoninergic raphe neurons are involved in mediating both of these effects. Spinally, the 5-HT3 receptor contributes to the increase and the 5-HT1A receptor to the decrease of neuropathic hypersensitivity induced by amygdaloid glutamate.

  20. Effect of R3487/MEM3454, a novel nicotinic alpha7 receptor partial agonist and 5-HT3 antagonist on sustained attention in rats.

    PubMed

    Rezvani, Amir H; Kholdebarin, Ehsan; Brucato, Frederic H; Callahan, Patrick M; Lowe, David A; Levin, Edward D

    2009-03-17

    It is well established that nicotinic systems in the brain are critically involved in attentional processes in both animals and humans. The current study assessed the effects of a novel nicotinic alpha7 receptor partial agonist and 5-HT3 antagonist, R3487/MEM3454 (also referred to as R3487 or MEM 3454) on sustained attention in rats performing an operant visual signal detection task. The effects of R3487/MEM3454 were compared to those of the acetylcholinesterase inhibitor/nicotinic alpha7 allosteric positive modulator galanthamine. Adult female Sprague-Dawley rats were injected subcutaneously with R3487/MEM3454 (0.03, 0.1, 0.15, 0.3 and 0.6 mg/kg), galanthamine (0.25, 0.5, 1, 2 mg/kg) or vehicle 30 min before the attentional test. In the second study, the time-dependent effects of R3487/MEM3454 were assessed by injecting the compound (0.6 mg/kg, s.c.) at different pretreatment intervals (30, 60 or 90 min) before the start of the attentional task. Our results show a significant dose-effect for R3487/MEM3454 on percent hit accuracy performance without any significant alteration on percent correct rejection performance. In the time-dependent test, R3487/MEM3454 significantly increased the percent hit accuracy performance when animals were injected 60 min before the start of the attentional task. Administration of galanthamine failed to significantly increase percent hit accuracy performance and increasing the dose of galanthamine produced a decrease in percent correct rejection performance. The present findings with R3487/MEM3454 suggest that nicotinic alpha7 receptors and/or 5-HT3 receptors may play an important role in modulating sustained attention and that R3487/MEM3454 may have therapeutic potential in improving sustained attention in humans.

  1. X-ray analysis of the effect of the 5-HT3 receptor antagonist granisetron on gastrointestinal motility in rats repeatedly treated with the antitumoral drug cisplatin.

    PubMed

    Vera, Gema; López-Pérez, Ana Esther; Martínez-Villaluenga, María; Cabezos, Pablo Antonio; Abalo, Raquel

    2014-08-01

    Cancer chemotherapy is associated with the development of numerous adverse effects, including nausea, emesis and other alterations in gastrointestinal (GI) motility. The administration of 5-HT3 receptor antagonists has provided a clinical advance in the treatment of chemotherapy-induced vomiting but these drugs lose efficacy throughout chronic treatment. The effects of these drugs in experimental animals under chronic administration are not well known. Our aim was to study, using radiographic methods, the effect of the 5-HT3 receptor antagonist granisetron on GI dysmotility induced in the rat by repeated cisplatin administration. First, invasive methods were used to select a dose of granisetron capable of reducing increased stomach weight due to acute cisplatin administration (6 mg/kg, ip). Second, rats received two intraperitoneal (ip) injections once a week for 4 weeks: granisetron (1 mg/kg, ip) or saline and, thirty min later, saline or cisplatin (2 mg/kg, ip). Body weight gain was measured throughout treatment. Radiological techniques were used to determine the acute (after first dose) and chronic (after last dose) effects of cisplatin and/or granisetron on GI motility. Repeated cisplatin-induced weight loss which granisetron did not prevent. Gastric emptying was delayed after the first cisplatin administration. Granisetron completely prevented this effect. After weekly administration, cisplatin-induced gastric dysmotility was enhanced and granisetron was not capable of completely preventing this effect. Granisetron prevents gastric emptying alterations, but its efficacy decreases throughout antineoplastic treatment. This might be due to the enhanced effect of cisplatin.

  2. Effect of a novel 5-HT3 receptor antagonist 4i, in corticosterone-induced depression-like behavior and oxidative stress in mice.

    PubMed

    Gupta, Deepali; Radhakrishnan, Mahesh; Kurhe, Yeshwant

    2015-04-01

    Stress in our daily life severely affects the normal physiology of the biological system. Dysregulation of hypothalamic-pituitary-adrenal (HPA) axis has been implicated in the development of depression-like behavior, which remains under diagnosed and poorly treated. Exogenous corticosterone (CORT) administration has been demonstrated to develop a depression model, which has shown to mimic HPA-axis induced depression-like state in rodents. In the present study, the effect of a novel 5HT3 receptor, 4i was examined on CORT induced depression in mice. CORT (30mg/kg, subcutaneously) was given for 4-weeks to mice in control group, while mice in drug treated group were given 4i (0.5-1mg/kg, intraperitoneally)/fluoxetine (as a positive control, 10mg/kg), for the last 2-weeks of CORT dosing. Repeated CORT dosing caused depression-like behavior in mice as indicated by increased despair effects in forced swim test (FST) and anhedonia in sucrose preference test. In addition, CORT administration induced oxidative load in the brain with significant increase in pro-oxidant (lipid peroxidation and nitrite levels) markers and a substantial decline in anti-oxidant defense (catalase and reduced glutathione levels) system, indicating a direct effect of stress hormones in the induction of the brain oxidative damage. On the other hand, 4i and fluoxetine treatment reversed the CORT induced depressive-like deficits. Furthermore, 4i and fluoxetine prevented CORT induced oxidative brain insults, which may plausibly demonstrate one of the key mechanisms for antidepressant-like effects of the compounds. Thus, the study suggests that 5HT3 antagonist; 4i may be implicated as pharmacological intervention targeting depressive-like anomaly associated with HPA-axis dysregulation.

  3. Effects of serotonin 5-HT3 receptor antagonists on stress-induced colonic hyperalgesia and diarrhoea in rats: a comparative study with opioid receptor agonists, a muscarinic receptor antagonist and a synthetic polymer.

    PubMed

    Hirata, T; Keto, Y; Nakata, M; Takeuchi, A; Funatsu, T; Akuzawa, S; Sasamata, M; Miyata, K

    2008-05-01

    In this study, we examined the effects of serotonin (5-HT)3 receptor antagonists (5-HT3RAs) including ramosetron, alosetron, and cilansetron on colonic nociceptive threshold in rats. Furthermore, we established a restraint stress-induced colonic hyperalgesia model in rats, and compared the inhibitory effects of 5-HT3RAs on restraint stress-induced colonic hyperalgesia and diarrhoea with those of loperamide, trimebutine, tiquizium and polycarbophil. The colonic nociceptive threshold was measured as the balloon pressure at the time the rat showed a nociceptive response during colonic distension by an intrarectally inserted balloon. Oral administration of ramosetron (3-30 microg kg(-1)), alosetron (30-300 microg kg(-1)), or cilansetron (30-300 microg kg(-1)) increased the colonic nociceptive threshold in a dose-dependent manner in non-stressed rats. Restraint stress for 1 h significantly decreased the colonic nociceptive threshold, but ramosetron (0.3-3 microg kg(-1)), alosetron (3-30 microg kg(-1)), cilansetron (3-30 microg kg(-1)) and trimebutine (100-1000 mg kg(-1)) significantly inhibited the decrease in the threshold. Loperamide (3-30 mg kg(-1)), tiquizium (100-1000 mg kg(-1)) and polycarbophil (1000 mg kg(-1)) did not affect the restraint stress-induced decrease in the colonic nociceptive threshold. All drugs tested in this study showed dose-dependent inhibition of restraint stress-induced diarrhoea in rats. These results indicate that, unlike existing antidiarrhoeal and spasmolytic agents, 5-HT3RAs have inhibitory effects on colonic nociception, and prevented restraint stress-induced both diarrhoea and hyperalgesia at almost the same doses in rats. This suggests that the 5-HT3RAs may be useful in ameliorating both colonic hyperalgesia and diarrhoea in patients with irritable bowel syndrome.

  4. Evidence for the involvement of the serotonergic 5-HT2A/C and 5-HT3 receptors in the antidepressant-like effect caused by oral administration of bis selenide in mice.

    PubMed

    Jesse, Cristiano R; Wilhelm, Ethel A; Bortolatto, Cristiani F; Nogueira, Cristina W

    2010-03-17

    The present study investigated a possible antidepressant-like activity of bis selenide using two predictive tests for antidepressant effect on rodents: the forced swimming test (FST) and the tail suspension test (TST). Bis selenide (0.5-5 mg/kg, p.o.) decreased the immobility time in the mouse FST and TST. The anti-immobility effect of bis selenide (1 mg/kg, p.o.) in the TST was prevented by the pretreatment of mice with p-chlorophenylalanine methyl ester (PCPA; 100 mg/kg, i.p., an inhibitor of serotonin synthesis), ketanserin (1 mg/kg, i.p., a 5-HT(2A/2C) receptor antagonist), and ondasentron (1 mg/kg, i.p., a 5-HT(3) receptor antagonist). Pretreatment of mice with prazosin (1 mg/kg, i.p., an alpha(1)-adrenoceptor antagonist), yohimbine (1 mg/kg, i.p., an alpha(2)-adrenoceptor antagonist), propranolol (2 mg/kg, i.p., a beta-adrenoceptor antagonist), SCH23390 (0.05 mg/kg, s.c., a dopamine D(1) receptor antagonist), sulpiride (50 mg/kg, i.p., a dopamine D(2) receptor antagonist), or WAY 100635 (0.1 mg/kg, s.c., a selective 5-HT(1A) receptor antagonist) did not block the antidepressant-like effect of bis selenide (1 mg/kg, p.o.) in the TST. Administration of bis selenide (0.1 mg/kg, p.o.) and fluoxetine (1 mg/kg), at subeffective doses, produced an antidepressant-like effect in the TST. Bis selenide did not alter Na(+) K(+) ATPase, MAO-A and MAO-B activities in whole brains of mice. Bis selenide produced an antidepressant-like effect in the mouse TST and FST, which may be related to the serotonergic system (5-HT(2A/2C) and 5-HT(3) receptors).

  5. Antidepressant and anxiolytic-like effects of 4n, a novel 5-HT3 receptor antagonist using behaviour based rodent models.

    PubMed

    Kumar, Baldev; Jindal, Ankur; Pandey, Dilip Kumar; Bhatt, Shvetank; Devadoss, Thangaraj; Mahesh, Radhakrishnan

    2012-09-01

    The present study was designed to investigate the putative antidepressant and anxiolytic-like effects of N-n-Butylquinoxalin-2-carboxamide (4n), a novel 5-HT3 receptor antagonist, with an optimal log P (2.01) and pA2 value (7.3) greater than ondansetron (6.9) using rodent behavioural models of depression and anxiety. Acute treatment of 4n (1-4 mg/kg, ip) in mice produced antidepressant-like effect in forced swim test (FST) without affecting the baseline locomotion in actophotometer test in mice. 4n (2-4 mg/kg, ip) treatment also potentiated the 5-hydroxytryptophan (5-HTP) induced head twitch response in mice. Further, 4n (1-4 mg/kg, ip) treatment antagonized reserpine induced hypothermia in rats. Chronic treatment (14 days) with 4n (1-4 mg/kg) and paroxetine (10 mg/kg) significantly attenuated the behavioural anomalies induced by bilateral olfactory bulbectomy in rats in modified open field paradigm. An anxiogenic-like behaviour was induced by light alone as the stimulus using light-dark aversion test. 4n (2-4 mg/kg, ip) treatment significantly increased no. of transitions between dark and lit area and the time spent in the lit area. In conclusion, these preliminary investigations confirm that 4n exhibited antidepressant and anxiolytic-like effects in rodent models of depression and anxiety.

  6. Acute treatment with 5-HT3 receptor antagonist, tropisetron, reduces immobility in intact female rats exposed to the forced swim test.

    PubMed

    Bravo, Gabriela; Maswood, Sharmin

    2006-10-01

    The effects of tropisetron, a 5-HT3 receptor antagonist, were evaluated in adult Fischer female rats exposed to the Forced Swim Test (FST). Rats selected on the days of proestrus or estrus was immersed in a cylinder of water for 2 consecutive days. Rats were exposed to the FST for 15 min on day 1 (pretest), followed by a 5-min session (test), 24 h later. The proestrous-estrous group consisted of rats that were exposed to the FST on their proestrous stage (pretest); then 24 h later the same rats were exposed to the FST on their estrous stage (test). Rats in the estrous-diestrous group were exposed to the FST on their estrous stage (pretest) and 24 h later on their diestrous stage (test). Rats were injected intraperitoneally with saline or 1.0 or 2.0 mg/kg tropisetron 30 min prior to exposure to the cylinder on the test day. Immobility, swimming, and struggling behaviors were scored for 5 min. There was a significant decline in immobility after treatment with 2.0 mg/kg tropisetron in both groups. In addition, a significant decline in swimming was observed in the estrous rats (proestrous-estrous group) after treatment with 2.0 mg/kg tropisetron. There were no significant effects of tropisetron on struggling in any groups examined.

  7. Ondansetron reverses anti-hypersensitivity from clonidine in rats following peripheral nerve injury: Role of γ-amino butyric acid in α2-adrenoceptor and 5-HT3 serotonin receptor analgesia

    PubMed Central

    Hayashida, Ken-ichiro; Kimura, Masafumi; Yoshizumi, Masaru; Hobo, Shotaro; Obata, Hideaki; Eisenach, James C.

    2012-01-01

    Introduction Monoaminergic pathways, impinging an α2-adrenoceptors and 5-HT3 serotonin receptors, modulate nociceptive transmission, but their mechanisms and interactions after neuropathic injury are unknown. Here we examine these interactions in rodents after nerve injury. Methods Male Sprague-Dawley rats following L5-L6 spinal nerve ligation (SNL) were used for either behavioral testing, in vivo microdialysis for γ-amino butyric acid (GABA) and acetylcholine release, or synaptosome preparation for GABA release. Results Intrathecal administration of the α2-adrenoceptor agonist (clonidine) and 5-HT3 receptor agonist (chlorophenylbiguanide) reduced hypersensitivity in SNL rats via GABA receptor-mediated mechanisms. Clonidine increased GABA and acetylcholine release in vivo in the spinal cord of SNL rats but not in normal rats. Clonidine-induced spinal GABA release in SNL rats was blocked by α2-adrenergic and nicotinic cholinergic antagonists. The 5-HT3 receptor antagonist ondansetron decreased and chlorophenylbiguanide increased spinal GABA release in both normal and SNL rats. In synaptosomes from the spinal dorsal horn of SNL rats, pre-synaptic GABA release was increased by nicotinic agonists and decreased by muscarinic and α2-adrenergic agonists. Spinally administered ondansetron significantly reduced clonidine-induced anti-hypersensitivity and spinal GABA release in SNL rats. Conclusion These results suggest that spinal GABA contributes to anti-hypersensitivity from intrathecal α2-adrenergic and 5-HT3 receptor agonists in the neuropathic pain state, that cholinergic neuroplasticity after nerve injury is critical for α2-adrenoceptor-mediated GABA release, and that blockade of spinal 5-HT3 receptors reduces α2-adrenoceptor-mediated anti-hypersensitivity via reducing total GABA release. PMID:22722575

  8. Spinal 5-HT1A, not the 5-HT1B or 5-HT3 receptors, mediates descending serotonergic inhibition for late-phase mechanical allodynia of carrageenan-induced peripheral inflammation.

    PubMed

    Kim, Joung Min; Jeong, Seong Wook; Yang, Jihoon; Lee, Seong Heon; Kim, Woon Mo; Jeong, Seongtae; Bae, Hong Beom; Yoon, Myung Ha; Choi, Jeong Il

    2015-07-23

    Previous electrophysiological studies demonstrated a limited role of 5-hydroxytryptamine 3 receptor (5-HT3R), but facilitatory role of 5-HT1AR and 5-HT1BR in spinal nociceptive processing of carrageenan-induced inflammatory pain. The release of spinal 5-HT was shown to peak in early-phase and return to baseline in late-phase of carrageenan inflammation. We examined the role of the descending serotonergic projections involving 5-HT1AR, 5-HT1BR, and 5-HT3R in mechanical allodynia of early- (first 4h) and late-phase (24h after) carrageenan-induced inflammation. Intrathecal administration of 5-HT produced a significant anti-allodynic effect in late-phase, but not in early-phase. Similarly, intrathecal 5-HT1AR agonist (8-OH-DPAT) attenuated the intensity of late-phase allodynia in a dose dependent fashion which was antagonized by 5-HT1AR antagonist (WAY-100635), but produced no effect on the early-phase allodynia. However, other agonists or antagonists of 5-HT1BR (CP-93129, SB-224289) and 5-HT3R (m-CPBG, ondansetron) did not produce any anti- or pro-allodynic effect in both early- and late- phase allodynia. These results suggest that spinal 5-HT1A, but not 5-HT1B or 5-HT3 receptors mediate descending serotonergic inhibition on nociceptive processing of late-phase mechanical allodynia in carrageenan-induced inflammation.

  9. Neuropharmacological evaluation of a novel 5-HT3 receptor antagonist (6g) on chronic unpredictable mild stress-induced changes in behavioural and brain oxidative stress parameters in mice

    PubMed Central

    Bhatt, Shvetank; Radhakrishnan, Mahesh; Jindal, Ankur; Devadoss, Thangaraj; Dhar, Arghya Kusum

    2014-01-01

    Aim: The aim of the study was to evaluate a novel 5 HT3 receptor antagonist (6g) on chronic stress induced changes in behavioural and brain oxidative stress parameter in mice. A complicated relationship exists among stressful stimuli, body's reaction to stress and the onset of clinical depression. Chronic unpredictable stressors can produce a situation similar to human depression, and such animal models can be used for the preclinical evaluation of antidepressants. Materials and Methods: In the present study, a novel and potential 5-HT3 receptor antagonist (4-benzylpiperazin-1-yl)(3-methoxyquinoxalin-2-yl) methanone (6g) with good Log P (3.08) value and pA2(7.5) values, synthesized in our laboratory was investigated to study the effects on chronic unpredictable mild stress (CUMS)-induced behavioural and biochemical alterations in mice. Mice were subjected to different stress paradigms daily for a period of 28 days to induce depressive-like behaviour. Results: The results showed that CUMS caused depression-like behaviour in mice, as indicated by the significant (P < 0.05) decrease in sucrose consumption and locomotor activity and increase in immobility the forced swim test. In addition, it was found that lipid peroxidation and nitrite levels were significantly (P < 0.05) increased, whereas glutathione levels, superoxide dismutase and catalase activities decreased in brain tissue of CUMS-treated mice. ‘6g’ (1 and 2 mg/kg, p.o., 21 days) and fluoxetine treatment (20 mg/kg, p.o., 21 days) significantly (P < 0.05) reversed the CUMS-induced behavioural (increased immobility period, reduced sucrose preference and decreased locomotor activity) and biochemical (increased lipid peroxidation; decreased glutathione levels, superoxide dismutase and catalase activities). However fluoxetine treatment (20 mg/kg, p.o., 21 days) significantly decreased the nitrite level in the brain while ‘6g’ (1 and 2 mg/kg, p.o., 21 days) did not show significant (P < 0.05) effect on the

  10. Effect of acute and chronic treatment with QCF-3 (4-benzylpiperazin-1-yl) (quinoxalin-2-yl) methanone, a novel 5-HT(3) receptor antagonist, in animal models of depression.

    PubMed

    Devadoss, Thangaraj; Pandey, Dilip K; Mahesh, Radhakrishnan; Yadav, Shushil K

    2010-01-01

    The serotonin type 3 (5-HT(3)) receptor is unique among the seven recognized serotonin receptor "families". The existence serotonin type 3 receptor (5-HT(3)) in neuro-anatomical regions stimulated the research interest for novel therapeutic targets such as anxiety, depression, nociception and cognitive function. In the current study, (4-benzylpiperazin-1-yl) (quinoxalin-2-yl) methanone (QCF-3), a novel 5-HT(3) receptor antagonist, with an optimal log P (the logarithm of the ratio of the concentrations of the un-ionized solute in the solvents is called log P) and significant pA2 value (is a negative logarithm of the molar concentration of antagonist required to reduce the effect of multiple dose agonist to that of single dose) was screened for its anti-depressant potential using rodent behavioral models of depression. Psycho-pharmacological investigations involved acute and chronic treatment (14 days) with QCF-3 and assessment of behavior during the forced swim test (FST) and tail suspension test (TST) in mice and olfactory bulbectomised rats. A dose response study in mice revealed an initial anti-depressant-like effect of QCF-3 (0.5-4 mg/kg, ip) in the FST and TST. Interaction studies showed that QCF-3 (1 and 2 mg/kg) significantly enhanced the antidepressant action of fluoxetine and bupropion in the FST and TST, respectively. QCF-3 (1 and 2 mg/kg) potentiated the 5-hydroxytryptophan (5-HTP) induced head twitches response in mice and reversed reserpine-induced hypothermia in rats. Further, OBX rats exhibited behavioral anomalies in the open field and hyper-emotionality tests that were attenuated by chronic QCF-3 treatment. In conclusion, this behavioral study describes an antidepressant-like effect of QCF-3 in rodent behavioral models of depression.

  11. Importance of M2-M3 loop in governing properties of genistein at the α7 nicotinic acetylcholine receptor inferred from α7/5-HT3A chimera.

    PubMed

    Grønlien, Jens Halvard; Ween, Hilde; Thorin-Hagene, Kirsten; Cassar, Steven; Li, Jinhe; Briggs, Clark A; Gopalakrishnan, Murali; Malysz, John

    2010-11-25

    Genistein and 5-hydroxyindole (5-HI) potentiate the α7 nicotinic acetylcholine receptor current by primarily increasing peak amplitude, a property of type I α7 positive allosteric modulation. In this study, the effects of these two compounds were investigated at two different α7/5-HT(3) chimeras (chimera 1, comprising of extracellular α7 N-terminus fused to the remainder of 5-HT(3A), and chimera 2 containing an additional α7 encoded M2-M3 loop), and wild-type α7 and 5-HT(3A) receptors. Agonist-evoked responses, examined by expression of the chimeras in Xenopus laevis oocytes or HEK-293 cells, revealed that currents decayed slower and compounds {rank order: N-[(3R)-1-azabicyclo[2.2.2]oct-3-yl]-4-chlorobenzamide hydrochloride (PNU-282987)~2-(1,4-diazabicyclo[3.2.2]nonan-4-yl)-5-phenyl-1,3,4-oxadiazole (NS6784)>acetylcholine>choline} were more potent in chimera 2 than chimera 1 or α7 receptors. In chimera 2, genistein and 5-HI potentiated agonist-evoked responses (EC(50): 4-5 μM for genistein and 300-500 μM for 5-HI) and at higher concentrations evoked current directly consistent with ago-allosteric modulation. At chimera 1 and 5-HT(3A) receptors, neither compound directly evoked any current and 5-HI, only at chimera 1, was able to potentiate agonist-evoked responses. Genistein and 5-HI did not inhibit the binding of the α7 agonist [(3)H](1S,4S)-2,2-dimethyl-5-(6-phenylpyridazin-3-yl)-5-aza-2-azoniabicyclo[2.2.1] heptane ([(3)H]A-585539) to rat brain or chimera 2. In summary, this study supports the role of the M2-M3 loop being critical for the positive allosteric effect of genistein, but not 5-HI, and in agonist-evoked response fine-tuning. The identification of distinct α7 receptor modulatory sites offers unique opportunities for developing CNS therapeutics and understanding its pharmacology.

  12. The N-methyl-D-aspartate receptor channel blockers memantine, MRZ 2/579 and other amino-alkyl-cyclohexanes antagonise 5-HT(3) receptor currents in cultured HEK-293 and N1E-115 cell systems in a non-competitive manner.

    PubMed

    Rammes, G; Rupprecht, R; Ferrari, U; Zieglgänsberger, W; Parsons, C G

    2001-06-22

    The type 3 serotonin (5-HT(3)) receptor is a ligand-gated ion channel. In concentration-clamp experiments, we investigated the effects of the uncompetitive N-methyl-D-aspartate (NMDA) receptor antagonists memantine, amantadine and MRZ 2/579 on 5-HT receptors stabley expressed in HEK-293 cells and on native 5-HT(3) receptors in the N1E-115 cell line. All agents antagonized serotonin (10 microM)-induced inward currents with similar potency to that reported for NMDA receptors. This effect was characterized by inducing a pronounced receptor desensitization, and was probably non-competitive and voltage-independent. In contrast, (S)-ketamine was much weaker as an antagonist of 5-HT(3) receptors than NMDA receptors. Similar effects on 5-HT(3) receptors have been reported previously for a variety of anti-depressants and it is possible that the clinical anti-depressant effects reported for both memantine and amantadine are mediated, at least in part, by antagonistic effects at 5-HT(3) receptors.

  13. Analysis of free ACh and 5-HT in milk from four different species and their bioactivity on 5-HT(3) and nACh receptors.

    PubMed

    Gallegos-Perez, Jose-Luis; Limon, Agenor; Reyes-Ruiz, Jorge M; Alshanqeeti, Ali S; Aljohi, Mohammad A; Miledi, Ricardo

    2014-07-25

    Milk is one of the most beneficial aliments and is highly recommended in normal conditions; however, in certain disorders, like irritable bowel syndrome, cow milk and dairy products worsen the gastric symptoms and their use is not recommended. Among the most recognized milk-induced gatrointestinal symptoms are abdominal pain, nausea and vomiting, which are processes controlled by cholinergic and serotonergic transmission. Whether the presence of bioavailable ACh and 5-HT in milk may contribute to normal peristalsis, or to the developing of these symptoms, is not known. In this work we attempt to determine whether the content of free ACh and 5-HT is of physiological significance in milk from four different species: cow (bovine), goat, camel and human. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was used to identify and quantify free ACh and 5-HT in milk, and activation of the serotonergic and cholinergic ionotropic receptors was investigated using electrophysiological experiments. Our principal hypothesis was that milk from these four species had sufficient free ACh and 5-HT to activate their correspondent receptors expressed in a heterologous system. Our results showed a more complex picture, in which free ACh and 5-HT and their ability to activate cholinergic and serotonergic receptors are not correlated. This work is a first step to elucidate whether 5-HT and ACh, at the concentrations present in the milk, can be associated to a direct function in the GI.

  14. Spinal 5-HT3AR contributes to BmK I-induced inflammatory pain in rats.

    PubMed

    Fu, Jin; Jiao, Yun-Lu; Li, Zheng-Wei; Ji, Yong-Hua

    2015-06-25

    Subcutaneous injection of BmK I could be adopted to well establish a novel pain model. Moreover, 5-hydroxytryptamine (serotonin, 5-HT) receptor is involved in regulating animal pain-related behaviors. However, the underlying mechanism of 5-HT3R on BmK I-induced pain remains unclear. Animal behavioral testing, RT-PCR and Western blotting were used to yield the following results: first, intraplantar (i.pl.) injection of BmK I (10 μg) induced elevated mRNA and protein levels of 5-HT3AR in bilateral L4-L5 spinal cord; Second, intrathecal (i.t.) injection of ondansetron (a specific antagonist of 5-HT3AR) reduced spontaneous pain responses, attenuated unilateral thermal and bilateral mechanical hypersensitivity elicited by BmK I; Microglia could be activated by BmK I (i.pl.) in both sides of L4-L5 spinal cord, and this effect was reversed by intrathecal pre-treatment with 5-HT3AR antagonist. Meanwhile, the 5-HT3AR in L4-L5 spinal cord was almost co-localized with NeuN (a marker of nerve cell), but not co-expressed with Iba-1 (a marker of microglia). Finally, the expression level of CX3CL1 and CX3CR1 was reduced by intrathecal pre-treatment with ondansetron. Our results indicate that both 5-HT3AR signaling pathway and microglia are activated in the process of induction and maintenance of BmK I-induced pain nociception. Meanwhile, our results suggest that the neuronal 5-HT3AR may communicate with microglia indirectly via CX3CL1 which is involved in regulating the BmK I-induced hyperalgesia and sensitization.

  15. Dual role of serotonin in the acquisition and extinction of reward-driven learning: involvement of 5-HT1A, 5-HT2A and 5-HT3 receptors.

    PubMed

    Frick, Luciana Romina; Bernardez-Vidal, Micaela; Hocht, Christian; Zanutto, Bonifacio Silvano; Rapanelli, Maximiliano

    2015-01-15

    Serotonin (5-HT) has been proposed as a possible encoder of reward. Nevertheless, the role of this neurotransmitter in reward-based tasks is not well understood. Given that the major serotonergic circuit in the rat brain comprises the dorsal raphe nuclei and the medial prefrontal cortex (mPFC), and because the latter structure is involved in the control of complex behaviors and expresses 1A (5-HT1A), 2A (5-HT2A), and 3 (5-HT3) receptors, the aim was to study the role of 5-HT and of these receptors in the acquisition and extinction of a reward-dependent operant conditioning task. Long Evans rats were trained in an operant conditioning task while receiving fluoxetine (serotonin reuptake inhibitor, 10mg/kg), tianeptine (serotonin reuptake enhancer, 10mg/kg), buspirone (5-HT1A partial agonist, 10mg/kg), risperidone (5-HT2A antagonist, 1mg/kg), ondansetron (5-HT3 antagonist, 2mg/kg) or vehicle. Then, animals that acquired the operant conditioning without any treatment were trained to extinct the task in the presence of the pharmacological agents. Fluoxetine impaired acquisition but improved extinction. Tianeptine administration induced the opposite effects. Buspirone induced a mild deficit in acquisition and had no effects during the extinction phase. Risperidone administration resulted in learning deficits during the acquisition phase, although it promoted improved extinction. Ondansetron treatment showed a deleterious effect in the acquisition phase and an overall improvement in the extinction phase. These data showed a differential role of 5-HT in the acquisition and extinction of an operant conditioning task, suggesting that it may have a dual function in reward encoding.

  16. Sleep Deprivation-Induced Blood-Brain Barrier Breakdown and Brain Dysfunction are Exacerbated by Size-Related Exposure to Ag and Cu Nanoparticles. Neuroprotective Effects of a 5-HT3 Receptor Antagonist Ondansetron.

    PubMed

    Sharma, Aruna; Muresanu, Dafin F; Lafuente, José V; Patnaik, Ranjana; Tian, Z Ryan; Buzoianu, Anca D; Sharma, Hari S

    2015-10-01

    Military personnel are often subjected to sleep deprivation (SD) during combat operations. Since SD is a severe stress and alters neurochemical metabolism in the brain, a possibility exists that acute or long-term SD will influence blood-brain barrier (BBB) function and brain pathology. This hypothesis was examined in young adult rats (age 12 to 14 weeks) using an inverted flowerpot model. Rats were placed over an inverted flowerpot platform (6.5 cm diameter) in a water pool where the water levels are just 3 cm below the surface. In this model, animals can go to sleep for brief periods but cannot achieve deep sleep as they would fall into water and thus experience sleep interruption. These animals showed leakage of Evans blue in the cerebellum, hippocampus, caudate nucleus, parietal, temporal, occipital, cingulate cerebral cortices, and brain stem. The ventricular walls of the lateral and fourth ventricles were also stained blue, indicating disruption of the BBB and the blood-cerebrospinal fluid barrier (BCSFB). Breakdown of the BBB or the BCSFB fluid barrier was progressive in nature from 12 to 48 h but no apparent differences in BBB leakage were seen between 48 and 72 h of SD. Interestingly, rats treated with metal nanoparticles, e.g., Cu or Ag, showed profound exacerbation of BBB disruption by 1.5- to 4-fold, depending on the duration of SD. Measurement of plasma and brain serotonin showed a close correlation between BBB disruption and the amine level. Repeated treatment with the serotonin 5-HT3 receptor antagonist ondansetron (1 mg/kg, s.c.) 4 and 8 h after SD markedly reduced BBB disruption and brain pathology after 12 to 24 h SD but not following 48 or 72 h after SD. However, TiO2-nanowired ondansetron (1 mg/kg, s.c) in an identical manner induced neuroprotection in rats following 48 or 72 h SD. However, plasma and serotonin levels were not affected by ondansetron treatment. Taken together, our observations are the first to show that (i) SD could induce BBB

  17. Inhibitory effects of ramosetron, a potent and selective 5-HT3-receptor antagonist, on conditioned fear stress-induced abnormal defecation and normal defecation in rats: comparative studies with antidiarrheal and spasmolytic agents.

    PubMed

    Hirata, Takuya; Funatsu, Toshiyuki; Keto, Yoshihiro; Akuzawa, Shinobu; Sasamata, Masao; Miyata, Keiji

    2008-02-01

    We examined the effect of ramosetron, a potent serotonin (5-HT)(3)-receptor antagonist for irritable bowel syndrome with diarrhea, on conditioned fear stress (CFS)-induced defecation and normal (non-stressed) defecation in rats and compared ramosetron with the antidiarrheal agent loperamide and the spasmolytic agents trimebutine and tiquizium. Ramosetron, loperamide, trimebutine, and tiquizium significantly inhibited CFS-induced defecation in a dose-dependent manner with ED(50) (95% confidence limit) values of 0.019 (0.01 - 0.028), 9.4 (4.0 - 22), 850 (520 - 2,400), and 300 (190 - 450) mg/kg, respectively. A significant effect of ramosetron on CFS-induced defecation appeared at 10 min after dosing and was sustained for 8 h. In contrast, loperamide, trimebutine, and tiquizium significantly inhibited CFS-induced defecation between 1 - 8, 1 - 4, and 1 - 8 h after administration, respectively. High doses of ramosetron did not affect normal defecation, whereas loperamide, trimebutine, and tiquizium significantly inhibited this process. In conclusion, ramosetron has potent, rapid-onset, and long-lasting inhibitory effects on CFS-induced defecation in rats, but does not influence normal defecation. The present findings indicate that ramosetron will be a useful therapeutic agent for irritable bowel syndrome with diarrhea, showing greater efficacy and safety than other antidiarrheal and spasmolytic agents.

  18. Stimulation of 5-HT1A, 5-HT1B, 5-HT2A/2C, 5-HT3 and 5-HT4 receptors or 5-HT uptake inhibition: short- and long-term memory.

    PubMed

    Meneses, Alfredo

    2007-11-22

    In order to determine whether short- (STM) and long-term memory (LTM) function in serial or parallel manner, serotonin (5-hydroxtryptamine, 5-HT) receptor agonists were tested in autoshaping task. Results show that control-vehicle animals were modestly but significantly mastering the autoshaping task as illustrated by memory scores between STM and LTM. Thus, post-training administration of 8-OHDPAT (agonist for 5-HT(1A/7) receptors) only at 0.250 and 0.500 mg/kg impaired both STM and LTM. CGS12066 (agonist for 5-HT(1B)) produced biphasic affects, at 5.0 mg/kg impaired STM but at 1.0 and 10.0 mg/kg, respectively, improved or impaired LTM. DOI (agonist for 5-HT(2A/2C) receptors) dose-dependently impaired STM and, at 10.0 mg/kg only impaired LTM. Both, STM and LTM were impaired by either mCPP (mainly agonist for 5-HT(2C) receptors) or mesulergine (mainly antagonist for 5-HT(2C) receptors) lower dose. The 5-HT(3) agonist mCPBG at 1.0 impaired STM and its higher dose impaired both STM and LTM. RS67333 (partial agonist for 5-HT(4) receptors), at 5.0 and 10.0 mg/kg facilitated both STM and LTM. The higher dose of fluoxetine (a 5-HT uptake inhibitor) improved both STM and LTM. Using as head-pokes during CS as an indirect measure of food-intake showed that of 30 memory changes, 21 of these were unrelated to the former. While some STM or LTM impairments can be attributed to decrements in food-intake, but not memory changes (either increase or decreases) produced by 8-OHDPAT, CGS12066, RS67333 or fluoxetine. Except for animals treated with DOI, mCPBG or fluoxetine, other groups treated with 5-HT agonists 6 h following autoshaping training showed similar LTM and unmodified CS-head-pokes scores.

  19. Ondansetron, a selective 5-HT3 antagonist, antagonizes methamphetamine-induced anorexia in mice.

    PubMed

    Ginawi, O T; Al-Majed, A A; Al-Suwailem, A K

    2005-03-01

    Effects of some selective serotonergic (5-HT) antagonists on methamphetamine-induced anorexia were investigated in male mice. The least possible dose of methamphetamine alone that caused significant anorectic activity was 11 micromolkg(-1), i.p. (2 mgkg(-1)). Various doses of some selective serotonergic receptor antagonists were administered half an hour before the above mentioned dose of methamphetamine. Methiothepin potentiated, whereas NAN-190, methysergide, mianserin and ondansetron antagonized methamphetamine-induced anorectic activity. The least possible doses of these antagonists which modified methamphetamine-induced anorexia were as follows: methiothepin (1.1 micromolkg(-1), i.p.), NAN-190 (4.2 micromolkg(-1), i.p.), methysergide (2.1 micromolkg(-1), i.p.), mianserin (3.3 micromolkg(-1), i.p.) and ondansetron (0.003 micromolkg(-1), i.p.). The serotonergic antagonists at the above mentioned doses did not modify the food intake of animals not treated with methamphetamine, except for methiothepin, which produced a significant reduction, and mianserin, which produced a significant increase in food intake. The results of the present study indicated that the anorectic activity induced by methamphetamine is related to the interactions of methamphetamine with 5-HT receptor. Since a very small dose (0.003 micromolkg(-1)) of ondansetron (the 5-HT(3) antagonist), as compared with the other antagonists used in this study, antagonized the anorexia induced by methamphetamine, the 5-HT(3) receptor is likely to be the site for this interaction.

  20. Systemic injection of p-chloroamphetamine eliminates the effect of the 5-HT3 compounds on learning.

    PubMed

    Hong, E; Meneses, A

    1996-04-01

    There is evidence that 5-HT3 antagonists enhance learning and memory; however, their mechanisms of action are unknown. The aim of the present work was to investigate further the role of 5-HT3 receptors involved in learning, using the specific 5-HT3 agonist 1-(m-chlorophenyl)-biguanide (mCPBG) and the 5-HT3 antagonists ondansetron and tropisetron. p-Chloroamphetamine (PCA) pretreatment was used to determine whether pre- or postsynaptic 5-HT3 receptors are involved in learning. The posttraining intraperitoneal (IP) injection of each drug was analyzed on a lever-press response on autoshaping, which is an associative learning task. The results showed that mCPBG impaired retention of the conditioned response (CR), whereas tropisetron and ondansetron improved it. In other animals, PCA alone did not affect CR but was able to block the effects of the 5-HT3 ligands. The present data suggest that the actions of 5-HT3 compounds could be due to their interaction with presynaptic 5-HT3 receptors.

  1. Shuyu Capsules Relieve Premenstrual Syndrome Depression by Reducing 5-HT3AR and 5-HT3BR Expression in the Rat Brain

    PubMed Central

    Li, Fang; Feng, Jizhen; Gao, Dongmei; Wang, Jieqiong; Song, Chunhong; Wei, Sheng

    2016-01-01

    The effects of the Shuyu capsule on 5-HT3AR and 5-HT3BR expression in a rat model of premenstrual syndrome (PMS) depression and on 5-HT3AR and 5-HT3BR expression and hippocampal neuron 5-HT3 channel current were investigated, to elucidate its mechanism of action against PMS depression. PMS depression model rats were divided into depression and Shuyu- and fluoxetine-treated groups, which were compared to control rats for frontal lobe and hippocampal 5-HT3AR and 5-HT3BR expression and behavior. The depressed model rats displayed symptoms of depression, which were reduced in treated and normal control rats. Frontal lobe and hippocampal 5-HT3AR and 5-HT3BR levels were significantly higher in the model versus the control group and were significantly lower in the Shuyu group. As compared to control rats, the 5-HT3R channel current in the model group was significantly higher; the 5-HT3R channel current in hippocampal neurons treated with serum from Shuyu group rats was significantly lower than that in those treated with model group serum. Thus, PMS depression may be related to 5-HT3AR and 5-HT3BR expression and increased 5-HT3 channel current. Shuyu capsules rectified abnormal 5-HT3AR and 5-HT3BR expression and 5-HT3 channel current changes in a rat model; this finding may provide insight into treating PMS depression. PMID:27725889

  2. Structural, conformational, biochemical, and pharmacological study of some amides derived from 3,7-dimethyl-3,7-diazabicyclo [3.3.1] nonan-9-amine as potential 5-HT 3 receptor antagonists

    NASA Astrophysics Data System (ADS)

    Fernández, M. J.; Huertas, R. M.; Gálvez, E.; Orjales, A.; Berisa, A.; Labeaga, L.; Garcia, A. G.; Uceda, G.; Server-Carrió, J.; Martinez-Ripoll, M.

    1995-12-01

    A series of amides derived from 3,7-dimethyl-3,7-diazabicyclo [3.3.1] nonan-9-amine have been synthesized and examined by 1H and 13C NMR spectroscopy and the crystal structure of 9-(2,4,6-trichlorobenzamido)-3,7-dimethyl-3,7-diazabicyclo[3.3.1] nonane hydrochloride ( 4a·HCl) has been determined by X-ray diffraction. These compounds adopt an almost perfect chair-chair conformation with the NCH 3 groups in equatorial position. This conformation is nearly the same as that observed for compound 4a in the solid state. From binding studies of compounds 4a-c, compound 4b demonstrated the ability to efficiently displace [ 3H]GR65630 bound to bovine brain area postrema membranes to an extent comparable to MDL 72222. In the von Bezold-Jarish reflex, compound 4b showed significant results at a dose of 25 mg Kg -1. It is shown for the first time that a series of compounds with a bispidine skeleton linked through an amide moiety to several aromatic rings, shows 5-HT 3 antagonistic profiles.

  3. Protective effects of a novel 5-HT3 receptor antagonist, N-n-butyl-3-methoxy quinoxaline-2-carboxamide (6o) against chronic unpredictable mild stress-induced behavioral changes and biochemical alterations.

    PubMed

    Bhatt, Shvetank; Mahesh, Radhakrishnan; Jindal, Ankur; Devadoss, Thangaraj

    2014-07-01

    Stimulation of high oxidative stress in the brain is considered as an important factor for neurotoxicity towards the pathophysiology of chronic stress-induced depression disorder. In the present research, a potential 5-HT₃ receptor antagonist N-n-butyl-3-methoxy quinoxaline-2-carboxamide (6o) having good Log P (2.60) and pA₂ (7.7) values was examined for its effect on the behavioral and biochemical changes induced by the chronic unpredictable mild stress (CUMS) model. In the current investigation mice were introduced to different stress procedures daily for a period of 28 days to induce a depressive-like behavior. The results show that CUMS caused a depression-like behavior in mice, as indicated by the significant decrease in sucrose consumption and locomotor activity and increase in immobility in the forced swim test (FST). Moreover, it was found that oxidative stress markers such as lipid peroxide and nitrite levels were significantly increased, whereas, antioxidant enzymes such as glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) levels were decreased in the brain tissue of CUMS-subjected mice. "Compound 6o" (1 and 2 mg/kg, p.o.) and fluoxetine treatment (20 mg/kg, p.o.) for a period of 21 days altered the CUMS-induced behavioral (increased immobility period, reduced sucrose preference and decreased locomotor activity) and biochemical (increased lipid peroxide, increased brain nitrite; decreased GSH, SOD and CAT levels) alterations. Moreover normal mice treated with "compound 6o" (2 mg/kg, p.o.) showed a significant decrease in the duration of immobility in FST as compared to normal vehicle treated mice. In conclusion, "compound 6o" produced antidepressant-like effects in behavioral despair paradigm in chronically stressed mice by restoring antioxidant enzyme activity.

  4. Activation of serotonin 3 receptors changes in vivo auditory responses in the mouse inferior colliculus

    PubMed Central

    Bohorquez, Alexander; Hurley, Laura M.

    2009-01-01

    Metabotropic serotonin receptors such as 5-HT1A and 5-HT1B receptors shape the level, selectivity, and timing of auditory responses in the inferior colliculus (IC). Less is known about the effects of ionotropic 5-HT3 receptors, which are cation channels that depolarize neurons. In the current study, the influence of the 5-HT3 receptor on auditory responses in vivo was explored by locally iontophoresing a 5-HT3 receptor agonist and antagonists onto single neurons recorded extracellularly in mice. Three main findings emerge from these experiments. First, activation of the 5-HT3 receptor can either facilitate or suppress auditory responses, but response suppressions are not consistent with 5-HT3 effects on presynaptic GABAergic neurons. Both response facilitations and suppressions are less pronounced in neurons with high precision in response latency, suggesting functional differences in the role of receptor activation for different classes of neuron. Finally, the effects of 5-HT3 activation vary across repetition rate within a subset of single neurons, suggesting that the influence of receptor activation sometimes varies with the level of activity. These findings contribute to the view of the 5-HT3 receptor as an important component of the serotonergic infrastructure in the IC, with effects that are complex and neuron- selective. PMID:19236912

  5. Anti-depressant like activity of N-n-butyl-3-methoxyquinoxaline-2-carboxamide (6o) a 5-HT3 receptor antagonist.

    PubMed

    Bhatt, Shvetank; Mahesh, Radhakrishnan; Devadoss, Thangaraj; Jindal, Ankur

    2013-06-01

    The compound 6o (at 0.5, 1 and 2 mg/kg, ip) with optimum log P and pA2 value, was subjected to forced swim test (FST) and tail suspension test (TST). The compound 6o significantly reduced the duration of immobility in mice without affecting the base line locomotion in actophotometer. Moreover, 6o (2 mg/kg, ip), potentiated the 5-hydroxytryptophan (5-HTP)-induced head twitch responses in mice and at 1 and 2 mg/kg, ip antagonized the reserpine-induced hypothermia (RIH) in rats. In interaction studies with various standard drugs/ligands using FST, 6o (1 and 2 mg/kg, ip) potentiated the anti-depressant effect fluoxetine (5 mg/kg, ip) and reversed the depressant effect of parthenolide (1 mg/kg, ip) by reducing the duration of immobility. Furthermore, 6o (1 and 2 mg/kg, ip) potentiated the effect of bupropion (10 mg/kg, ip) in TST. The behavioural anomalies of the olfactory bulbectomised (OBX) rats were augmented by chronic 6o (1 and 2 mg/kg) treatment as observed from the modified open field test (parameters: ambulation, rearing, fecal pellet). The results suggest that compound 6o exhibited anti-depressant like effect in rodent models of depression.

  6. Activation and modulation of recombinantly expressed serotonin receptor type 3A by terpenes and pungent substances.

    PubMed

    Ziemba, Paul M; Schreiner, Benjamin S P; Flegel, Caroline; Herbrechter, Robin; Stark, Timo D; Hofmann, Thomas; Hatt, Hanns; Werner, Markus; Gisselmann, Günter

    2015-11-27

    Serotonin receptor type 3 (5-HT3 receptor) is a ligand-gated ion channel that is expressed in the central nervous system (CNS) as well as in the peripheral nervous system (PNS). The receptor plays an important role in regulating peristalsis of the gastrointestinal tract and in functions such as emesis, cognition and anxiety. Therefore, a variety of pharmacologically active substances target the 5-HT3 receptor to treat chemotherapy-induced nausea and vomiting. The 5-HT3 receptors are activated, antagonized, or modulated by a wide range of chemically different substances, such as 2-methyl-serotonin, phenylbiguanide, setrones, or cannabinoids. Whereas the action of all of these substances is well described, less is known about the effect of terpenoids or fragrances on 5-HT3A receptors. In this study, we screened a large number of natural odorous and pungent substances for their pharmacological action on recombinantly expressed human 5-HT3A receptors. The receptors were functionally expressed in Xenopus oocytes and characterized by electrophysiological recordings using the two-electrode voltage-clamp technique. A screening of two odorous mixes containing a total of 200 substances revealed that the monoterpenes, thymol and carvacrol, act as both weak partial agonists and positive modulators on the 5-HT3A receptor. In contrast, the most effective blockers were the terpenes, citronellol and geraniol, as well as the pungent substances gingerol, capsaicin and polygodial. In our study, we identified new modulators of 5-HT3A receptors out of the classes of monoterpenes and vanilloid substances that frequently occur in various plants.

  7. Design and validation of a homogeneous time-resolved fluorescence cell-based assay targeting the ligand-gated ion channel 5-HT3A.

    PubMed

    Blanc, Emilie; Wagner, Patrick; Plaisier, Fabrice; Schmitt, Martine; Durroux, Thierry; Bourguignon, Jean-Jacques; Partiseti, Michel; Dupuis, Elodie; Bihel, Frederic

    2015-09-01

    Ligand-gated ion channels (LGICs) are considered as attractive protein targets in the search for new therapeutic agents. Nowadays, this strategy involves the capability to screen large chemical libraries. We present a new Tag-lite ligand binding assay targeting LGICs on living cells. This technology combines the use of suicide enzyme tags fused to channels of interest with homogeneous time-resolved fluorescence (HTRF) as the detection readout. Using the 5-HT3 receptor as system model, we showed that the pharmacology of the HALO-5HT3 receptor was identical to that of the native receptor. After validation of the assay by using 5-HT3 agonists and antagonists of reference, a pilot screen enabled us to identify azelastine, a well-known histamine H1 antagonist, as a potent 5-HT3 antagonist. This interesting result was confirmed with electrophysiological experiments. The method described here is easy to implement and could be applicable for other LGICs, opening new ways for the screening of chemical libraries.

  8. Transcriptomic and anatomic parcellation of 5-HT3AR expressing cortical interneuron subtypes revealed by single-cell RNA sequencing

    PubMed Central

    Frazer, Sarah; Prados, Julien; Niquille, Mathieu; Cadilhac, Christelle; Markopoulos, Foivos; Gomez, Lucia; Tomasello, Ugo; Telley, Ludovic; Holtmaat, Anthony; Jabaudon, Denis; Dayer, Alexandre

    2017-01-01

    Cortical GABAergic interneurons constitute a highly diverse population of inhibitory neurons that are key regulators of cortical microcircuit function. An important and heterogeneous group of cortical interneurons specifically expresses the serotonin receptor 3A (5-HT3AR) but how this diversity emerges during development is poorly understood. Here we use single-cell transcriptomics to identify gene expression patterns operating in Htr3a-GFP+ interneurons during early steps of cortical circuit assembly. We identify three main molecular types of Htr3a-GFP+ interneurons, each displaying distinct developmental dynamics of gene expression. The transcription factor Meis2 is specifically enriched in a type of Htr3a-GFP+ interneurons largely confined to the cortical white matter. These MEIS2-expressing interneurons appear to originate from a restricted region located at the embryonic pallial–subpallial boundary. Overall, this study identifies MEIS2 as a subclass-specific marker for 5-HT3AR-containing interstitial interneurons and demonstrates that the transcriptional and anatomical parcellation of cortical interneurons is developmentally coupled. PMID:28134272

  9. Block of the delayed rectifier current (IK) by the 5-HT3 antagonists ondansetron and granisetron in feline ventricular myocytes.

    PubMed

    de Lorenzi, F G; Bridal, T R; Spinelli, W

    1994-10-01

    1. We investigated the effects of two 5-HT3 antagonists, ondansetron and granisetron, on the action potential duration (APD) and the delayed rectifier current (IK) of feline isolated ventricular myocytes. Whole-cell current and action potential recordings were performed at 37 degrees C with the patch clamp technique. 2. Ondansetron and granisetron blocked IK with a KD of 1.7 +/- 1.0 and 4.3 +/- 1.7 microM, respectively. At a higher concentration (30 microM), both drugs blocked the inward rectifier (IKl). 3. The block of IK was dependent on channel activation. Both drugs slowed the decay of IK tail currents and produced a crossover with the pre-drug current trace. These results are consistent with block and unblock from the open state of the channel. 4. Granisetron showed an intrinsic voltage-dependence as the block increased with depolarization. The equivalent voltage-dependency of block (delta) was 0.10 +/- 0.04, suggesting that granisetron blocks from the intracellular side at a binding site located 10% across the transmembrane electrical field. 5. Ondansetron (1 microM) and granisetron (3 microM) prolonged APD by about 30% at 0.5 Hz. The prolongation of APD by ondansetron was abolished at faster frequencies (3 Hz) showing reverse rate dependence. 6. In conclusion, the 5-HT3 antagonists, ondansetron and granisetron, are open state blockers of the ventricular delayed rectifier and show a clear class III action.

  10. A pharmacological analysis of serotonergic receptors: effects of their activation of blockade in learning.

    PubMed

    Meneses, A; Hong, E

    1997-02-01

    1. The authors have tested several 5-HT selective agonists and antagonists (5-HT1A/1B, 5-HT2A/2B/2C, 5-HT3 or 5-HT4), an uptake inhibitor and 5-HT depletors in the autoshaping learning task. 2. The present work deals with the receptors whose stimulation increases or decreases learning. 3. Impaired consolidation of learning was observed after the presynaptic activation of 5-HT1B, 5-HT3 or 5-HT4 or the blockade of postsynaptic 5-HT2C/2B receptors. 4. In contrast, an improvement occurred after the presynaptic activation of 5-HT1A, 5-HT2C, and the blockade of presynaptic 5-HT2A, 5-HT2C and 5-HT3 receptors. 5. The blockade of postsynaptic 5-HT1A, 5-HT1B, 5-HT3 or 5-HT4 receptors and 5-HT inhibition of synthesis and its depletion did no alter learning by themselves. 6. The present data suggest that multiple pre- and postsynaptic serotonergic receptors are involved in the consolidation of learning. 7. Stimulation of most 5-HT receptors increases learning, however, some of 5-HT subtypes seem to limit the data storage. 8. Furthermore, the role of 5-HT receptors in learning seem to require an interaction with glutamatergic, GABAergic and cholinergic neurotransmission systems.

  11. Differences in regional cerebral blood flow response to a 5HT3 antagonist in early- and late-onset cocaine-dependent subjects.

    PubMed

    Adinoff, Bryon; Devous, Michael D; Williams, Mark J; Harris, Thomas S; Best, Susan E; Dong, Hongyun; Zielinski, Tanya

    2014-03-01

    5-hydroxytryptamine 3 (5HT3) receptors are important modulators of mesostriatal dopaminergic transmission and have been implicated in the pathophysiology of cocaine reward, withdrawal and self-administration. In addition, the 5HT3 antagonist ondansetron is effective in treating early-onset, but not late-onset, alcohol-dependent subjects. To explore the role of 5HT3 receptor systems in cocaine addiction using functioning imaging, we administered ondansetron to 23 abstinent, treatment-seeking cocaine-addicted and 22 sex-, age- and race-matched healthy control participants. Differences between early- (first use before 20 years, n = 10) and late-onset (first use after 20 years, n = 10) cocaine-addicted subjects were also assessed. On two separate days, subjects were administered ondansetron (0.15 mg/kg intravenously over 15 minutes) or saline. Regional cerebral blood flow (rCBF) was measured following each infusion with single photon emission computed tomography. No significant rCBF differences between the cocaine-addicted and control participants were observed following ondansetron relative to saline. Early-onset subjects, however, showed increased (P < 0.001) right posterior parahippocampal rCBF following ondansetron. In contrast, late-onset subjects showed decreased rCBF following ondansetron in an overlapping region of the right parahippocampal/hippocampal gyrus. Early-onset subjects also displayed increased rCBF in the left anterior insula and subthalamic nucleus following ondansetron; late-onset subjects showed decreased rCBF in the right anterior insula. These findings suggest that the age of drug use onset is associated with serotonergic biosignatures in cocaine-addicted subjects. Further clarification of these alterations may guide targeted treatment with serotonergic medications similar to those successfully used in alcohol-dependent patients.

  12. Competitive interaction of agonists and antagonists with 5-HT3 recognition sites in membranes of neuroblastoma cells labelled with (/sup 3/H)ICS 205-930

    SciTech Connect

    Hoyer, D.; Neijt, H.C.; Karpf, A.

    1989-01-01

    (3H)ICS 205-930 labelled 5-HT3 recognition sites in membranes prepared from murine neuroblastoma N1E-115 cells. Binding was rapid, reversible, saturable and stereoselective to an apparently homogeneous population of sites. Kinetic studies revealed that agonists and antagonists produced a monophasic dissociation reaction of (3H)ICS 205-930 from its recognition sites. The dissociation rate constant of the radioligand was similar whether the dissociation was induced by an agonist or an antagonist. Competition studies carried out with agonists and antagonists also suggested the presence of a homogeneous population of (3H)ICS 205-930 recognition sites. Competition curves were best fit for a 1 site model. (3H)ICS 205-930 binding sites displayed the pharmacological profile of a 5-HT3 receptor. The interactions of agonists and antagonists with (3H)ICS 205-930 recognition sites were apparently competitive in nature, as demonstrated in kinetic and equilibrium experiments. In saturation experiments carried out with (3H)ICS 205-930 in the presence and the absence of unlabelled agonists and antagonists, apparent Bmax values were not reduced whereas apparent Kd values were increased in the presence of competing ligands. There was a good agreement between apparent pKB values calculated for the competing ligands in saturation experiments and pKd values calculated from competition experiments. The present data demonstrate that (3H)ICS 205-930 labels a homogeneous population of sites at which agonists and antagonists interact competitively.

  13. Fragment library screening reveals remarkable similarities between the G protein-coupled receptor histamine H₄ and the ion channel serotonin 5-HT₃A.

    PubMed

    Verheij, Mark H P; de Graaf, Chris; de Kloe, Gerdien E; Nijmeijer, Saskia; Vischer, Henry F; Smits, Rogier A; Zuiderveld, Obbe P; Hulscher, Saskia; Silvestri, Linda; Thompson, Andrew J; van Muijlwijk-Koezen, Jacqueline E; Lummis, Sarah C R; Leurs, Rob; de Esch, Iwan J P

    2011-09-15

    A fragment library was screened against the G protein-coupled histamine H(4) receptor (H(4)R) and the ligand-gated ion channel serotonin 5-HT(3A) (5-HT(3A)R). Interestingly, significant overlap was found between H(4)R and 5-HT(3A)R hit sets. The data indicates that dual active H(4)R and 5 HT(3A)R fragments have a higher complexity than the selective compounds which has important implications for chemical genomics approaches. The results of our fragment-based library screening study illustrate similarities in ligand recognition between H(4)R and 5-HT(3A)R and have important consequences for selectivity profiling in ongoing drug discovery efforts on H(4)R and 5-HT(3A)R. The affinity profiles of our fragment screening studies furthermore match the chemical properties of the H(4)R and 5-HT(3A)R binding sites and can be used to define molecular interaction fingerprints to guide the in silico prediction of protein-ligand interactions and structure.

  14. Multiple 5-HT receptors in the guinea-pig superior cervical ganglion.

    PubMed Central

    Watkins, C. J.; Newberry, N. R.

    1996-01-01

    1. We have studied the pharmacology of the depolarization by 5-hydroxytryptamine (5-HT) of the guinea-pig isolated superior cervical ganglion (SCG) using the grease-gap technique. We studied the effects of selective and non-selective antagonists on the responses to 5-HT and other 5-HT receptor agonists. 2. We have extended the pharmacology of the 5-HT3 receptor in this preparation by studying the effects of granisetron, BRL 46470 and mianserin on the concentration-response curve (CRC) to 2-methyl-5-HT. As with other 5-HT3 receptor antagonists, these compounds exhibited a lower affinity for guinea-pig 5-HT3 receptors than for rat 5-HT3 receptors. 3. We have confirmed that low concentrations of 5-HT (< or = 1 microM) mediate ketanserin-sensitive responses and higher concentrations of 5-HT also recruit 5-HT3 receptors. The responses to low concentrations of 5-HT were antagonized by low concentrations of ketanserin, spiperone, mianserin, DOI and LSD indicating probably mediation by 5-HT2A receptors. At high concentrations, the hallucinogen, DOI, but not LSD, evoked a ketanserin-sensitive depolarization. 4. Although mianserin could bind to the 5-HT2A receptors in this preparation, we could not demonstrate a down-regulation of depolarizations evoked by these receptors after a 10 day oral treatment with mianserin (10 mg kg-1, daily). 5. 5-Carboxamidotryptamine (5-CT) evoked a prolonged depolarization. Although high concentrations of 5-CT (> or = microM) appeared to activate 5-HT2A receptors, lower concentrations of 5-CT evoked a response with a distinct pharmacology. After studying the action of 20 selective and non-selective 5-HT receptor ligands we believe that this response may be mediated by a novel receptor; but its pharmacology is closest to that of receptors in the 5-HT2 receptor family. Like 5-CT, 5-HT (3-300 microM) could evoke an LSD-sensitive response in the presence of the 5-HT2 receptor antagonist, ketanserin and the 5-HT3 receptor antagonist, tropisetron

  15. Functional properties of a cloned 5-hydroxytryptamine ionotropic receptor subunit: comparison with native mouse receptors.

    PubMed Central

    Hussy, N; Lukas, W; Jones, K A

    1994-01-01

    1. A comparative study of the whole-cell and single-channel properties of cloned and native mouse 5-hydroxytryptamine ionotropic receptors (5-HT3) was undertaken using mammalian cell lines expressing the cloned 5-HT3 receptor subunit A (5-HT3R-A), superior cervical ganglia (SCG) neurones and N1E-115 cells. 2. No pharmacological difference was found in the sensitivity to the agonists 5-HT and 2-methyl-5-HT, or to the antagonists d-tubocurare and 3-tropanyl-3,5-dichlorobenzoate (MDL-72222). 3. Current-voltage (I-V) relationships of whole-cell currents showed inward rectification in the three preparations. Rectification was stronger both in cells expressing the 5-HT3R-A subunit and in N1E-115 cells when compared with SCG neurones. 4. No clear openings could be resolved in 5-HT-activated currents in patches excised from cells expressing the 5-HT3R-A subunit or N1E-115 cells. Current fluctuation analysis of whole-cell and excised-patch records revealed a slope conductance of 0.4-0.6 pS in both preparations. Current-voltage relationships of these channels showed strong rectification that fully accounted for the whole-cell voltage dependence. 5. In contrast, single channels of about 10 pS were activated by 5-HT in patches excised from SCG neurones. The weak voltage dependence of their conductance did not account completely for the rectification of whole-cell currents. A lower unitary conductance (3.4 pS) was inferred from whole-cell noise analysis. 6. We conclude that the receptor expressed from the cloned cDNA is indistinguishable from the 5-HT3 receptor of N1E-115 cells, suggesting an identical structure for these two receptors. The higher conductance and different voltage dependence of the 5-HT3 receptor in SCG neurones might indicate the participation of an additional subunit in the structure of native ganglionic 5-HT3 receptors. Homo-oligomeric 5-HT3R-A channels may also be present as suggested by the lower conductance estimated by whole-cell noise analysis. PMID

  16. 5HT3 Antagonists versus Dexamethasone in the Prevention of PONV in Patients Undergoing Laparoscopic Cholecystectomy: A Meta-Analysis of RCTs.

    PubMed

    Zhou, Chengmao; Zhu, Yu; Liu, Zhen; Ruan, Lin

    2016-01-01

    Background. 5HT3 antagonist, an antiemetic alternative to dexamethasone, is an effective drug for the prevention of postoperative nausea and vomiting (PONV). Methods. PubMed and The Cochrane Library (from inception to June 2016) were searched for relevant RCTs (randomized controlled trials). Results. Seven trials, totaling 682 patients, were included in this meta-analysis. This meta-analysis demonstrated that 5HT3 antagonist was as effective as dexamethasone in preventing PONV (RR, 1.12; 95% CI, [0.86, 1.45]; P = 0.40) within 24 hours of laparoscopic cholecystectomy, and no significant heterogeneity was observed among the studies (I(2) = 0%; P = 0.98). During the early postoperative period (0-6 h), 5HT3 antagonists were superior to dexamethasone in reducing POV (RR, 0.31; 95% CI, [0.11, 0.93]; P = 0.04), while, in other postoperative stages (6-12 h, 12-24 h, and 0-24 h), it was not more effective in the prevention of POV than dexamethasone. And no significant difference was found in the prevention of PON between 5HT3 antagonists and dexamethasone at different postoperative periods (0-6 h, 6-12 h, 12-24 h, and 0-24 h). Conclusions. As a result, it is advisable to encourage 5HT3 antagonists as an alternative to dexamethasone for the prevention of PONV in patients undergoing laparoscopic cholecystectomy.

  17. 5HT3 Antagonists versus Dexamethasone in the Prevention of PONV in Patients Undergoing Laparoscopic Cholecystectomy: A Meta-Analysis of RCTs

    PubMed Central

    Zhou, Chengmao; Zhu, Yu; Liu, Zhen

    2016-01-01

    Background. 5HT3 antagonist, an antiemetic alternative to dexamethasone, is an effective drug for the prevention of postoperative nausea and vomiting (PONV). Methods. PubMed and The Cochrane Library (from inception to June 2016) were searched for relevant RCTs (randomized controlled trials). Results. Seven trials, totaling 682 patients, were included in this meta-analysis. This meta-analysis demonstrated that 5HT3 antagonist was as effective as dexamethasone in preventing PONV (RR, 1.12; 95% CI, [0.86, 1.45]; P = 0.40) within 24 hours of laparoscopic cholecystectomy, and no significant heterogeneity was observed among the studies (I2 = 0%; P = 0.98). During the early postoperative period (0–6 h), 5HT3 antagonists were superior to dexamethasone in reducing POV (RR, 0.31; 95% CI, [0.11, 0.93]; P = 0.04), while, in other postoperative stages (6–12 h, 12–24 h, and 0–24 h), it was not more effective in the prevention of POV than dexamethasone. And no significant difference was found in the prevention of PON between 5HT3 antagonists and dexamethasone at different postoperative periods (0–6 h, 6–12 h, 12–24 h, and 0–24 h). Conclusions. As a result, it is advisable to encourage 5HT3 antagonists as an alternative to dexamethasone for the prevention of PONV in patients undergoing laparoscopic cholecystectomy. PMID:27891523

  18. Role of the 5HT3 Receptor in Alcohol Drinking and Aggression Using a Transgenic Mouse Model

    DTIC Science & Technology

    2006-09-01

    found for each N1 [F(1,35) = 56.0, P < 0.0005], N3, [F(1,35) = 33.85, P < 0.0005] and N5 6 generations [F(1,35) = 6.33, P < 0.017]. Interactions of...presence was also found for N1 [F(1,51) = 10.9, P < 0.003] and N5 [F(1,51) = 11.32, P < 0.001]. A background x transgene presence interaction was...0.0005] were found, as was an interaction between background and transgene presence [F(2,51) = 13.93, P < 0.0005]. For the measure of percent time spent

  19. Systemic paracetamol-induced analgesic and antihyperalgesic effects through activation of descending serotonergic pathways involving spinal 5-HT₇ receptors.

    PubMed

    Dogrul, Ahmet; Seyrek, Melik; Akgul, Emin Ozgur; Cayci, Tuncer; Kahraman, Serdar; Bolay, Hayrunnisa

    2012-02-29

    Although some studies have shown the essential role of descending serotonergic pathways and spinal 5-HT(1A), 5-HT(2A), or 5-HT(3) receptors in the antinociceptive effects of paracetamol, other studies have presented conflicting results, and the particular subtype of spinal 5-HT receptors involved in paracetamol-induced analgesia remains to be clarified. Recent studies have demonstrated the importance of spinal 5-HT(7) receptors in descending serotonergic pain inhibitory pathways. In this study, we investigated the role of descending serotonergic pathways and spinal 5-HT(7) receptors compared with 5-HT(3) and 5-HT(2A) receptors in the antinociceptive and antihyperalgesic effects of paracetamol. Tail-flick, hot plate and plantar incision tests were used to determine nociception in male BALB/c mice. Lesion of serotonergic bulbospinal pathways was performed by intrathecal (i.th.) injection of 5,7-dihydroxytryptamine (5,7-DHT), and spinal 5-HT levels were measured by HPLC. To evaluate the particular subtypes of the spinal 5-HT receptors, the selective 5-HT(7), 5-HT(3) and 5-HT(2A) receptor antagonists SB 269970, ondansetron and ketanserin, respectively, were given i.th. after oral administration of paracetamol. Oral paracetamol (200, 400 and 600 mg/kg) elicits dose-dependent antinociceptive and antihyperalgesic effects. I.th. pretreatment with 5,7-DHT (50 μg) sharply reduced 5-HT levels in the spinal cord. Depletion of spinal 5-HT totally abolished the antinociceptive and antihyperalgesic effects of paracetamol. I.th. injection of SB 2669970 (10 μg) blocked the antinociceptive and antihyperalgesic effects of paracetamol, but ondansetron and ketanserin (10 μg) did not. Our findings suggest that systemic administration of paracetamol may activate descending serotonergic pathways and spinal 5-HT(7) receptors to produce a central antinociceptive and antihyperalgesic effects.

  20. Serotonin activates catecholamine neurons in the solitary tract nucleus by increasing spontaneous glutamate inputs.

    PubMed

    Cui, Ran Ji; Roberts, Brandon L; Zhao, Huan; Zhu, Mingyan; Appleyard, Suzanne M

    2012-11-14

    Serotonin (5-HT) is a critical neurotransmitter in the control of autonomic functions. 5-HT(3) receptors participate in vagal afferent feedback to decrease food intake and regulate cardiovascular reflexes; however, the phenotype of the solitary tract nucleus (NTS) neurons involved is not known. A(2)/C(2) catecholamine (CA) neurons in the NTS are directly activated by visceral afferents and are important for the control of food intake and cardiovascular function, making them good candidates to respond to and mediate the effects of serotonin at the level of the NTS. This study examines serotonin's effects on NTS-CA neurons using patch-clamp techniques and transgenic mice expressing an enhanced green fluorescent protein driven by the tyrosine hydroxylase (TH) promoter (TH-EGFP) to identify catecholamine neurons. Serotonin increased the frequency of spontaneous glutamate excitatory postsynaptic currents (sEPSCs) in >90% of NTS-TH-EGFP neurons, an effect blocked by the 5-HT(3) receptor antagonist ondansetron and mimicked by the 5-HT(3) receptor agonists SR5227 and mCPBG. In contrast, 5-HT(3) receptor agonists increased sEPSCs on a minority (<30%) of non-TH neurons. 5-HT(3) receptor agonists increased the frequency, but not the amplitude, of mini-EPSCs, suggesting that their actions are presynaptic. 5-HT(3) receptor agonists increased the firing rate of TH-EGFP neurons, an effect dependent on the increased spontaneous glutamate inputs as it was blocked by the ionotropic glutamate antagonist NBQX, but independent of visceral afferent activation. These results demonstrate a cellular mechanism by which serotonin activates NTS-TH neurons and suggest a pathway by which it can increase catecholamine release in target regions to modulate food intake, motivation, stress, and cardiovascular function.

  1. Serotonin Activates Catecholamine Neurons in the Solitary Tract Nucleus by Increasing Spontaneous Glutamate Inputs

    PubMed Central

    Cui, Ran Ji; Roberts, Brandon L.; Zhao, Huan; Zhu, Mingyan

    2012-01-01

    Serotonin (5-HT) is a critical neurotransmitter in the control of autonomic functions. 5-HT3 receptors participate in vagal afferent feedback to decrease food intake and regulate cardiovascular reflexes; however, the phenotype of the solitary tract nucleus (NTS) neurons involved is not known. A2/C2 catecholamine (CA) neurons in the NTS are directly activated by visceral afferents and are important for the control of food intake and cardiovascular function, making them good candidates to respond to and mediate the effects of serotonin at the level of the NTS. This study examines serotonin's effects on NTS-CA neurons using patch-clamp techniques and transgenic mice expressing an enhanced green fluorescent protein driven by the tyrosine hydroxylase (TH) promoter (TH-EGFP) to identify catecholamine neurons. Serotonin increased the frequency of spontaneous glutamate excitatory postsynaptic currents (sEPSCs) in >90% of NTS-TH-EGFP neurons, an effect blocked by the 5-HT3 receptor antagonist ondansetron and mimicked by the 5-HT3 receptor agonists SR5227 and mCPBG. In contrast, 5-HT3 receptor agonists increased sEPSCs on a minority (<30%) of non-TH neurons. 5-HT3 receptor agonists increased the frequency, but not the amplitude, of mini-EPSCs, suggesting that their actions are presynaptic. 5-HT3 receptor agonists increased the firing rate of TH-EGFP neurons, an effect dependent on the increased spontaneous glutamate inputs as it was blocked by the ionotropic glutamate antagonist NBQX, but independent of visceral afferent activation. These results demonstrate a cellular mechanism by which serotonin activates NTS-TH neurons and suggest a pathway by which it can increase catecholamine release in target regions to modulate food intake, motivation, stress, and cardiovascular function. PMID:23152635

  2. Metal interactions with voltage- and receptor-activated ion channels.

    PubMed Central

    Vijverberg, H P; Oortgiesen, M; Leinders, T; van Kleef, R G

    1994-01-01

    Effects of Pb and several other metal ions on various distinct types of voltage-, receptor- and Ca-activated ion channels have been investigated in cultured N1E-115 mouse neuroblastoma cells. Experiments were performed using the whole-cell voltage clamp and single-channel patch clamp techniques. External superfusion of nanomolar to submillimolar concentrations of Pb causes multiple effects on ion channels. Barium current through voltage-activated Ca channels is blocked by micromolar concentrations of Pb, whereas voltage-activated Na current appears insensitive. Neuronal type nicotinic acetylcholine receptor-activated ion current is blocked by nanomolar concentrations of Pb and this block is reversed at micromolar concentrations. Serotonin 5-HT3 receptor-activated ion current is much less sensitive to Pb. In addition, external superfusion with micromolar concentrations of Pb as well as of Cd and aluminum induces inward current, associated with the direct activation of nonselective cation channels by these metal ions. In excised inside-out membrane patches of neuroblastoma cells, micromolar concentrations of Ca activate small (SK) and big (BK) Ca-activated K channels. Internally applied Pb activates SK and BK channels more potently than Ca, whereas Cd is approximately equipotent to Pb with respect to SK channel activation, but fails to activate BK channels. The results show that metal ions cause distinct, selective effects on the various types of ion channels and that metal ion interaction sites of ion channels may be highly selective for particular metal ions. PMID:7531139

  3. Quipazine reduces food intake in the rat by activation of 5-HT2-receptors.

    PubMed Central

    Hewson, G.; Leighton, G. E.; Hill, R. G.; Hughes, J.

    1988-01-01

    1. To determine which subtype(s) of 5-hydroxytryptamine (5-HT) receptor are involved in the anorectic action of quipazine, the ability of selective antagonists at 5-HT2- and 5-HT3-receptors, and an antagonist at 5-HT1-like receptors, to block this response were investigated in non-deprived rats, trained to eat a palatable diet. 2. Quipazine (0.5-8 mg kg-1, i.p.) produced a dose-related reduction in the intake of palatable diet. 3. The anorectic effect of 4 mg kg-1 quipazine was antagonized by the nonselective 5-HT-receptor antagonist methysergide (5 mg kg-1, i.p.) and by the selective 5-HT2-receptor antagonists ketanserin (1 mg kg-1 and 2.5 mg kg-1, i.p.) and ritanserin (0.5 mg kg-1 and 1 mg kg-1, i.p.). The selective 5-HT3-receptor antagonist GR38032F (1 mg kg-1, i.p.) and (-)-pindolol (4 mg kg-1, i.p.), which blocks some of the effects mediated at 5-HT1-like receptors, did not block the reduction in food intake produced by this dose of quipazine. 4. None of the 5-HT-receptor antagonists had any effect on food intake when they were administered alone, suggesting that endogenous 5-HT is not involved in the tonic control of food intake under the conditions of these experiments. 5. It is concluded that the anorectic action of quipazine is mediated, at least in part, by activation of 5-HT2-receptors. PMID:2906561

  4. Influence of Polymorphisms in the HTR3A and HTR3B Genes on Experimental Pain and the Effect of the 5-HT3 Antagonist Granisetron

    PubMed Central

    Hedenberg-Magnusson, Britt; List, Thomas; Svensson, Peter; Schalling, Martin

    2016-01-01

    The aim of this study was to investigate experimentally if 5-HT3 single nucleotide polymorphisms (SNP) contribute to pain perception and efficacy of the 5-HT3-antagonist granisetron and sex differences. Sixty healthy participants were genotyped regarding HTR3A (rs1062613) and HTR3B (rs1176744). First, pain was induced by bilateral hypertonic saline injections (HS, 5.5%, 0.2 mL) into the masseter muscles. Thirty min later the masseter muscle on one side was pretreated with 0.5 mL granisetron (1 mg/mL) and on the other side with 0.5 mL placebo (isotonic saline) followed by another HS injection (0.2 mL). Pain intensity, pain duration, pain area and pressure pain thresholds (PPTs) were assessed after each injection. HS evoked moderate pain, with higher intensity in the women (P = 0.023), but had no effect on PPTs. None of the SNPs influenced any pain variable in general, but compared to men, the pain area was larger in women carrying the C/C (HTR3A) (P = 0.015) and pain intensity higher in women with the A/C alleles (HTR3B) (P = 0.019). Pre-treatment with granisetron reduced pain intensity, duration and area to a lesser degree in women (P < 0.05), but the SNPs did not in general influence the efficacy of granisetron. Women carrying the C/T & T/T (HTR3A) genotype had less reduction of pain intensity (P = 0.041) and area (P = 0.005), and women with the C/C genotype (HTR3B) had less reduction of pain intensity (P = 0.030), duration (P = 0.030) and area compared to men (P = 0.017). In conclusion, SNPs did not influence experimental muscle pain or the effect of granisetron on pain variables in general, but there were some sex differences in pain variables that seem to be influenced by genotypes. However, due to the small sample size further research is needed before any firm conclusions can be drawn. PMID:28002447

  5. Differentiated effects of the multimodal antidepressant vortioxetine on sleep architecture: Part 2, pharmacological interactions in rodents suggest a role of serotonin-3 receptor antagonism

    PubMed Central

    Leiser, Steven C; Iglesias-Bregna, Deborah; Westrich, Ligia; Pehrson, Alan L; Sanchez, Connie

    2015-01-01

    Antidepressants often disrupt sleep. Vortioxetine, a multimodal antidepressant acting through serotonin (5-HT) transporter (SERT) inhibition, 5-HT3, 5-HT7 and 5-HT1D receptor antagonism, 5-HT1B receptor partial agonism, and 5-HT1A receptor agonism, had fewer incidences of sleep-related adverse events reported in depressed patients. In the accompanying paper a polysomnographic electroencephalography (sleep-EEG) study of vortioxetine and paroxetine in healthy subjects indicated that at low/intermediate levels of SERT occupancy, vortioxetine affected rapid eye movement (REM) sleep differently than paroxetine. Here we investigated clinically meaningful doses (80–90% SERT occupancy) of vortioxetine and paroxetine on sleep-EEG in rats to further elucidate the serotoninergic receptor mechanisms mediating this difference. Cortical EEG, electromyography (EMG), and locomotion were recorded telemetrically for 10 days, following an acute dose, from rats receiving vortioxetine-infused chow or paroxetine-infused water and respective controls. Sleep stages were manually scored into active wake, quiet wake, and non-REM or REM sleep. Acute paroxetine or vortioxetine delayed REM onset latency (ROL) and decreased REM episodes. After repeated administration, vortioxetine yielded normal sleep-wake rhythms while paroxetine continued to suppress REM. Paroxetine, unlike vortioxetine, increased transitions from non-REM to wake, suggesting fragmented sleep. Next, we investigated the role of 5-HT3 receptors in eliciting these differences. The 5-HT3 receptor antagonist ondansetron significantly reduced paroxetine’s acute effects on ROL, while the 5-HT3 receptor agonist SR57227A significantly increased vortioxetine’s acute effect on ROL. Overall, our data are consistent with the clinical findings that vortioxetine impacts REM sleep differently than paroxetine, and suggests a role for 5-HT3 receptor antagonism in mitigating these differences. PMID:26174134

  6. Differentiated effects of the multimodal antidepressant vortioxetine on sleep architecture: Part 2, pharmacological interactions in rodents suggest a role of serotonin-3 receptor antagonism.

    PubMed

    Leiser, Steven C; Iglesias-Bregna, Deborah; Westrich, Ligia; Pehrson, Alan L; Sanchez, Connie

    2015-10-01

    Antidepressants often disrupt sleep. Vortioxetine, a multimodal antidepressant acting through serotonin (5-HT) transporter (SERT) inhibition, 5-HT3, 5-HT7 and 5-HT1D receptor antagonism, 5-HT1B receptor partial agonism, and 5-HT1A receptor agonism, had fewer incidences of sleep-related adverse events reported in depressed patients. In the accompanying paper a polysomnographic electroencephalography (sleep-EEG) study of vortioxetine and paroxetine in healthy subjects indicated that at low/intermediate levels of SERT occupancy, vortioxetine affected rapid eye movement (REM) sleep differently than paroxetine. Here we investigated clinically meaningful doses (80-90% SERT occupancy) of vortioxetine and paroxetine on sleep-EEG in rats to further elucidate the serotoninergic receptor mechanisms mediating this difference. Cortical EEG, electromyography (EMG), and locomotion were recorded telemetrically for 10 days, following an acute dose, from rats receiving vortioxetine-infused chow or paroxetine-infused water and respective controls. Sleep stages were manually scored into active wake, quiet wake, and non-REM or REM sleep. Acute paroxetine or vortioxetine delayed REM onset latency (ROL) and decreased REM episodes. After repeated administration, vortioxetine yielded normal sleep-wake rhythms while paroxetine continued to suppress REM. Paroxetine, unlike vortioxetine, increased transitions from non-REM to wake, suggesting fragmented sleep. Next, we investigated the role of 5-HT3 receptors in eliciting these differences. The 5-HT3 receptor antagonist ondansetron significantly reduced paroxetine's acute effects on ROL, while the 5-HT3 receptor agonist SR57227A significantly increased vortioxetine's acute effect on ROL. Overall, our data are consistent with the clinical findings that vortioxetine impacts REM sleep differently than paroxetine, and suggests a role for 5-HT3 receptor antagonism in mitigating these differences.

  7. SPINAL CORD MECHANISMS MEDIATING BEHAVIORAL HYPERALGESIA INDUCED BY NEUROKININ-1 TACHYKININ RECEPTOR ACTIVATION IN THE ROSTRAL VENTROMEDIAL MEDULLA

    PubMed Central

    Lagraize, S. C.; Guo, W.; Yang, K.; Wei, F.; Ren, K.; Dubner, R.

    2010-01-01

    Hyperalgesia in animal injury models is linked to activation of descending raphespinal modulatory circuits originating in the rostral ventromedial medulla (RVM). A neurokinin-1 (NK-1) receptor antagonist microinjected into the RVM before or after inflammation produced by complete Freund’s adjuvant (CFA) resulted in an attenuation of thermal hyperalgesia. A transient (acute) or a continuous infusion of Substance P (SP) microinjected into the RVM of non-inflamed animals led to similar pain hypersensitivity. Intrathecal pretreatment or post-treatment of a 5-HT3 receptor antagonist (Y-25130 or ondansetron) blocked the SP-induced hyperalgesia. The SP-induced hyperalgesia was both GABAA and NMDA receptor-dependent after pre- and post-treatment with selective antagonists at the spinal level. A microinjection of SP into the RVM also led to increased NMDA NR1 receptor subunit phosphorylation in spinal cord tissue. The GABAA receptor-mediated hyperalgesia involved a shift in the anionic gradient in dorsal horn nociceptive neurons and an increase in phosphorylated NKCC1 protein (isoform of the Na-K-Cl cotransporter). Following a low dose of SP infused into the RVM, intrathecal muscimol (GABAA agonist) increased SP-induced thermal hyperalgesia, phosphorylated NKCC1 protein expression, and NMDA NR1 subunit phosphorylation in the spinal cord. The thermal hyperalgesia was blocked by intrathecal gabazine, the GABAA receptor antagonist, and MK-801, the NMDA receptor channel blocker. These findings indicate that NK-1 receptors in the RVM are involved in SP-induced thermal hyperalgesia, this hyperalgesia is 5-HT3-receptor dependent at the spinal level, and involves the functional interaction of spinal GABAA and NMDA receptors. PMID:20888891

  8. Ethanol Stabilizes the Open State of Single 5-Hydroxytryptamine3A(QDA) Receptors

    PubMed Central

    Feinberg-Zadek, Paula L.

    2010-01-01

    Ethanol enhancement of 5-hydroxytryptamine (5-HT)3A receptor-mediated responses may have important consequences in the intoxicating and addictive properties of ethanol. Although the exact mechanism is unknown, ethanol-mediated enhancement of 5-HT3 receptor current has been proposed to occur due to stabilization of the open-channel state. It has not been possible to directly measure the open state of the channel due to the extremely low single-channel conductance of 5-HT3A channels. Recently, three arginine residues within the large intracellular loop of the 5-HT3A subunit were substituted by their equivalent residues (glutamine, aspartate, and alanine) of the 5-HT3B subunit to produce a 5-HT3A(QDA) subunit that forms functional homomeric channels exhibiting a measurable single-channel conductance. Using whole-cell rapid-agonist application techniques and the cell-attached single-channel recording configuration, we examined human 5-HT3A(QDA) receptors expressed in human embryonic kidney 293 cells. The agonist sensitivity, macroscopic kinetics, and modulation by ethanol were similar between mutant and wild-type channels, suggesting the substitutions had not altered these channel structure-function properties. The open time histogram for single-channel events mediated by 5-HT3A(QDA) receptors in the presence of maximal 5-HT was best fit by three exponentials, but in the presence of ethanol a fourth open state was evident. In summary, the QDA substitution greatly enhanced single-channel conductance with little effect on 5-HT3A channel's kinetic properties and ethanol enhances agonist action on 5-HT3A receptors by inducing a new, long-lived open-channel state. Furthermore, the 5-HT3A(QDA) receptor appears to be suitable for pharmacological studies of 5-HT3A receptor modulation at a single-channel level. PMID:20200118

  9. Serotonin receptor modulators in the treatment of irritable bowel syndrome

    PubMed Central

    Fayyaz, Mohammad; Lackner, Jeffrey M

    2008-01-01

    The aim of this article is to review the pathophysiology and clinical role of serotonin receptor modulators used in the treatment of irritable bowel syndrome. Serotonin is an important monoamine neurotransmitter that plays a key role in the initiation of peristaltic and secretory refl exes, and in modulation of visceral sensations. Several serotonin receptor subtypes have been characterized, of which 5HT3, 5HT4, and 5HT1b are the most important for GI function. 5HT4 agonists (eg, tegaserod) potentiate peristalsis initiated by 5HT1 receptor stimulation. 5HT4 agonists are therefore useful in constipation predominant form of IBS and in chronic constipation. 5HT3 antagonists (Alosetron and Cilansetron) prevent the activation of 5HT3 receptors on extrinsic afferent neurons and can decrease the visceral pain associated with IBS. These agents also retard small intestinal and colonic transit, and are therefore useful in diarrhea-predominant IBS. Tegaserod has been demonstrated in several randomized, placebo controlled trials to relieve global IBS symptoms as well as individual symptoms of abdominal discomfort, number of bowel movements and stool consistency. Several randomized, controlled trials have shown that alosetron relieves pain, improves bowel function, and provides global symptom improvement in women with diarrhea-predominant irritable bowel syndrome. However, ischemic colitis and severe complications of constipation have been major concerns leading to voluntary withdrawal of Alosetron from the market followed by remarketing with a comprehensive risk management program. PMID:18728719

  10. Substituted 2-Aminopyrimidines Selective for α7-Nicotinic Acetylcholine Receptor Activation and Association with Acetylcholine Binding Proteins.

    PubMed

    Kaczanowska, Katarzyna; Camacho Hernandez, Gisela Andrea; Bendiks, Larissa; Kohs, Larissa; Cornejo-Bravo, Jose Manuel; Harel, Michal; Finn, M G; Taylor, Palmer

    2017-03-15

    Through studies with ligand binding to the acetylcholine binding protein (AChBP), we previously identified a series of 4,6-substituted 2-aminopyrimidines that associate with this soluble surrogate of the nicotinic acetylcholine receptor (nAChR) in a cooperative fashion, not seen for classical nicotinic agonists and antagonists. To examine receptor interactions of this structural family on ligand-gated ion channels, we employed HEK cells transfected with cDNAs encoding three requisite receptor subtypes: α7-nAChR, α4β2-nAChR, and a serotonin receptor (5-HT3AR), along with a fluorescent reporter. Initial screening of a series of over 50 newly characterized 2-aminopyrimidines with affinity for AChBP showed only two to be agonists on the α7-nAChR below 10 μM concentration. Their unique structural features were incorporated into design of a second subset of 2-aminopyrimidines yielding several congeners that elicited α7 activation with EC50 values of 70 nM and Kd values for AChBP in a similar range. Several compounds within this series exhibit specificity for the α7-nAChR, showing no activation or antagonism of α4β2-nAChR or 5-HT3AR at concentrations up to 10 μM, while others were weaker antagonists (or partial agonists) on these receptors. Analysis following cocrystallization of four ligand complexes with AChBP show binding at the subunit interface, but with an orientation or binding pose that differs from classical nicotinic agonists and antagonists and from the previously analyzed set of 2-aminopyrimidines that displayed distinct cooperative interactions with AChBP. Orientations of aromatic side chains of these complexes are distinctive, suggesting new modes of binding at the agonist-antagonist site and perhaps an allosteric action for heteromeric nAChRs.

  11. Vortioxetine, a novel antidepressant with multimodal activity: review of preclinical and clinical data.

    PubMed

    Sanchez, Connie; Asin, Karen E; Artigas, Francesc

    2015-01-01

    Vortioxetine, a novel antidepressant for the treatment of major depressive disorder (MDD), is a 5-HT3, 5-HT7 and 5-HT1D receptor antagonist, 5-HT1B receptor partial agonist, 5-HT1A receptor agonist and serotonin (5-HT) transporter (SERT) inhibitor. Here we review its preclinical and clinical properties and discuss translational aspects. Vortioxetine increases serotonergic, noradrenergic, dopaminergic, cholinergic, histaminergic and glutamatergic neurotransmission in brain structures associated with MDD. These multiple effects likely derive from its interaction with 5-HT-receptor-mediated negative feedback mechanisms controlling neuronal activity. In particular, 5-HT3 receptors may play a prominent role, since their blockade i) increases pyramidal neuron activity by removing 5-HT3 receptor-mediated excitation of GABA interneurons, and ii) augments SSRI effects on extracellular 5-HT. However, modulation of the other 5-HT receptor subtypes also likely contributes to vortioxetine's pharmacological effects. Preclinical animal models reveal differences from SSRIs and SNRIs, including antidepressant-like activity, increased synaptic plasticity and improved cognitive function. Vortioxetine had clinical efficacy in patients with MDD: 11 placebo-controlled studies (including one in elderly) with efficacy in 8 (7 positive, 1 supportive), 1 positive active comparator study plus a positive relapse prevention study. In two positive studies, vortioxetine was superior to placebo in pre-defined cognitive outcome measures. The clinically effective dose range (5-20mg/day) spans ~50 to >80% SERT occupancy. SERT and 5-HT3 receptors are primarily occupied at 5mg, while at 20mg, all targets are likely occupied at functionally relevant levels. The side-effect profile is similar to that of SSRIs, with gastrointestinal symptoms being most common, and a low incidence of sexual dysfunction and sleep disruption possibly ascribed to vortioxetine's receptor modulation.

  12. Anxiolytic-like effects observed in rats exposed to the elevated zero-maze following treatment with 5-HT2/5-HT3/5-HT4 ligands

    PubMed Central

    Bell, Rob; Duke, Aaron A.; Gilmore, Paula E.; Page, Deaglan; Bègue, Laurent

    2014-01-01

    The present study examined the effects of administering selective 5-HT antagonists and agonists to rats tested in the elevated zero-maze (EZM) model of anxiety. The EZM paradigm has advantages over the elevated plus-maze (EPM) paradigm with respect to measuring anxiety, yet has been utilized less frequently. Three experiments were conducted each with a diazepam control (0.25, 0.5 and 0.75 mg/kg). In the first experiment, we administered the 5-HT2C antagonist RS 102221 (0.5, 1.0, and 2.0 mg/kg) and 5-HT2C agonist MK-212 (0.25, 0.5 and 0.75 mg/kg); in the second experiment, we administered the 5-HT3 antagonist Y-25130 (0.1, 1.0 and 3.0 mg/kg) and 5-HT3 agonist SR 57227A (0.1, 1.0 and 3.0 mg/kg), and in the third experiment, we administered the 5-HT4 antagonist RS 39604 (0.01, 0.1, 1.0 mg/kg) and 5-HT4 agonist RS 67333 (0.01, 0.1 and 0.5 mg/kg). The administration of 5-HT2/3/4 subtype antagonists all generated behavioral profiles indicative of anxiolytic-like effects in the EZM, which was apparent from examination of both traditional and ethological measures. While little effect was observed from 5-HT2 and 5-HT3 agonists, the 5-HT4 agonist RS 67333 was found to produce a paradoxical anxiolytic-like effect similar to that produced by the 5-HT4 antagonist RS 39604. We conclude by discussing the implications of these findings. PMID:24457553

  13. The serotonin receptor mediates changes in autonomic neurotransmission and gastrointestinal transit induced by heat-killed Lactobacillus brevis SBC8803.

    PubMed

    Horii, Y; Nakakita, Y; Misonou, Y; Nakamura, T; Nagai, K

    2015-01-01

    Lactobacilli exhibit several health benefits in mammals, including humans. Our previous reports established that heat-killed Lactobacillus brevis SBC8803 (SBC8803) increased both efferent gastric vagal nerve activity and afferent intestinal vagal nerve activity in rats. We speculated that this strain could be useful for the treatment of gastrointestinal (GI) disorders. In this study, we examined the effects of SBC8803 on peristalsis and the activity of the efferent celiac vagal nerve innervating the intestine in rats. First, we examined the effects of intraduodenal (ID) administration of SBC8803 on efferent celiac vagal nerve activity (efferent CVNA) in urethane-anesthetised rats using electrophysiological studies. The effects of intravenous injection of the serotonin 5-HT3 receptor antagonist granisetron on changes in efferent CVNA due to ID administration of SBC8803 were also investigated. Finally, the effects of oral gavage of SBC8803 on GI transit were analysed using the charcoal propulsion method in conscious rats treated with or without granisetron. ID administration of SBC8803 increased efferent CVNA. Pretreatment with granisetron eliminated SBC8803-dependent changes in efferent CVNA. Furthermore, oral gavage of SBC8803 significantly accelerated GI transit, while pretreatment with granisetron inhibited GI transit. Our findings suggested that SBC8803 increased efferent CVNA and GI transit of charcoal meal via 5-HT3 receptors. Moreover, SBC8803 enhanced the activity of efferent vagal nerve innervating the intestine and promoted peristalsis via 5-HT3 receptors.

  14. Serotonin receptor 3A controls interneuron migration into the neocortex

    PubMed Central

    Murthy, Sahana; Niquille, Mathieu; Hurni, Nicolas; Limoni, Greta; Frazer, Sarah; Chameau, Pascal; van Hooft, Johannes A.; Vitalis, Tania; Dayer, Alexandre

    2014-01-01

    Neuronal excitability has been shown to control the migration and cortical integration of reelin-expressing cortical interneurons (INs) arising from the caudal ganglionic eminence (CGE), supporting the possibility that neurotransmitters could regulate this process. Here we show that the ionotropic serotonin receptor 3A (5-HT3AR) is specifically expressed in CGE-derived migrating interneurons and upregulated while they invade the developing cortex. Functional investigations using calcium imaging, electrophysiological recordings and migration assays indicate that CGE-derived INs increase their response to 5-HT3AR activation during the late phase of cortical plate invasion. Using genetic loss-of-function approaches and in vivo grafts, we further demonstrate that the 5-HT3AR is cell autonomously required for the migration and proper positioning of reelin-expressing CGE-derived INs in the neocortex. Our findings reveal a requirement for a serotonin receptor in controlling the migration and laminar positioning of a specific subtype of cortical IN. PMID:25409778

  15. Dopamine D2/3 receptor antagonism reduces activity-based anorexia

    PubMed Central

    Klenotich, S J; Ho, E V; McMurray, M S; Server, C H; Dulawa, S C

    2015-01-01

    Anorexia nervosa (AN) is an eating disorder characterized by severe hypophagia and weight loss, and an intense fear of weight gain. Activity-based anorexia (ABA) refers to the weight loss, hypophagia and paradoxical hyperactivity that develops in rodents exposed to running wheels and restricted food access, and provides a model for aspects of AN. The atypical antipsychotic olanzapine was recently shown to reduce both AN symptoms and ABA. We examined which component of the complex pharmacological profile of olanzapine reduces ABA. Mice received 5-HT2A/2C, 5-HT3, dopamine D1-like, D2, D3 or D2/3 antagonist treatment, and were assessed for food intake, body weight, wheel running and survival in ABA. D2/3 receptor antagonists eticlopride and amisulpride reduced weight loss and hypophagia, and increased survival during ABA. Furthermore, amisulpride produced larger reductions in weight loss and hypophagia than olanzapine. Treatment with either D3 receptor antagonist SB277011A or D2 receptor antagonist L-741,626 also increased survival. All the other treatments either had no effect or worsened ABA. Overall, selective antagonism of D2 and/or D3 receptors robustly reduces ABA. Studies investigating the mechanisms by which D2 and/or D3 receptors regulate ABA, and the efficacy for D2/3 and/or D3 antagonists to treat AN, are warranted. PMID:26241351

  16. Thiocolchicoside inhibits the activity of various subtypes of recombinant GABA(A) receptors expressed in Xenopus laevis oocytes.

    PubMed

    Mascia, Maria Paola; Bachis, Elisabetta; Obili, Nicola; Maciocco, Elisabetta; Cocco, Giovanni Antonio; Sechi, Gian Pietro; Biggio, Giovanni

    2007-03-08

    Thiocolchicoside is a myorelaxant drug with anti-inflammatory and analgesic properties as well as pronounced convulsant activity. To characterize the mechanisms of action of this drug at the molecular level, we examined its effects on the function of various recombinant neurotransmitter receptors expressed in Xenopus oocytes. Electrophysiological recordings from recombinant human gamma-aminobutyric acid type A (GABA(A)) receptors consisting of alpha1beta1gamma2L, alpha1beta2gamma2L, or alpha2beta2gamma2L subunit combinations revealed that thiocolchicoside inhibited GABA-evoked Cl(-) currents with similar potencies (median inhibitory concentrations of 0.13 to 0.2 microM) and in a competitive manner. Consistent with previous observations, thiocolchicoside also inhibited the binding of GABA to rat cerebral cortical membranes. Thiocolchicoside inhibited the function of recombinant human strychnine-sensitive glycine receptors composed of the alpha1 subunit with a potency (median inhibitory concentration of 47 microM) lower than that apparent with recombinant GABA(A) receptors. It also inhibited the function of human nicotinic acetylcholine receptors composed of the alpha4 and beta2 subunits, but this effect was only partial and apparent at high concentrations. In contrast, thiocolchicoside had no effect on the function of 5-HT(3A) serotonin receptors. Our results thus provide molecular evidence that the epileptogenic activity of thiocolchicoside might be due to inhibition of the function of inhibitory receptors in the central nervous system, especially that of GABA(A) receptors.

  17. Activation of the gut calcium-sensing receptor by peptide agonists reduces rapid elevation of plasma glucose in response to oral glucose load in rats.

    PubMed

    Muramatsu, Maya; Hira, Tohru; Mitsunaga, Arimi; Sato, Eri; Nakajima, Shingo; Kitahara, Yoshiro; Eto, Yuzuru; Hara, Hiroshi

    2014-06-15

    The calcium-sensing receptor (CaSR) is expressed in various tissues, including the gastrointestinal tract. To investigate the role of gut CaSR on glycemic control, we examined whether single oral administration of CaSR agonist peptides affected the glycemic response in rats. Glucose tolerance tests were performed under oral or duodenal administration of various CaSR agonist peptides (γGlu-Cys, protamine, and poly-d-lysine hydrobromide) in conscious rats. Involvement of CaSR was determined by using a CaSR antagonist. Signaling pathways underlying CaSR agonist-modified glycemia were investigated using gut hormone receptor antagonists. The gastric emptying rate after the administration of CaSR agonist peptides was measured by the phenol red recovery method. Oral and duodenal administration of CaSR agonist peptides attenuated glycemic responses under the oral glucose tolerance test, but the administration of casein did not. The promotive effect on glucose tolerance was weakened by luminal pretreatment with a CaSR antagonist. Treatment with a 5-HT3 receptor antagonist partially diminished the glucose-lowering effect of peptides. Furthermore, the gastric emptying rate was decreased by duodenal administration of CaSR agonist peptides. These results demonstrate that activation of the gut CaSR by peptide agonists promotes glucose tolerance in conscious rats. 5-HT3 receptor and the delayed gastric emptying rate appear to be involved in the glucose-lowering effect of CaSR agonist peptides. Thus, activation of gut CaSR by dietary peptides reduces glycemic responses so that gut CaSR may be a potential target for the improvement of postprandial glycemia.

  18. Antidepressant-like activity of aroxyalkyl derivatives of 2-methoxyphenylpiperazine and evidence for the involvement of serotonin receptor subtypes in their mechanism of action.

    PubMed

    Kubacka, Monika; Mogilski, Szczepan; Bednarski, Marek; Nowiński, Leszek; Dudek, Magdalena; Żmudzka, Elżbieta; Siwek, Agata; Waszkielewicz, Anna M; Marona, Henryk; Satała, Grzegorz; Bojarski, Andrzej; Filipek, Barbara; Pytka, Karolina

    2016-02-01

    Since serotonin (5-HT) is strongly involved in the etiology and pathophysiology of depression, the development of new antidepressants is still based on the serotonergic system. The complexity of serotonergic system provides an opportunity for the development of compounds with multiple and complementary mechanism of action. This study describes serotonin receptor profile, functional characterization, and pharmacological in vivo evaluation of new aroxyalkyl derivatives of 2-methoxyphenylpiperazine. The obtained results allowed for the identification of compound 3, (1-[3-(2,6-dimethylphenoxy)propyl]-4-(2-methoxyphenyl)piperazine hydrochloride), a partial 5-HT1A receptor agonist, and 5-HT2A receptor antagonist, with high affinity toward 5-HT7 receptors, showing antidepressant- and anxiolytic-like properties. Moreover, 5-HT1A receptor activation is crucial for the antidepressant-like activity of compound 3. The rest of the compounds (except compounds 1 and 9) showed antidepressant but not anxiolytic-like properties, which did not result from 5-HT1A receptors activation. Furthermore, the compounds are 5-HT1A and weak 5-HT3 receptors antagonists, and some of them 5-HT2A antagonists. Moreover, none of the studied compounds impaired motor coordination at antidepressant-like doses. Since the studied compounds exhibited activity in behavioral assays and interacted with various receptors, the results of our experiments are very promising and require further studies.

  19. Synergistic effect of 5-HT1A and σ1 receptor activation on prefrontal dopaminergic transmission under circulating steroid deficiency.

    PubMed

    Hiramatsu, Naoki; Ago, Yukio; Hasebe, Shigeru; Nishimura, Akira; Mori, Kazuya; Takuma, Kazuhiro; Matsuda, Toshio

    2013-12-01

    Serotonin (5-HT)1A and σ1 receptors have been implicated in psychiatric disorders. We previously found that combined 5-HT reuptake inhibition and σ1 receptor activation has a synergistic effect on prefrontal dopaminergic transmission in adrenalectomized/castrated mice lacking circulating steroid hormones. In the present study, we examined the mechanisms underlying this neurochemical synergism. Systemic administration of fluvoxamine, a selective 5-HT reuptake inhibitor with agonistic activity towards the σ1 receptor, increased prefrontal dopamine (DA) levels, and adrenalectomy/castration potentiated this fluvoxamine-induced increase in DA. This enhancement of DA release was blocked by WAY100635 (a 5-HT1A receptor antagonist), but not by ritanserin (a 5-HT2 receptor antagonist), azasetron (a 5-HT3 receptor antagonist) or SB269970 (a 5-HT7 receptor antagonist). Individually, osemozotan (a 5-HT1A receptor agonist) and (+)-SKF-10,047 (a σ1 receptor agonist) did not alter prefrontal monoamine levels in adrenalectomized/castrated and sham-operated mice differentially. In contrast, co-administration of these drugs increased prefrontal DA levels to a greater extent in adrenalectomized/castrated mice than in sham-operated animals. Furthermore, co-administration of osemozotan and (+)-SKF-10,047 increased expression of the neuronal activity marker c-Fos in the ventral tegmental area of adrenalectomized/castrated mice, but not in sham-operated animals. These findings suggest that combined activation of 5-HT1A and σ1 receptors has a synergistic effect on prefrontal dopaminergic transmission under circulating steroid deficiency, and that this interaction may play an important role in the regulation of the prefrontal DA system.

  20. Serotonergic receptor mechanisms underlying antidepressant-like action in the progesterone withdrawal model of hormonally induced depression in rats.

    PubMed

    Li, Yan; Raaby, Kasper F; Sánchez, Connie; Gulinello, Maria

    2013-11-01

    Hormonally induced mood disorders such as premenstrual dysphoric disorder (PMDD) are characterized by a range of physical and affective symptoms including anxiety, irritability, anhedonia, social withdrawal and depression. Studies demonstrated rodent models of progesterone withdrawal (PWD) have a high level of constructive and descriptive validity to model hormonally-induced mood disorders in women. Here we evaluate the effects of several classes of antidepressants in PWD female Long-Evans rats using the forced swim test (FST) as a measure of antidepressant activity. The study included fluoxetine, duloxetine, amitriptyline and an investigational multimodal antidepressant, vortioxetine (5-HT(3), 5-HT(7) and 5-HT(1D) receptor antagonist; 5-HT(1B) receptor partial agonist; 5-HT(1A) receptor agonist; inhibitor of the serotonin transporter (SERT)). After 14 days of administration, amitriptyline and vortioxetine significantly reduced immobility in the FST whereas fluoxetine and duloxetine were ineffective. After 3 injections over 48 h, neither fluoxetine nor duloxetine reduced immobility, whereas amitriptyline and vortioxetine significantly reduced FST immobility during PWD. When administered acutely during PWD, the 5-HT(1A) receptor agonist, flesinoxan, significantly reduced immobility, whereas the 5-HT(1A) receptor antagonist, WAY-100635, increased immobility. The 5-HT(3) receptor antagonist, ondansetron, significantly reduced immobility, whereas the 5-HT(3) receptor agonist, SR-57227, increased immobility. The 5-HT(7) receptor antagonist, SB-269970, was inactive, although the 5-HT(7) receptor agonist, AS-19, significantly increased PWD-induced immobility. None of the compounds investigated (ondansetron, flesinoxan and SB-269970) improved the effect of fluoxetine during PWD. These data indicate that modulation of specific 5-HT receptor subtypes is critical for manipulating FST immobility in this model of hormone-induced depression.

  1. Dipicrylamine Modulates GABAρ1 Receptors through Interactions with Residues in the TM4 and Cys-Loop Domains.

    PubMed

    Limon, Agenor; Estrada-Mondragón, Argel; Ruiz, Jorge M Reyes; Miledi, Ricardo

    2016-04-01

    Dipicrylamine (DPA) is a commonly used acceptor agent in Förster resonance energy transfer experiments that allows the study of high-frequency neuronal activity in the optical monitoring of voltage in living cells. However, DPA potently antagonizes GABAA receptors that contain α1 and β2 subunits by a mechanism which is not clearly understood. In this work, we aimed to determine whether DPA modulation is a general phenomenon of Cys-loop ligand-gated ion channels (LGICs), and whether this modulation depends on particular amino acid residues. For this, we studied the effects of DPA on human homomeric GABAρ1, α7 nicotinic, and 5-HT3A serotonin receptors expressed in Xenopus oocytes. Our results indicate that DPA is an allosteric modulator of GABAρ1 receptors with an IC50 of 1.6 µM, an enhancer of α7 nicotinic receptors at relatively high concentrations of DPA, and has little, if any, effect on 5-HT3A receptors. DPA antagonism of GABAρ1 was strongly enhanced by preincubation, was slightly voltage-dependent, and its washout was accelerated by bovine serum albumin. These results indicate that DPA modulation is not a general phenomenon of LGICs, and structural differences between receptors may account for disparities in DPA effects. In silico modeling of DPA docking to GABAρ1, α7 nicotinic, and 5-HT3A receptors suggests that a hydrophobic pocket within the Cys-loop and the M4 segment in GABAρ1, located at the extracellular/membrane interface, facilitates the interaction with DPA that leads to inhibition of the receptor. Functional examinations of mutant receptors support the involvement of the M4 segment in the allosteric modulation of GABAρ1 by DPA.

  2. Involvement of serotonin receptor subtypes in the antidepressant-like effect of beta receptor agonist Amibegron (SR 58611A): an experimental study.

    PubMed

    Tanyeri, Pelin; Buyukokuroglu, Mehmet Emin; Mutlu, Oguz; Ulak, Güner; Yıldız Akar, Füruzan; Komsuoglu Celikyurt, Ipek; Erden, Bekir Faruk

    2013-04-01

    New therapeutic strategies against depression, with less side effects and thus greater efficacy in larger proportion of depressed patients, are needed. Amibegron (SR58611A) is the first selective β3 adrenergic agent that has been shown to possess a profile of antidepressant activity in rodents. To investigate the involvement of serotonin receptors in the effects of amibegron, we used the serotonin 5HT1A receptor antagonist WAY-100635 (WAY) or serotonin 5HT2A-2C receptor antagonist ketanserin or serotonin 5HT3 receptor antagonist ondansetron in mice forced swimming test (FST). The locomotor activity was evaluated by measuring the total distance moved in the apparatus and the speed of the animals in the open field test. Imipramine (30mg/kg) significantly reduced immobility time compared to vehicle-treated group while amibegron (5 and 10mg/kg) dose dependently reduced immobility time in the FST. WAY(0.1mg/kg), ondansetron (1mg/kg), ketanserin(5mg/kg) had no effect on immobility time in naive mice while all of the drugs partially and significantly reversed amibegron (10mg/kg) induced decreasement in the immobility time in FST. None of the drugs alter locomotor activity in the open field test. The antidepressant-like effect of amibegron in the FST seems to be mediated by an interaction with serotonin 5-HT1A, serotonin 5-HT2A-2C and serotonin 5-HT3 receptors.

  3. Intracerebroventricular injection of trazodone produces 5-HT receptor subtype mediated anti-nociception at the supraspinal and spinal levels.

    PubMed

    Zhang, Rihui; Nagata, Tomonari; Hayashi, Takayuki; Miyata, Mariko; Kawakami, Yoriko

    2004-10-01

    Serotonin (5-HT) mediated anti-nociceptive effects induced by an anti-depressant, trazodone, are related to 5-HT(1A) receptor activities at the supraspinal level. 5-HT(3) receptor activation via the descending anti-nociceptive pathways may contribute to the trazodone mediated anti-nociception at the spinal level. Intracerebroventricular (i.c.v.) injection of trazodone dose-dependently impaired nociceptive responses in the formalin test in mice. Six and 15 microg of trazodone inhibited the early (P<0.05 or 0.01) and the late phases of the formalin test (P<0.05 or 0.01), while 3 microg had no effect. We examined the effects of a selective 5-HT(1A) receptor antagonist, WAY-100635, a single injection of which induced hyperalgesia (P<0.05), and blocked the anti-nociceptive effects of trazodone (P<0.01) when the two were simultaneously injected i.c.v. Intrathecal (i.t.) injection of a selective 5-HT(3) receptor antagonist, 3-tropanylindole-3-carboxylate hydrochloride, blocked the anti-nociceptive effects of i.c.v. trazodone (P<0.01), while WAY-100635 (i.t.) did not impair trazodone mediated anti-nociception. Trazodone mediated anti-nocicepton is related to serotonergic activity at both the supraspinal and the spinal level.

  4. Possible involvement of β₁ receptors in various emetogen-induced increases in salivary amylase activity in rats.

    PubMed

    Fukui, Hideo; Suyama, Yoshimi; Iwachido, Takako; Miwa, Eri

    2011-01-01

    We investigated the inhibitory effects of β₁- or β₂-adrenoceptor (AR) antagonists on salivary amylase secretion produced by various emetic agents, such as cisplatin, apomorphine, and lithium chloride (LiCl), or the non-emetic agent β(½)-AR agonist isoprenaline in rats. We also determined the inhibitory effect of metoclopramide, a dopamine D₂-receptor antagonist, on increases in the salivary amylase activity induced by apomorphine or granisetron, a 5-HT(3)-receptor antagonist, on LiCl-induced increased salivary amylase activity. Isoprenaline (0.01 mg/kg, s.c.) produced an increase in salivary amylase and the increase was inhibited by the β(½)-AR antagonist propranolol (5 mg/kg, s.c.) and β₁-AR antagonist atenolol (2 mg/kg, s.c.) but not by the β₂-AR antagonist butoxamine (8 mg/kg, s.c.). The increased amylase activity induced by cisplatin (15 mg/kg, i.v.), apomorphine (3 mg/kg, s.c.), or LiCl (120 mg/kg, i.p.) was inhibited significantly by atenolol (2 mg/kg, s.c.) but not by butoxamine (8 mg/kg, s.c.). In addition, increases in amylase activities induced by apomorphine and LiCl were inhibited significantly by metoclopramide (10 mg/kg, i.v.) and granisetron (3 mg/kg, i.v.), respectively. These results suggest that salivary amylase secretion induced by various emetogens is involved in β₁-adrenoceptor activity and that salivary amylase activity is useful to detect emetogens with no direct β₁-AR activation in rats, a species that does not exhibit vomiting.

  5. Expression of Serotonin2C Receptors in Pyramidal and GABAergic Neurons of Rat Prefrontal Cortex: A Comparison with Striatum.

    PubMed

    Santana, Noemí; Artigas, Francesc

    2016-06-01

    The prefrontal cortex (PFC) is enriched in several serotonin receptors, including 5-HT1A-R, 5-HT2A-R, and 5-HT3-R. These receptors modulate PFC activity due to their expression in large neuronal populations (5-HT1A-R, 5-HT2A-R) or in selected GABAergic populations (5-HT3-R). They are also relevant for antidepressant and antipsychotic drug action. Less is known about the localization of 5-HT2C-R, for which atypical antipsychotics show high affinity. Here, we report on the cellular distribution of 5-HT2C-R in rat PFC and striatum, using double in situ hybridization histochemistry. In PFC, 5-HT2C-R are expressed in pyramidal (VGLUT1-positive) and GABAergic (GAD-positive) neurons, including parvalbumin-positive neurons. There is a marked dorso-ventral gradient in the proportion of VGLUT1-positive cells expressing 5-HT2C-R (9% in the cingulate cortex, 61% in the tenia tecta and 66% in the piriform cortex), less marked for GABAergic neurons (13-27%). There is also a laminar gradient, with more cells expressing 5-HT2C-R in deep (V-VI) than in intermediate (II-III) layers. In common with 5-HT3-R, layer I GABAergic cells express 5-HT2C-R. The proportion of 5-HT2C-R-expressing striatal neurons was 23% (dorsolateral caudate-putamen), 37% (ventromedial caudate-putamen), 53% (nucleus accumbens-core), and 49% (nucleus accumbens-shell). These results help to better understand the serotonergic modulation of PFC-based networks, including basal ganglia circuits, and atypical antipsychotic drug action.

  6. Cloning and expression of ligand-gated ion-channel receptor L2 in central nervous system

    SciTech Connect

    Houtani, Takeshi; Munemoto, Yumi; Kase, Masahiko; Sakuma, Satoru; Tsutsumi, Toshiyuki; Sugimoto, Tetsuo . E-mail: sugimoto@takii.kmu.ac.jp

    2005-09-23

    An orphan receptor of ligand-gated ion-channel type (L2, also termed ZAC according to the presence of zinc ion for channel activation) was identified by computer-assisted search programs on human genome database. The L2 protein shares partial homology with serotonin receptors 5HT3A and 5HT3B. We have cloned L2 cDNA derived from human caudate nucleus and characterized the exon-intron structure as follows: (1) The L2 protein has four transmembrane regions (M1-M4) and a long cytoplasmic loop between M3 and M4. (2) The sequence is conserved in species including chimpanzee, dog, cow, and opossum. (3) Nine exons form its protein-coding region and especially exon 5 corresponds to a disulfide bond region on the amino-terminal side. Our analysis using multiple tissue cDNA panels revealed that at least two splicing variants of L2 mRNA are present. The cDNA PCR amplification study revealed that L2 mRNA is expressed in tissues including brain, pancreas, liver, lung, heart, kidney, and skeletal muscle while 5HT3A mRNA could be detected in brain, heart, placenta, lung, kidney, pancreas, and skeletal muscle, and 5HT3B mRNA in brain, kidney, and skeletal muscle, suggesting different significance in tissue expression of these receptors. Regional expression of L2 mRNA and protein was examined in brain. The RT-PCR studies confirmed L2 mRNA expression in hippocampus, striatum, amygdala, and thalamus in adult brain. The L2 protein was immunolocalized by using antipeptide antibodies. Immunostained tissue sections revealed that L2-like immunoreactivity was dominantly expressed in the hippocampal CA3 pyramidal cells and in the polymorphic layer of the dentate gyrus. We analyzed the expression of L2 protein in HEK293 cells using GFP fusion protein reporter system. Western blots revealed that L2 protein confers sugar chains on the extracellular side. In transfected HEK293 cells, cellular membranes and intracellular puncta were densely labeled with GFP, suggesting selective dispatch to the

  7. Role of catecholamines and serotonin receptor subtypes in nefopam-induced antinociception.

    PubMed

    Girard, Philippe; Coppé, Marie-Claude; Verniers, Danielle; Pansart, Yannick; Gillardin, Jean-Marie

    2006-09-01

    The non-opiate analgesic nefopam has been shown to inhibit monoamines uptake, but little is known about receptor subtypes effectively involved in its analgesic effect. In vitro binding assays yielded the following measures of affinity (IC(50)): serotonergic 5-HT(2C) (1.4 microM), 5-HT(2A) (5.1 microM), 5-HT(3) (22.3 microM), 5-HT(1B) (41.7 microM), 5-HT(1A) (64.9 microM), adrenergic alpha(1) (15.0 microM) and dopaminergic D(1) (100 microM). Subcutaneous nefopam administration dose-dependently inhibited pain in acetic acid-induced writhing (1-30 mg kg(-1)) and formalin (1-10 mg kg(-1)) tests in the mouse. Pretreatments with adrenergic alpha(1) (prazosin) and alpha(2) (yohimbine), and serotonergic 5-HT(1B) (GR127935) receptor antagonists significantly increased the nefopam ED(50) in the writhing test. The serotonergic 5-HT(2C) (RS102221) and the dopaminergic D(2) (sulpiride) receptor antagonists inhibited nefopam antinociception in the formalin test. However, in both tests, nefopam analgesic activity was not modified by the following receptor antagonists: dopaminergic D(1) (SCH23390), serotonergic 5-HT(1A) (NAN-190, WAY100635), 5-HT(2A) (R96544, ketanserin), 5-HT(3) (tropisetron), and 5-HT(4) (SDZ205557). In conclusion, nefopam analgesic activity could be modulated by the adrenergic alpha(1) and alpha(2) receptors, the dopaminergic D(2) receptors, and the serotonergic 5-HT(1B) and 5-HT(2C) receptor subtypes.

  8. Efficacy and safety of 5-hydroxytryptamine 3 receptor antagonists in irritable bowel syndrome: A systematic review and meta-analysis of randomized controlled trials

    PubMed Central

    Tang, Yurong; Xiong, Wenjie; Shen, Xiaoxue; Jiang, Ling; Lin, Lin

    2017-01-01

    Aim We assessed the efficacy and safety of 5-hydroxytryptamine (5-HT3) receptor antagonists in adults with non-constipated irritable bowel syndrome (IBS) or diarrhea-predominant IBS (IBS-D). Methods We searched PubMed, MEDLINE, EMBASE, and the Cochrane Controlled Trials Register for randomized controlled trials (RCTs) involving adults with non-constipated IBS or IBS-D that compared 5-HT3 receptor antagonists with placebo or other conventional treatment. Dichotomous symptom data were pooled to obtain the relative risk (RR) and 95% confidence intervals (CIs) for improving global IBS symptoms, abdominal pain and abnormal bowel habits, or stool consistency symptoms after therapy, and adverse events, including constipation. Meta- analysis was performed with Mantel Haenszel method using Revman 5.3 software. Results We included 21 RCTs; 16 were high quality (Jadad score ≥ 4). The pooled RR of global IBS symptoms improved by 5-HT3 receptor antagonists versus placebo or mebeverine was 1.56 (95% CI: 1.43–1.71); alosetron, ramosetron, and cilansetron had similar treatment effects. The pooled RR of abdominal pain relieved by 5-HT3 receptor antagonists versus placebo was 1.33 (95% CI: 1.26–1.39). The pooled RR showed that 5-HT3 receptor antagonists improved abnormal bowel habits or stool consistency symptoms (RR = 1.63, 95% CI: 1.33, 1.99). The pooled RR of adverse events following 5-HT3 receptor antagonist treatment was 1.15 (95% CI: 1.08, 1.22). Subgroup analysis indicated that alosetron had a high rate of adverse effects (RR = 1.16, 95% CI: 1.08, 1.25); adverse events following ramosetron treatment were not statistically significantly different. 5-HT3 receptor antagonists were likelier to cause constipation: the pooled RR of constipation developing with 5-HT3 receptor antagonist versus placebo was 3.71 (95% CI: 2.98–4.61). However, constipation was likelier in patients with non-constipated IBS after taking 5-HT3 receptor antagonists than in patients with IBS-D only

  9. Anxiogenic activity of Myristica fragrans seeds.

    PubMed

    Sonavane, G S; Sarveiya, V P; Kasture, V S; Kasture, S B

    2002-01-01

    In the present study, the n-hexane extract of Myristica fragrans (MF) seeds, acetone-insoluble part of the n-hexane extract (AIMF) and trimyristin (TM) were assessed for their anxiogenic activity. The MF (10 and 30 mg/kg), AIMF (30, 100, and 300 mg/kg), and TM (10, 30, and 100 mg/kg) administered intraperitoneally exhibited anxiogenic activity in elevated plus-maze (EPM) paradigm. The open-field test and hole-board test were also used to assess anxiogenic activity of AIMF and TM. In the EPM test, MF, AIMF, and TM decreased the time spent by mice in the open arm and the entries in the open arm. Further, the effect of diazepam (1 mg/kg i.p.), serotonin 5-HT3 receptor antagonist, ondansetron (1 mg/kg i.p.), and 5-HT1A receptor agonist, buspirone (1 mg/kg i.p.), on the occupancy in open arm and entries in open arm was significantly reduced by TM. In the open-field test, AIMF as well as TM reduced the number of rearing and locomotion. Both TM and AIMF reduced the number of head pock in the hole-board test. Inhibition of anxiolytic activity of ondansetron (5-HT3 receptor antagonist), buspirone (5-HT1A receptor agonist), and diazepam [acting on gamma-aminobutyric acid (GABAA) receptor] suggests a nonspecific anxiogenic activity of TM and also a link between 5-HT and GABA systems in the anxiogenic activity of TM.

  10. Mechanism for the activation of glutamate receptors

    Cancer.gov

    Scientists at the NIH have used a technique called cryo-electron microscopy to determine a molecular mechanism for the activation and desensitization of ionotropic glutamate receptors, a prominent class of neurotransmitter receptors in the brain and spina

  11. The effects of 5-HT on articular sensory receptors in normal and arthritic rats.

    PubMed Central

    Birrell, G. J.; McQueen, D. S.; Iggo, A.; Grubb, B. D.

    1990-01-01

    1. The effects of intra arterial (i.a.) injections of 5-hydroxytryptamine (5-HT, 1-100 micrograms) on the discharge of (a) identified articular high threshold mechanoreceptors and (b) unidentified chemosensitive receptors in the ankle joint have been studied electrophysiologically in anaesthetized normal and arthritic rats. Recordings were made from a fine branch of the medial plantar nerve. 2. 5-HT increased the mechanical responsiveness of high threshold nociceptive mechanoreceptors with C and A delta fibre afferents in both normal and adjuvant-arthritic rats. Receptors in arthritic joints were more sensitive to 5-HT than were those from normal joints. 3. 5-HT produced a complex response from both types of articular receptors following i.a. injection. Two separate components were identified: (a) a fast transient burst of activity was obtained within 10 s of this injection in 66% of units from normal animals and 45% from arthritics, followed by (b) a delayed slow longer-lasting excitation seen in 62% of the units examined from normals and 77% of units from arthritic rats. 4. Increased mechanoreceptor responsiveness produced by 5-HT was reduced or abolished by the 5-HT3 receptor antagonists studied (MDL 72222, ICS 205-930, or GR 38032F, in single doses of 100 micrograms kg-1, i.a.). 5. Fast excitation showed marked tachyphylaxis and was antagonized by MDL 72222, ICS 205-930 or GR 38032F. It was unaffected by ketanserin (100 micrograms kg-1, i.a.). Delayed excitation was reduced or abolished by ketanserin but was unaffected by the 5-HT3-receptor antagonists.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2076487

  12. Peripheral and spinal 5-HT receptors participate in cholestatic itch and antinociception induced by bile duct ligation in rats

    PubMed Central

    Tian, Bin; Wang, Xue-Long; Huang, Ya; Chen, Li-Hua; Cheng, Ruo-Xiao; Zhou, Feng-Ming; Guo, Ran; Li, Jun-Cheng; Liu, Tong

    2016-01-01

    Although 5-HT has been implicated in cholestatic itch and antinociception, two common phenomena in patients with cholestatic disease, the roles of 5-HT receptor subtypes are unclear. Herein, we investigated the roles of 5-HT receptors in itch and antinociception associated with cholestasis, which was induced by common bile duct ligation (BDL) in rats. 5-HT-induced enhanced scratching and antinociception to mechanical and heat stimuli were demonstrated in BDL rats. 5-HT level in the skin and spinal cord was significantly increased in BDL rats. Quantitative RT-PCR analysis showed 5-HT1B, 5-HT1D, 5-HT2A, 5-HT3A, 5-HT5B, 5-HT6, and 5-HT7 were up-regulated in peripheral nervous system and 5-HT1A, 5-HT1F, 5-HT2B, and 5-HT3A were down-regulated in the spinal cord of BDL rats. Intradermal 5-HT2, 5-HT3, and 5-HT7 receptor agonists induced scratching in BDL rats, whereas 5-HT3 agonist did not induce scratching in sham rats. 5-HT1A, 5-HT2, 5-HT3, and 5-HT7 agonists or antagonists suppressed itch in BDL rats. 5-HT1A agonist attenuated, but 5-HT1A antagonist enhanced antinociception in BDL rats. 5-HT2 and 5-HT3 agonists or antagonists attenuated antinociception in BDL rats. Our data suggested peripheral and central 5-HT system dynamically participated in itch and antinociception under cholestasis condition and targeting 5-HT receptors may be an effective treatment for cholestatic itch. PMID:27824106

  13. Ethanol and Mesolimbic Serotonin/Dopamine Interactions Via 5-HT1B Receptors

    DTIC Science & Technology

    2006-03-01

    5 - HT3 receptor antagonist antagonized systemic ethanol- induced increases of DA release in the VTA [10] or the NACC [9]. Moreover, the...experiments with a selective 5 -HT1B receptor antagonist such as SB 216641 are required to strengthen this conclusion. The future experiments will be... receptor antagonist ), but not BRL 15572 (a 5 -HT1D/1A receptor antagonist ) or WAY 100635 (a 5 -HT1A receptor antagonist ). Administration

  14. Serotonin receptors involved in antidepressant effects.

    PubMed

    Artigas, Francesc

    2013-01-01

    The neurotransmitter serotonin (5-hdroxytryptamine; 5-HT) has been implicated in the pathophysiology and treatment of major depression since the serendipitous discovery of antidepressant drugs in the 1950s. However, despite the generalised use of serotonin-enhancing drugs, such as the selective serotonin reuptake inhibitors (SSRIs) and the dual serotonin and norepinephrine reuptake inhibitors (SNRIs), the exact neurobiological mechanisms involved in the therapeutic action of these drugs are poorly understood. Better knowledge of these mechanisms may help to identify new therapeutic targets and to overcome the two main limitations of current treatments: reduced efficacy and slowness of action. Here I review the preclinical and clinical evidence supporting the involvement of different 5-HT receptors in the therapeutic action of antidepressant drugs. Presynaptic 5-HT(1A) and 5-HT(1B) autoreceptors play a major detrimental role in antidepressant treatments, as their activation by the excess of the active (extracellular) 5-HT fraction produced by serotonin transporter (SERT) blockade reduces presynaptic serotonergic function. Conversely, stimulation of postsynaptic 5-HT(1A) receptors in corticolimbic networks appears beneficial for the antidepressant action. The 5-HT(2) receptor family is also involved as 5-HT(2A/2C) receptor blockade improves the antidepressant action of SSRIs, and recent data suggest that 5-HT(2B) receptor activation enhances serotonergic activity. Less is known from the rest of postsynaptic 5-HT receptors. However, 5-HT(3) receptor blockade augments the 5-HT increase evoked by SERT inhibition, and 5-HT(4) receptor activation may have antidepressant effects on its own. Finally, blockade of 5-HT(6) and 5-HT(7) receptors appears also to augment the antidepressant effects of SERT inhibition.

  15. High-throughput Analysis of Mammalian Olfactory Receptors: Measurement of Receptor Activation via Luciferase Activity

    PubMed Central

    Trimmer, Casey; Snyder, Lindsey L.; Mainland, Joel D.

    2014-01-01

    Odorants create unique and overlapping patterns of olfactory receptor activation, allowing a family of approximately 1,000 murine and 400 human receptors to recognize thousands of odorants. Odorant ligands have been published for fewer than 6% of human receptors1-11. This lack of data is due in part to difficulties functionally expressing these receptors in heterologous systems. Here, we describe a method for expressing the majority of the olfactory receptor family in Hana3A cells, followed by high-throughput assessment of olfactory receptor activation using a luciferase reporter assay. This assay can be used to (1) screen panels of odorants against panels of olfactory receptors; (2) confirm odorant/receptor interaction via dose response curves; and (3) compare receptor activation levels among receptor variants. In our sample data, 328 olfactory receptors were screened against 26 odorants. Odorant/receptor pairs with varying response scores were selected and tested in dose response. These data indicate that a screen is an effective method to enrich for odorant/receptor pairs that will pass a dose response experiment, i.e. receptors that have a bona fide response to an odorant. Therefore, this high-throughput luciferase assay is an effective method to characterize olfactory receptors—an essential step toward a model of odor coding in the mammalian olfactory system. PMID:24961834

  16. Design and Synthesis of a New Series of 4-Heteroarylamino-1'-azaspiro[oxazole-5,3'-bicyclo[2.2.2]octanes as α7 Nicotinic Receptor Agonists. 1. Development of Pharmacophore and Early Structure-Activity Relationship.

    PubMed

    Cook, James; Zusi, F Christopher; McDonald, Ivar M; King, Dalton; Hill, Matthew D; Iwuagwu, Christiana; Mate, Robert A; Fang, Haiquan; Zhao, Rulin; Wang, Bei; Cutrone, Jingfang; Ma, Baoqing; Gao, Qi; Knox, Ronald J; Matchett, Michele; Gallagher, Lizbeth; Ferrante, Meredith; Post-Munson, Debra; Molski, Thaddeus; Easton, Amy; Miller, Regina; Jones, Kelli; Digavalli, Siva; Healy, Francine; Lentz, Kimberley; Benitex, Yulia; Clarke, Wendy; Natale, Joanne; Siuciak, Judith A; Lodge, Nicholas; Zaczek, Robert; Denton, Rex; Morgan, Daniel; Bristow, Linda J; Macor, John E; Olson, Richard E

    2016-12-22

    The design and synthesis of a series of quinuclidine-containing spirooxazolidines ("spiroimidates") and their utility as α7 nicotinic acetylcholine receptor partial agonists are described. Selected members of the series demonstrated excellent selectivity for α7 over the highly homologous 5-HT3A receptor. Modification of the N-spiroimidate heterocycle substituent led to (1S,2R,4S)-N-isoquinolin-3-yl)-4'H-4-azaspiro[bicyclo[2.2.2]octane-2,5'oxazol]-2'-amine (BMS-902483), a potent α7 partial agonist, which improved cognition in preclinical rodent models.

  17. Antidepressant & anxiolytic activities of N-(pyridin-3-yl) quinoxalin-2-carboxamide: A novel serotonin type 3 receptor antagonist in behavioural animal models

    PubMed Central

    Pandey, Dilip Kumar; Devadoss, Thangraj; Modak, Neha; Mahesh, Radhakrishnan

    2016-01-01

    Background & objectives: Alteration in the serotonin leads to the psychological illness, such as depression, anxiety, schizophrenia, eating disorders, obsessive-compulsive disorder, panic disorders and migraines. The objective of the current study was to investigate the antidepressant and anxiolytic activities of N-(pyridin-3-yl) quinoxalin-2-carboxamide (QCF-21), a novel 5-HT3 receptor antagonist in preclinical models of depression and anxiety. Methods: Antidepressant activity was evaluated in preliminary tests such as forced swim and tail suspension tests (FST & TST). Anti-anxiety effect of QCF-21 was investigated by employing elevated plus maze (EPM), light/dark and hole board tests. Olfactory bulbectomy (OBX) in rats was used as chronic model of depression. Mechanistic test of QCF-21 was evaluated by reserpine-induced hypothermia and 5-hydroxytryptophan (5-HTP)-induced head-twitch response. Results: The dose-response study revealed an initial antidepressant-like effect of QCF-21(0.25-1 mg/kg, i.p.) in the FST and TST and anxiolytic-like effect in EPM, light and dark and hole board tests. QCF-21 potentiated the 5-HTP-induced head-twitches response in mice and reversed reserpine-induced hypothermia in rats. QCF-21 significantly reversed the behavioural anomalies post-OBX in rats. Interpretation & conclusions: The present findings indicate the potential antidepressant-like and anxiolytic-like effects of QCF-21 at low doses in rodent behavioural models of depression and anxiety. Further studies need to be done to understand the underlying mechanism. PMID:28256473

  18. Using Nuclear Receptor Activity to Stratify Hepatocarcinogens

    PubMed Central

    Shah, Imran; Houck, Keith; Judson, Richard S.; Kavlock, Robert J.; Martin, Matthew T.; Reif, David M.; Wambaugh, John; Dix, David J.

    2011-01-01

    Background Nuclear receptors (NR) are a superfamily of ligand-activated transcription factors that control a range of cellular processes. Persistent stimulation of some NR is a non-genotoxic mechanism of rodent liver cancer with unclear relevance to humans. Here we report on a systematic analysis of new in vitro human NR activity data on 309 environmental chemicals in relationship to their liver cancer-related chronic outcomes in rodents. Results The effects of 309 environmental chemicals on human constitutive androstane receptors (CAR/NR1I3), pregnane X receptor (PXR/NR1I2), aryl hydrocarbon receptor (AhR), peroxisome proliferator-activated receptors (PPAR/NR1C), liver X receptors (LXR/NR1H), retinoic X receptors (RXR/NR2B) and steroid receptors (SR/NR3) were determined using in vitro data. Hepatic histopathology, observed in rodents after two years of chronic treatment for 171 of the 309 chemicals, was summarized by a cancer lesion progression grade. Chemicals that caused proliferative liver lesions in both rat and mouse were generally more active for the human receptors, relative to the compounds that only affected one rodent species, and these changes were significant for PPAR (p0.001), PXR (p0.01) and CAR (p0.05). Though most chemicals exhibited receptor promiscuity, multivariate analysis clustered them into relatively few NR activity combinations. The human NR activity pattern of chemicals weakly associated with the severity of rodent liver cancer lesion progression (p0.05). Conclusions The rodent carcinogens had higher in vitro potency for human NR relative to non-carcinogens. Structurally diverse chemicals with similar NR promiscuity patterns weakly associated with the severity of rodent liver cancer progression. While these results do not prove the role of NR activation in human liver cancer, they do have implications for nuclear receptor chemical biology and provide insights into putative toxicity pathways. More importantly, these findings suggest the

  19. Synthesis and structure-activity relationships of a new model of arylpiperazines. 5. Study of the physicochemical influence of the pharmacophore on 5-HT(1a)/alpha(1)-adrenergic receptor affinity: synthesis of a new derivative with mixed 5-HT(1a)/d(2) antagonist properties.

    PubMed

    López-Rodríguez, M L; Morcillo, M J; Fernández, E; Porras, E; Orensanz, L; Beneytez, M E; Manzanares, J; Fuentes, J A

    2001-01-18

    In this paper we have designed and synthesized a test series of 32 amide arylpiperazine derivatives VI in order to gain insight into the physicochemical influence of the pharmacophores of 5-HT(1A) and alpha(1)-adrenergic receptors. The training set was designed applying a fractional factorial design using six physicochemical descriptors. The amide moiety is a bicyclohydantoin or a diketopiperazine (X = -(CH(2))(3)-, -(CH(2))(4)-; m = 0, 1), the spacer length is 3 or 4 methylene units, which are the optimum values for both receptors, and the aromatic substituent R occupies the ortho- or meta-position and has been selected from a database of 387 substituents using the EDISFAR program. The 5-HT(1A) and alpha(1)-adrenergic receptor binding affinities of synthesized compounds VI (1-32) have been determined. This data set has been used to derive classical quantitative structure-activity relationships (QSAR) and neural networks models for both receptors (following paper). A comparison of these models gives information for the design of the new ligand EF-7412 (46) (5-HT(1A): K(i) = 27 nM; alpha(1): K(i) > 1000 nM). This derivative displays affinity for the dopamine D(2) receptor (K(i) = 22 nM) and is selective versus all other receptors examined (5-HT(2A), 5-HT(3), 5-HT(4) and Bz; K(i) > 1000 nM). EF-7412 (46) acts as an antagonist in vivo in pre- and postsynaptic 5-HT(1A) receptor sites and as an antagonist in the dopamine D(2) receptor. Thus, EF-7412 (46) is a derivative with mixed 5-HT(1A)/D(2) antagonist properties and this derivative could be useful as a pharmacological tool.

  20. Mechanism of FGF receptor dimerization and activation

    NASA Astrophysics Data System (ADS)

    Sarabipour, Sarvenaz; Hristova, Kalina

    2016-01-01

    Fibroblast growth factors (fgfs) are widely believed to activate their receptors by mediating receptor dimerization. Here we show, however, that the FGF receptors form dimers in the absence of ligand, and that these unliganded dimers are phosphorylated. We further show that ligand binding triggers structural changes in the FGFR dimers, which increase FGFR phosphorylation. The observed effects due to the ligands fgf1 and fgf2 are very different. The fgf2-bound dimer structure ensures the smallest separation between the transmembrane (TM) domains and the highest possible phosphorylation, a conclusion that is supported by a strong correlation between TM helix separation in the dimer and kinase phosphorylation. The pathogenic A391E mutation in FGFR3 TM domain emulates the action of fgf2, trapping the FGFR3 dimer in its most active state. This study establishes the existence of multiple active ligand-bound states, and uncovers a novel molecular mechanism through which FGFR-linked pathologies can arise.

  1. 5-hydroxytryptamine stimulation of phospholipase D activity in the rabbit isolated mesenteric artery.

    PubMed

    Hinton, J M; Adams, D; Garland, C J

    1999-04-01

    1. The involvement of phospholipase D (PLD) in the 5-hydroxytryptamine 5-HT1B/5-HT1D-signalling pathway was assessed in the rabbit isolated mesenteric artery. 2. RT-PCR analysis of mesenteric smooth muscle cells revealed a strong signal corresponding to mRNA transcript for the 5-HT1B receptor. The PCR fragment corresponded to the known sequence for the 5-HT1B receptor. No signal corresponding to 5-HT1D mRNA was detected. 3. Neither 5-HT (3 microM) nor KCl (45 mM) individually stimulated any significant increase in the smooth muscle concentration of [33P]-PtdBut to reflect PLD activity. However, in the presence of KCl (45 mM), 5-HT evoked a concentration-dependent increase in [33P]-PtdBut, to a maximum of 84% with 5-HT (3 microM). 4. [33P]-PtdBut accumulation evoked by 5-HT in the presence of KCl was abolished in nominally calcium-free Krebs-Henseleit Buffer (KHB) or with the selective protein kinase C inhibitor, Ro-31 8220 (10 microM, 20 min). 5. 5-HT (3 microM) in the presence of KCl (45 mM) failed to increase either the accumulation of [33P]-phosphatidic acid in the presence of butanol, or total [3H]-inositol phosphates ([3H]-InsP) in the presence of LiCl (10 mM). 6. 5-HT (0.1-1 microM) abolished forskolin (1 microM) stimulated increases in cyclic AMP (15 fold increase), an action which was pertussis toxin-sensitive. 7. Therefore, in the presence of raised extracellular potassium 5-HT can stimulate PLD via 5-HT1B receptors in the rabbit mesenteric artery. This action requires extracellular calcium and the activation of protein kinase C. These characteristics are identical to the profile for 5-HT1B/5-HT1D-receptor evoked contraction in vascular smooth muscle cells, suggesting a role for PLD in this response to 5-HT.

  2. Serotonin-3 receptors in the posterior ventral tegmental area regulate ethanol self-administration of alcohol-preferring (P) rats.

    PubMed

    Rodd, Zachary A; Bell, Richard L; Oster, Scott M; Toalston, Jamie E; Pommer, Tylene J; McBride, William J; Murphy, James M

    2010-05-01

    Several studies indicated the involvement of serotonin-3 ([5-hydroxy tryptamine] 5-HT(3)) receptors in regulating alcohol-drinking behavior. The objective of this study was to determine the involvement of 5-HT(3) receptors within the ventral tegmental area (VTA) in regulating ethanol self-administration by alcohol-preferring (P) rats. Standard two-lever operant chambers (Coulbourn Instruments, Allentown, PA) were used to examine the effects of seven consecutive bilateral microinfusions of ICS 205-930 (ICS), a 5-HT(3) receptor antagonist, directly into the posterior VTA on the acquisition and maintenance of 15% (vol/vol) ethanol self-administration. P rats readily acquired ethanol self-administration by the fourth session. The three highest doses (0.125, 0.25, and 1.25 microg) of ICS prevented acquisition of ethanol self-administration. During the acquisition postinjection period, all rats treated with ICS demonstrated higher responding on the ethanol lever, with the highest dose producing the greatest effect. In contrast, during the maintenance phase, the three highest doses (0.75, 1.0, and 1.25 microg) of ICS significantly increased responding on the ethanol lever; after the 7-day dosing regimen, responding on the ethanol lever returned to control levels. Microinfusion of ICS into the posterior VTA did not alter the low responding on the water lever and did not alter saccharin (0.0125% wt/v) self-administration. Microinfusion of ICS into the anterior VTA did not alter ethanol self-administration. Overall, the results of this study suggest that 5-HT(3) receptors in the posterior VTA of the P rat may be involved in regulating ethanol self-administration. In addition, chronic operant ethanol self-administration and/or repeated treatments with a 5-HT(3) receptor antagonist may alter neuronal circuitry within the posterior VTA.

  3. Contractile 5-HT1 receptors in human isolated pial arterioles: correlation with 5-HT1D binding sites.

    PubMed Central

    Hamel, E.; Bouchard, D.

    1991-01-01

    1. The 5-hydroxytryptamine (5-HT) receptor responsible for inducing vasoconstriction in human isolated pial arterioles has been pharmacologically characterized. 2. Of several 5-HT agonists tested, 5-carboxamidotryptamine (5-CT) was the most potent and the rank order of agonist potency can be summarized as: 5-CT greater than 5-HT greater than RU 24969 = alpha-methyl-5-HT = methysergide much greater than MDL 72832 = 2-methyl-5-HT much greater than 2-dipropylamino-8-hydroxy-1,2,3,4-tetrahydro-naphthalene (8-OH-DPAT). With few exceptions, the maximal contractile responses of these agonists were comparable to that induced by 5-HT. 3. A correlation analysis performed between the agonists vascular potency (pD2 values) and their affinities (pKD values) published at various subtypes of 5-HT binding sites showed a positive significant correlation with rat cortical 5-HT1B (r = 0.86; P less than 0.01) and human caudate 5-HT1D (r = 0.98; P less than 0.005) subtypes. 4. Selective antagonists at 5-HT2 (ketanserin, mianserin, MDL 11939) and 5-HT3 (MDL 72222) sites were totally devoid of inhibitory activity on the 5-HT-induced contraction, an observation which agreed with the agonist data and further excluded activation of these receptors. In contrast, the 5-HT1-like/5-HT2 antagonist methiothepin and the non-selective 5-HT1D compound metergoline inhibited with high affinity the contraction induced by 5-HT with respective pA2 values of 8.55 +/- 0.16 and 6.88 +/- 0.05. This contractile response was, however, insensitive to 5-HT1B (propranolol) and 5-HT1C (mesulergine, mianserin) antagonists.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2043924

  4. Synergistic effect of 5-hydroxytryptamine 3 and neurokinin 1 receptor antagonism in rodent models of somatic and visceral pain.

    PubMed

    Greenwood-Van Meerveld, Beverley; Mohammadi, Ehsan; Tyler, Karl; Pietra, Claudio; Bee, Lucy A; Dickenson, Anthony

    2014-10-01

    Synergistic activity has been observed between serotonergic 5-hydroxytryptamine 3 (5-HT3) and tachykinergic neurokinin 1 (NK1) receptor-mediated responses. This study investigated the efficacy of a 5-HT3 antagonist, palonosetron, and a NK1 antagonist, netupitant, alone or in combination in rodent models of somatic and visceral colonic hypersensitivity. In a rat model of experimental neuropathic pain, somatic hypersensitivity was quantified by the number of ipsilateral paw withdrawals to a von Frey filament (6g). Electrophysiologic responses were recorded in the dorsal horn neurons after mechanical or thermal stimuli. Acute colonic hypersensitivity was induced experimentally in rats by infusing dilute acetic acid (0.6%) directly into the colon. Colonic sensitivity was assessed by a visceromotor behavioral response quantified as the number of abdominal contractions in response to graded isobaric pressures (0-60 mm Hg) of colorectal distension. Palonosetron or netupitant was administered alone or in combination via oral gavage. When dosed alone, both significantly reduced somatic sensitivity, decreased the evoked response of spinal dorsal horn neurons to mechanical or thermal stimulation, and caused significant (P < 0.05) inhibition of colonic hypersensitivity in a dose-dependent manner. The combined administration of palonosetron and netupitant at doses that were ineffective alone significantly reduced both somatic and visceral sensitivity and decreased the evoked response of spinal dorsal horn neurons to mechanical or thermal stimulation. In summary, the combination of palonosetron with a NK1 receptor antagonist showed synergistic analgesic activity in rodent models of somatic and visceral hypersensitivity, and may prove to be a useful therapeutic approach to treat pain associated with irritable bowel syndrome.

  5. Using Nuclear Receptor Activity to Stratify Hepatocarcinogens

    EPA Science Inventory

    Nuclear receptors (NR) are a superfamily of ligand-activated transcription factors that control a range of cellular processes. Persistent stimulation of some NR is a non-genotoxic mechanism of rodent liver cancer with unclear relevance to humans. Here we report on a systematic an...

  6. A possible significant role of zinc and GPR39 zinc sensing receptor in Alzheimer disease and epilepsy.

    PubMed

    Khan, Muhammad Zahid

    2016-04-01

    Zinc the essential trace element, plays a significant role in the brain development and in the proper brain functions at every stage of life. Misbalance of zinc (Zn(2+)) ions in the central nervous system is involved in the pathogenesis of numerous neurodegenerative disorders such as Alzheimer's disease, Depression, and Epilepsy. In brain, Zn(2+) has been identified as a ligand, capable of activating and inhibiting the receptors including the NMDA-type glutamate receptors (NMDARs), GABAA receptors, nicotinic acetylcholine receptors (nAChRs), glycine receptors (glyR) and serotonin receptors (5-HT3). Recently GPR39 has been identified as a zinc-specific receptor, widely expressed in brain tissues including the frontal cortex, amygdala, and hippocampus. GPR39, when binding with Zn(2+) has shown promising therapeutic potentials. This review presents current knowledge regarding the role of GPR39 zinc sensing receptor in brain, with a focus on Alzheimer's disease and Epilepsy. Although the results are encouraging, further research is needed to clarify zinc and GPR39 role in the treatment of Alzheimer's disease and Epilepsy.

  7. Constitutive Activation of the Aromatic Hydrocarbon Receptor

    PubMed Central

    Chang, Ching-Yi; Puga, Alvaro

    1998-01-01

    The ligand-activated aromatic hydrocarbon receptor (AHR) dimerizes with the AHR nuclear translocator (ARNT) to form a functional complex that transactivates expression of the cytochrome P-450 CYP1A1 gene and other genes in the dioxin-inducible [Ah] gene battery. Previous work from this laboratory has shown that the activity of the CYP1A1 enzyme negatively regulates this process. To study the relationship between CYP1A1 activity and Ah receptor activation we used CYP1A1-deficient mouse hepatoma c37 cells and CYP1A1- and AHR-deficient African green monkey kidney CV-1 cells. Using gel mobility shift and luciferase reporter gene expression assays, we found that c37 cells that had not been exposed to exogenous Ah receptor ligands already contained transcriptionally active AHR-ARNT complexes, a finding that we also observed in wild-type Hepa-1 cells treated with Ellipticine, a CYP1A1 inhibitor. In CV-1 cells, transient expression of AHR and ARNT leads to high levels of AHR–ARNT-dependent luciferase gene expression even in the absence of an agonist. Using a green fluorescent protein-tagged AHR, we showed that elevated reporter gene expression correlates with constitutive nuclear localization of the AHR. Transcriptional activation of the luciferase reporter gene observed in CV-1 cells is significantly decreased by (i) expression of a functional CYP1A1 enzyme, (ii) competition with chimeric or truncated AHR proteins containing the AHR ligand-binding domain, and (iii) treatment with the AHR antagonist α-naphthoflavone. These results suggest that a CYP1A1 substrate, which accumulates in cells lacking CYP1A1 enzymatic activity, is an AHR ligand responsible for endogenous activation of the Ah receptor. PMID:9418899

  8. Receptor Dissociation and B-Cell Activation.

    PubMed

    Yang, Jianying; Reth, Michael

    2016-01-01

    The B-cell antigen receptor (BCR) is one of the most abundant receptors on the surface of B cells with roughly 100,000-200,000 copies per cell. Signaling through the BCR is crucial for the activation and differentiation of B cells. Unlike other receptors, the BCR can be activated by a large set of structurally different ligands, but the molecular mechanism of BCR activation is still a matter of controversy. Although dominant for a long time, the cross-link model (CLM) of BCR activation is not supported by recent studies of the nanoscale organization of the BCR on the surface of resting B cells. In contrast to the prediction of CLM, the numerous BCR complexes on these cells are not randomly distributed monomers but rather form oligomers which reside within membrane confinements. This finding is more in line with the dissociation activation model (DAM), wherein B-cell activation is accompanied by an opening of the auto-inhibited BCR oligomers instead of a cross-linking of the BCR monomers. In this review, we discuss in detail the new findings and their implications for BCR signaling.

  9. Cyclophosphamide causes activation of protein kinase A (PKA) in the brainstem of vomiting least shrews (Cryptotis parva).

    PubMed

    Alkam, Tursun; Chebolu, Seetha; Darmani, Nissar A

    2014-01-05

    Complete control of emesis caused by cyclophosphamide (CPA) is of immense interest to both patients and physicians. Serotonin 5-HT3- and tachykinin NK1-receptor antagonists are widely used antiemetics in clinic, but they fail to completely control CPA-induced emesis. New antiemetic targets for the full control of CPA-induced vomiting are lacking. We therefore examined the effects of CPA on emetic targets downstream of 5-HT3- and NK1- receptors in an attempt to better understand the molecular bases of CPA-induced emesis. Acute CPA (200 mg/kg, i.p.) administration in the least shrew caused a biphasic pattern of emesis over a 40 h observation period, with maximal peak vomit frequency during the 1st hour of treatment (acute phase), followed by a delayed-phase which peaks at 27th hour. The NK1 receptor mRNA levels increased significantly at 8 h post-CPA treatment in the brainstem, and at 28 h in the whole intestine. Substance P mRNA levels tended to increase both in the brainstem and intestine at most time-points post-CPA injection, however due to large variability, they failed to attain significance. Likewise, protein expression profiles of both NK1- and 5-HT3 -receptors in the brainstem were unchanged at any time-point. However, phosphorylation levels of protein kinase A (PKA), but not of extracellular signal-regulated protein kinase 1/2 (ERK1/2), were increased at 2, 8, 22, 28, and 33 h time-points after the treatment with CPA. Moreover, brainstem but not frontal cortex cAMP tissue levels tended to be elevated at most time-points, but significant increases occurred only at 1 and 2 h post-CPA treatment. The phosphodiesterase inhibitor, rolipram, caused significant increases in shrew brainstem cAMP levels which were associated with its capacity to produce vomiting, while pretreatment with SQ22536, an inhibitor of adenylyl cyclase, prevented rolipram-induced emesis. The results demonstrate that accumulation of cAMP and subsequent activation of PKA in the brainstem may

  10. Equivalent Activities of Repulsive Axon Guidance Receptors

    PubMed Central

    Long, Hong; Yoshikawa, Shingo

    2016-01-01

    Receptors on the growth cone at the leading edge of elongating axons play critical guidance roles by recognizing cues via their extracellular domains and transducing signals via their intracellular domains, resulting in changes in direction of growth. An important concept to have emerged in the axon guidance field is the importance of repulsion as a major guidance mechanism. Given the number and variety of different repulsive receptors, it is generally thought that there are likely to be qualitative differences in the signals they transduce. However, the nature of these possible differences is unknown. By creating chimeras using the extracellular and intracellular domains of three different Drosophila repulsive receptors, Unc5, Roundabout (Robo), and Derailed (Drl) and expressing them in defined cells within the embryonic nervous system, we examined the responses elicited by their intracellular domains systematically. Surprisingly, we found no qualitative differences in growth cone response or axon growth, suggesting that, despite their highly diverged sequences, each intracellular domain elicits repulsion via a common pathway. In terms of the signaling pathway(s) used by the repulsive receptors, mutations in the guanine nucleotide exchange factor Trio strongly enhance the repulsive activity of all three intracellular domains, suggesting that repulsion by Unc5, Robo, and Drl, and perhaps repulsion in general, involves Trio activity. SIGNIFICANCE STATEMENT A prevailing concept that has emerged in the axon guidance field is the importance of repulsion as a guidance mechanism for steering axons to their appropriate targets. Given the number and variety of different repulsive receptors, it is generally thought that there are differences in the signals that they transduce. However, this has never been tested directly. We have used the advanced genetics of Drosophila to compare directly the outputs of different repulsive receptors. Surprisingly, we found no qualitative

  11. Antidepressant-like activity of 2-(4-phenylpiperazin-1-yl)-1, 8-naphthyridine-3-carboxylic acid (7a), a 5-HT₃ receptor antagonist in behaviour based rodent models: evidence for the involvement of serotonergic system.

    PubMed

    Gautam, Baldev Kumar; Jindal, Ankur; Dhar, Arghya Kusum; Mahesh, Radhakrishnan

    2013-08-01

    The present study was designed to investigate the putative antidepressant-like activity of 7a, a 5-HT₃ receptor antagonist, (although indirect evidence of 5-HT3 antagonism) with an optimal log P (3.35) and pA₂ value (7.6) greater than ondansetron (pA₂--6.6) using behavioural tests battery of depression. Acute treatment of 7a (0.5-2 mg/kg, i.p.) in mice produced antidepressant-like effects in forced swim test (FST) and tail suspension test (TST) without affecting the baseline locomotion in actophotometer test in mice. Moreover, the combination of a sub-effective dose of 7a (0.25 mg/kg, i.p.) and fluoxetine (5 mg/kg, i.p.) produced an anti-immobility effect in mouse FST. Pretreatment of mice with p-chlorophenylalanine methyl ester (PCPA; 100 mg/kg, i.p., an inhibitor of serotonin (5-HT) synthesis, for 4 consecutive days) and 1-(m-Chlorophenyl)-biguanide (mCPBG, 10 mg/kg, i.p., a 5-HT₃ receptor agonist) prevented the anti-immobility effects of 7a (2 mg/kg, i.p.) in the mouse FST. In addition, 7a (0.5-2 mg/kg, i.p.) treatment also potentiated the 5-hydroxytryptophan (5-HTP) and pargyline induced head twitch response in mice. Furthermore, sub-chronic treatment (14 days) with 7a (0.5-2 mg/kg, i.p.) and paroxetine (10 mg/kg, i.p.) significantly attenuated the behavioural anomalies induced by bilateral olfactory bulbectomy in rats in a modified open field paradigm. These results suggest that the antidepressant-like action of 7a may be mediated by an interaction with the serotonergic system and this molecule should be further investigated as an alternative therapeutic approach for the treatment of depression.

  12. Endogenous GABAA receptor activity suppresses glioma growth.

    PubMed

    Blanchart, A; Fernando, R; Häring, M; Assaife-Lopes, N; Romanov, R A; Andäng, M; Harkany, T; Ernfors, P

    2017-02-09

    Although genome alterations driving glioma by fueling cell malignancy have largely been resolved, less is known of the impact of tumor environment on disease progression. Here, we demonstrate functional GABAA receptor-activated currents in human glioblastoma cells and show the existence of a continuous GABA signaling within the tumor cell mass that significantly affects tumor growth and survival expectancy in mouse models. Endogenous GABA released by tumor cells, attenuates proliferation of the glioma cells with enriched expression of stem/progenitor markers and with competence to seed growth of new tumors. Our results suggest that GABA levels rapidly increase in tumors impeding further growth. Thus, shunting chloride ions by a maintained local GABAA receptor activity within glioma cells has a significant impact on tumor development by attenuating proliferation, reducing tumor growth and prolonging survival, a mechanism that may have important impact on therapy resistance and recurrence following tumor resection.

  13. Evidence that the anorexia induced by lipopolysaccharide is mediated by the 5-HT2C receptor.

    PubMed

    von Meyenburg, Claudia; Langhans, Wolfgang; Hrupka, Brian J

    2003-01-01

    Rats consistently reduce their food intake following injections of bacterial lipopolysaccharides (LPS). Because inhibition of serotonergic (5-HT) activity by 8-OH-DPAT (5-HT(1A) activation) attenuates LPS-induced anorexia, we conducted a series of studies to examine whether other 5-HT-receptors are involved in the mediation of peripheral LPS-induced anorexia. In all experiments, rats were injected with LPS (100 microg/kg body weight [BW] ip) at lights out (hour 0). Antagonists were administered peripherally at hour 4, shortly after the onset of anorexia, which presumably follows the enhanced cytokine production after LPS. Food intake was then recorded during the subsequent 2 h or longer. 5-HT receptor antagonists cyanopindolol and SB 224289 (5-HT(1B)), ketanserin (5-HT(2A)), RS-102221 (5-HT(2C)), and metoclopramide (5-HT(3)) failed to attenuate LPS-induced anorexia. In contrast, both ritanserin (5-HT(2A/C)-receptor antagonist) (0.5 mg/kg BW) and SB 242084 (5-HT(2C)) (0.3 mg/kg BW) attenuated LPS-induced anorexia at doses that did not alter food intake in non-LPS-treated rats (all P<.01). Our results suggest that at least part of the anorexia following peripheral LPS administration is mediated through an enhanced 5-HT-ergic activity and the 5-HT(2C) receptor.

  14. Differential classification of vascular smooth muscle and endothelial cell 5-HT receptors by use of tryptamine analogues.

    PubMed Central

    Leff, P.; Martin, G. R.; Morse, J. M.

    1987-01-01

    In ring preparations of the rabbit external jugular vein contracted with the thromboxane-mimetic U-46619, submicromolar concentrations of 5-hydroxytryptamine (5-HT) and chemically related analogues produced relaxations that were dependent on the integrity of the vascular endothelium. The receptor mediating endothelium-dependent relaxations was evidently similar to previously described endothelial 5-HT receptors since relaxation responses to alpha-methyl-5-HT were not blocked by atropine, (+/-)-propranolol, yohimbine, indomethacin, ketanserin or MDL-72222, but were non-competitively antagonized by methysergide, methiothepin and cyproheptadine. The activities of some tryptamine agonists and antagonists at the endothelial 5-HT receptor in rabbit jugular vein were compared with their activities at the smooth muscle 5-HT2-receptor in rabbit aortic rings. Differences in the tryptamines' affinities and relative efficacies showed that the endothelial 5-HT receptor was not of the 5-HT2-type. The high agonist potencies of 5-HT and 5-carboxamidotryptamine, the susceptibility to antagonism by both methiothepin and methysergide and the resistance to blockade by selective 5-HT2 and 5-HT3 ('M') receptor antagonists implies that the endothelial receptor belongs to the '5-HT1-like' class. However, the agonist potency order 5-HT = alpha-methyl-5-HT greater than 5-carboxamidotryptamine suggested that the receptor is not the same as the peripheral '5-HT1-like' receptors reported to mediate directly contraction of the dog saphenous vein or relaxation of vascular and non-vascular smooth muscles. At these receptors, the potency order is 5-carboxamidotryptamine greater than 5-HT greater than alpha-methyl-5-HT. These results constitute preliminary evidence that peripheral '5-HT1-like' receptors, like central 5-HT1 recognition sites, are a heterogeneous population. Further comparative studies with a wider range of receptor probes are necessary to establish whether or not these receptors

  15. CERAPP: Collaborative Estrogen Receptor Activity Prediction Project

    PubMed Central

    Mansouri, Kamel; Abdelaziz, Ahmed; Rybacka, Aleksandra; Roncaglioni, Alessandra; Tropsha, Alexander; Varnek, Alexandre; Zakharov, Alexey; Worth, Andrew; Richard, Ann M.; Grulke, Christopher M.; Trisciuzzi, Daniela; Fourches, Denis; Horvath, Dragos; Benfenati, Emilio; Muratov, Eugene; Wedebye, Eva Bay; Grisoni, Francesca; Mangiatordi, Giuseppe F.; Incisivo, Giuseppina M.; Hong, Huixiao; Ng, Hui W.; Tetko, Igor V.; Balabin, Ilya; Kancherla, Jayaram; Shen, Jie; Burton, Julien; Nicklaus, Marc; Cassotti, Matteo; Nikolov, Nikolai G.; Nicolotti, Orazio; Andersson, Patrik L.; Zang, Qingda; Politi, Regina; Beger, Richard D.; Todeschini, Roberto; Huang, Ruili; Farag, Sherif; Rosenberg, Sine A.; Slavov, Svetoslav; Hu, Xin; Judson, Richard S.

    2016-01-01

    Background: Humans are exposed to thousands of man-made chemicals in the environment. Some chemicals mimic natural endocrine hormones and, thus, have the potential to be endocrine disruptors. Most of these chemicals have never been tested for their ability to interact with the estrogen receptor (ER). Risk assessors need tools to prioritize chemicals for evaluation in costly in vivo tests, for instance, within the U.S. EPA Endocrine Disruptor Screening Program. Objectives: We describe a large-scale modeling project called CERAPP (Collaborative Estrogen Receptor Activity Prediction Project) and demonstrate the efficacy of using predictive computational models trained on high-throughput screening data to evaluate thousands of chemicals for ER-related activity and prioritize them for further testing. Methods: CERAPP combined multiple models developed in collaboration with 17 groups in the United States and Europe to predict ER activity of a common set of 32,464 chemical structures. Quantitative structure–activity relationship models and docking approaches were employed, mostly using a common training set of 1,677 chemical structures provided by the U.S. EPA, to build a total of 40 categorical and 8 continuous models for binding, agonist, and antagonist ER activity. All predictions were evaluated on a set of 7,522 chemicals curated from the literature. To overcome the limitations of single models, a consensus was built by weighting models on scores based on their evaluated accuracies. Results: Individual model scores ranged from 0.69 to 0.85, showing high prediction reliabilities. Out of the 32,464 chemicals, the consensus model predicted 4,001 chemicals (12.3%) as high priority actives and 6,742 potential actives (20.8%) to be considered for further testing. Conclusion: This project demonstrated the possibility to screen large libraries of chemicals using a consensus of different in silico approaches. This concept will be applied in future projects related to other

  16. How IGF-1 activates its receptor

    PubMed Central

    Kavran, Jennifer M; McCabe, Jacqueline M; Byrne, Patrick O; Connacher, Mary Katherine; Wang, Zhihong; Ramek, Alexander; Sarabipour, Sarvenaz; Shan, Yibing; Shaw, David E; Hristova, Kalina; Cole, Philip A; Leahy, Daniel J

    2014-01-01

    The type I insulin-like growth factor receptor (IGF1R) is involved in growth and survival of normal and neoplastic cells. A ligand-dependent conformational change is thought to regulate IGF1R activity, but the nature of this change is unclear. We point out an underappreciated dimer in the crystal structure of the related Insulin Receptor (IR) with Insulin bound that allows direct comparison with unliganded IR and suggests a mechanism by which ligand regulates IR/IGF1R activity. We test this mechanism in a series of biochemical and biophysical assays and find the IGF1R ectodomain maintains an autoinhibited state in which the TMs are held apart. Ligand binding releases this constraint, allowing TM association and unleashing an intrinsic propensity of the intracellular regions to autophosphorylate. Enzymatic studies of full-length and kinase-containing fragments show phosphorylated IGF1R is fully active independent of ligand and the extracellular-TM regions. The key step triggered by ligand binding is thus autophosphorylation. DOI: http://dx.doi.org/10.7554/eLife.03772.001 PMID:25255214

  17. Intrinsic Relative Activities of Opioid Agonists in Activating Gα proteins and Internalizing Receptor: Differences between Human and Mouse Receptors

    PubMed Central

    DiMattio, Kelly M.; Ehlert, Frederick J.; Liu-Chen, Lee-Yuan

    2015-01-01

    Several investigators recently identified biased opioid receptor (KOP receptor) agonists. However, no comprehensive study of the functional selectivity of available KOP receptor agonists at the human and mouse KOP receptors (hKOP receptor and mKOP receptor, respectively) has been published. Here we examined the ability of over 20 KOP receptor agonists to activate G proteins and to internalize the receptor. Clonal neuro-2a mouse neuroblastoma (N2a) cells stably transfected with the hKOP receptor or mKOP receptor were used. We employed agonist-induced [35S]GTPγS binding and KOP receptor internalization as measures of activation of G protein and β-arrestin pathways, respectively. The method of Ehlert and colleagues was used to quantify intrinsic relative activities at G protein activation (RAi−G) and receptor internalization (RAi−I) and the degree of functional selectivity between the two [Log RAi−G − Log RAi−I, RAi−G/RAi−I and bias factor]. The parameter, RAi, represents a relative estimate of agonist affinity for the active receptor state that elicits a given response. The endogenous ligand dynorphin A (1–17) was designated as the balanced ligand with a bias factor of 1. Interestingly, we found that there were species differences in functional selectivity. The most striking differences were for 12-epi-salvinorin A, U69,593, and ICI-199,441. 12-Epi-salvinorin A was highly internalization-biased at the mKOP receptor, but apparently G protein-biased at hKOP receptor. U69,593 was much more internalization-biased at mKOP receptor than hKOP receptor. ICI199,441 showed internalization-biased at the mKOP receptor and G protein-biased at the hKOP receptor. Possible mechanisms for the observed species differences are discussed. PMID:26057692

  18. Neuronal Nicotinic Acetylcholine Receptor Structure and Function and Response to Nicotine.

    PubMed

    Dani, John A

    2015-01-01

    Nicotinic acetylcholine receptors (nAChRs) belong to the "Cys-loop" superfamily of ligand-gated ion channels that includes GABAA, glycine, and serotonin (5-HT3) receptors. There are 16 homologous mammalian nAChR subunits encoded by a multigene family. These subunits combine to form many different nAChR subtypes with various expression patterns, diverse functional properties, and differing pharmacological characteristics. Because cholinergic innervation is pervasive and nAChR expression is extremely broad, practically every area of the brain is impinged upon by nicotinic mechanisms. This review briefly examines the structural and functional properties of the receptor/channel complex itself. The review also summarizes activation and desensitization of nAChRs by the low nicotine concentrations obtained from tobacco. Knowledge of the three-dimensional structure and the structural characteristics of channel gating has reached an advanced stage. Likewise, the basic functional properties of the channel also are reasonably well understood. It is these receptor/channel properties that underlie the participation of nAChRs in nearly every anatomical region of the mammalian brain.

  19. Activation of Neurotensin Receptor Type 1 Attenuates Locomotor Activity

    PubMed Central

    Vadnie, Chelsea A.; Hinton, David J.; Choi, Sun; Choi, YuBin; Ruby, Christina L.; Oliveros, Alfredo; Prieto, Miguel L.; Park, Jun Hyun; Choi, Doo-Sup

    2014-01-01

    Intracerebroventricular administration of neurotensin (NT) suppresses locomotor activity. However, the brain regions that mediate the locomotor depressant effect of NT and receptor subtype-specific mechanisms involved are unclear. Using a brain-penetrating, selective NT receptor type 1 (NTS1) agonist PD149163, we investigated the effect of systemic and brain region-specific NTS1 activation on locomotor activity. Systemic administration of PD149163 attenuated the locomotor activity of C57BL/6J mice both in a novel environment and in their homecage. However, mice developed tolerance to the hypolocomotor effect of PD149163 (0.1 mg/kg, i.p.). Since NTS1 is known to modulate dopaminergic signaling, we examined whether PD149163 blocks dopamine receptor-mediated hyperactivity. Pretreatment with PD149163 (0.1 or 0.05 mg/kg, i.p.) inhibited D2R agonist bromocriptine (8 mg/kg, i.p.)-mediated hyperactivity. D1R agonist SKF81297 (8 mg/kg, i.p.)-induced hyperlocomotion was only inhibited by 0.1 mg/kg of PD149163. Since the nucleus accumbens (NAc) and medial prefrontal cortex (mPFC) have been implicated in the behavioral effects of NT, we examined whether microinjection of PD149163 into these regions reduces locomotion. Microinjection of PD149163 (2 pmol) into the NAc, but not the mPFC suppressed locomotor activity. In summary, our results indicate that systemic and intra-NAc activation of NTS1 is sufficient to reduce locomotion and NTS1 activation inhibits D2R-mediated hyperactivity. Our study will be helpful to identify pharmacological factors and a possible therapeutic window for NTS1-targeted therapies for movement disorders. PMID:24929110

  20. Peroxisome Proliferator Activated Receptors and Lipoprotein Metabolism

    PubMed Central

    Kersten, Sander

    2008-01-01

    Plasma lipoproteins are responsible for carrying triglycerides and cholesterol in the blood and ensuring their delivery to target organs. Regulation of lipoprotein metabolism takes place at numerous levels including via changes in gene transcription. An important group of transcription factors that mediates the effect of dietary fatty acids and certain drugs on plasma lipoproteins are the peroxisome proliferator activated receptors (PPARs). Three PPAR isotypes can be distinguished, all of which have a major role in regulating lipoprotein metabolism. PPARα is the molecular target for the fibrate class of drugs. Activation of PPARα in mice and humans markedly reduces hepatic triglyceride production and promotes plasma triglyceride clearance, leading to a clinically significant reduction in plasma triglyceride levels. In addition, plasma high-density lipoprotein (HDL)-cholesterol levels are increased upon PPARα activation in humans. PPARγ is the molecular target for the thiazolidinedione class of drugs. Activation of PPARγ in mice and human is generally associated with a modest increase in plasma HDL-cholesterol and a decrease in plasma triglycerides. The latter effect is caused by an increase in lipoprotein lipase-dependent plasma triglyceride clearance. Analogous to PPARα, activation of PPARβ/δ leads to increased plasma HDL-cholesterol and decreased plasma triglyceride levels. In this paper, a fresh perspective on the relation between PPARs and lipoprotein metabolism is presented. The emphasis is on the physiological role of PPARs and the mechanisms underlying the effect of synthetic PPAR agonists on plasma lipoprotein levels. PMID:18288277

  1. Identification of Gene Markers for Activation of the Nuclear Receptor Pregnane X Receptor

    EPA Science Inventory

    Many environmentally-relevant chemicals and drugs activate the nuclear receptor pregnane X receptor (PXR). Activation of PXR in the mouse liver can lead to increases in liver weight in part through increased hepatocyte replication similar to chemicals that activate other nuclear ...

  2. Aryl biphenyl-3-ylmethylpiperazines as 5-HT7 receptor antagonists.

    PubMed

    Kim, Jeeyeon; Kim, Youngjae; Tae, Jinsung; Yeom, Miyoung; Moon, Bongjin; Huang, Xi-Ping; Roth, Bryan L; Lee, Kangho; Rhim, Hyewhon; Choo, Il Han; Chong, Youhoon; Keum, Gyochang; Nam, Ghilsoo; Choo, Hyunah

    2013-11-01

    The 5-HT7 receptor (5-HT7 R) is a promising therapeutic target for the treatment of depression and neuropathic pain. The 5-HT7 R antagonist SB-269970 exhibited antidepressant-like activity, whereas systemic administration of the 5-HT7 R agonist AS-19 significantly inhibited mechanical hypersensitivity and thermal hyperalgesia. In our efforts to discover selective 5-HT7 R antagonists or agonists, aryl biphenyl-3-ylmethylpiperazines were designed, synthesized, and biologically evaluated against the 5-HT7 R. Among the synthesized compounds, 1-([2'-methoxy-(1,1'-biphenyl)-3-yl]methyl)-4-(2-methoxyphenyl)piperazine (28) was the best binder to the 5-HT7 R (pKi =7.83), and its antagonistic property was confirmed by functional assays. The selectivity profile of compound 28 was also recorded for the 5-HT7 R over other serotonin receptor subtypes, such as 5-HT1 R, 5-HT2 R, 5-HT3 R, and 5-HT6 R. In a molecular modeling study, the 2-methoxyphenyl moiety attached to the piperazine ring of compound 28 was proposed to be essential for the antagonistic function.

  3. Model for growth hormone receptor activation based on subunit rotation within a receptor dimer

    SciTech Connect

    Brown, Richard J.; Adams, Julian J.; Pelekanos, Rebecca A.; Wan, Yu; McKinstry, William J.; Palethorpe, Kathryn; Seeber, Ruth M.; Monks, Thea A.; Eidne, Karin A.; Parker, Michael W.; Waters, Michael J.

    2010-07-13

    Growth hormone is believed to activate the growth hormone receptor (GHR) by dimerizing two identical receptor subunits, leading to activation of JAK2 kinase associated with the cytoplasmic domain. However, we have reported previously that dimerization alone is insufficient to activate full-length GHR. By comparing the crystal structure of the liganded and unliganded human GHR extracellular domain, we show here that there is no substantial change in its conformation on ligand binding. However, the receptor can be activated by rotation without ligand by inserting a defined number of alanine residues within the transmembrane domain. Fluorescence resonance energy transfer (FRET), bioluminescence resonance energy transfer (BRET) and coimmunoprecipitation studies suggest that receptor subunits undergo specific transmembrane interactions independent of hormone binding. We propose an activation mechanism involving a relative rotation of subunits within a dimeric receptor as a result of asymmetric placement of the receptor-binding sites on the ligand.

  4. OXYTOCIN INDUCES SOCIAL COMMUNICATION BY ACTIVATING ARGININEVASOPRESSIN V1A RECEPTORS AND NOT OXYTOCIN RECEPTORS

    PubMed Central

    SONG, Zhimin; MCCANN, Katharine E.; MCNEILL, John K.; LARKIN, Tony E.; HUHMAN, Kim L.; ALBERS, H. Elliott

    2014-01-01

    Arginine-vasopressin (AVP) and oxytocin (OT) and their receptors are very similar in structure. As a result, at least some of the effects of these peptides may be the result of crosstalk between their canonical receptors. The present study investigated this hypothesis by determining whether the induction of flank marking, a form of social communication in Syrian hamsters, by OT is mediated by the OT receptor or the AVP V1a receptor. Intracerebroventricular (ICV) injections of OT or AVP induced flank marking in a dose-dependent manner although the effects of AVP were approximately 100 times greater than those of OT. Injections of highly selective V1a receptor agonists but not OT receptor agonists induced flank marking, and V1a receptor antagonists but not OT receptor antagonists significantly inhibited the ability of OT to induce flank marking. Lastly, injection of alpha-melanocyte-stimulating hormone (α-MSH), a peptide that stimulates OT but not AVP release, significantly increased odor-induced flank marking, and these effects were blocked by a V1a receptor antagonist. These data demonstrate that OT induces flank marking by activating AVP V1a and not OT receptors, suggesting that the V1a receptor should be considered to be an OT receptor as well as an AVP receptor. PMID:25173438

  5. RELAXIN ACTIVATES PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR GAMMA

    PubMed Central

    Singh, Sudhir; Bennett, Robert G

    2009-01-01

    SUMMARY Relaxin is a polypeptide hormone that triggers multiple signaling pathways through its receptor RXFP1. Many of relaxin’s functions, including vascular and antifibrotic effects, are similar to those induced by activation of PPARγ. In this study, we tested the hypothesis that relaxin signaling through RXFP1 would activate PPARγ activity. In cells overexpressing RXFP1 (HEK-RXFP1), relaxin increased transcriptional activity through a PPAR response element (PPRE) in a concentration-dependent manner. In cells lacking RXFP1, relaxin had no effect. Relaxin increased both the baseline activity and the response to the PPARγ agonists rosiglitazone and 15d-PGJ2, but not to agonists of PPARα or PPARδ. In HEK-RXFP1 cells infected with adenovirus expressing PPARγ, relaxin increased transcriptional activity through PPRE, and this effect was blocked with an adenovirus expressing a dominant-negative PPARγ. Knockdown of PPARγ using siRNA resulted in a decrease in the response to both relaxin and rosiglitazone. Both relaxin and rosiglitazone increased expression of the PPARγ target genes CD36 and LXRα in HEK-RXFP1 and in THP-1 cells naturally expressing RXFP1. Relaxin did not increase PPARγ mRNA or protein levels. Treatment of cells with GW9662, an inhibitor of PPARγ ligand binding, effectively blocked rosiglitazone-induced PPARγ activation, but had no effect on relaxin activation of PPARγ. These results suggest that relaxin activates PPARγ activity, and increases the overall response in the presence PPARγ agonists. This activation is dependent on the presence of RXFP1. Furthermore, relaxin activates PPARγ via a ligand-independent mechanism. These studies represent the first report that relaxin can activate the transcriptional activity of PPARγ. PMID:19712722

  6. Mineralocorticoid receptor activation in obesity hypertension.

    PubMed

    Nagase, Miki; Fujita, Toshiro

    2009-08-01

    Obesity hypertension and metabolic syndrome have become major public health concerns. Nowadays, aldosterone is recognized as an important mediator of cardiovascular and renal damage. In the kidney, aldosterone injures glomerular visceral epithelial cells (podocytes), the final filtration barrier to plasma macromolecules, leading to proteinuria and glomerulosclerosis. Mineralocorticoid receptor (MR) antagonists effectively ameliorate proteinuria in patients or in animal models of hypertension, diabetes mellitus and chronic kidney disease (CKD), as well as in patients who experience 'aldosterone breakthrough.' Recently, clinical and experimental studies have shown that plasma aldosterone concentration is associated with obesity hypertension and metabolic syndrome. We showed that spontaneously hypertensive rats (SHR)/cp, an experimental model of obesity hypertension and metabolic syndrome, are prone to glomerular podocyte injury, proteinuria and left ventricular diastolic dysfunction, especially when the animals are fed a high-salt diet. Inappropriate activation of the aldosterone/MR system underlies the renal and cardiac injuries. Adipocyte-derived aldosterone-releasing factors (ARFs), although still unidentified, may account for aldosterone excess and the resultant target organ complication in SHR/cp. On the other hand, recent studies have shown that MR activation triggers target organ disease even in normal or low aldosterone states. We identified a small GTP (guanosine triphosphate)-binding protein, Rac1, as a novel activator of MR, and showed that this ligand-independent MR activation by Rac1 contributes to the nephropathy of several CKD models. We expect that ARFs and Rac1 can be novel therapeutic targets for metabolic syndrome and CKD. Future large-scale clinical trials are awaited to prove the efficacy of MR blockade in patients with obesity hypertension and metabolic syndrome.

  7. Sigma-1 receptors modulate functional activity of rat splenocytes.

    PubMed

    Liu, Y; Whitlock, B B; Pultz, J A; Wolfe, S A

    1995-06-01

    Neuroleptics, opiates, and cocaine are commonly prescribed for or abused by humans. Although primarily used for their actions at other receptors in brain, these compounds also act at sigma receptors. We have previously identified sigma-1 receptors on human peripheral blood leukocytes and rat spleen, and in the present study we demonstrate a correlation between the pharmacology of these receptors and the ability of drugs to suppress concanavalin A-induced splenocyte proliferation. These results support the hypothesis that sigma-1 receptors regulate functional activities of immune cells, and suggest that sigma agonists may cause changes in immune competence in vivo.

  8. Sigma Receptors Suppress Multiple Aspects of Microglial Activation

    PubMed Central

    Hall Aaron, A.; Yelenis, Herrera; Ajmo Craig, T.; Javier, Cuevas; Pennypacker Keith, R.

    2009-01-01

    During brain injury, microglia become activated and migrate to areas of degenerating neurons. These microglia release pro-inflammatory cytokines and reactive oxygen species causing additional neuronal death. Microglia express high levels of sigma receptors, however, the function of these receptors in microglia and how they may affect the activation of these cells remain poorly understood. Using primary rat microglial cultures, it was found that sigma receptor activation suppresses the ability of microglia to rearrange their actin cytoskeleton, migrate, and release cytokines in response to the activators adenosine triphosphate (ATP), monocyte chemoattractant protein 1 (MCP-1), and lipopolysaccharide (LPS). Next, the role of sigma receptors in the regulation of calcium signaling during microglial activation was explored. Calcium fluorometry experiments in vitro show that stimulation of sigma receptors suppressed both transient and sustained intracellular calcium elevations associated with the microglial response to these activators. Further experiments showed that sigma receptors suppress microglial activation by interfering with increases in intracellular calcium. In addition, sigma receptor activation also prevented membrane ruffling in a calcium-independent manner, indicating that sigma receptors regulate the function of microglia via multiple mechanisms. PMID:19031439

  9. The Orphan Nuclear Receptor TR4 Is a Vitamin A-activated Nuclear Receptor

    SciTech Connect

    Zhou, X. Edward; Suino-Powell, Kelly M.; Xu, Yong; Chan, Cee-Wah; Tanabe, Osamu; Kruse, Schoen W.; Reynolds, Ross; Engel, James Douglas; Xu, H. Eric

    2015-11-30

    Testicular receptors 2 and 4 (TR2/4) constitute a subgroup of orphan nuclear receptors that play important roles in spermatogenesis, lipid and lipoprotein regulation, and the development of the central nervous system. Currently, little is known about the structural features and the ligand regulation of these receptors. Here we report the crystal structure of the ligand-free TR4 ligand binding domain, which reveals an autorepressed conformation. The ligand binding pocket of TR4 is filled by the C-terminal half of helix 10, and the cofactor binding site is occupied by the AF-2 helix, thus preventing ligand-independent activation of the receptor. However, TR4 exhibits constitutive transcriptional activity on multiple promoters, which can be further potentiated by nuclear receptor coactivators. Mutations designed to disrupt cofactor binding, dimerization, or ligand binding substantially reduce the transcriptional activity of this receptor. Importantly, both retinol and retinoic acid are able to promote TR4 to recruit coactivators and to activate a TR4-regulated reporter. These findings demonstrate that TR4 is a ligand-regulated nuclear receptor and suggest that retinoids might have a much wider regulatory role via activation of orphan receptors such as TR4.

  10. Quantifying agonist activity at G protein-coupled receptors.

    PubMed

    Ehlert, Frederick J; Suga, Hinako; Griffin, Michael T

    2011-12-26

    When an agonist activates a population of G protein-coupled receptors (GPCRs), it elicits a signaling pathway that culminates in the response of the cell or tissue. This process can be analyzed at the level of a single receptor, a population of receptors, or a downstream response. Here we describe how to analyze the downstream response to obtain an estimate of the agonist affinity constant for the active state of single receptors. Receptors behave as quantal switches that alternate between active and inactive states (Figure 1). The active state interacts with specific G proteins or other signaling partners. In the absence of ligands, the inactive state predominates. The binding of agonist increases the probability that the receptor will switch into the active state because its affinity constant for the active state (K(b)) is much greater than that for the inactive state (K(a)). The summation of the random outputs of all of the receptors in the population yields a constant level of receptor activation in time. The reciprocal of the concentration of agonist eliciting half-maximal receptor activation is equivalent to the observed affinity constant (K(obs)), and the fraction of agonist-receptor complexes in the active state is defined as efficacy (ε) (Figure 2). Methods for analyzing the downstream responses of GPCRs have been developed that enable the estimation of the K(obs) and relative efficacy of an agonist. In this report, we show how to modify this analysis to estimate the agonist K(b) value relative to that of another agonist. For assays that exhibit constitutive activity, we show how to estimate K(b) in absolute units of M(-1). Our method of analyzing agonist concentration-response curves consists of global nonlinear regression using the operational model. We describe a procedure using the software application, Prism (GraphPad Software, Inc., San Diego, CA). The analysis yields an estimate of the product of K(obs) and a parameter proportional to efficacy (

  11. Correlating Structural and Energetic Changes in Glycine Receptor Activation*

    PubMed Central

    Scott, Suzanne; Lynch, Joseph W.; Keramidas, Angelo

    2015-01-01

    Pentameric ligand-gated ion channels (pLGICs) mediate fast chemoelectrical transduction in the nervous system. The mechanism by which the energy of ligand binding leads to current-conducting receptors is poorly understood and may vary among family members. We addressed these questions by correlating the structural and energetic mechanisms by which a naturally occurring M1 domain mutation (α1Q−26′E) enhances receptor activation in homo- and heteromeric glycine receptors. We systematically altered the charge of spatially clustered residues at positions 19′ and 24′, in the M2 and M2-M3 linker domains, respectively, which are known to be critical to efficient receptor activation, on a background of α1Q−26′E. Changes in the durations of single receptor activations (clusters) and conductance were used to determine interaction coupling energies, which we correlated with conformational displacements as measured in pLGIC crystal structures. Presence of the α1Q−26′E enhanced cluster durations and reduced channel conductance in homo- and heteromeric receptors. Strong coupling between α1−26′ and α119′ across the subunit interface suggests an important role in receptor activation. A lack of coupling between α1−26′ and α124′ implies that 24′ mutations disrupt activation via other interactions. A similar lack of energetic coupling between α1−26′ and reciprocal mutations in the β subunit suggests that this subunit remains relatively static during receptor activation. However, the channel effects of α1Q−26′E on α1β receptors suggests at least one α1-α1 interface per pentamer. The coupling-energy change between α1−26′ and α119′ correlates with a local structural rearrangement essential for pLGIC activation, implying it comprises a key energetic pathway in activating glycine receptors and other pLGICs. PMID:25572390

  12. Tools and techniques to study ligand-receptor interactions and receptor activation by TNF superfamily members.

    PubMed

    Schneider, Pascal; Willen, Laure; Smulski, Cristian R

    2014-01-01

    Ligands and receptors of the TNF superfamily are therapeutically relevant targets in a wide range of human diseases. This chapter describes assays based on ELISA, immunoprecipitation, FACS, and reporter cell lines to monitor interactions of tagged receptors and ligands in both soluble and membrane-bound forms using unified detection techniques. A reporter cell assay that is sensitive to ligand oligomerization can identify ligands with high probability of being active on endogenous receptors. Several assays are also suitable to measure the activity of agonist or antagonist antibodies, or to detect interactions with proteoglycans. Finally, self-interaction of membrane-bound receptors can be evidenced using a FRET-based assay. This panel of methods provides a large degree of flexibility to address questions related to the specificity, activation, or inhibition of TNF-TNF receptor interactions in independent assay systems, but does not substitute for further tests in physiologically relevant conditions.

  13. Insect Repellents: Modulators of Mosquito Odorant Receptor Activity

    DTIC Science & Technology

    2010-08-01

    molecular pathways through allosteric regulation of various proteins including proteases [39,40], the cannabinoid receptor 1 (CB1) [41], the a7 nicotinic...41. Price MR, Baillie GL, Thomas A, Stevenson LA, Easson M, et al. (2005) Allosteric modulation of the cannabinoid CB1 receptor . Mol Pharmacol 68...Insect Repellents: Modulators of Mosquito Odorant Receptor Activity Jonathan D. Bohbot, Joseph C. Dickens* Invasive Insect Biocontrol and Behavior

  14. Activation of human peroxisome-activated receptor-gamma ...

    EPA Pesticide Factsheets

    Obesity in children has become an epidemic and recent research suggests a possible contribution from exposure to environmental chemicals. Several chemicals, such as phthalates, brominated flame retardants, and perfluorinated chemicals, are common in house dust on floors where children play and are suspected obesogens. Obesogens can act via a mechanism that involves activation of peroxisome proliferator-activated receptor-gamma (PPARy). A previous study found that dust collected from children’s homes binds to PPARy. Here, we investigated the ability of house dust to activate PPARy in a transiently transfected cell assay. Dust samples were collected in 2012 from carpeted and hardwood floors in children’s homes using thimbles fitted into a vacuum cleaner hose (“TEO” samples), or from homes in an adult cohort NIEHS study. Dust was extracted with 50:50 hexane:acetone, sonicated, centrifuged, and the organic layer collected. This was repeated 2X. The extracts were filtered to remove particulates, dried with purified nitrogen, and reconstituted in DMS0 at 200 ug/ul. COS-1 cells were transfected for 24 hrs with a human PPARy vector containing a luciferase reporter, and exposed for 24 hrs to negative controls water or DMSO (0.1%), positive controls Troglitazone (3 uM in water) or Rosiglitazone (100 nM in DMSO), or dust extracts serially diluted in DMEM at 50, 100, and 200 ug/ml in 0.1% DMSO. Cells were lysed and luciferase activity was measured. Data were log-tra

  15. P2 receptors activated by uracil nucleotides--an update.

    PubMed

    Brunschweiger, Andreas; Müller, Christa E

    2006-01-01

    Pyrimidine nucleotides, including UTP, UDP and UDP-glucose, are important signaling molecules which activate G protein-coupled membrane receptors (GPCRs) of the P2Y family. Four distinct pyrimidine nucleotide-sensitive P2Y receptor subtypes have been cloned, P2Y2, P2Y4, P2Y6 and P2Y14. P2Y2 and P2Y4 receptors are activated by UTP (the P2Y2, and the rat but not the human P2Y4 receptor are also activated by ATP), the P2Y6 receptor is activated by UDP, and the P2Y14 receptor by UDP-glucose. Furthermore, non-P2Y GPCRs, the cysteinylleukotriene receptors (CysLT1R and CysLT2R) have been described to be activated by UDP in addition to activation by cysteinylleukotrienes. While P2Y2, P2Y4, and P2Y6 receptor activation results in stimulation of phospholipase C, the P2Y14 receptor is coupled to inhibition of adenylate cyclase. Derivatives and analogs of the physiological nucleotides UTP, UDP and ATP have been synthesized and evaluated in order to obtain enzymatically stable, subtype-selective agonists. The P2Y2 receptor agonists diuridine tetraphosphate (diquafosol) and the uracil-cytosine dinucleotide denufosol are currently undergoing clinical trials for dry eye disease, retinal detachment disease, upper respiratory tract symptoms, and cystic fibrosis, respectively. The first antagonists for P2Y2 and P2Y6 receptors that appear to be selective versus other P2Y receptor subtypes have recently been described. Selective antagonists for P2Y4 and P2Y14 receptors are still lacking. Uracil nucleotide-sensitive P2Y receptor subtypes may constitute future targets for the treatment of certain cancer types, vascular diseases, inflammatory diseases, and immunomodulatory intervention. They have also been proposed to play a role in neurodegenerative diseases. This article is an updated version of "P2-Pyrimidinergic Receptors and Their Ligands" by C. E. Müller published in Curr. Pharm. Des. 2002, 8, 2353-2369.

  16. Serotonergic system and its role in epilepsy and neuropathic pain treatment: a review based on receptor ligands.

    PubMed

    Panczyk, Katarzyna; Golda, Sylwia; Waszkielewicz, Anna; Zelaszczyk, Dorota; Gunia-Krzyzak, Agnieszka; Marona, Henryk

    2015-01-01

    The serotonergic system is involved in pathomechanisms of both epilepsy and neuropathic pain. So far, participation in the epileptogenesis and maintenance of epilepsy was proved for 5-HT1A, 5-HT2C, 5-HT3, 5-HT4 and 5-HT7 receptors as well as 5-HTT serotonin transporter. Depending on the receptor type or its localization, its stimulation may increase or decrease neuronal excitability. According to the available data, neuropathic pain mechanisms involve 5-HT1A/1B/1D, 5-HT2A/2B/2C, 5-HT3, 5-HT4, 5-HT6, 5-HT7 receptors and 5-HTT serotonin transporter. Changes in their expression modulate pain mainly by affecting the transmission through serotonergic descending pathways. Several compounds, whose mechanisms of action base on influence on the serotonergic system, are already in use. These are 5-HT3 agonists (triptans) in case of migraine, tricyclic antidepressants or monoamine reuptake inhibitors in neuropathic pain treatment. In addition, selective and non-selective ligands are tested for their anticonvulsant or analgesic properties. Some ED50 values have been already obtained in such animal models as maximal electroshock (MES)-induced seizures (epilepsy), spinal nerve ligation (SNL), chronic constriction injury (CCI) or formalin (neuropathic pain). This review shows that in case of drug discovery within the serotonergic system one must take into account special significance of factors such as: the species, the type of model, the route of administration, and the dose range.

  17. [Regulation of G protein-coupled receptor kinase activity].

    PubMed

    Haga, T; Haga, K; Kameyama, K; Nakata, H

    1994-09-01

    Recent progress on the activation of G protein-coupled receptor kinases is reviewed. beta-Adrenergic receptor kinase (beta ARK) is activated by G protein beta gamma -subunits, which interact with the carboxyl terminal portion of beta ARK. Muscarinic receptor m2-subtypes are phosphorylated by beta ARK1 in the central part of the third intracellular loop (I3). Phosphorylation of I3-GST fusion protein by beta ARK1 is synergistically stimulated by the beta gamma -subunits and mastoparan or a peptide corresponding to portions adjacent to the transmembrane segments of m2-receptors or by beta gamma -subunits and the agonist-bound I3-deleted m2 variant. These results indicate that agonist-bound receptors serve as both substrates and activators of beta ARK.

  18. Prothymosin Alpha Selectively Enhances Estrogen Receptor Transcriptional Activity by Interacting with a Repressor of Estrogen Receptor Activity

    PubMed Central

    Martini, Paolo G. V.; Delage-Mourroux, Regis; Kraichely, Dennis M.; Katzenellenbogen, Benita S.

    2000-01-01

    We find that prothymosin alpha (PTα) selectively enhances transcriptional activation by the estrogen receptor (ER) but not transcriptional activity of other nuclear hormone receptors. This selectivity for ER is explained by PTα interaction not with ER, but with a 37-kDa protein denoted REA, for repressor of estrogen receptor activity, a protein that we have previously shown binds to ER, blocking coactivator binding to ER. We isolated PTα, known to be a chromatin-remodeling protein associated with cell proliferation, using REA as bait in a yeast two-hybrid screen with a cDNA library from MCF-7 human breast cancer cells. PTα increases the magnitude of ERα transcriptional activity three- to fourfold. It shows lesser enhancement of ERβ transcriptional activity and has no influence on the transcriptional activity of other nuclear hormone receptors (progesterone receptor, glucocorticoid receptor, thyroid hormone receptor, or retinoic acid receptor) or on the basal activity of ERs. In contrast, the steroid receptor coactivator SRC-1 increases transcriptional activity of all of these receptors. Cotransfection of PTα or SRC-1 with increasing amounts of REA, as well as competitive glutathione S-transferase pulldown and mammalian two-hybrid studies, show that REA competes with PTα (or SRC-1) for regulation of ER transcriptional activity and suppresses the ER stimulation by PTα or SRC-1, indicating that REA can function as an anticoactivator in cells. Our data support a model in which PTα, which does not interact with ER, selectively enhances the transcriptional activity of the ER but not that of other nuclear receptors by recruiting the repressive REA protein away from ER, thereby allowing effective coactivation of ER with SRC-1 or other coregulators. The ability of PTα to directly interact in vitro and in vivo with REA, a selective coregulator of the ER, thereby enabling the interaction of ER with coactivators, appears to explain its ability to selectively enhance

  19. Plant cysteine proteases that evoke itch activate protease-activated receptors

    PubMed Central

    Reddy, V.B.; Lerner, E.A.

    2013-01-01

    Background Bromelain, ficin and papain are cysteine proteases from plants that produce itch upon injection into skin. Their mechanism of action has not been considered previously. Objectives To determine the mechanism by which these proteases function. Methods The ability of these proteases to activate protease-activated receptors was determined by ratiometric calcium imaging. Results We show here that bromelain, ficin and papain activate protease-activated receptors 2 and 4. Conclusions Bromelain, ficin and papain function as signalling molecules and activate protease-activated receptors. Activation of these receptors is the likely mechanism by which these proteases evoke itch. PMID:20491769

  20. Endomorphins fully activate a cloned human mu opioid receptor.

    PubMed

    Gong, J; Strong, J A; Zhang, S; Yue, X; DeHaven, R N; Daubert, J D; Cassel, J A; Yu, G; Mansson, E; Yu, L

    1998-11-13

    Endomorphins were recently identified as endogenous ligands with high selectivity for mu opioid receptors. We have characterized the ability of endomorphins to bind to and functionally activate the cloned human mu opioid receptor. Both endomorphin-1 and endomorphin-2 exhibited binding selectivity for the mu opioid receptor over the delta and kappa opioid receptors. Both agonists inhibited forskolin-stimulated increase of cAMP in a dose-dependent fashion. When the mu opioid receptor was coexpressed in Xenopus oocytes with G protein-activated K+ channels, application of either endomorphin activated an inward K+ current. This activation was dose-dependent and blocked by naloxone. Both endomorphins acted as full agonists with efficacy similar to that of [D-Ala2,N-Me-Phe4,Gly-ol5]enkephalin (DAMGO). These data indicate that endomorphins act as full agonists at the human mu opioid receptor, capable of stimulating the receptor to inhibit the cAMP/adenylyl cyclase pathway and activate G-protein-activated inwardly rectifying potassium (GIRK) channels.

  1. Human Receptor Activation by Aroclor 1260, a Polychlorinated Biphenyl Mixture

    PubMed Central

    Wahlang, Banrida; Falkner, K. Cameron; Clair, Heather B.; Al-Eryani, Laila; Prough, Russell A.; States, J. Christopher; Coslo, Denise M.; Omiecinski, Curtis J.; Cave, Matthew C.

    2014-01-01

    Polychlorinated biphenyls (PCBs) are persistent environmental toxicants, present in 100% of U.S. adults and dose-dependently associated with obesity and non-alcoholic fatty liver disease (NAFLD). PCBs are predicted to interact with receptors previously implicated in xenobiotic/energy metabolism and NAFLD. These receptors include the aryl hydrocarbon receptor (AhR), pregnane xenobiotic receptor (PXR), constitutive androstane receptor (CAR), peroxisome proliferator-activated receptors (PPARs), liver-X-receptor (LXRα), and farnesoid-X-receptor (FXR). This study evaluates Aroclor 1260, a PCB mixture with congener composition mimicking that of human adipose tissue, and selected congeners, as potential ligands for these receptors utilizing human hepatoma-derived (HepG2) and primate-derived (COS-1) cell lines, and primary human hepatocytes. Aroclor 1260 (20 μg/ml) activated AhR, and PCB 126, a minor component, was a potent inducer. Aroclor 1260 activated PXR in a simple concentration-dependent manner at concentrations ≥10 μg/ml. Among the congeners tested, PCBs 138, 149, 151, 174, 183, 187, and 196 activated PXR. Aroclor 1260 activated CAR2 and CAR3 variants at lower concentrations and antagonize CAR2 activation by the CAR agonist, CITCO, at higher concentrations (≥20 μg/ml). Additionally, Aroclor 1260 induced CYP2B6 in primary hepatocytes. At subtoxic doses, Aroclor 1260 did not activate LXR or FXR and had no effect on LXR- or FXR-dependent induction by the agonists T0901317 or GW4064, respectively. Aroclor 1260 (20 μg/ml) suppressed PPARα activation by the agonist nafenopin, although none of the congeners tested demonstrated significant inhibition. The results suggest that Aroclor 1260 is a human AhR, PXR and CAR3 agonist, a mixed agonist/antagonist for CAR2, and an antagonist for human PPARα. PMID:24812009

  2. Activating Receptor Signals Drive Receptor Diversity in Developing Natural Killer Cells

    PubMed Central

    Freund, Jacquelyn; May, Rebecca M.; Li, Hongchuan; McCullen, Matthew; Zhang, Bin; Lenvik, Todd; Cichocki, Frank; Anderson, Stephen K.; Kambayashi, Taku

    2016-01-01

    It has recently been appreciated that NK cells exhibit many features reminiscent of adaptive immune cells. Considerable heterogeneity exists with respect to the ligand specificity of individual NK cells and as such, a subset of NK cells can respond, expand, and differentiate into memory-like cells in a ligand-specific manner. MHC I-binding inhibitory receptors, including those belonging to the Ly49 and KIR families, are expressed in a variegated manner, which creates ligand-specific diversity within the NK cell pool. However, how NK cells determine which inhibitory receptors to express on their cell surface during a narrow window of development is largely unknown. In this manuscript, we demonstrate that signals from activating receptors are critical for induction of Ly49 and KIR receptors during NK cell development; activating receptor-derived signals increased the probability of the Ly49 bidirectional Pro1 promoter to transcribe in the forward versus the reverse direction, leading to stable expression of Ly49 receptors in mature NK cells. Our data support a model where the balance of activating and inhibitory receptor signaling in NK cells selects for the induction of appropriate inhibitory receptors during development, which NK cells use to create a diverse pool of ligand-specific NK cells. PMID:27500644

  3. Characterization of peroxisome proliferator-activiated receptor alpha (PPARalpha)-independent effects of PPARalpha activators in the rodent liver: Di(2-ethylehexyl) phthalate activates the constitutive activated receptor

    EPA Science Inventory

    Peroxisome proliferator chemicals (PPC) are thought to mediate their effects in rodents on hepatocyte growth and liver cancer through the nuclear receptor peroxisome proliferator-activated receptor alpha (PPARalpha). Recent studies indicate that the plasticizer di-2-ethylhexyl ph...

  4. Activation of the orphan receptor tyrosine kinase ALK by zinc.

    PubMed

    Bennasroune, Aline; Mazot, Pierre; Boutterin, Marie-Claude; Vigny, Marc

    2010-08-06

    Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase essentially and transiently expressed during development of the central and peripheral nervous system. The nature of the cognate ligand of this receptor in Vertebrates is still a matter of debate. During synaptic transmission the release of ionic zinc found in vesicles of certain glutamatergic and gabaergic terminals may act as a neuromodulator by binding to pre- or post-synaptic receptors. Recently, zinc has been shown to activate the receptor tyrosine kinase, TrkB, independently of neurotrophins. This activation occurs via increasing the Src family kinase activity. In the present study, we investigated whether the ALK activity could be modulated by extracellular zinc. We first showed that zinc alone rapidly activates ALK. This activation is dependent of ALK tyrosine kinase activity and dimerization of the receptor but is independent of Src family kinase activity. In contrast, addition of sodium pyrithione, a zinc ionophore, led to a further activation of ALK. This stronger activation is dependent of Src family kinase but independent of ALK activity and dimerization. In conclusion, zinc could constitute an endogenous ligand of ALK in vertebrates.

  5. Protease-activated receptor-2 (PAR2) in cardiovascular system.

    PubMed

    Bucci, Mariarosaria; Roviezzo, Fiorentina; Cirino, Giuseppe

    2005-10-01

    Vascular system is constituted by a complex and articulate network, e.g. arteries, arterioles, venules and veins, that requires a high degree of coordination between different elemental cell types. Proteinase-activated receptors (PARs) constitute a recent described family of 7-transmembrane G protein-coupled receptors that are activated by proteolysis. In recent years several evidence have been accumulated for an involvement of this receptor in the response to endothelial injury in vitro and in vivo experimental settings suggesting a role for PAR2 in the pathophysiology of cardiovascular system. This review will deal with the role of PAR2 receptor in the cardiovascular system analyzing both in vivo and in vitro published data. In particular this review will deal with the role of this receptor in vascular reactivity, ischemia/reperfusion injury, coronary atherosclerotic lesions and angiogenesis.

  6. Structure and dynamics of a constitutively active neurotensin receptor

    PubMed Central

    Krumm, Brian E.; Lee, Sangbae; Bhattacharya, Supriyo; Botos, Istvan; White, Courtney F.; Du, Haijuan; Vaidehi, Nagarajan; Grisshammer, Reinhard

    2016-01-01

    Many G protein-coupled receptors show constitutive activity, resulting in the production of a second messenger in the absence of an agonist; and naturally occurring constitutively active mutations in receptors have been implicated in diseases. To gain insight into mechanistic aspects of constitutive activity, we report here the 3.3 Å crystal structure of a constitutively active, agonist-bound neurotensin receptor (NTSR1) and molecular dynamics simulations of agonist-occupied and ligand-free receptor. Comparison with the structure of a NTSR1 variant that has little constitutive activity reveals uncoupling of the ligand-binding domain from conserved connector residues, that effect conformational changes during GPCR activation. Furthermore, molecular dynamics simulations show strong contacts between connector residue side chains and increased flexibility at the intracellular receptor face as features that coincide with robust signalling in cells. The loss of correlation between the binding pocket and conserved connector residues, combined with altered receptor dynamics, possibly explains the reduced neurotensin efficacy in the constitutively active NTSR1 and a facilitated initial engagement with G protein in the absence of agonist. PMID:27924846

  7. Structure and dynamics of a constitutively active neurotensin receptor

    SciTech Connect

    Krumm, Brian E.; Lee, Sangbae; Bhattacharya, Supriyo; Botos, Istvan; White, Courtney F.; Du, Haijuan; Vaidehi, Nagarajan; Grisshammer, Reinhard

    2016-12-07

    Many G protein-coupled receptors show constitutive activity, resulting in the production of a second messenger in the absence of an agonist; and naturally occurring constitutively active mutations in receptors have been implicated in diseases. To gain insight into mechanistic aspects of constitutive activity, we report here the 3.3 Å crystal structure of a constitutively active, agonist-bound neurotensin receptor (NTSR1) and molecular dynamics simulations of agonist-occupied and ligand-free receptor. Comparison with the structure of a NTSR1 variant that has little constitutive activity reveals uncoupling of the ligand-binding domain from conserved connector residues, that effect conformational changes during GPCR activation. Furthermore, molecular dynamics simulations show strong contacts between connector residue side chains and increased flexibility at the intracellular receptor face as features that coincide with robust signalling in cells. The loss of correlation between the binding pocket and conserved connector residues, combined with altered receptor dynamics, possibly explains the reduced neurotensin efficacy in the constitutively active NTSR1 and a facilitated initial engagement with G protein in the absence of agonist.

  8. Activation of 5-HT7 receptors increases neuronal platelet-derived growth factor β receptor expression.

    PubMed

    Vasefi, Maryam S; Kruk, Jeff S; Liu, Hui; Heikkila, John J; Beazely, Michael A

    2012-03-09

    Several antipsychotics have a high affinity for 5-HT7 receptors yet despite intense interest in the 5-HT7 receptor as a potential drug target to treat psychosis, the function and signaling properties of 5-HT7 receptors in neurons remain largely uncharacterized. In primary mouse hippocampal and cortical neurons, as well as in the SH-SY5Y cell line, incubation with 5-HT, 5-carboxamidotryptamine (5-CT), or 5-HT7 receptor-selective agonists increases the expression of platelet-derived growth factor (PDGF)β receptors. The increased PDGFβ receptor expression is cyclic AMP-dependent protein kinase (PKA)-dependent, suggesting that 5-HT7 receptors couple to Gα(s) in primary neurons. Interestingly, up-regulated PDGFβ receptors display an increased basal phosphorylation state at the phospholipase Cγ-activating tyrosine 1021. This novel linkage between the 5-HT7 receptor and the PDGF system may be an important GPCR-neurotrophic factor signaling pathway in neurons.

  9. Multiple switches in G protein-coupled receptor activation.

    PubMed

    Ahuja, Shivani; Smith, Steven O

    2009-09-01

    The activation mechanism of G protein-coupled receptors has presented a puzzle that finally may be close to solution. These receptors have a relatively simple architecture consisting of seven transmembrane helices that contain just a handful of highly conserved amino acids, yet they respond to light and a range of chemically diverse ligands. Recent NMR structural studies on the active metarhodopsin II intermediate of the visual receptor rhodopsin, along with the recent crystal structure of the apoprotein opsin, have revealed multiple structural elements or 'switches' that must be simultaneously triggered to achieve full activation. The confluence of several required structural changes is an example of "coincidence counting", which is often used by nature to regulate biological processes. In ligand-activated G protein-coupled receptors, the presence of multiple switches may provide an explanation for the differences between full, partial and inverse agonists.

  10. 5-HT7 receptor activation promotes an increase in TrkB receptor expression and phosphorylation

    PubMed Central

    Samarajeewa, Anshula; Goldemann, Lolita; Vasefi, Maryam S.; Ahmed, Nawaz; Gondora, Nyasha; Khanderia, Chandni; Mielke, John G.; Beazely, Michael A.

    2014-01-01

    The serotonin (5-HT) type 7 receptor is expressed throughout the CNS including the cortex and hippocampus. We have previously demonstrated that the application of 5-HT7 receptor agonists to primary hippocampal neurons and SH-SY5Y cells increases platelet-derived growth factor (PDGF) receptor expression and promotes neuroprotection against N-methyl-D-aspartate-(NMDA)-induced toxicity. The tropomyosin-related kinase B (TrkB) receptor is one of the receptors for brain-derived neurotrophic factor (BDNF) and is associated with neurodevelopmental and neuroprotective effects. Application of LP 12 to primary cerebral cortical cultures, SH-SY5Y cells, as well as the retinal ganglion cell line, RGC-5, increased both the expression of full length TrkB as well as its basal phosphorylation state at tyrosine 816. The increase in TrkB expression and phosphorylation was observed as early as 30 min after 5-HT7 receptor activation. In addition to full-length TrkB, kinase domain-deficient forms may be expressed and act as dominant-negative proteins toward the full length receptor. We have identified distinct patterns of TrkB isoform expression across our cell lines and cortical cultures. Although TrkB receptor expression is regulated by cyclic AMP and Gαs-coupled GPCRs in several systems, we demonstrate that, depending on the model system, pathways downstream of both Gαs and Gα12 are involved in the regulation of TrkB expression by 5-HT7 receptors. Given the number of psychiatric and degenerative diseases associated with TrkB/BDNF deficiency and the current interest in developing 5-HT7 receptor ligands as pharmaceuticals, identifying signaling relationships between these two receptors will aid in our understanding of the potential therapeutic effects of 5-HT7 receptor ligands. PMID:25426041

  11. 5-HT7 receptor activation promotes an increase in TrkB receptor expression and phosphorylation.

    PubMed

    Samarajeewa, Anshula; Goldemann, Lolita; Vasefi, Maryam S; Ahmed, Nawaz; Gondora, Nyasha; Khanderia, Chandni; Mielke, John G; Beazely, Michael A

    2014-01-01

    The serotonin (5-HT) type 7 receptor is expressed throughout the CNS including the cortex and hippocampus. We have previously demonstrated that the application of 5-HT7 receptor agonists to primary hippocampal neurons and SH-SY5Y cells increases platelet-derived growth factor (PDGF) receptor expression and promotes neuroprotection against N-methyl-D-aspartate-(NMDA)-induced toxicity. The tropomyosin-related kinase B (TrkB) receptor is one of the receptors for brain-derived neurotrophic factor (BDNF) and is associated with neurodevelopmental and neuroprotective effects. Application of LP 12 to primary cerebral cortical cultures, SH-SY5Y cells, as well as the retinal ganglion cell line, RGC-5, increased both the expression of full length TrkB as well as its basal phosphorylation state at tyrosine 816. The increase in TrkB expression and phosphorylation was observed as early as 30 min after 5-HT7 receptor activation. In addition to full-length TrkB, kinase domain-deficient forms may be expressed and act as dominant-negative proteins toward the full length receptor. We have identified distinct patterns of TrkB isoform expression across our cell lines and cortical cultures. Although TrkB receptor expression is regulated by cyclic AMP and Gαs-coupled GPCRs in several systems, we demonstrate that, depending on the model system, pathways downstream of both Gαs and Gα12 are involved in the regulation of TrkB expression by 5-HT7 receptors. Given the number of psychiatric and degenerative diseases associated with TrkB/BDNF deficiency and the current interest in developing 5-HT7 receptor ligands as pharmaceuticals, identifying signaling relationships between these two receptors will aid in our understanding of the potential therapeutic effects of 5-HT7 receptor ligands.

  12. Activation of the p75 neurotrophin receptor through conformational rearrangement of disulphide-linked receptor dimers

    PubMed Central

    Vilar, Marçal; Charalampopoulos, Ioannis; Kenchappa, Rajappa S.; Simi, Anastasia; Karaca, Esra; Reversi, Alessandra; Choi, Soyoung; Bothwell, Mark; Mingarro, Ismael; Friedman, Wilma J.; Schiavo, Giampietro; Bastiaens, Philippe I. H.; Verveer, Peter J.; Carter, Bruce D.; Ibáñez, Carlos F.

    2010-01-01

    SUMMARY Ligand-mediated dimerization has emerged as a universal mechanism of growth factor receptor activation. Recent structural studies have shown that neurotrophins interact with dimers of the p75 neurotrophin receptor (p75NTR), but the actual mechanism of receptor activation has remained elusive. Here we show that p75NTR forms disulphide-linked dimers independently of neurotrophin binding through the highly conserved Cys257 in its transmembrane domain. Mutation of Cys257 abolished neurotrophin-dependent receptor activity but did not affect downstream signaling by the p75NTR/NgR/Lingo-1 complex in response to MAG, indicating the existence of distinct, ligand-specific activation mechanisms for p75NTR. FRET experiments revealed a close association of p75NTR intracellular domains that was transiently disrupted by conformational changes induced upon NGF binding. Although mutation of Cys257 did not alter the oligomeric state of p75NTR, the mutant receptor was no longer able to propagate conformational changes to the cytoplasmic domain upon ligand binding. We propose that neurotrophins activate p75NTR by a novel mechanism involving rearrangement of disulphide-linked receptor subunits. PMID:19376068

  13. Mincle suppresses Toll-like receptor 4 activation.

    PubMed

    Greco, Stephanie H; Mahmood, Syed Kashif; Vahle, Anne-Kristin; Ochi, Atsuo; Batel, Jennifer; Deutsch, Michael; Barilla, Rocky; Seifert, Lena; Pachter, H Leon; Daley, Donnele; Torres-Hernandez, Alejandro; Hundeyin, Mautin; Mani, Vishnu R; Miller, George

    2016-07-01

    Regulation of Toll-like receptor responses is critical for limiting tissue injury and autoimmunity in both sepsis and sterile inflammation. We found that Mincle, a C-type lectin receptor, regulates proinflammatory Toll-like receptor 4 signaling. Specifically, Mincle ligation diminishes Toll-like receptor 4-mediated inflammation, whereas Mincle deletion or knockdown results in marked hyperresponsiveness to lipopolysaccharide in vitro, as well as overwhelming lipopolysaccharide-mediated inflammation in vivo. Mechanistically, Mincle deletion does not up-regulate Toll-like receptor 4 expression or reduce interleukin 10 production after Toll-like receptor 4 ligation; however, Mincle deletion decreases production of the p38 mitogen-activated protein kinase-dependent inhibitory intermediate suppressor of cytokine signaling 1, A20, and ABIN3 and increases expression of the Toll-like receptor 4 coreceptor CD14. Blockade of CD14 mitigates the increased sensitivity of Mincle(-/-) leukocytes to Toll-like receptor 4 ligation. Collectively, we describe a major role for Mincle in suppressing Toll-like receptor 4 responses and implicate its importance in nonmycobacterial models of inflammation.

  14. Differential trafficking of AMPA receptors following activation of NMDA receptors and mGluRs.

    PubMed

    Sanderson, Thomas M; Collingridge, Graham L; Fitzjohn, Stephen M

    2011-07-27

    The removal of AMPA receptors from synapses is a major component of long-term depression (LTD). How this occurs, however, is still only partially understood. To investigate the trafficking of AMPA receptors in real-time we previously tagged the GluA2 subunit of AMPA receptors with ecliptic pHluorin and studied the effects of NMDA receptor activation. In the present study we have compared the effect of NMDA receptor and group I mGluR activation, using GluA2 tagged with super ecliptic pHluorin (SEP-GluA2) expressed in cultured hippocampal neurons. Surprisingly, agonists of the two receptors, which are both able to induce chemical forms of LTD, had clearly distinct effects on AMPA receptor trafficking. In agreement with our previous work we found that transient NMDA receptor activation results in an initial decrease in surface GluA2 from extrasynaptic sites followed by a delayed reduction in GluA2 from puncta (putative synapses). In contrast, transient activation of group I mGluRs, using DHPG, led to a pronounced but more delayed decrease in GluA2 from the dendritic shafts. Surprisingly, there was no average change in the fluorescence of the puncta. Examination of fluorescence at individual puncta, however, indicated that alterations did take place, with some puncta showing an increase and others a decrease in fluorescence. The effects of DHPG were, like DHPG-induced LTD, prevented by treatment with a protein tyrosine phosphatase (PTP) inhibitor. The electrophysiological correlate of the effects of DHPG in the SEP-GluA2 infected cultures was a reduction in mEPSC frequency with no change in amplitude. The implications of these findings for the initial mechanisms of expression of both NMDA receptor- and mGluR-induced LTD are discussed.

  15. Platelet-activating factor: receptors and signal transduction.

    PubMed

    Chao, W; Olson, M S

    1993-06-15

    During the past two decades, studies describing the chemistry and biology of PAF have been extensive. This potent phosphoacylglycerol exhibits a wide variety of physiological and pathophysiological effects in various cells and tissues. PAF acts, through specific receptors and a variety of signal transduction systems, to elicit diverse biochemical responses. Several important future directions can be enumerated for the characterization of PAF receptors and their attendant signalling mechanisms. The recent cloning and sequence analysis of the gene for the PAF receptor will allow a number of important experimental approaches for characterizing the structure and analysing the function of the various domains of the receptor. Using molecular genetic and immunological technologies, questions relating to whether there is receptor heterogeneity, the precise mechanism(s) for the regulation of the PAF receptor, and the molecular details of the signalling mechanisms in which the PAF receptor is involved can be explored. Another area of major significance is the examination of the relationship between the signalling response(s) evoked by PAF binding to its receptor and signalling mechanisms activated by a myriad of other mediators, cytokines and growth factors. A very exciting recent development in which PAF receptors undoubtedly play a role is in the regulation of the function of various cellular adhesion molecules. Finally, there remain many incompletely characterized physiological and pathophysiological situations in which PAF and its receptor play a crucial signalling role. Our laboratory has been active in the elucidation of several tissue responses in which PAF exhibits major autocoid signalling responses, e.g. hepatic injury and inflammation, acute and chronic pancreatitis, and cerebral stimulation and/or trauma. As new experimental strategies are developed for characterizing the fine structure of the molecular mechanisms involved in tissue injury and inflammation, the

  16. Modulation of the hypoxic sensory response of the carotid body by 5-hydroxytryptamine: role of the 5-HT2 receptor.

    PubMed

    Jacono, F J; Peng, Y-J; Kumar, G K; Prabhakar, N R

    2005-02-15

    Previous studies have shown that glomus cells of the carotid body express 5-hydroxytryptamine (5-HT). The aim of this study was to elucidate the role of 5-HT on the hypoxic sensory response (HSR) of the carotid body. Sensory activity was recorded from multi-fiber (n=16) and single-fiber (n=8) preparations of ex vivo carotid bodies harvested from anesthetized, adult rats. 5-HT (3 microM) had no significant effect on the magnitude or on the onset of the HSR. However, 5-HT consistently prolonged the time necessary for the sensory activity to return to baseline following the termination of the hypoxic challenge. Ketanserin (40 microM), a 5-HT2 receptor antagonist completely prevented 5-HT-induced prolongation of the HSR, whereas had no effect on the control HSR (onset, magnitude, and time for decay without 5-HT). Carotid bodies expressed 5-HT, but hypoxia did not facilitate 5-HT release. These observations suggest that 5-HT is not critical for the HSR of the rat carotid body, but it modulates the dynamics of the HSR via its action on 5-HT2 receptors.

  17. Retinoic Acid-mediated Nuclear Receptor Activation and Hepatocyte Proliferation

    PubMed Central

    Bushue, Nathan; Wan, Yu-Jui Yvonne

    2016-01-01

    Due to their well-known differentiation and apoptosis-inducing abilities, retinoic acid (RA) and its analogs have strong anti-cancer efficacy in human cancers. However, in vivo RA is a liver mitogen. While speculation has persisted that RA-mediated signaling is likely involved in hepatocyte proliferation during liver regeneration, direct evidence is still required. Findings in support of this proposition include observations that a release of retinyl palmitate (the precursor of RA) occurs in liver stellate cells following liver injury. Nevertheless, the biological action of this released vitamin A is virtually unknown. More likely is that the released vitamin A is converted to RA, the biological form, and then bound to a specific receptor (retinoid x receptor; RXRα), which is most abundantly expressed in the liver. Considering the mitogenic effects of RA, the RA-activated RXRα would likely then influence hepatocyte proliferation and liver tissue repair. At present, the mechanism by which RA stimulates hepatocyte proliferation is largely unknown. This review summarizes the activation of nuclear receptors (peroxisome proliferator activated receptor-α, pregnane x receptor, constitutive androstane receptor, and farnesoid x receptor) in an RXRα dependent manner to induce hepatocyte proliferation, providing a link between RA and its proliferative role. PMID:27635169

  18. Anti-Hu antibodies activate enteric and sensory neurons

    PubMed Central

    Li, Qin; Michel, Klaus; Annahazi, Anita; Demir, Ihsan E.; Ceyhan, Güralp O.; Zeller, Florian; Komorowski, Lars; Stöcker, Winfried; Beyak, Michael J.; Grundy, David; Farrugia, Gianrico; De Giorgio, Roberto; Schemann, Michael

    2016-01-01

    IgG of type 1 anti-neuronal nuclear antibody (ANNA-1, anti-Hu) specificity is a serological marker of paraneoplastic neurological autoimmunity (including enteric/autonomic) usually related to small-cell lung carcinoma. We show here that IgG isolated from such sera and also affinity-purified anti-HuD label enteric neurons and cause an immediate spike discharge in enteric and visceral sensory neurons. Both labelling and activation of enteric neurons was prevented by preincubation with the HuD antigen. Activation of enteric neurons was inhibited by the nicotinic receptor antagonists hexamethonium and dihydro-β-erythroidine and reduced by the P2X antagonist pyridoxal phosphate-6-azo (benzene-2,4-disulfonic acid (PPADS) but not by the 5-HT3 antagonist tropisetron or the N-type Ca-channel blocker ω-Conotoxin GVIA. Ca++ imaging experiments confirmed activation of enteric neurons but not enteric glia. These findings demonstrate a direct excitatory action of ANNA-1, in particular anti-HuD, on visceral sensory and enteric neurons, which involves nicotinic and P2X receptors. The results provide evidence for a novel link between nerve activation and symptom generation in patients with antibody-mediated gut dysfunction. PMID:27905561

  19. Mycobacterium tuberculosis Activates Human Macrophage Peroxisome Proliferator-Activated Receptor γ Linking Mannose Receptor Recognition to Regulation of Immune Responses

    PubMed Central

    Rajaram, Murugesan V. S.; Brooks, Michelle N.; Morris, Jessica D.; Torrelles, Jordi B.; Azad, Abul K.; Schlesinger, Larry S.

    2010-01-01

    Mycobacterium tuberculosis enhances its survival in macrophages by suppressing immune responses in part through its complex cell wall structures. Peroxisome proliferator-activated receptor γ (PPARγ), a nuclear receptor superfamily member, is a transcriptional factor that regulates inflammation and has high expression in alternatively activated alveolar macrophages and macrophage-derived foam cells, both cell types relevant to tuberculosis pathogenesis. In this study, we show that virulent M. tuberculosis and its cell wall mannose-capped lipoarabinomannan induce PPARγ expression through a macrophage mannose receptor-dependent pathway. When activated, PPARγ promotes IL-8 and cyclooxygenase 2 expression, a process modulated by a PPARγ agonist or antagonist. Upstream, MAPK-p38 mediates cytosolic phospholipase A2 activation, which is required for PPARγ ligand production. The induced IL-8 response mediated by mannose-capped lipoarabinomannan and the mannose receptor is independent of TLR2 and NF-κB activation. In contrast, the attenuated Mycobacterium bovis bacillus Calmette-Guérin induces less PPARγ and preferentially uses the NF-κB–mediated pathway to induce IL-8 production. Finally, PPARγ knockdown in human macrophages enhances TNF production and controls the intracellular growth of M. tuberculosis. These data identify a new molecular pathway that links engagement of the mannose receptor, an important pattern recognition receptor for M. tuberculosis, with PPARγ activation, which regulates the macrophage inflammatory response, thereby playing a role in tuberculosis pathogenesis. PMID:20554962

  20. Fatty acids and retinoids control lipid metabolism through activation of peroxisome proliferator-activated receptor-retinoid X receptor heterodimers.

    PubMed Central

    Keller, H; Dreyer, C; Medin, J; Mahfoudi, A; Ozato, K; Wahli, W

    1993-01-01

    The nuclear hormone receptors called PPARs (peroxisome proliferator-activated receptors alpha, beta, and gamma) regulate the peroxisomal beta-oxidation of fatty acids by induction of the acyl-CoA oxidase gene that encodes the rate-limiting enzyme of the pathway. Gel retardation and cotransfection assays revealed that PPAR alpha heterodimerizes with retinoid X receptor beta (RXR beta; RXR is the receptor for 9-cis-retinoic acid) and that the two receptors cooperate for the activation of the acyl-CoA oxidase gene promoter. The strongest stimulation of this promoter was obtained when both receptors were exposed simultaneously to their cognate activators. Furthermore, we show that natural fatty acids, and especially polyunsaturated fatty acids, activate PPARs as potently as does the hypolipidemic drug Wy 14,643, the most effective activator known so far. Moreover, we discovered that the synthetic arachidonic acid analogue 5,8,11,14-eicosatetraynoic acid is 100 times more effective than Wy 14,643 in the activation of PPAR alpha. In conclusion, our data demonstrate a convergence of the PPAR and RXR signaling pathways in the regulation of the peroxisomal beta-oxidation of fatty acids by fatty acids and retinoids. Images Fig. 1 Fig. 2 PMID:8384714

  1. Heterodimeric interaction between retinoid X receptor alpha and orphan nuclear receptor OR1 reveals dimerization-induced activation as a novel mechanism of nuclear receptor activation.

    PubMed Central

    Wiebel, F F; Gustafsson, J A

    1997-01-01

    OR1 is a member of the steroid/thyroid hormone nuclear receptor superfamily which has been described to mediate transcriptional responses to retinoids and oxysterols. On a DR4 response element, an OR1 heterodimer with the nuclear receptor retinoid X receptor alpha (RXR alpha) has been described to convey transcriptional activation in both the absence and presence of the RXR ligand 9-cis retinoic acid, the mechanisms of which have remained unclear. Here, we dissect the effects of RXR alpha and OR1 ligand-binding domain interaction on transcriptional regulation and the role of the respective carboxy-terminal activation domains (AF-2s) in the absence and presence of the RXR ligand, employing chimeras of the nuclear receptors containing the heterologous GAL4 DNA-binding domain as well as natural receptors. The results show that the interaction of the RXR and OR1 ligand-binding domains unleashes a transcription activation potential that is mainly dependent on the AF-2 of OR1, indicating that interaction with RXR activates OR1. This defines dimerization-induced activation as a novel function of heterodimeric interaction and mechanism of receptor activation not previously described for nuclear receptors. Moreover, we present evidence that activation of OR1 occurs by a conformational change induced upon heterodimerization with RXR. PMID:9199332

  2. Protease-Activated Receptors and other G-Protein-Coupled Receptors: the Melanoma Connection.

    PubMed

    Rosero, Rebecca A; Villares, Gabriel J; Bar-Eli, Menashe

    2016-01-01

    The vast array of G-protein-coupled receptors (GPCRs) play crucial roles in both physiological and pathological processes, including vision, coagulation, inflammation, autophagy, and cell proliferation. GPCRs also affect processes that augment cell proliferation and metastases in many cancers including melanoma. Melanoma is the deadliest form of skin cancer, yet limited therapeutic modalities are available to patients with metastatic melanoma. Studies have found that both chemokine receptors and protease-activated receptors, both of which are GPCRs, are central to the metastatic melanoma phenotype and may serve as potential targets in novel therapies against melanoma and other cancers.

  3. Cardiovascular effects of selective agonists and antagonists of histamine H3 receptors in the anaesthetized rat.

    PubMed

    Coruzzi, G; Gambarelli, E; Bertaccini, G; Timmerman, H

    1995-06-01

    The cardiovascular responses to a series of selective histamine H3 receptor agonists, (R) alpha-methylhistamine, imetit and immepip and selective antagonists, thioperamide, clobenpropit and clophenpropit, were studied in anaesthetized rats. At 0.003-1 mumol/kg i.v. doses, H3 agonists failed to produce any significant change in the basal blood pressure and heart rate. Larger doses of (R) alpha-methylhistamine increased the blood pressure and heart rate and higher doses of imetit caused vasodepressor responses and reduced heart rate, whereas immepip proved virtually inactive. While (R) alpha-methylhistamine-induced effects were not blocked by histamine H1-, H2- and H3-receptor antagonists, they were however reduced by idazoxan and propranolol, which indicates that the mechanisms involved are adrenergic. The effects induced by imetit are not related to histamine H3 receptors but are mediated by indirect (via 5HT3 receptors) cholinergic mechanisms, since these effects were prevented by 1 mg/kg i.v. atropine and by 0.1 mg/kg i.v. ondansetron. Similarly, the H3 antagonists per se failed to change basal cardiovascular function up to 10 mumol/kg i.v. and only at 30 mumol/kg i.v. were marked decreases observed in the blood pressure and heart rate with a significant reduction in the effects of noradrenaline. These data indicate that in anaesthetized rats, histamine H3 receptor activation or blockade has no effect on basal cardiovascular function. The effects recorded after the administration of large doses of (R) alpha-methylhistamine and imetit are clearly unrelated to histamine H3 receptors and should be taken into account when using these compounds as H3 ligands for "in vivo" experiments.

  4. Endothelin-converting enzyme 2 differentially regulates opioid receptor activity

    PubMed Central

    Gupta, A; Fujita, W; Gomes, I; Bobeck, E; Devi, L A

    2015-01-01

    BACKGROUND AND PURPOSE Opioid receptor function is modulated by post-activation events such as receptor endocytosis, recycling and/or degradation. While it is generally understood that the peptide ligand gets co-endocytosed with the receptor, relatively few studies have investigated the role of the endocytosed peptide and peptide processing enzymes in regulating receptor function. In this study, we focused on endothelin-converting enzyme 2 (ECE2), a member of the neprilysin family of metallopeptidases that exhibits an acidic pH optimum, localizes to an intracellular compartment and selectively processes neuropeptides including opioid peptides in vitro, and examined its role in modulating μ receptor recycling and resensitization. EXPERIMENTAL APPROACH The effect of ECE2 inhibition on hydrolysis of the endocytosed peptide was examined using thin-layer chromatography and on μ opioid receptor trafficking using either elisa or microscopy. The effect of ECE2 inhibition on receptor signalling was measured using a cAMP assay and, in vivo, on antinociception induced by intrathecally administered opioids by the tail-flick assay. KEY RESULTS The highly selective ECE2 inhibitor, S136492, significantly impaired μ receptor recycling and signalling by only those ligands that are ECE2 substrates and this was seen both in heterologous cells and in cells endogenously co-expressing μ receptors with ECE2. We also found that ECE2 inhibition attenuated antinociception mediated only by opioid peptides that are ECE2 substrates. CONCLUSIONS AND IMPLICATIONS These results suggest that ECE2, by selectively processing endogenous opioid peptides in the endocytic compartment, plays a role in modulating opioid receptor activity. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2 PMID:24990314

  5. Activation and inhibition of erythropoietin receptor function: role of receptor dimerization.

    PubMed Central

    Watowich, S S; Hilton, D J; Lodish, H F

    1994-01-01

    Members of the cytokine receptor superfamily have structurally similar extracellular ligand-binding domains yet diverse cytoplasmic regions lacking any obvious catalytic domains. Many of these receptors form ligand-induced oligomers which are likely to participate in transmembrane signaling. A constitutively active (factor-independent) mutant of the erythropoietin receptor (EPO-R), R129C in the exoplasmic domain, forms disulfide-linked homodimers, suggesting that the wild-type EPO-R is activated by ligand-induced homodimerization. Here, we have taken two approaches to probe the role EPO-R dimerization plays in signal transduction. First, on the basis of the crystal structure of the ligand-bound, homodimeric growth hormone receptor (GH-R) and sequence alignment between the GH-R and EPO-R, we identified residues of the EPO-R which may be involved in intersubunit contacts in an EPO-R homodimer. Residue 129 of the EPO-R corresponds to a residue localized to the GH-R dimer interface region. Alanine or cysteine substitutions were introduced at four other residues of the EPO-R predicted to be in the dimer interface region. Substitution of residue E-132 or E-133 with cysteine renders the EPO-R constitutively active. Like the arginine-to-cysteine mutation at position 129 in the exoplasmic domain (R129C), E132C and E133C form disulfide-linked homodimers, suggesting that constitutive activity is due to covalent dimerization. In the second approach, we have coexpressed the wild-type EPO-R with inactive mutants of the receptor missing all or part of the cytosolic domain. These truncated receptors have a dominant inhibitory effect on the proliferative action of the wild-type receptor. Taken together, these results strengthen the hypothesis that an initial step in EPO- and EPO-R-mediated signal transduction is ligand-induced receptor dimerization. Images PMID:8196600

  6. Clinically used selective oestrogen receptor modulators increase LDL receptor activity in primary human lymphocytes

    PubMed Central

    Cerrato, F; Fernández-Suárez, M E; Alonso, R; Alonso, M; Vázquez, C; Pastor, O; Mata, P; Lasunción, M A; Gómez-Coronado, D

    2015-01-01

    Background and Purpose Treatment with selective oestrogen receptor modulators (SERMs) reduces low-density lipoprotein (LDL) cholesterol levels. We assessed the effect of tamoxifen, raloxifene and toremifene and their combinations with lovastatin on LDL receptor activity in lymphocytes from normolipidaemic and familial hypercholesterolaemic (FH) subjects, and human HepG2 hepatocytes and MOLT-4 lymphoblasts. Experimental Approach Lymphocytes were isolated from peripheral blood, treated with different compounds, and 1,1′-dioctadecyl-3,3,3,3′-tetramethylindocarbocyanine perchlorate (DiI)-labelled LDL uptake was analysed by flow cytometry. Key Results Tamoxifen, toremifene and raloxifene, in this order, stimulated DiI-LDL uptake by lymphocytes by inhibiting LDL-derived cholesterol trafficking and subsequent down-regulation of LDL receptor expression. Differently to what occurred in HepG2 and MOLT-4 cells, only tamoxifen consistently displayed a potentiating effect with lovastatin in primary lymphocytes. The SERM-mediated increase in LDL receptor activity was not altered by the anti-oestrogen ICI 182 780 nor was it reproduced by 17β-oestradiol. However, the tamoxifen-active metabolite endoxifen was equally effective as tamoxifen. The SERMs produced similar effects on LDL receptor activity in heterozygous FH lymphocytes as in normal lymphocytes, although none of them had a potentiating effect with lovastatin in heterozygous FH lymphocytes. The SERMs had no effect in homozygous FH lymphocytes. Conclusions and Implications Clinically used SERMs up-regulate LDL receptors in primary human lymphocytes. There is a mild enhancement between SERMs and lovastatin of lymphocyte LDLR activity, the potentiation being greater in HepG2 and MOLT-4 cells. The effect of SERMs is independent of oestrogen receptors but is preserved in the tamoxifen-active metabolite endoxifen. This mechanism may contribute to the cholesterol-lowering action of SERMs. PMID:25395200

  7. Monitoring leptin activity using the chicken leptin receptor.

    PubMed

    Hen, Gideon; Yosefi, Sera; Ronin, Ana; Einat, Paz; Rosenblum, Charles I; Denver, Robert J; Friedman-Einat, Miriam

    2008-05-01

    We report on the construction of a leptin bioassay based on the activation of chicken leptin receptor in cultured cells. A human embryonic kidney (HEK)-293 cell line, stably transfected with the full-length cDNA of chicken leptin receptor together with a STAT3-responsive reporter gene specifically responded to recombinant human and Xenopus leptins. The observed higher sensitivity of chicken leptin receptor to the former is in agreement with the degree of sequence similarity among these species (about 60 and 38% identical amino acids between humans and chickens, and between humans and Xenopus respectively). The specific activation of signal transduction through the chicken leptin receptor, shown here for the first time, suggests that the transition of Gln269 (implicated in the Gln-to-Pro Zucker fatty mutation in rats) to Glu in chickens does not impair its activity. Analysis of leptin-like activity in human serum samples of obese and lean subjects coincided well with leptin levels determined by RIA. Serum samples of pre- and post partum cows showed a tight correlation with the degree of adiposity. However, specific activation of the chicken leptin receptor in this assay was not observed with serum samples from broiler or layer chickens (representing fat and lean phenotypes respectively) or with those from turkey. Similar leptin receptor activation profiles were observed with cells transfected with human leptin receptor. Further work is needed to determine whether the lack of leptin-like activity in the chicken serum samples is due to a lack of leptin in this species or simply to a serum level of leptin that is below the detection threshold.

  8. Platelet-activating factor (PAF) receptor and genetically engineered PAF receptor mutant mice.

    PubMed

    Ishii, S; Shimizu, T

    2000-01-01

    Platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) is a biologically active phospholipid mediator. Although PAF was initially recognized for its potential to induce platelet aggregation and secretion, intense investigations have elucidated potent biological actions of PAF in a broad range of cell types and tissues, many of which also produce the molecule. PAF acts by binding to a unique G-protein-coupled seven transmembrane receptor. PAF receptor is linked to intracellular signal transduction pathways, including turnover of phosphatidylinositol, elevation in intracellular calcium concentration, and activation of kinases, resulting in versatile bioactions. On the basis of numerous pharmacological reports, PAF is thought to have many pathophysiological and physiological functions. Recently advanced molecular technics enable us not only to clone PAF receptor cDNAs and genes, but also generate PAF receptor mutant animals, i.e., PAF receptor-overexpressing mouse and PAF receptor-deficient mouse. These mutant mice gave us a novel and specific approach for identifying the pathophysiological and physiological functions of PAF. This review also describes the phenotypes of these mutant mice and discusses them by referring to previously reported pharmacological and genetical data.

  9. Immunohistochemical quantitation of oestrogen receptors and proliferative activity in oestrogen receptor positive breast cancer.

    PubMed Central

    Jensen, V; Ladekarl, M

    1995-01-01

    AIM--To evaluate the effect of the duration of formalin fixation and of tumour heterogeneity on quantitative estimates of oestrogen receptor content (oestrogen receptor index) and proliferative activity (MIB-1 index) in breast cancer. METHODS--Two monoclonal antibodies, MIB-1 and oestrogen receptor, were applied to formalin fixed, paraffin wax embedded tissue from 25 prospectively collected oestrogen receptor positive breast carcinomas, using a microwave antigen retrieval method. Tumour tissue was allocated systematically to different periods of fixation to ensure minimal intraspecimen variation. The percentages of MIB-1 positive and oestrogen receptor positive nuclei were estimated in fields of vision sampled systematically from the entire specimen and from the whole tumour area of one "representative" cross-section. RESULTS--No correlation was found between the oestrogen receptor and MIB-1 indices and the duration of formalin fixation. The estimated MIB-1 and oestrogen receptor indices in tissue sampled systematically from the entire tumour were closely correlated with estimates obtained in a "representative" section. The intra- and interobserver correlation of the MIB-1 index was good, although a slight systematical error at the second assessment of the intraobserver study was noted. CONCLUSION--Quantitative estimates of oestrogen receptor content and proliferative activity are not significantly influenced by the period of fixation in formalin, varying from less than four hours to more than 48 hours. The MIB-1 and the oestrogen receptor indices obtained in a "representative" section do not deviate significantly from average indices determined in tissue samples from the entire tumour. Finally, the estimation of MIB-1 index is reproducible, justifying its routine use. PMID:7629289

  10. Receptor-Selective Agonists Induce Emesis and Fos Expression in the Brain and Enteric Nervous System of the Least Shrew (Cryptotis parva)

    PubMed Central

    Ray, Andrew P.; Chebolu, Seetha; Darmani, Nissar A.

    2009-01-01

    Research on the mechanisms of emesis has implicated multiple neurotransmitters via both central (dorsal vagal complex) and peripheral (enteric neurons and enterochromaffin cells) anatomical substrates. Taking advantage of advances in receptor-specific agonists, and utilizing Fos expression as a functional activity marker, this study demonstrates a strong, but incomplete, overlap in anatomical substrates for a variety of emetogens. We used cisplatin and specific agonists to 5-HT3 serotonergic, D2/D3 dopaminergic, and NK1 tachykininergic receptors to induce vomiting in the least shrew (Cryptotis parva), and quantified the resulting Fos expression. The least shrew is a small mammal whose responses to emetic challenges are very similar to its human counterparts. In all cases, the enteric nervous system, nucleus of the solitary tract, and dorsal motor nucleus of the vagus demonstrated significantly increased Fos immunoreactivity (Fos-IR). However, Fos-IR induction was notably absent from the area postrema following the dopaminergic and NK1 receptor-specific agents. Two brain nuclei not usually discussed regarding emesis, the dorsal raphe nucleus and paraventricular thalamic nucleus, also demonstrated increased emesis-related Fos-IR. Taken together, these data suggest the dorsal vagal complex is part of a common pathway for a variety of distinct emetogens, but there are central emetic substrates, both medullary and diencephalic, that can be accessed without directly stimulating the area postrema. PMID:19699757

  11. Identification of COUP-TFII Orphan Nuclear Receptor as a Retinoic Acid–Activated Receptor

    PubMed Central

    Kruse, Schoen W; Suino-Powell, Kelly; Zhou, X. Edward; Kretschman, Jennifer E; Reynolds, Ross; Vonrhein, Clemens; Xu, Yong; Wang, Liliang; Tsai, Sophia Y; Tsai, Ming-Jer; Xu, H. Eric

    2008-01-01

    The chicken ovalbumin upstream promoter-transcription factors (COUP-TFI and II) make up the most conserved subfamily of nuclear receptors that play key roles in angiogenesis, neuronal development, organogenesis, cell fate determination, and metabolic homeostasis. Although the biological functions of COUP-TFs have been studied extensively, little is known of their structural features or aspects of ligand regulation. Here we report the ligand-free 1.48 Å crystal structure of the human COUP-TFII ligand-binding domain. The structure reveals an autorepressed conformation of the receptor, where helix α10 is bent into the ligand-binding pocket and the activation function-2 helix is folded into the cofactor binding site, thus preventing the recruitment of coactivators. In contrast, in multiple cell lines, COUP-TFII exhibits constitutive transcriptional activity, which can be further potentiated by nuclear receptor coactivators. Mutations designed to disrupt cofactor binding, dimerization, and ligand binding, substantially reduce the COUP-TFII transcriptional activity. Importantly, retinoid acids are able to promote COUP-TFII to recruit coactivators and activate a COUP-TF reporter construct. Although the concentration needed is higher than the physiological levels of retinoic acids, these findings demonstrate that COUP-TFII is a ligand-regulated nuclear receptor, in which ligands activate the receptor by releasing it from the autorepressed conformation. PMID:18798693

  12. Identification of COUP-TFII Orphan Nuclear Receptor as a Retinoic Acid-Activated Receptor

    SciTech Connect

    Kruse, Schoen W; Suino-Powell, Kelly; Zhou, X Edward; Kretschman, Jennifer E; Reynolds, Ross; Vonrhein, Clemens; Xu, Yong; Wang, Liliang; Tsai, Sophia Y; Tsai, Ming-Jer; Xu, H Eric

    2010-01-12

    The chicken ovalbumin upstream promoter-transcription factors (COUP-TFI and II) make up the most conserved subfamily of nuclear receptors that play key roles in angiogenesis, neuronal development, organogenesis, cell fate determination, and metabolic homeostasis. Although the biological functions of COUP-TFs have been studied extensively, little is known of their structural features or aspects of ligand regulation. Here we report the ligand-free 1.48 {angstrom} crystal structure of the human COUP-TFII ligand-binding domain. The structure reveals an autorepressed conformation of the receptor, where helix {alpha}10 is bent into the ligand-binding pocket and the activation function-2 helix is folded into the cofactor binding site, thus preventing the recruitment of coactivators. In contrast, in multiple cell lines, COUP-TFII exhibits constitutive transcriptional activity, which can be further potentiated by nuclear receptor coactivators. Mutations designed to disrupt cofactor binding, dimerization, and ligand binding, substantially reduce the COUP-TFII transcriptional activity. Importantly, retinoid acids are able to promote COUP-TFII to recruit coactivators and activate a COUP-TF reporter construct. Although the concentration needed is higher than the physiological levels of retinoic acids, these findings demonstrate that COUP-TFII is a ligand-regulated nuclear receptor, in which ligands activate the receptor by releasing it from the autorepressed conformation.

  13. Toll-like receptors 2 and 4 exert opposite effects on the contractile response induced by serotonin in mouse colon: role of serotonin receptors.

    PubMed

    Forcén, R; Latorre, E; Pardo, J; Alcalde, A I; Murillo, M D; Grasa, L

    2016-08-01

    What is the central question of this study? The action of Toll-like receptors (TLRs) 2 and 4 on the motor response to serotonin in mouse colon has not previously been reported. What is the main finding and its importance? Toll-like receptors 2 and 4 modulate the serotonin-induced contractile response in mouse colon by modifying the expression of serotonin (5-HT) receptors. Alterations in 5-HT2A and 5-HT2C receptors explain the increase of the response to serotonin in TLR2(-/-) mice. Alterations in 5-HT2C and 5-HT4 receptors explain the suppression of the response to serotonin in TLR4(-/-) mice. The microbiota, through Toll-like receptors (TLRs), may regulate gastrointestinal motility by activating neuroendocrine mechanisms. We evaluated the influence of TLR2 and TLR4 in spontaneous contractions and in the serotonin (5-HT)-induced motor response in mouse colon, and assessed the 5-HT receptors involved. Muscle contractility studies to evaluate the intestinal spontaneous motility and the response to 5-HT were performed in the colon from wild-type (WT), TLR2(-/-) , TLR4(-/-) and TLR2/4 double knockout (DKO) mice. The 5-HT receptor mRNA expression was determined by real-time PCR. The amplitude and frequency of the spontaneous contractions of the colon were smaller in TLR4(-/-) and TLR2/4 DKO mice with respect to WT mice. In WT, TLR2(-/-) and TLR2/4 DKO mice, 100 μm 5-HT evoked a contractile response. The contractile response induced by 5-HT was significantly higher in TLR2(-/-) than in WT mice. In TLR4(-/-) mice, 5-HT did not evoke any contractile response. The mRNA expression of 5-HT2A was increased in TLR2(-/-) and TLR2/4 DKO mice. The 5-HT2C and 5-HT4 mRNA expressions were increased in TLR4(-/-) and TLR2/4 DKO mice. The 5-HT2C mRNA expression was diminished in TLR2(-/-) mice. The 5-HT3 mRNA expression was increased in TLR2(-/-) , TLR4(-/-) and TLR2/4 DKO mice. The 5-HT7 mRNA expression was diminished in TLR2/4 DKO mice. In WT, TLR2(-/-) and TLR2/4 DKO mice, 5-HT2

  14. Polyphenols in alcoholic beverages activating constitutive androstane receptor CAR.

    PubMed

    Yao, Ruiqing; Yasuoka, Akihito; Kamei, Asuka; Kitagawa, Yoshinori; Rogi, Tomohiro; Taieishi, Norifumi; Tsuruoka, Nobuo; Kiso, Yoshionobu; Misaka, Takumi; Abe, Keiko

    2011-01-01

    The constitutive androstane receptor CAR is a xenosensing nuclear receptor that can be activated by natural polyphenols such as flavonoids and catechins. We examined alcoholic beverage phytochemicals for their ability to activate CAR. HepG2 cells were transfected with CAR expression vector and its reporter gene, and then treated with trans-resveratrol, ellagic acid, β-caryophyllene, myrcene, and xanthohumol. A luciferase assay revealed that ellagic acid and trans-resveratrol activated both human and mouse CAR. Since CAR regulates many genes involved in energy metabolism, the possibility exists that these polyphenols would reduce the risk of certain alcohol-induced metabolic disorders with the help of CAR.

  15. Activation of Group I Metabotropic Glutamate Receptors Potentiates Heteromeric Kainate Receptors

    PubMed Central

    Wetherington, Jonathon; Shaw, Renee; Serrano, Geidy; Swanger, Sharon; Dingledine, Raymond

    2013-01-01

    Kainate receptors (KARs), a family of ionotropic glutamate receptors, are widely expressed in the central nervous system and are critically involved in synaptic transmission. KAR activation is influenced by metabotropic glutamate receptor (mGlu) signaling, but the underlying mechanisms are not understood. We undertook studies to examine how mGlu modulation affects activation of KARs. Confocal immunohistochemistry of rat hippocampus and cultured rat cortex revealed colocalization of the high-affinity KAR subunits with group I mGlu receptors. In hippocampal and cortical cultures, the calcium signal caused by activation of native KARs was potentiated by activation of group I mGlu receptors. In Xenopus laevis oocytes, activation of group I mGlu receptors potentiated heteromeric but not homomeric KAR-mediated currents, with no change in agonist potency. The potentiation of heteromeric KARs by mGlu1 activation was attenuated by GDPβS, blocked by an inhibitor of phospholipase C or the calcium chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA), prolonged by the phosphatase inhibitor okadaic acid, but unaffected by the tyrosine kinase inhibitor lavendustin A. Protein kinase C (PKC) inhibition reduced the potentiation by mGlu1 of GluK2/GluK5, and conversely, direct activation of PKC by phorbol 12-myristate,13-acetate potentiated GluK2/GluK5. Using site-directed mutagenesis, we identified three serines (Ser833, Ser836, and Ser840) within the membrane proximal region of the GluK5 C-terminal domain that, in combination, are required for mGlu1-mediated potentiation of KARs. Together, these data suggest that phosphorylation of key residues in the C-terminal domain changes the overall charge of this domain, resulting in potentiated agonist responses. PMID:23066089

  16. Modular Activating Receptors in Innate and Adaptive Immunity.

    PubMed

    Berry, Richard; Call, Matthew E

    2017-03-14

    Triggering of cell-mediated immunity is largely dependent on the recognition of foreign or abnormal molecules by a myriad of cell surface-bound receptors. Many activating immune receptors do not possess any intrinsic signaling capacity but instead form noncovalent complexes with one or more dimeric signaling modules that communicate with a common set of kinases to initiate intracellular information-transfer pathways. This modular architecture, where the ligand binding and signaling functions are detached from one another, is a common theme that is widely employed throughout the innate and adaptive arms of immune systems. The evolutionary advantages of this highly adaptable platform for molecular recognition are visible in the variety of ligand-receptor interactions that can be linked to common signaling pathways, the diversification of receptor modules in response to pathogen challenges, and the amplification of cellular responses through incorporation of multiple signaling motifs. Here we provide an overview of the major classes of modular activating immune receptors and outline the current state of knowledge regarding how these receptors assemble, recognize their ligands, and ultimately trigger intracellular signal transduction pathways that activate immune cell effector functions.

  17. Pronociceptive response elicited by TRPA1 receptor activation in mice.

    PubMed

    Andrade, E L; Luiz, A P; Ferreira, J; Calixto, J B

    2008-03-18

    Ankyrin-repeat transient receptor potential 1 (TRPA1) is a member of the transient receptor potential (TRP) channel family and it is found in sensory neurons. In the present study, we found that TRPA1 receptor activation with allyl isothiocyanate or cinnamaldehyde caused dose-dependent spontaneous nociception when injected into the mouse hind paw. Very similar results were obtained when stimulating transient receptor potential vanilloid 1 (TRPV1) receptors with capsaicin. Pretreatment with the TRP receptor antagonist Ruthenium Red (1 nmol/paw) inhibited capsaicin-(0.1 nmol/paw) and allyl isothiocyanate-(1 nmol/paw) induced nociceptive responses. However, the nonselective TRPV1 receptor antagonist capsazepine (1 nmol/paw) and the selective TRPV1 receptor antagonist SB 366791 (1 nmol/paw) only attenuated capsaicin-induced nociception. In contrast, the intrathecal treatment with TRPA1 antisense oligodeoxynucleotide (2.5 nmol/site) and the degeneration of the subset of primary afferent fibers sensitive to capsaicin significantly reduced allyl isothiocyanate-induced nociception. Consequently to TRPA1 antisense oligodeoxynucleotide treatment there was a marked decrease of the expression of TRPA1 receptor in both sciatic nervous and spinal cord segments. Moreover, capsaicin and allyl isothiocyanate-induced nociception were not significantly changed by chemical sympathectomy produced by guanethidine. The previous degranulation of mast cells by compound 48/80 and treatment with antagonist H(1) receptor antagonist pyrilamine (400 microg/paw) both significantly inhibited the capsaicin- and allyl isothiocyanate-induced nociception. The selective NK(1) receptor antagonist N(2)-[(4R)-4-hydroxy-1-(1-methyl-1H-indol-3-yl) carbony-1-L-prolyl]-N-methyl-N-phenylmethyl-3-2-(2-naphtyl)-L-alaninamide (10 nmol/paw) reduced either capsaicin- or allyl isothiocyanate-induced nociception. Collectively, the present findings demonstrate that the TRPA1 agonist allyl isothiocyanate produces a

  18. Motogenic and morphogenic activity of epithelial receptor tyrosine kinases

    PubMed Central

    1996-01-01

    Receptor tyrosine kinases play essential roles in morphogenesis and differentiation of epithelia. Here we examined various tyrosine kinase receptors, which are preferentially expressed in epithelia (c-met, c- ros, c-neu, and the keratin growth factor [KGF] receptor), for their capacity to induce cell motility and branching morphogenesis of epithelial cells. We exchanged the ligand-binding domain of these receptors by the ectodomain of trkA and could thus control signaling by the new ligand, NGF. We demonstrate here that the tyrosine kinases of c- met, c-ros, c-neu, the KGF receptor, and trkA, but not the insulin receptor, induced scattering and increased motility of kidney epithelial cells in tissue culture. Mutational analysis suggests that SHC binding is essential for scattering and increased cell motility induced by trkA. The induction of motility in epithelial cells is thus an important feature of various receptor tyrosine kinases, which in vivo play a role in embryogenesis and metastasis. In contrast, only the c-met receptor promoted branching morphogenesis of kidney epithelial cells in three-dimensional matrices, which resemble the formation of tubular epithelia in development. Interestingly, the ability of c-met to induce morphogenesis could be transferred to trkA, when in a novel receptor hybrid COOH-terminal sequences of c-met (including Y14 to Y16) were fused to the trkA kinase domain. These data demonstrate that tubulogenesis of epithelia is a restricted activity of tyrosine kinases, as yet only demonstrated for the c-met receptor. We predict the existence of specific substrates that mediate this morphogenesis signal. PMID:8655582

  19. Glucocorticoid receptor activation and inactivation in cultured human lymphocytes.

    PubMed

    Wheeler, R H; Leach, K L; La Forest, A C; O'Toole, T E; Wagner, R; Pratt, W B

    1981-01-10

    Although glucocorticoids are not cytolytic for and do not inhibit the growth of the IM-9 line of cultured human lymphoblasts, these cells have a high steroid-binding capacity. We have used IM-9 cells in order to examine whether unoccupied glucocorticoid receptors are inactivated and activated in intact cells. when IM-9 cells are incubated in glucose-free medium in a nitrogen atmosphere, both their ability to bind triamcinolone acetonide and their ATP levels decline and, when glucose and oxygen are reintroduced, ATP levels and receptor activity return. The specific glucocorticoid-binding activity of cytosol prepared from cells exposed to various degrees of energy limitation is directly correlated with the ATP content. Receptor activation in intact cells is rapid and independent of protein synthesis. Cytosol prepared from inactivated cells cannot be activated by addition of ATP. The inactivation of glucocorticoid receptors that occurs when cytosol from normal IM-9 cells is incubated at 25 degrees C is inhibited by molybdate, vanadate, fluoride, ATP, and several other nucleotides. The experiments with intact human lymphoblasts suggest that assays of specific glucocorticoid-binding capacity do not necessarily reflect the cellular content of receptor protein.

  20. Novel benzopolycyclic amines with NMDA receptor antagonist activity.

    PubMed

    Valverde, Elena; Sureda, Francesc X; Vázquez, Santiago

    2014-05-01

    A new series of benzopolycyclic amines active as NMDA receptor antagonists were synthesized. Most of them exhibited increased activity compared with related analogues previously published. All the tested compounds were more potent than clinically approved amantadine and one of them displayed a lower IC50 value than memantine, an anti-Alzheimer's approved drug.

  1. Peroxisome proliferator-activated receptor alpha and the ketogenic diet.

    PubMed

    Cullingford, Tim

    2008-11-01

    Peroxisome proliferator-activated receptor alpha (PPARalpha) is a drug/fatty acid-activated trans cription factor involved in the starvation response, and is thus relevant to the ketogenic diet (KD). This article summarizes research indicating the role of PPARalpha in central and peripheral nervous system function with particular reference to downstream targets relevant to anticonvulsant action.

  2. Extended Synaptotagmin Interaction with the Fibroblast Growth Factor Receptor Depends on Receptor Conformation, Not Catalytic Activity.

    PubMed

    Tremblay, Michel G; Herdman, Chelsea; Guillou, François; Mishra, Prakash K; Baril, Joëlle; Bellenfant, Sabrina; Moss, Tom

    2015-06-26

    We previously demonstrated that ESyt2 interacts specifically with the activated FGF receptor and is required for a rapid phase of receptor internalization and for functional signaling via the ERK pathway in early Xenopus embryos. ESyt2 is one of the three-member family of Extended Synaptotagmins that were recently shown to be implicated in the formation of endoplasmic reticulum (ER)-plasma membrane (PM) junctions and in the Ca(2+) dependent regulation of these junctions. Here we show that ESyt2 is directed to the ER by its putative transmembrane domain, that the ESyts hetero- and homodimerize, and that ESyt2 homodimerization in vivo requires a TM adjacent sequence but not the SMP domain. ESyt2 and ESyt3, but not ESyt1, selectively interact in vivo with activated FGFR1. In the case of ESyt2, this interaction requires a short TM adjacent sequence and is independent of receptor autophosphorylation, but dependent on receptor conformation. The data show that ESyt2 recognizes a site in the upper kinase lobe of FGFR1 that is revealed by displacement of the kinase domain activation loop during receptor activation.

  3. Allosteric Activation of a G Protein-coupled Receptor with Cell-penetrating Receptor Mimetics*

    PubMed Central

    Zhang, Ping; Leger, Andrew J.; Baleja, James D.; Rana, Rajashree; Corlin, Tiffany; Nguyen, Nga; Koukos, Georgios; Bohm, Andrew; Covic, Lidija; Kuliopulos, Athan

    2015-01-01

    G protein-coupled receptors (GPCRs) are remarkably versatile signaling systems that are activated by a large number of different agonists on the outside of the cell. However, the inside surface of the receptors that couple to G proteins has not yet been effectively modulated for activity or treatment of diseases. Pepducins are cell-penetrating lipopeptides that have enabled chemical and physical access to the intracellular face of GPCRs. The structure of a third intracellular (i3) loop agonist, pepducin, based on protease-activated receptor-1 (PAR1) was solved by NMR and found to closely resemble the i3 loop structure predicted for the intact receptor in the on-state. Mechanistic studies revealed that the pepducin directly interacts with the intracellular H8 helix region of PAR1 and allosterically activates the receptor through the adjacent (D/N)PXXYYY motif through a dimer-like mechanism. The i3 pepducin enhances PAR1/Gα subunit interactions and induces a conformational change in fluorescently labeled PAR1 in a very similar manner to that induced by thrombin. As pepducins can potentially be made to target any GPCR, these data provide insight into the identification of allosteric modulators to this major drug target class. PMID:25934391

  4. Neural and Behavioral Correlates of PTSD and Alcohol Use

    DTIC Science & Technology

    2013-10-01

    Table 2). For example, activation of postsynaptic excitatory 5-HT2 or 5-HT3 receptors in the amygdala decreases social interaction and increases...anxiety-like behavior, whereas antagonism of 5-HT3 receptors in particular increases social interaction and decreases anxiety-like behaviors, suggesting...while activation of these receptors increases social interaction and decreases anxiety behavior (Table 2). Thus like the some findings from the

  5. In vitro screening of major neurotransmitter systems possibly involved in the mechanism of action of antibodies to S100 protein in released-active form

    PubMed Central

    Gorbunov, Evgeniy A; Ertuzun, Irina A; Kachaeva, Evgeniya V; Tarasov, Sergey A; Epstein, Oleg I

    2015-01-01

    Experimentally and clinically, it was shown that released-active form of antibodies to S100 protein (RAF of Abs to S100) exerts a wide range of pharmacological activities: anxiolytic, antiasthenic, antiaggressive, stress-protective, antihypoxic, antiischemic, neuroprotective, and nootropic. The purpose of this study was to determine the influence of RAF of Abs to S100 on major neurotransmitter systems (serotoninergic, GABAergic, dopaminergic, and on sigma receptors as well) which are possibly involved in its mechanism of pharmacological activity. Radioligand binding assays were used for assessment of the drug influence on ligand–receptor interaction. [35S]GTPγS binding assay, cyclic adenosine monophosphate HTRF™, cellular dielectric spectroscopy assays, and assays based on measurement of intracellular concentration of Ca2+ ions were used for assessment of agonist or antagonist properties of the drug toward receptors. RAF of Abs to S100 increased radioligand binding to 5-HT1F, 5-HT2B, 5-HT2Cedited, 5-HT3, and to D3 receptors by 142.0%, 131.9%, 149.3%, 120.7%, and 126.3%, respectively. Also, the drug significantly inhibited specific binding of radioligands to GABAB1A/B2 receptors by 25.8%, and to both native and recombinant human sigma1 receptors by 75.3% and 40.32%, respectively. In the functional assays, it was shown that the drug exerted antagonism at 5-HT1B, D3, and GABAB1A/B2 receptors inhibiting agonist-induced responses by 23.24%, 32.76%, and 30.2%, respectively. On the contrary, the drug exerted an agonist effect at 5-HT1A receptors enhancing receptor functional activity by 28.0%. The pharmacological profiling of RAF of Abs to S100 among 27 receptor provides evidence for drug-related modification of major neurotransmitter systems. PMID:26604768

  6. Regulation of Proteome Maintenance Gene Expression by Activators of Peroxisome Proliferator-Activated Receptor a (PPARa)

    EPA Science Inventory

    The nuclear receptor peroxisome proliferator-activated receptor alpha (PPARa) is activated by a large number of xenobiotic and hypolipidemic compounds called peroxisome proliferator chemicals (PPC). One agonist of PPARa (WY-14,643) regulates responses in the mouse liver to chemic...

  7. Androgen receptor serine 81 mediates Pin1 interaction and activity

    PubMed Central

    La Montagna, Raffaele; Caligiuri, Isabella; Maranta, Pasquale; Lucchetti, Chiara; Esposito, Luca; Paggi, Marco G.; Toffoli, Giuseppe; Rizzolio, Flavio; Giordano, Antonio

    2012-01-01

    Hormone-dependent tumors are characterized by deregulated activity of specific steroid receptors, allowing aberrant expression of many genes involved in cancer initiation, progression and metastasis. In prostate cancer, the androgen receptor (AR) protein has pivotal functions, and over the years it has been the target of different drugs. AR is a nuclear receptor whose activity is regulated by a phosphorylation mechanism controlled by hormone and growth factors. Following phosphorylation, AR interacts with many cofactors that closely control its function. Among such cofactors, Pin1 is a peptidyl-prolyl isomerase that is involved in the control of protein phosphorylation and has a prognostic value in prostate cancer. In the present study, we demonstrate that ARSer81 is involved in the interaction with Pin1, and that this interaction is important for the transcriptional activity of AR. Since Pin1 expression positively correlates with tumor grade, our results suggest that Pin1 can participate in this process by modulating AR function. PMID:22894932

  8. Interfering with mineralocorticoid receptor activation: the past, present, and future

    PubMed Central

    2014-01-01

    Aldosterone is a potent mineralocorticoid produced by the adrenal gland. Aldosterone binds to and activates the mineralocorticoid receptor (MR) in a plethora of tissues, but the cardiovascular actions of aldosterone are of primary interest clinically. Although MR antagonists were developed as antihypertensive agents, they are now considered to be important therapeutic options for patients with heart failure. Specifically, blocking only the MR has proven to be a difficult task because of its similarity to other steroid receptors, including the androgen and progesterone receptors. This lack of specificity caused the use of the first-generation mineralocorticoid receptor antagonists to be fraught with difficulty because of the side effects produced by drug administration. However, in recent years, several advances have been made that could potentially increase the clinical use of agents that inhibit the actions of aldosterone. These will be discussed here along with some examples of the beneficial effects of these new therapeutic agents. PMID:25165560

  9. Glycine Potentiates AMPA Receptor Function through Metabotropic Activation of GluN2A-Containing NMDA Receptors

    PubMed Central

    Li, Li-Jun; Hu, Rong; Lujan, Brendan; Chen, Juan; Zhang, Jian-Jian; Nakano, Yasuko; Cui, Tian-Yuan; Liao, Ming-Xia; Chen, Jin-Cao; Man, Heng-Ye; Feng, Hua; Wan, Qi

    2016-01-01

    NMDA receptors are Ca2+-permeable ion channels. The activation of NMDA receptors requires agonist glutamate and co-agonist glycine. Recent evidence indicates that NMDA receptor also has metabotropic function. Here we report that in cultured mouse hippocampal neurons, glycine increases AMPA receptor-mediated currents independent of the channel activity of NMDA receptors and the activation of glycine receptors. The potentiation of AMPA receptor function by glycine is antagonized by the inhibition of ERK1/2. In the hippocampal neurons and in the HEK293 cells transfected with different combinations of NMDA receptors, glycine preferentially acts on GluN2A-containing NMDA receptors (GluN2ARs), but not GluN2B-containing NMDA receptors (GluN2BRs), to enhance ERK1/2 phosphorylation independent of the channel activity of GluN2ARs. Without requiring the channel activity of GluN2ARs, glycine increases AMPA receptor-mediated currents through GluN2ARs. Thus, these results reveal a metabotropic function of GluN2ARs in mediating glycine-induced potentiation of AMPA receptor function via ERK1/2 activation. PMID:27807405

  10. Modulation of Opioid Receptor Ligand Affinity and Efficacy Using Active and Inactive State Receptor Models

    PubMed Central

    Anand, Jessica P.; Purington, Lauren C.; Pogozheva, Irina D.; Traynor, John R.; Mosberg, Henry I.

    2012-01-01

    Mu opioid receptor (MOR) agonists are widely used for the treatment of pain; however chronic use results in the development of tolerance and dependence. It has been demonstrated that co-administration of a MOR agonist with a delta opioid receptor (DOR) antagonist maintains the analgesia associated with MOR agonists, but with reduced negative side effects. Using our newly refined opioid receptor models for structure-based ligand design, we have synthesized several pentapeptides with tailored affinity and efficacy profiles. In particular, we have obtained pentapeptides 8, Tyr-c(S-S)[DCys-1Nal-Nle-Cys]NH2, and 12, Tyr-c(S-S)[DCys-1Nal-Nle-Cys]OH, which demonstrates high affinity and full agonist behavior at MOR, high affinity but very low efficacy for DOR, and minimal affinity for the kappa opioid receptor (KOR). Functional properties of these peptides as MOR agonists/DOR antagonists lacking undesired KOR activity make them promising candidates for future in vivo studies of MOR/DOR interactions. Subtle structural variation of 12, by substituting D-Cys5 for L-Cys5, generated analog 13 which maintains low nanomolar MOR and DOR affinity, but which displays no efficacy at either receptor. These results demonstrate the power and utility of accurate receptor models for structure-based ligand design, as well as the profound sensitivity of ligand function on its structure. PMID:22882801

  11. Extracellular loop 2 in the FSH receptor is crucial for ligand mediated receptor activation.

    PubMed

    Dupakuntla, Madhavi; Pathak, Bhakti; Roy, Binita Sur; Mahale, Smita D

    2012-10-15

    The present study aims to determine the role of the specific residues of the extracellular loops (ELs) of the FSH receptor (FSHR) in hormone binding and receptor activation. By substituting the sequences of each of the ELs of human FSHR with those of the luteinizing hormone/choriogonadotropin receptor (LH/CGR), we generated three mutant constructs where the three ELs were individually replaced. A fourth construct had all the three substituted ELs. The receptor expression and hormone binding ability of the mutants were comparable to that of the wild type. Hormone-induced signaling and internalization were lower in the EL2 substitution mutant (EL2M). In this mutant, the EL2 of FSHR was substituted with the corresponding loop of LH/CGR. Interestingly, homology modeling revealed a change in the orientation of EL2 in the mutant receptor. Thus, disruption of EL2 affected overall receptor function, suggesting the role of FSHR specific residues of the loop in ligand mediated signaling.

  12. Modulation of Receptor Phosphorylation Contributes to Activation of Peroxisome Proliferator Activated Receptor α by Dehydroepiandrosterone and Other Peroxisome Proliferators

    PubMed Central

    Tamasi, Viola; Miller, Kristy K. Michael; Ripp, Sharon L.; Vila, Ermin; Geoghagen, Thomas E.; Prough, Russell A.

    2008-01-01

    Dehydroepiandrosterone (DHEA), a C19 human adrenal steroid, activates peroxisome proliferator-activated receptor α (PPARα) in vivo but does not ligand-activate PPARα in transient transfection experiments. We demonstrate that DHEA regulates PPARα action by altering both the levels and phosphorylation status of the receptor. Human hepatoma cells (HepG2) were transiently transfected with the expression plasmid encoding PPARα and a plasmid containing two copies of fatty acyl coenzyme oxidase (FACO) peroxisome-proliferator activated receptor responsive element consensus oligonucleotide in a luciferase reporter gene. Nafenopin treatment increased reporter gene activity in this system, whereas DHEA treatment did not. Okadaic acid significantly decreased nafenopin-induced reporter activity in a concentration-dependent manner. Okadaic acid treatment of primary rat hepatocytes decreased both DHEA- and nafenopin-induced FACO activity in primary rat hepatocytes. DHEA induced both PPARα mRNA and protein levels, as well as PP2A message in primary rat hepatocytes. Western blot analysis showed that the serines at positions 12 and 21 were rapidly dephosphorylated upon treatment with DHEA and nafenopin. Results using specific protein phosphatase inhibitors suggested that protein phosphatase 2A (PP2A) is responsible for DHEA action, and protein phosphatase 1 might be involved in nafenopin induction. Mutation of serines at position 6, 12, and 21 to an uncharged alanine residue significantly increased transcriptional activity, whereas mutation to negative charged aspartate residues (mimicking receptor phosphorylation) decreased transcriptional activity. DHEA action involves induction of PPARα mRNA and protein levels as well as increased PPARα transcriptional activity through decreasing receptor phosphorylation at serines in the AF1 region. PMID:18079279

  13. Positive allosteric modulators of α7 nicotinic acetylcholine receptors affect neither the function of other ligand- and voltage-gated ion channels and acetylcholinesterase, nor β-amyloid content.

    PubMed

    Arias, Hugo R; Ravazzini, Federica; Targowska-Duda, Katarzyna M; Kaczor, Agnieszka A; Feuerbach, Dominik; Boffi, Juan C; Draczkowski, Piotr; Montag, Dirk; Brown, Brandon M; Elgoyhen, Ana Belén; Jozwiak, Krzysztof; Puia, Giulia

    2016-07-01

    The activity of positive allosteric modulators (PAMs) of α7 nicotinic acetylcholine receptors (AChRs), including 3-furan-2-yl-N-p-tolyl-acrylamide (PAM-2), 3-furan-2-yl-N-o-tolylacrylamide (PAM-3), and 3-furan-2-yl-N-phenylacrylamide (PAM-4), was tested on a variety of ligand- [i.e., human (h) α7, rat (r) α9α10, hα3-containing AChRs, mouse (m) 5-HT3AR, and several glutamate receptors (GluRs)] and voltage-gated (i.e., sodium and potassium) ion channels, as well as on acetylcholinesterase (AChE) and β-amyloid (Aβ) content. The functional results indicate that PAM-2 inhibits hα3-containing AChRs (IC50=26±6μM) with higher potency than that for NR1aNR2B and NR1aNR2A, two NMDA-sensitive GluRs. PAM-2 affects neither the activity of m5-HT3ARs, GluR5/KA2 (a kainate-sensitive GluR), nor AChE, and PAM-4 does not affect agonist-activated rα9α10 AChRs. Relevant clinical concentrations of PAM-2-4 do not inhibit Nav1.2 and Kv3.1 ion channels. These PAMs slightly enhance the activity of GluR1 and GluR2, two AMPA-sensitive GluRs. PAM-2 does not change the levels of Aβ42 in an Alzheimer's disease mouse model (i.e., 5XFAD). The molecular docking and dynamics results using the hα7 model suggest that the active sites for PAM-2 include the intrasubunit (i.e., PNU-120596 locus) and intersubunit sites. These results support our previous study showing that these PAMs are selective for the α7 AChR, and clarify that the procognitive/promnesic/antidepressant activity of PAM-2 is not mediated by other targets.

  14. Memory retrieval requires ongoing protein synthesis and NMDA receptor activity-mediated AMPA receptor trafficking.

    PubMed

    Lopez, Joëlle; Gamache, Karine; Schneider, Rilla; Nader, Karim

    2015-02-11

    Whereas consolidation and reconsolidation are considered dynamic processes requiring protein synthesis, memory retrieval has long been considered a passive readout of previously established plasticity. However, previous findings suggest that memory retrieval may be more dynamic than previously thought. This study therefore aimed at investigating the molecular mechanisms underlying memory retrieval in the rat. Infusion of protein synthesis inhibitors (rapamycin or anisomycin) in the amygdala 10 min before memory retrieval transiently impaired auditory fear memory expression, suggesting ongoing protein synthesis is required to enable memory retrieval. We then investigated the role of protein synthesis in NMDA receptor activity-mediated AMPA receptor trafficking. Coinfusion of an NMDA receptor antagonist (ifenprodil) or infusion of an AMPA receptor endocytosis inhibitor (GluA23Y) before rapamycin prevented this memory impairment. Furthermore, rapamycin transiently decreased GluA1 levels at the postsynaptic density (PSD), but did not affect extrasynaptic sites. This effect at the PSD was prevented by an infusion of GluA23Y before rapamycin. Together, these data show that ongoing protein synthesis is required before memory retrieval is engaged, and suggest that this protein synthesis may be involved in the NMDAR activity-mediated trafficking of AMPA receptors that takes place during memory retrieval.

  15. A bacterial tyrosine phosphatase inhibits plant pattern recognition receptor activation.

    PubMed

    Macho, Alberto P; Schwessinger, Benjamin; Ntoukakis, Vardis; Brutus, Alexandre; Segonzac, Cécile; Roy, Sonali; Kadota, Yasuhiro; Oh, Man-Ho; Sklenar, Jan; Derbyshire, Paul; Lozano-Durán, Rosa; Malinovsky, Frederikke Gro; Monaghan, Jacqueline; Menke, Frank L; Huber, Steven C; He, Sheng Yang; Zipfel, Cyril

    2014-03-28

    Innate immunity relies on the perception of pathogen-associated molecular patterns (PAMPs) by pattern-recognition receptors (PRRs) located on the host cell's surface. Many plant PRRs are kinases. Here, we report that the Arabidopsis receptor kinase EF-TU RECEPTOR (EFR), which perceives the elf18 peptide derived from bacterial elongation factor Tu, is activated upon ligand binding by phosphorylation on its tyrosine residues. Phosphorylation of a single tyrosine residue, Y836, is required for activation of EFR and downstream immunity to the phytopathogenic bacterium Pseudomonas syringae. A tyrosine phosphatase, HopAO1, secreted by P. syringae, reduces EFR phosphorylation and prevents subsequent immune responses. Thus, host and pathogen compete to take control of PRR tyrosine phosphorylation used to initiate antibacterial immunity.

  16. Immunomodulatory effects of endogenous and synthetic peptides activating opioid receptors.

    PubMed

    Pomorska, Dorota K; Gach, Katarzyna; Janecka, Anna

    2014-01-01

    The main role of endogenous opioid peptides is the modulation of pain. Opioid peptides exert their analgesic activity by binding to the opioid receptors distributed widely in the central nervous system (CNS). However, opioid receptors are also found on tissues and organs outside the CNS, including the cells of the immune system, indicating that opioids are capable of exerting additional effects in periphery. Morphine, which is a gold standard in the treatment of chronic pain, is well-known for its immunosuppressive effects. Much less is known about the immunomodulatory effects exerted by endogenous (enkephalins, endorphins, dynorphins and endomorphins) and synthetic peptides activating opioid receptors. In this review we tried to summarize opioid peptide-mediated modulation of immune cell functions which can be stimulatory as well as inhibitory.

  17. Structural basis for selective activation of ABA receptors

    SciTech Connect

    Peterson, Francis C.; Burgie, E. Sethe; Park, Sang-Youl; Jensen, Davin R.; Weiner, Joshua J.; Bingman, Craig A.; Chang, Chia-En A.; Cutler, Sean R.; Phillips, Jr., George N.; Volkman, Brian F.

    2010-11-01

    Changing environmental conditions and lessening fresh water supplies have sparked intense interest in understanding and manipulating abscisic acid (ABA) signaling, which controls adaptive responses to drought and other abiotic stressors. We recently discovered a selective ABA agonist, pyrabactin, and used it to discover its primary target PYR1, the founding member of the PYR/PYL family of soluble ABA receptors. To understand pyrabactin's selectivity, we have taken a combined structural, chemical and genetic approach. We show that subtle differences between receptor binding pockets control ligand orientation between productive and nonproductive modes. Nonproductive binding occurs without gate closure and prevents receptor activation. Observations in solution show that these orientations are in rapid equilibrium that can be shifted by mutations to control maximal agonist activity. Our results provide a robust framework for the design of new agonists and reveal a new mechanism for agonist selectivity.

  18. Lysophospholipid activation of G protein-coupled receptors.

    PubMed

    Mutoh, Tetsuji; Chun, Jerold

    2008-01-01

    One of the major lipid biology discoveries in last decade was the broad range of physiological activities of lysophospholipids that have been attributed to the actions of lysophospholipid receptors. The most well characterized lysophospholipids are lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P). Documented cellular effects of these lipid mediators include growth-factor-like effects on cells, such as proliferation, survival, migration, adhesion, and differentiation. The mechanisms for these actions are attributed to a growing family of 7-transmembrane, G protein-coupled receptors (GPCRs). Their pathophysiological actions include immune modulation, neuropathic pain modulation, platelet aggregation, wound healing, vasopressor activity, and angiogenesis. Here we provide a brief introduction to receptor-mediated lysophospholipid signaling and physiology, and then discuss potential therapeutic roles in human diseases.

  19. Protease-activated receptors and prostaglandins in inflammatory lung disease

    PubMed Central

    Peters, Terence; Henry, Peter J

    2009-01-01

    Protease-activated receptors (PARs) are a novel family of G protein-coupled receptors. Signalling through PARs typically involves the cleavage of an extracellular region of the receptor by endogenous or exogenous proteases, which reveals a tethered ligand sequence capable of auto-activating the receptor. A considerable body of evidence has emerged over the past 20 years supporting a prominent role for PARs in a variety of human physiological and pathophysiological processes, and thus substantial attention has been directed towards developing drug-like molecules that activate or block PARs via non-proteolytic pathways. PARs are widely expressed within the respiratory tract, and their activation appears to exert significant modulatory influences on the level of bronchomotor tone, as well as on the inflammatory processes associated with a range of respiratory tract disorders. Nevertheless, there is debate as to whether the principal response to PAR activation is an augmentation or attenuation of airways inflammation. In this context, an important action of PAR activators may be to promote the generation and release of prostanoids, such as prostglandin E2, which have well-established anti-inflammatory effects in the lung. In this review, we primarily focus on the relationship between PARs, prostaglandins and inflammatory processes in the lung, and highlight their potential role in selected respiratory tract disorders, including pulmonary fibrosis, asthma and chronic obstructive pulmonary disease. This article is part of a themed issue on Mediators and Receptors in the Resolution of Inflammation. To view this issue visit http://www3.interscience.wiley.com/journal/121548564/issueyear?year=2009 PMID:19845685

  20. Nuclear Receptor Activity and Liver Cancer Lesion Progression

    EPA Science Inventory

    Nuclear receptors (NRs) are ligand-activated transcription factors that control diverse cellular processes. Chronic stimulation of some NRs is a non-genotoxic mechanism of rodent liver cancer with unclear relevance to humans. We explored this question using human CAR, PXR, PPARα,...

  1. Covalent agonists for studying G protein-coupled receptor activation

    PubMed Central

    Weichert, Dietmar; Kruse, Andrew C.; Manglik, Aashish; Hiller, Christine; Zhang, Cheng; Hübner, Harald; Kobilka, Brian K.; Gmeiner, Peter

    2014-01-01

    Structural studies on G protein-coupled receptors (GPCRs) provide important insights into the architecture and function of these important drug targets. However, the crystallization of GPCRs in active states is particularly challenging, requiring the formation of stable and conformationally homogeneous ligand-receptor complexes. Native hormones, neurotransmitters, and synthetic agonists that bind with low affinity are ineffective at stabilizing an active state for crystallogenesis. To promote structural studies on the pharmacologically highly relevant class of aminergic GPCRs, we here present the development of covalently binding molecular tools activating Gs-, Gi-, and Gq-coupled receptors. The covalent agonists are derived from the monoamine neurotransmitters noradrenaline, dopamine, serotonin, and histamine, and they were accessed using a general and versatile synthetic strategy. We demonstrate that the tool compounds presented herein display an efficient covalent binding mode and that the respective covalent ligand-receptor complexes activate G proteins comparable to the natural neurotransmitters. A crystal structure of the β2-adrenoreceptor in complex with a covalent noradrenaline analog and a conformationally selective antibody (nanobody) verified that these agonists can be used to facilitate crystallogenesis. PMID:25006259

  2. The cardiovascular effects of peroxisome proliferator-activated receptor agonists.

    PubMed

    Friedland, Sayuri N; Leong, Aaron; Filion, Kristian B; Genest, Jacques; Lega, Iliana C; Mottillo, Salvatore; Poirier, Paul; Reoch, Jennifer; Eisenberg, Mark J

    2012-02-01

    Although peroxisome proliferator-activated receptor agonists are prescribed to improve cardiovascular risk factors, their cardiovascular safety is controversial. We therefore reviewed the literature to identify landmark randomized controlled trials evaluating the effect of peroxisome proliferator-activated receptor gamma agonists (pioglitazone and rosiglitazone), alpha agonists (fenofibrate and gemfibrozil), and pan agonists (bezafibrate, muraglitazar, ragaglitazar, tesaglitazar, and aleglitazar) on cardiovascular outcomes. Pioglitazone may modestly reduce cardiovascular events but also may increase the risk of bladder cancer. Rosiglitazone increases the risk of myocardial infarction and has been withdrawn in European and restricted in the United States. Fibrates improve cardiovascular outcomes only in select subgroups: fenofibrate in diabetic patients with metabolic syndrome, gemfibrozil in patients with dyslipidemia, and bezafibrate in patients with diabetes or metabolic syndrome. The cardiovascular safety of the new pan agonist aleglitazar, currently in phase II trials, remains to be determined. The heterogenous effects of peroxisome proliferator-activated receptor agonists to date highlight the importance of postmarketing surveillance. The critical question of why peroxisome proliferator-activated receptor agonists seem to improve cardiovascular risk factors without significantly improving cardiovascular outcomes requires further investigation.

  3. Characterization of the 5-HT receptor subtypes involved in the motor behaviours produced by intrathecal administration of 5-HT agonists in rats.

    PubMed Central

    Fone, K. C.; Robinson, A. J.; Marsden, C. A.

    1991-01-01

    1. The motor behavioural effects of intrathecal injections of 5-hydroxytryptamine (5-HT) and a variety of 5-HT receptor agonists were examined in adult Wistar rats to establish; (a) which 5-HT receptor subtype/s elicit each behaviour and (b) whether these receptors are located within the spinal cord. 2. Intrathecal injection of 5-methoxy-N,N'-dimethyltryptamine (5-MeODMT), (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride (DOI) or 2,5-dimethoxy-alpha,4-dimethylbenzene ethamine hydrochloride (DOM) produced dose-related back muscle contractions (BMC) and wet dog shakes (WDS) which were both markedly attenuated by intraperitoneal pretreatment with either ritanserin (1 mg kg-1), ketanserin (0.16 mg kg-1) or mianserin (0.6 mg kg-1) indicating the involvement of 5-HT2 receptors in both these motor behaviours. Both fluoxetine (1-20 mg kg-1, i.p.) and high doses of 5-HT (50 micrograms) following fluoxetine (5 mg kg-1, i.p.) also elicited BMC, further confirming the involvement of 5-HT in this behaviour. 3. Intrathecal 5-carboxamidotryptamine (5-CT) evoked a marked wet-dog shake response without producing any BMC. Intrathecal pretreatment with 8-hydroxy-2-(di-n-propylamino)tetraline (8-OH-DPAT) enhanced, while in contrast 2-methyl-5-HT pretreatment attenuated, 5-HT agonist-induced BMC without affecting WDS. These data suggest that the spinal 5-HT2 receptors mediating BMC are positively modulated by 5-HT1A but negatively influenced by 5-HT3 receptor activation and may be of a different subtype to the supra-spinal 5-HT2 receptors which elicit WDS.(ABSTRACT TRUNCATED AT 250 WORDS) Images Figure 1 Figure 5 PMID:1832068

  4. The Search for Endogenous Activators of the Aryl Hydrocarbon Receptor

    PubMed Central

    Nguyen, Linh P.; Bradfield, Christopher A.

    2008-01-01

    In its simplest aspect, this review is an attempt to describe the major ligand classes of the aryl hydrocarbon receptor (AHR). A grander objective is to provide models that may help define the physiological activator or “endogenous ligand” of the AHR. We begin by presenting evidence that supports a developmental function for the AHR. This is followed by proposing mechanisms by which an endogenous ligand and consequent AHR activation might be important during normal physiology and development. With this background, we then present a survey of the known xenobiotic, endogenous, dietary and “un-conventional” activators of the AHR. When possible, this includes information about their induction potency, receptor binding affinity and potential for exposure. Because of the essential function of the AHR in embryonic development, we discuss the candidacy of each of these compounds as physiologically important activators. PMID:18076143

  5. Dietary modulation of peroxisome proliferator-activated receptor gamma.

    PubMed

    Marion-Letellier, R; Déchelotte, P; Iacucci, M; Ghosh, S

    2009-04-01

    Peroxisome proliferator-activated receptor gamma (PPAR gamma) is a nuclear receptor that regulates intestinal inflammation. PPAR gamma is highly expressed in the colon and can be activated by various dietary ligands. A number of fatty acids such as polyunsaturated fatty acids or eicosanoids are considered as endogenous PPAR gamma activators. Nevertheless, other nutrients such as glutamine, spicy food or flavonoids are also able to activate PPAR gamma. As PPAR gamma plays a key role in bacterial induced inflammation, anti-inflammatory properties of probiotics may be mediated through PPAR gamma. The aims of the present review are to discuss of the potential roles of dietary compounds in modulating intestinal inflammation through PPAR gamma.

  6. Identification of prostaglandin E2 receptor subtype 2 as a receptor activated by OxPAPC.

    PubMed

    Li, Rongsong; Mouillesseaux, Kevin P; Montoya, Dennis; Cruz, Daniel; Gharavi, Navid; Dun, Martin; Koroniak, Lukasz; Berliner, Judith A

    2006-03-17

    Oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine (OxPAPC), which has been shown to accumulate in atherosclerotic lesions and other sites of chronic inflammation, activates endothelial cells (EC) to bind monocytes by activation of endothelial beta1 integrin and subsequent deposition of fibronectin on the apical surface. Our previous studies suggest this function of OxPAPC is mediated via a Gs protein-coupled receptor (GPCR). PEIPC (1-palmitoyl-2-epoxyisoprostane E2-sn-glycero-3-phosphorylcholine) is the most active lipid in OxPAPC that activates this pathway. We screened a number of candidate GPCRs for their interaction with OxPAPC and PEIPC, using a reporter gene assay; we identified prostaglandin E2 receptor EP2 and prostaglandin D2 receptor DP as responsive to OxPAPC. We focused on EP2, which is expressed in ECs, monocytes, and macrophages. OxPAPC component PEIPC, but not POVPC, activated EP2 with an EC50 of 108.6 nmol/L. OxPAPC and PEIPC were also able to compete with PGE2 for binding to EP2 in a ligand-binding assay. The EP2 specific agonist butaprost was shown to mimic the effect of OxPAPC on the activation of beta1 integrin and the stimulation of monocyte binding to endothelial cells. Butaprost also mimicked the effect of OxPAPC on the regulation of tumor necrosis factor-alpha and interleukin-10 in monocyte-derived cells. EP2 antagonist AH6809 blocked the activation of EP2 by OxPAPC in HEK293 cells and blocked the interleukin-10 response to PEIPC in monocytic THP-1 cells. These results suggest that EP2 functions as a receptor for OxPAPC and PEIPC, either as the phospholipid ester or the released fatty acid, in both endothelial cells and macrophages.

  7. Silencing of the constitutive activity of the dopamine D1B receptor. Reciprocal mutations between D1 receptor subtypes delineate residues underlying activation properties.

    PubMed

    Charpentier, S; Jarvie, K R; Severynse, D M; Caron, M G; Tiberi, M

    1996-11-08

    Recently, we have shown that the dopamine D1B/D5 receptor displays binding and coupling properties that are reminiscent of those of the constitutively activated G protein-coupled receptors when compared with the related D1A/D1 receptor subtype (Tiberi, M., and Caron, M. G. (1994) J. Biol. Chem. 269, 27925-27931). The carboxyl-terminal region of the third cytoplasmic loop of several G protein-coupled receptors has been demonstrated to be important for the regulation of the equilibrium between inactive and active receptor conformations. In this cytoplasmic region, the primary structure of dopamine D1A and D1B receptors differs by only two residues: Phe264/Arg266 are present in D1A receptor compared with Ile288/Lys290 in the D1B receptor. To investigate whether these structural differences could account for the distinct binding and coupling properties of these dopamine receptor subtypes, we swapped the variant residues located in the carboxyl-terminal region by site-directed mutagenesis. The exchange of the D1A receptor residue Phe264 by the D1B receptor counterpart isoleucine led to a D1A receptor mutant exhibiting D1B-like constitutive properties. In contrast, substitution of D1B receptor Ile288 by the D1A receptor counterpart phenylalanine resulted in a loss of constitutive activation of the D1B receptor with binding and coupling properties similar to the D1A receptor. The Arg/Lys substitution had no effect on the function of either receptor. These results demonstrate that the carboxyl-terminal region, and in particular residue Ile288, is a major determinant of the constitutive activity of the dopamine D1B receptor. Moreover, these results establish that not only can agonist-independent activity of a receptor be induced, but when given the appropriate mutation, it can be reversed or silenced.

  8. [Structural regularities in activated cleavage sites of thrombin receptors].

    PubMed

    Mikhaĭlik, I V; Verevka, S V

    1999-01-01

    Comparison of thrombin receptors activation splitting sites sequences testifies to their similarity both in activation splitting sites of protein precursors and protein proteinase inhibitors reactive sites. In all these sites corresponded to effectory sites P2'-positions are placed by hydrophobic amino-acids only. The regularity defined conforms with previous thesis about the role of effectory S2'-site in regulation of the processes mediated by serine proteinases.

  9. The aryl hydrocarbon receptor and glucocorticoid receptor interact to activate human metallothionein 2A

    SciTech Connect

    Sato, Shoko; Shirakawa, Hitoshi; Tomita, Shuhei; Tohkin, Masahiro; Gonzalez, Frank J.; Komai, Michio

    2013-11-15

    Although the aryl hydrocarbon receptor (AHR) and glucocorticoid receptor (GR) play essential roles in mammalian development, stress responses, and other physiological events, crosstalk between these receptors has been the subject of much debate. Metallothioneins are classic glucocorticoid-inducible genes that were reported to increase upon treatment with AHR agonists in rodent tissues and cultured human cells. In this study, the mechanism of human metallothionein 2A (MT2A) gene transcription activation by AHR was investigated. Cotreatment with 3-methylcholanthrene and dexamethasone, agonists of AHR and GR respectively, synergistically increased MT2A mRNA levels in HepG2 cells. MT2A induction was suppressed by RNA interference against AHR or GR. Coimmunoprecipitation experiments revealed a physical interaction between AHR and GR proteins. Moreover, chromatin immunoprecipitation assays indicated that AHR was recruited to the glucocorticoid response element in the MT2A promoter. Thus, we provide a novel mechanism whereby AHR modulates expression of human MT2A via the glucocorticoid response element and protein–protein interactions with GR. - Highlights: • Aryl hydrocarbon receptor forms a complex with glucocorticoid receptor in cells. • Human metallothionein gene is regulated by the AHR and GR interaction. • AHR–GR complex binds to glucocorticoid response element in metallothionein gene. • We demonstrated a novel transcriptional mechanism via AHR and GR interaction.

  10. Structural insights into µ-opioid receptor activation.

    PubMed

    Huang, Weijiao; Manglik, Aashish; Venkatakrishnan, A J; Laeremans, Toon; Feinberg, Evan N; Sanborn, Adrian L; Kato, Hideaki E; Livingston, Kathryn E; Thorsen, Thor S; Kling, Ralf C; Granier, Sébastien; Gmeiner, Peter; Husbands, Stephen M; Traynor, John R; Weis, William I; Steyaert, Jan; Dror, Ron O; Kobilka, Brian K

    2015-08-20

    Activation of the μ-opioid receptor (μOR) is responsible for the efficacy of the most effective analgesics. To shed light on the structural basis for μOR activation, here we report a 2.1 Å X-ray crystal structure of the murine μOR bound to the morphinan agonist BU72 and a G protein mimetic camelid antibody fragment. The BU72-stabilized changes in the μOR binding pocket are subtle and differ from those observed for agonist-bound structures of the β2-adrenergic receptor (β2AR) and the M2 muscarinic receptor. Comparison with active β2AR reveals a common rearrangement in the packing of three conserved amino acids in the core of the μOR, and molecular dynamics simulations illustrate how the ligand-binding pocket is conformationally linked to this conserved triad. Additionally, an extensive polar network between the ligand-binding pocket and the cytoplasmic domains appears to play a similar role in signal propagation for all three G-protein-coupled receptors.

  11. A transgenic zebrafish model for monitoring glucocorticoid receptor activity

    PubMed Central

    Krug, Randall G.; Poshusta, Tanya L.; Skuster, Kimberly J.; Berg, MaKayla R.; Gardner, Samantha L.; Clark, Karl J.

    2014-01-01

    Gene regulation resulting from glucocorticoid receptor and glucocorticoid response element interactions is a hallmark feature of stress response signaling. Imbalanced glucocorticoid production and glucocorticoid receptor activity have been linked to socio-economically crippling neuropsychiatric disorders, and accordingly there is a need to develop in vivo models to help understand disease progression and management. Therefore, we developed the transgenic SR4G zebrafish reporter line with six glucocorticoid response elements used to promote expression of a short half-life green fluorescent protein following glucocorticoid receptor activation. Herein, we document the ability of this reporter line to respond to both chronic and acute exogenous glucocorticoid treatment. The green fluorescent protein expression in response to transgene activation was high in a variety of tissues including the brain, and provided single cell resolution in the effected regions. The specificity of these responses is demonstrated using the partial agonist mifepristone and mutation of the glucocorticoid receptor. Importantly, the reporter line also modeled the temporal dynamics of endogenous stress response signaling, including the increased production of the glucocorticoid cortisol following hyperosmotic stress and the fluctuations of basal cortisol concentrations with the circadian rhythm. Taken together, these results characterize our newly developed reporter line for elucidating environmental or genetic modifiers of stress response signaling, which may provide insights to the neuronal mechanisms underlying neuropsychiatric disorders such as major depressive disorder. PMID:24679220

  12. Receptor for bombesin with associated tyrosine kinase activity.

    PubMed Central

    Cirillo, D M; Gaudino, G; Naldini, L; Comoglio, P M

    1986-01-01

    The neuropeptide bombesin is known for its potent mitogenic activity on murine 3T3 fibroblasts and other cells. Recently it has been implicated in the pathogenesis of small cell lung carcinoma, in which it acts through an autocrine loop of growth stimulation. Phosphotyrosine (P-Tyr) antibodies have been successfully used to recognize the autophosphorylated receptors for known growth factors. In Swiss 3T3 fibroblasts, phosphotyrosine antibodies identified a 115,000-Mr cell surface protein (p115) that became phosphorylated on tyrosine as a specific response to bombesin stimulation of quiescent cells. The extent of phosphorylation was dose dependent and correlated with the mitogenic effect induced by bombesin, measured by [3H]thymidine incorporation. Tyrosine phosphorylation of p115 was detectable minutes after the addition of bombesin, and its time course paralleled that described for the binding of bombesin to its receptor. Immunocomplexes of phosphorylated p115 and phosphotyrosine antibodies bound 125I-labeled [Tyr4]bombesin in a specific and saturable manner and displayed an associated tyrosine kinase activity enhanced by bombesin. Furthermore, the 125I-labeled bombesin analog gastrin-releasing peptide, bound to intact live cells, was coprecipitated with p115. These data strongly suggest that p115 participates in the structure and function of the surface receptor for bombesin, a new member of the family of growth factor receptors with associated tyrosine kinase activity. Images PMID:2432404

  13. 5-Hydroxytryptamine-induced tachycardia in the pig: possible involvement of a new type of 5-hydroxytryptamine receptor.

    PubMed Central

    Bom, A. H.; Duncker, D. J.; Saxena, P. R.; Verdouw, P. D.

    1988-01-01

    1. The mechanism of 5-hydroxytryptamine (5-HT)-induced tachycardia is species-dependent and is mediated directly or indirectly either by '5-HT1-like' (cat), 5-HT2 (rat, dog) or 5-HT3 (rabbit) receptors, or by an action similar to tyramine (guinea-pig). The present investigation is devoted to the analysis of the positive chronotropic effect of 5-HT in the pentobarbitone-anaesthetized pig. 2. Intravenous bolus injections of 5-HT (3, 10 and 30 micrograms kg-1) in pigs resulted in dose-dependent increases in heart rate of 24 +/- 2, 38 +/- 3 and 51 +/- 3 beats min-1, respectively (n = 39). Topical application of a high concentration of 5-HT (150 micrograms kg-1 in 5 ml) on the right atrium was also followed by tachycardia (38 +/- 6 beats min-1, n = 4). 3. A number of drugs which antagonize responses mediated by different 5-HT receptors--phenoxybenzamine, methiothepin, metergoline, methysergide and mesulergine ('5-HT1-like' and 5-HT2 receptors), ketanserin, cyproheptadine, pizotifen and mianserin (5-HT2 receptors), and MDL 72222 and ICS 205-930 (5-HT3 receptors)--did not attenuate the chronotropic responses to 5-HT. 4. The 5-HT-induced tachycardia was also not affected by antagonists at alpha- and beta-adrenoceptors, muscarinic, nicotinic, histamine and dopamine receptors, and calcium channels. 5. Selective inhibitors of 5-HT-uptake, indalpine and fluvoxamine, themselves increased porcine heart rate and facilitated 5-HT-induced tachycardia both in magnitude and in duration.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3370393

  14. Regulation of ligands for the NKG2D activating receptor

    PubMed Central

    Raulet, David H.; Gasser, Stephan; Gowen, Benjamin G.; Deng, Weiwen; Jung, Heiyoun

    2014-01-01

    NKG2D is an activating receptor expressed by all NK cells and subsets of T cells. It serves as a major recognition receptor for detection and elimination of transformed and infected cells and participates in the genesis of several inflammatory diseases. The ligands for NKG2D are self-proteins that are induced by pathways that are active in certain pathophysiological states. NKG2D ligands are regulated transcriptionally, at the level of mRNA and protein stability, and by cleavage from the cell surface. In some cases, ligand induction can be attributed to pathways that are activated specifically in cancer cells or infected cells. We review the numerous pathways that have been implicated in the regulation of NKG2D ligands, discuss the pathologic states in which those pathways are likely to act, and attempt to synthesize the findings into general schemes of NKG2D ligand regulation in NK cell responses to cancer and infection. PMID:23298206

  15. Peroxisome proliferator-activated receptor alpha target genes.

    PubMed

    Rakhshandehroo, Maryam; Knoch, Bianca; Müller, Michael; Kersten, Sander

    2010-01-01

    The peroxisome proliferator-activated receptor alpha (PPARα) is a ligand-activated transcription factor involved in the regulation of a variety of processes, ranging from inflammation and immunity to nutrient metabolism and energy homeostasis. PPARα serves as a molecular target for hypolipidemic fibrates drugs which bind the receptor with high affinity. Furthermore, PPARα binds and is activated by numerous fatty acids and fatty acid-derived compounds. PPARα governs biological processes by altering the expression of a large number of target genes. Accordingly, the specific role of PPARα is directly related to the biological function of its target genes. Here, we present an overview of the involvement of PPARα in lipid metabolism and other pathways through a detailed analysis of the different known or putative PPARα target genes. The emphasis is on gene regulation by PPARα in liver although many of the results likely apply to other organs and tissues as well.

  16. Peroxisome Proliferator-Activated Receptor Alpha Target Genes

    PubMed Central

    Rakhshandehroo, Maryam; Knoch, Bianca; Müller, Michael; Kersten, Sander

    2010-01-01

    The peroxisome proliferator-activated receptor alpha (PPARα) is a ligand-activated transcription factor involved in the regulation of a variety of processes, ranging from inflammation and immunity to nutrient metabolism and energy homeostasis. PPARα serves as a molecular target for hypolipidemic fibrates drugs which bind the receptor with high affinity. Furthermore, PPARα binds and is activated by numerous fatty acids and fatty acid-derived compounds. PPARα governs biological processes by altering the expression of a large number of target genes. Accordingly, the specific role of PPARα is directly related to the biological function of its target genes. Here, we present an overview of the involvement of PPARα in lipid metabolism and other pathways through a detailed analysis of the different known or putative PPARα target genes. The emphasis is on gene regulation by PPARα in liver although many of the results likely apply to other organs and tissues as well. PMID:20936127

  17. Biological Signaling: the Role of ``Electrostatic Epicenter'' in ``Protein Quake'' and Receptor Activation

    NASA Astrophysics Data System (ADS)

    Xie, Aihua; Kaledhonkar, Sandip; Kang, Zhouyang; Hendriks, Johnny; Hellingwerf, Klaas

    2013-03-01

    Activation of a receptor protein during biological signaling is often characterized by a two state model: a receptor state (also called ``off state'') for detection of a stimuli, and a signaling state (``on state'') for signal relay. Receptor activation is a process that a receptor protein is structurally transformed from its receptor state to its signaling state through substantial conformational changes that are recognizable by its downstream signal relay partner. What are the structural and energetic origins for receptor activation in biological signaling? We report extensive evidence that further support the role of ``electrostatic epicenter'' in driving ``protein quake'' and receptor activation. Photoactive yellow protein (PYP), a bacterial blue light photoreceptor protein for the negative phototaxis of a salt loving Halorhodospira halophia, is employed as a model system in this study. We will discuss potential applications of this receptor activation mechanism to other receptor proteins, including B-RAF receptor protein that is associated with many cancers.

  18. CINPA1 is an inhibitor of constitutive androstane receptor that does not activate pregnane X receptor.

    PubMed

    Cherian, Milu T; Lin, Wenwei; Wu, Jing; Chen, Taosheng

    2015-05-01

    Constitutive androstane receptor (CAR) and pregnane X receptor (PXR) are xenobiotic sensors that enhance the detoxification and elimination of xenobiotics and endobiotics by modulating the expression of genes encoding drug-metabolizing enzymes and transporters. Elevated levels of drug-metabolizing enzymes and efflux transporters, resulting from CAR activation in various cancers, promote the elimination of chemotherapeutic agents, leading to reduced therapeutic effectiveness and acquired drug resistance. CAR inhibitors, in combination with existing chemotherapeutics, could therefore be used to attenuate multidrug resistance in cancers. Interestingly, all previously reported CAR inverse-agonists are also activators of PXR, rendering them mechanistically counterproductive in tissues where both these xenobiotic receptors are present and active. We used a directed high-throughput screening approach, followed by subsequent mechanistic studies, to identify novel, potent, and specific small-molecule CAR inhibitors that do not activate PXR. We describe here one such inhibitor, CINPA1 (CAR inhibitor not PXR activator 1), capable of reducing CAR-mediated transcription with an IC50 of ∼70 nM. CINPA1 1) is a specific xenobiotic receptor inhibitor and has no cytotoxic effects up to 30 µM; 2) inhibits CAR-mediated gene expression in primary human hepatocytes, where CAR is endogenously expressed; 3) does not alter the protein levels or subcellular localization of CAR; 4) increases corepressor and reduces coactivator interaction with the CAR ligand-binding domain in mammalian two-hybrid assays; and 5) disrupts CAR binding to the promoter regions of target genes in chromatin immunoprecipitation assays. CINPA1 could be used as a novel molecular tool for understanding CAR function.

  19. Chronic Sarpogrelate Treatment Reveals 5-HT7 Receptor in the Serotonergic Inhibition of the Rat Vagal Bradycardia.

    PubMed

    García-Pedraza, José Ángel; García, Mónica; Martín, María Luisa; Eleno, Nélida; Morán, Asunción

    2017-01-01

    5-Hydroxytryptamine (5-HT) modulates the cardiac parasympathetic neurotransmission, inhibiting the bradyarrhythmia by 5-HT2 receptor activation. We aimed to determine whether the chronic selective 5-HT2 blockade (sarpogrelate) could modify the serotonergic modulation on vagal cardiac outflow in pithed rat. Bradycardic responses in rats treated with sarpogrelate (30 mg·kg·d; orally) were obtained by electrical stimulation of the vagal fibers (3, 6, and 9 Hz) or intravenous (IV) injections of acetylcholine (1, 5, and 10 μg/kg). 5-HT7 receptor expression was quantified by Western blot in vagus nerve and right atrium. The IV administration of 5-HT (10-200 μg/kg) dose dependently decreased the vagally induced bradycardia, and agonists 5-CT (5-HT1/7), 8-OH-DPAT (5-HT1A), or AS-19 (5-HT7) (50 μg/kg each) mimicked the 5-HT-induced inhibitory effect. Neither agonists CGS-12066B (5-HT1B), L-694,247 (5-HT1D), nor 1-phenylbiguanide (5-HT3) modified the electrically-induced bradycardic responses. Moreover, SB-258719 (5-HT7 antagonist) abolished the 5-HT-, 5-CT-, 8-OH-DPAT-, and AS-19-induced bradycardia inhibition; 5-HT or AS-19 did not modify the bradycardia induced by IV acetylcholine; and 5-HT7 receptor was expressed in both the vagus nerve and the right atrium. Our outcomes suggest that blocking chronically 5-HT2 receptors modifies the serotonergic influence on cardiac vagal neurotransmission exhibiting 5-HT as an exclusively inhibitory agent via prejunctional 5-HT7 receptor.

  20. Mammal-like striatal functions in Anolis. I. Distribution of serotonin receptor subtypes, and absence of striosome and matrix organization.

    PubMed

    Clark, E C; Baxter, L R

    2000-11-01

    Serotonin (5-HT) 5-HT(2A) and 5-HT(2C) receptors are thought to play important roles in the mammalian striatum. As basal ganglia functions in general are thought highly conserved among amniotes, we decided to use in situ autoradiographic methods to determine the occurrence and distribution of pharmacologically mammal-like 5-HT(2A) and 5-HT(2C) receptors in the lizard, Anolis carolinensis, with particular attention to the striatum. We also determined the distributions of 5-HT(1A), 5-HT(1B/D), 5 HT(3), and 5-HT(uptake) receptors for comparison. All 5-HT receptors examined showed pharmacological binding specificity, and forebrain binding density distributions that resembled those reported for mammals. Anolis 5 HT(2A/C) and 5-HT(1A) site distributions were similar in both in vivo and ex vivo binding experiments. 5-HT(2A & C) receptors occur in both high and low affinity states, the former having preferential affinity for (125)I-(+/-)-2,5-dimethoxy-4-iodo-amphetamine hydrochloride ((125)I-DOI). In mammals (125)I-DOI binding shows a patchy density distribution in the striatum, being more dense in striosomes than in surrounding matrix. There was no evidence of any such patchy density of (125)I-DOI binding in the anole striatum, however. As a further indication that anoles do not possess a striosome and matrix striatal organization, neither (3)H-naloxone binding nor histochemical staining for acetylcholinesterase activity (AChE) were patchy. AChE did show a band-like striatal distribution, however, similar to that seen in birds.

  1. Transcriptional activation by the thyroid hormone receptor through ligand-dependent receptor recruitment and chromatin remodelling.

    PubMed

    Grøntved, Lars; Waterfall, Joshua J; Kim, Dong Wook; Baek, Songjoon; Sung, Myong-Hee; Zhao, Li; Park, Jeong Won; Nielsen, Ronni; Walker, Robert L; Zhu, Yuelin J; Meltzer, Paul S; Hager, Gordon L; Cheng, Sheue-yann

    2015-04-28

    A bimodal switch model is widely used to describe transcriptional regulation by the thyroid hormone receptor (TR). In this model, the unliganded TR forms stable, chromatin-bound complexes with transcriptional co-repressors to repress transcription. Binding of hormone dissociates co-repressors and facilitates recruitment of co-activators to activate transcription. Here we show that in addition to hormone-independent TR occupancy, ChIP-seq against endogenous TR in mouse liver tissue demonstrates considerable hormone-induced TR recruitment to chromatin associated with chromatin remodelling and activated gene transcription. Genome-wide footprinting analysis using DNase-seq provides little evidence for TR footprints both in the absence and presence of hormone, suggesting that unliganded TR engagement with repressive complexes on chromatin is, similar to activating receptor complexes, a highly dynamic process. This dynamic and ligand-dependent interaction with chromatin is likely shared by all steroid hormone receptors regardless of their capacity to repress transcription in the absence of ligand.

  2. Conserved phosphorylation sites in the activation loop of the Arabidopsis phytosulfokine receptor PSKR1 differentially affect kinase and receptor activity

    PubMed Central

    Hartmann, Jens; Linke, Dennis; Bönniger, Christine; Tholey, Andreas; Sauter, Margret

    2015-01-01

    PSK (phytosulfokine) is a plant peptide hormone perceived by a leucine-rich repeat receptor kinase. Phosphosite mapping of epitope-tagged PSKR1 (phytosulfokine receptor 1) from Arabidopsis thaliana plants identified Ser696 and Ser698 in the JM (juxtamembrane) region and probably Ser886 and/or Ser893 in the AL (activation loop) as in planta phosphorylation sites. In vitro-expressed kinase was autophosphorylated at Ser717 in the JM, and at Ser733, Thr752, Ser783, Ser864, Ser911, Ser958 and Thr998 in the kinase domain. The LC–ESI–MS/MS spectra provided support that up to three sites (Thr890, Ser893 and Thr894) in the AL were likely to be phosphorylated in vitro. These sites are evolutionarily highly conserved in PSK receptors, indicative of a conserved function. Site-directed mutagenesis of the four conserved residues in the activation segment, Thr890, Ser893, Thr894 and Thr899, differentially altered kinase activity in vitro and growth-promoting activity in planta. The T899A and the quadruple-mutated TSTT-A (T890A/S893A/T894A/T899A) mutants were both kinase-inactive, but PSKR1(T899A) retained growth-promoting activity. The T890A and S893A/T894A substitutions diminished kinase activity and growth promotion. We hypothesize that phosphorylation within the AL activates kinase activity and receptor function in a gradual and distinctive manner that may be a means to modulate the PSK response. PMID:26472115

  3. Meta-chlorophenylpiperazine attenuates formalin-induced nociceptive responses through 5-HT1/2 receptors in both normal and diabetic mice.

    PubMed Central

    Takeshita, N.; Yamaguchi, I.

    1995-01-01

    1. This study was designed to investigate the effect of meta-chlorophenylpiperazine (m-CPP; a 5-hydroxytryptamine (5-HT) receptor agonist) on the formalin-induced nociceptive responses in normal, insulin-dependent streptozotocin (STZ) diabetic and non-insulin dependent genetically diabetic (db/db) mice. 2. A subcutaneous injection of diluted formalin (1% formaldehyde in 0.9% saline, 10 microliters) under the plantar surface of the left hindpaw induced biphasic nociceptive responses, the first and second phases considered to represent acute and chronic pain, respectively. The former response in db/db mice was significantly lower than those in normal mice, and the latter responses in STZ and db/db mice were significantly lower than those in normal mice. 3. In normal mice, m-CPP (0.32-3.2 mg ml-1, p.o.) exhibited potent antinociceptive activity, dose-dependently attenuating the first and second phase; the ID50 value of the second phase was 0.4 mg kg-1. m-CPP (0.32-3.2 mg kg-1, p.o.) also dose-dependently attenuated the formalin-induced nociceptive responses in STZ-induced diabetic mice and genetically diabetic db/db mice, and the activities were comparable to those in normal mice. 4. The antinociceptive activities of m-CPP (1 mg kg-1, p.o.) were significantly inhibited by pretreatment with pindolol (a 5-HT1-receptor antagonist, 1 mg kg-1, i.p.) or ketanserin (a 5-HT2 receptor antagonist, 1 mg kg-1, i.p.) but were hardly affected by ICS205-930 (a 5-HT3 receptor antagonist, 1 mg kg-1, i.p.). 5. These results suggest that m-CPP inhibits not only acute but also chronic pain transmission through 5-HT1 and 5-HT2 receptors, and that the 5-hydroxytryptaminergic antinociceptive pathways are little affected by diabetes. PMID:8719787

  4. Allosteric receptor activation by the plant peptide hormone phytosulfokine.

    PubMed

    Wang, Jizong; Li, Hongju; Han, Zhifu; Zhang, Heqiao; Wang, Tong; Lin, Guangzhong; Chang, Junbiao; Yang, Weicai; Chai, Jijie

    2015-09-10

    Phytosulfokine (PSK) is a disulfated pentapeptide that has a ubiquitous role in plant growth and development. PSK is perceived by its receptor PSKR, a leucine-rich repeat receptor kinase (LRR-RK). The mechanisms underlying the recognition of PSK, the activation of PSKR and the identity of the components downstream of the initial binding remain elusive. Here we report the crystal structures of the extracellular LRR domain of PSKR in free, PSK- and co-receptor-bound forms. The structures reveal that PSK interacts mainly with a β-strand from the island domain of PSKR, forming an anti-β-sheet. The two sulfate moieties of PSK interact directly with PSKR, sensitizing PSKR recognition of PSK. Supported by biochemical, structural and genetic evidence, PSK binding enhances PSKR heterodimerization with the somatic embryogenesis receptor-like kinases (SERKs). However, PSK is not directly involved in PSKR-SERK interaction but stabilizes PSKR island domain for recruitment of a SERK. Our data reveal the structural basis for PSKR recognition of PSK and allosteric activation of PSKR by PSK, opening up new avenues for the design of PSKR-specific small molecules.

  5. Tumor therapeutics by design: targeting and activation of death receptors.

    PubMed

    Wajant, Harald; Gerspach, Jeannette; Pfizenmaier, Klaus

    2005-02-01

    Due to their strong apoptosis-inducing capacity, the death receptor ligands CD95L, TNF and TRAIL have been widely viewed as potential cancer therapeutics. While clinical data with CD95L and TRAIL are not yet available, TNF is a registered drug, albeit only for loco-regional application in a limited number of indications. The TNF experience has told us that specific delivery and restricted action is a major challenge in the development of multifunctional, pleiotropically acting cytokines into effective cancer therapeutics. Thus, gene-therapeutic approaches and new cytokine variants have been designed over the last 10 years with the aim of increasing anti-tumoral activity and reducing systemic side effects. Here, we present our current view of the therapeutic potential of the death receptor ligands TNF, CD95L and TRAIL and of the progress made towards improving their efficacy by tumor targeting, use of gene therapy and genetic engineering. Results generated with newly designed fusion proteins suggest that enhanced tumor-directed activity and prevention of undesirable actions of death receptor ligands is possible, thereby opening up a useful therapeutic window for all of the death receptor ligands, including CD95L.

  6. Different phenolic compounds activate distinct human bitter taste receptors.

    PubMed

    Soares, Susana; Kohl, Susann; Thalmann, Sophie; Mateus, Nuno; Meyerhof, Wolfgang; De Freitas, Victor

    2013-02-20

    Bitterness is a major sensory attribute of several common foods and beverages rich in polyphenol compounds. These compounds are reported as very important for health as chemopreventive compounds, but they are also known to taste bitter. In this work, the activation of the human bitter taste receptors, TAS2Rs, by six polyphenol compounds was analyzed. The compounds chosen are present in a wide range of plant-derived foods and beverages, namely, red wine, beer, tea, and chocolate. Pentagalloylglucose (PGG) is a hydrolyzable tannin, (-)-epicatechin is a precursor of condensed tannins, procyanidin dimer B3 and trimer C2 belong to the condensed tannins, and malvidin-3-glucoside and cyanidin-3-glucoside are anthocyanins. The results show that the different compounds activate different combinations of the ~25 TAS2Rs. (-)-Epicatechin activated three receptors, TAS2R4, TAS2R5, and TAS2R39, whereas only two receptors, TAS2R5 and TAS2R39, responded to PGG. In contrast, malvidin-3-glucoside and procyanidin trimer stimulated only one receptor, TAS2R7 and TAS2R5, respectively. Notably, tannins are the first natural agonists found for TAS2R5 that display high potency only toward this receptor. The catechol and/or galloyl groups appear to be important structural determinants that mediate the interaction of these polyphenolic compounds with TAS2R5. Overall, the EC(50) values obtained for the different compounds vary 100-fold, with the lowest values for PGG and malvidin-3-glucoside compounds, suggesting that they could be significant polyphenols responsible for the bitterness of fruits, vegetables, and derived products even if they are present in very low concentrations.

  7. Pyrimidinergic Receptor Activation Controls Toxoplasma gondii Infection in Macrophages

    PubMed Central

    Moreira-Souza, Aline Cristina Abreu; Marinho, Ygor; Correa, Gladys; Santoro, Giani França; Coutinho, Claudia Mara Lara Melo; Vommaro, Rossiane Claudia; Coutinho-Silva, Robson

    2015-01-01

    Infection by the protozoan parasite Toxoplasma gondii is highly prevalent worldwide and may have serious clinical manifestations in immunocompromised patients. T. gondii is an obligate intracellular parasite that infects almost any cell type in mammalian hosts, including immune cells. The immune cells express purinergic P2 receptors in their membrane – subdivided into P2Y and P2X subfamilies - whose activation is important for infection control. Here, we examined the effect of treatment with UTP and UDP in mouse peritoneal macrophages infected with T. gondii tachyzoites. Treatment with these nucleotides reduced parasitic load by 90%, but did not increase the levels of the inflammatory mediators NO and ROS, nor did it modulate host cell death by apoptosis or necrosis. On the other hand, UTP and UDP treatments induced early egress of tachyzoites from infected macrophages, in a Ca2+-dependent manner, as shown by scanning electron microscopy analysis, and videomicroscopy. In subsequent infections, prematurely egressed parasites had reduced infectivity, and could neither replicate nor inhibit the fusion of lysosomes to the parasitophorous vacuole. The use of selective agonists and antagonists of the receptor subtypes P2Y2 and P2Y4 and P2Y6 showed that premature parasite egress may be mediated by the activation of these receptor subtypes. Our results suggest that the activity of P2Y host cell receptors controls T. gondii infection in macrophages, highlighting the importance of pyrimidinergic signaling for innate immune system response against infection. Finally the P2Y receptors should be considered as new target for the development of drugs against T. gondii infection. PMID:26192447

  8. Azemiopsin from Azemiops feae Viper Venom, a Novel Polypeptide Ligand of Nicotinic Acetylcholine Receptor*

    PubMed Central

    Utkin, Yuri N.; Weise, Christoph; Kasheverov, Igor E.; Andreeva, Tatyana V.; Kryukova, Elena V.; Zhmak, Maxim N.; Starkov, Vladislav G.; Hoang, Ngoc Anh; Bertrand, Daniel; Ramerstorfer, Joachim; Sieghart, Werner; Thompson, Andrew J.; Lummis, Sarah C. R.; Tsetlin, Victor I.

    2012-01-01

    Azemiopsin, a novel polypeptide, was isolated from the Azemiops feae viper venom by combination of gel filtration and reverse-phase HPLC. Its amino acid sequence (DNWWPKPPHQGPRPPRPRPKP) was determined by means of Edman degradation and mass spectrometry. It consists of 21 residues and, unlike similar venom isolates, does not contain cysteine residues. According to circular dichroism measurements, this peptide adopts a β-structure. Peptide synthesis was used to verify the determined sequence and to prepare peptide in sufficient amounts to study its biological activity. Azemiopsin efficiently competed with α-bungarotoxin for binding to Torpedo nicotinic acetylcholine receptor (nAChR) (IC50 0.18 ± 0.03 μm) and with lower efficiency to human α7 nAChR (IC50 22 ± 2 μm). It dose-dependently blocked acetylcholine-induced currents in Xenopus oocytes heterologously expressing human muscle-type nAChR and was more potent against the adult form (α1β1ϵδ) than the fetal form (α1β1γδ), EC50 being 0.44 ± 0.1 μm and 1.56 ± 0.37 μm, respectively. The peptide had no effect on GABAA (α1β3γ2 or α2β3γ2) receptors at a concentration up to 100 μm or on 5-HT3 receptors at a concentration up to 10 μm. Ala scanning showed that amino acid residues at positions 3–6, 8–11, and 13–14 are essential for binding to Torpedo nAChR. In biological activity azemiopsin resembles waglerin, a disulfide-containing peptide from the Tropidechis wagleri venom, shares with it a homologous C-terminal hexapeptide, but is the first natural toxin that blocks nAChRs and does not possess disulfide bridges. PMID:22613724

  9. Differential effects of quercetin glycosides on GABAC receptor channel activity.

    PubMed

    Kim, Hyeon-Joong; Lee, Byung-Hwan; Choi, Sun-Hye; Jung, Seok-Won; Kim, Hyun-Sook; Lee, Joon-Hee; Hwang, Sung-Hee; Pyo, Mi-Kyung; Kim, Hyoung-Chun; Nah, Seung-Yeol

    2015-01-01

    Quercetin, a representative flavonoid, is a compound of low molecular weight found in various colored plants and vegetables. Quercetin shows a wide range of neuropharmacological activities. In fact, quercetin naturally exists as monomer-(quercetin-3-O-rhamnoside) (Rham1), dimer-(Rutin), or trimer-glycosides [quercetin-3-(2(G)-rhamnosylrutinoside)] (Rham2) at carbon-3 in fruits and vegetables. The carbohydrate components are removed after ingestion into gastrointestinal systems. The role of the glycosides attached to quercetin in the regulation of γ-aminobutyric acid class C (GABAC) receptor channel activity has not been determined. In the present study, we examined the effects of quercetin glycosides on GABAC receptor channel activity by expressing human GABAC alone in Xenopus oocytes using a two-electrode voltage clamp technique and also compared the effects of quercetin glycosides with quercetin. We found that GABA-induced inward current (I GABA ) was inhibited by quercetin or quercetin glycosides. The inhibitory effects of quercetin and its glycosides on I GABA were concentration-dependent and reversible in the order of Rutin ≈ quercetin ≈ Rham 1 > Rham 2. The inhibitory effects of quercetin and its glycosides on I GABA were noncompetitive and membrane voltage-insensitive. These results indicate that quercetin and its glycosides regulate GABAC receptor channel activity through interaction with a different site from that of GABA, and that the number of carbohydrate attached to quercetin might play an important role in the regulation of GABAC receptor channel activity.

  10. An integrative framework of the skin receptors activation: mechanoreceptors activity patterns versus "labeled lines".

    PubMed

    Zeveke, Alexander V; Efes, Ekaterina D; Polevaya, Sofia A

    2013-03-01

    The paper presents a review of electrophysiological data which indicate the integrative mechanisms of information coded in the human and animal peripheral skin receptors. The activity of the skin sensory receptors was examined by applying various natural stimuli. It was revealed that numerous identical receptors respond to various stimuli (mechanical, temperature, and pain ones), but the spike patterns of these receptors were found to be specific for each stimulus. The description of characteristic structures of spike patterns in the cutaneous nerve fibers in response to five major modalities, namely: "touch", "pain", "vibration/breath", "cold", and "heat", is being presented. The recordings of the cutaneous physical state revealed a correlation between the patterns of spatiotemporal skin deformation and the receptors activity. A rheological state of the skin can be changed either in response to external temperature variation or by the sympathetic pilomotor activation. These results indicate that the skin sensory receptors activity may be considered as an integrative process. It depends not only on the receptors themselves, but also on the changes in the surrounding tissue and on the adaptive influence of the central nervous system. A new framework for the sensory channel system related to the skin is proposed on the basis of experimental results.

  11. Human peroxisome proliferator-activated receptor mRNA and protein expression during development

    EPA Science Inventory

    The peroxisome proliferator-activated receptors (PPAR) are nuclear hormone receptors that regulate lipid and glucose homeostasis and are important in reproduction and development. PPARs are targets ofpharmaceuticals and are also activated by environmental contaminants, including ...

  12. Allosterism and Structure in Thermally Activated Transient Receptor Potential Channels.

    PubMed

    Diaz-Franulic, Ignacio; Poblete, Horacio; Miño-Galaz, Germán; González, Carlos; Latorre, Ramón

    2016-07-05

    The molecular sensors that mediate temperature changes in living organisms are a large family of proteins known as thermosensitive transient receptor potential (TRP) ion channels. These membrane proteins are polymodal receptors that can be activated by cold or hot temperatures, depending on the channel subtype, voltage, and ligands. The stimuli sensors are allosterically coupled to a pore domain, increasing the probability of finding the channel in its ion conductive conformation. In this review we first discuss the allosteric coupling between the temperature and voltage sensor modules and the pore domain, and then discuss the thermodynamic foundations of thermo-TRP channel activation. We provide a structural overview of the molecular determinants of temperature sensing. We also posit an anisotropic thermal diffusion model that may explain the large temperature sensitivity of TRP channels. Additionally, we examine the effect of several ligands on TRP channel function and the evidence regarding their mechanisms of action.

  13. Morpheus: a conformation-activity relationships and receptor modeling package.

    PubMed

    Andrews, P R; Quint, G; Winkler, D A; Richardson, D; Sadek, M; Spurling, T H

    1989-09-01

    Our molecular modeling software package, MORPHEUS, allows the study of the interactions between biologically active molecules and their receptors. The package is capable of exploring the multidimensional conformational space accessible to each molecule of the data set under study. By specifying distance constraints or hypothetical receptor binding points, the package is able to filter the biologically accessible conformations of each active compound and deduce a three-dimensional model of the binding sites consistent with the properties of the agonists (or antagonists) under scrutiny. The electrostatic potentials in the environment of a putative binding site can also be investigated using the MORPHEUS package. The molecular modeling module CRYS-X, which is written in FORTRAN 77 for IBM PC machines, is capable of building, displaying and manipulating molecules.

  14. Skimmianine and related furoquinolines function as antagonists of 5-hydroxytryptamine receptors in animals.

    PubMed

    Cheng, J T; Chang, T K; Chen, I S

    1994-10-01

    1. Skimmianine, kokusaginine and confusameline, three furoquinolines extracted from the leaves of Evodia merrillii (Rutaceae), were investigated to characterize their selective effects on subtypes of 5-hydroxytryptamine (5-HT) receptors. 2. In the isolated membranes of rat cerebrocortex, using [3H]-5-HT and [3H]-ketanserin as radioligands, skimmianine and the two other furoquinolines displaced radioligand bindings in a concentration-dependent manner. Lower concentrations were required to affect [3H]-ketanserin binding than [3H]-5-HT binding in the order skimmianine > kokusaginine > confusameline. 3. Furoquinolines inhibited 5-HT-induced contraction mediated by 5-HT2 receptors in the presence of methiothepin in rat isolated aorta. Also, the combination of furoquinolines with ketanserin showed an additive antagonism. 4. These furoquinolines were inactive on the 5-carboxamidotryptamine-induced relaxation of guinea-pig ileum, a 5-HT1-mediated event. However, 5-HT-induced contraction via 5-HT2 receptors was reduced by these furoquinolines in a way similar to that in blood vessels. 5. The failure of these compounds to affect the 5-HT-induced Bezold-Jarisch-like reflex in anaesthetized rats, the major 5-HT3-mediated action, ruled out an action on 5-HT3 receptors. 6. The results obtained suggest that three furoquinoline alkaloids may act on 5-HT receptors in animals, more selectively to the 5-HT2 subtype, in the order of skimmianine > kokusaginine > confusameline.

  15. An allosteric role for receptor activity-modifying proteins in defining GPCR pharmacology

    PubMed Central

    J Gingell, Joseph; Simms, John; Barwell, James; Poyner, David R; Watkins, Harriet A; Pioszak, Augen A; Sexton, Patrick M; Hay, Debbie L

    2016-01-01

    G protein-coupled receptors are allosteric proteins that control transmission of external signals to regulate cellular response. Although agonist binding promotes canonical G protein signalling transmitted through conformational changes, G protein-coupled receptors also interact with other proteins. These include other G protein-coupled receptors, other receptors and channels, regulatory proteins and receptor-modifying proteins, notably receptor activity-modifying proteins (RAMPs). RAMPs have at least 11 G protein-coupled receptor partners, including many class B G protein-coupled receptors. Prototypic is the calcitonin receptor, with altered ligand specificity when co-expressed with RAMPs. To gain molecular insight into the consequences of this protein–protein interaction, we combined molecular modelling with mutagenesis of the calcitonin receptor extracellular domain, assessed in ligand binding and functional assays. Although some calcitonin receptor residues are universally important for peptide interactions (calcitonin, amylin and calcitonin gene-related peptide) in calcitonin receptor alone or with receptor activity-modifying protein, others have RAMP-dependent effects, whereby mutations decreased amylin/calcitonin gene-related peptide potency substantially only when RAMP was present. Remarkably, the key residues were completely conserved between calcitonin receptor and AMY receptors, and between subtypes of AMY receptor that have different ligand preferences. Mutations at the interface between calcitonin receptor and RAMP affected ligand pharmacology in a RAMP-dependent manner, suggesting that RAMP may allosterically influence the calcitonin receptor conformation. Supporting this, molecular dynamics simulations suggested that the calcitonin receptor extracellular N-terminal domain is more flexible in the presence of receptor activity-modifying protein 1. Thus, RAMPs may act in an allosteric manner to generate a spectrum of unique calcitonin receptor

  16. Aryl hydrocarbon receptor-independent activation of estrogen receptor-dependent transcription by 3-methylcholanthrene.

    PubMed

    Shipley, Jonathan M; Waxman, David J

    2006-06-01

    Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that stimulates transcription directed by xenobiotic response elements upstream of target genes. Recently, AhR ligands were reported to induce formation of an AhR-estrogen receptor (ER) complex, which can bind to estrogen response elements (EREs) and stimulate transcription of ER target genes. Presently, we investigate the effect of the AhR ligands 3-methylcholanthrene (3MC), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 3,3',4,4',5-pentachlorobiphenyl (BZ126) on ERE-regulated luciferase reporter activity and endogenous ER target gene expression. In MCF-7 human breast cancer cells, 3MC induced transcription of ER reporter genes containing native promoter sequences of the ER-responsive genes complement 3 and pS2 and heterologous promoters regulated by isolated EREs. Dose-response studies revealed that the concentration of 3MC required to half-maximally activate transcription (EC(50)) was >100-fold higher for an ER reporter (27-57 muM) than for an AhR reporter (86-250 nM) in both MCF-7 cells and in human endometrial cancer Ishikawa cells. 3MC also stimulated expression of the endogenous ER target genes amphiregulin, cathepsin D and progesterone receptor, albeit to a much lower extent than was achieved following stimulation with 17beta-estradiol. In Ishikawa cells, 3MC, but not BZ126 or TCDD, stimulated ERalpha-dependent reporter activity but did not induce expression of endogenous ER target genes. Finally, studies carried out in the AhR-positive rat hepatoma cell line 5L and the AhR-deficient variant BP8 demonstrated that ER reporter activity could be induced by 3MC in a manner that was independent of AhR and thus distinct from the AhR-ER 'hijacking' mechanism described recently. 3MC may thus elicit estrogenic activity by multiple mechanisms.

  17. Effects of tobacco ethylene receptor mutations on receptor kinase activity, plant growth and stress responses.

    PubMed

    Chen, Tao; Liu, Jun; Lei, Gang; Liu, Yun-Feng; Li, Zhi-Gang; Tao, Jian-Jun; Hao, Yu-Jun; Cao, Yang-Rong; Lin, Qing; Zhang, Wan-Ke; Ma, Biao; Chen, Shou-Yi; Zhang, Jin-Song

    2009-09-01

    Ethylene receptor is the first component of ethylene signaling that regulates plant growth, development and stress responses. Previously, we have demonstrated that tobacco subfamily 2 ethylene receptor NTHK1 had Ser/Thr kinase activity, and overexpression of NTHK1 caused large rosette, reduced ethylene sensitivity, and increased salt sensitivity in transgenic Arabidopsis plants. Here we found that N-box mutation in the NTHK1 kinase domain abolished the kinase activity and led to disruption of NTHK1 roles in conferring reduced ethylene sensitivity and salt sensitive response in transgenic Arabidopsis plants. However, N-box mutation had partial effects on NTHK1 regulation of rosette growth and expression of salt- and ethylene-responsive genes AtNAC2, AtERF1 and AtCor6.6. Mutation of conserved residues in the H box did not affect kinase activity, seedling growth, ethylene sensitivity or salt-induced epinasty in transgenic plants but did influence NTHK1 function in control of specific salt- and ethylene-responsive gene expression. Compared with NTHK1, the tobacco subfamily 1 ethylene receptor NtETR1 had His kinase activity and played a weak role in regulation of rosette growth, triple response and salt response. Mutation of the conserved His residue in the NtETR1 H box eliminated phosphorylation and altered the effect of Ntetr1-1 on reporter gene activity. These results imply that the Ser/Thr kinase activity of NTHK1 is differentially required for various responses, and NTHK1 plays a larger role than NtETR1.

  18. Involvement of local serotonin-2A but not serotonin-1B receptors in the reinforcing effects of ethanol within the posterior ventral tegmental area of female Wistar rats

    PubMed Central

    Ding, Zheng-Ming; Toalston, Jamie E.; Oster, Scott M.; McBride, William J.; Rodd, Zachary A.

    2010-01-01

    Rationale Previous studies indicated that ethanol could be self-infused into the posterior ventral tegmental area (p-VTA) and that activation of local serotonin-3 (5-HT3) receptors was involved. 5-HT1B and 5-HT2A receptors are involved in the effects of 5-HT and ethanol on VTA dopamine neurons. Objective The current study used the intracranial self-administration (ICSA) procedure to determine the involvement of local 5-HT1B and 5-HT2A receptors in the self-infusion of ethanol into the p-VTA. Materials and methods Female Wistar rats were implanted unilaterally with a guide cannula aimed at the p-VTA. Seven days after surgery, rats were placed into the two-lever operant conditioning chambers for ICSA tests. The tests consisted of four acquisition sessions with self-infusion of 200 mg% ethanol alone, two or three sessions with co-infusion of the 5-HT1B antagonist GR 55562 (10, 100, or 200 μM) or the 5-HT2A antagonist R-96544 (10, 100, or 200 μM) with 200 mg% ethanol, and one final session with 200 mg% ethanol alone. Results During the acquisition sessions, all rats readily self-infused ethanol and discriminated the active from inactive lever. Co-infusion of GR 55562, at all three doses, had no effect on the self-infusion of ethanol. In contrast, co-infusion of R-96544, at the two higher doses, attenuated responding on the active lever for ethanol infusion (p<0.05). Conclusion The results suggest that the reinforcing effects of ethanol within the p-VTA are modulated, at least in part, by activation of local 5-HT2A, but not 5-HT1B, receptors. PMID:19165471

  19. Pharmacological activation of lysophosphatidic acid receptors regulates erythropoiesis

    PubMed Central

    Lin, Kuan-Hung; Ho, Ya-Hsuan; Chiang, Jui-Chung; Li, Meng-Wei; Lin, Shi-Hung; Chen, Wei-Min; Chiang, Chi-Ling; Lin, Yu-Nung; Yang, Ya-Jan; Chen, Chiung-Nien; Lu, Jenher; Huang, Chang-Jen; Tigyi, Gabor; Yao, Chao-Ling; Lee, Hsinyu

    2016-01-01

    Lysophosphatidic acid (LPA), a growth factor-like phospholipid, regulates numerous physiological functions, including cell proliferation and differentiation. In a previous study, we have demonstrated that LPA activates erythropoiesis by activating the LPA 3 receptor subtype (LPA3) under erythropoietin (EPO) induction. In the present study, we applied a pharmacological approach to further elucidate the functions of LPA receptors during red blood cell (RBC) differentiation. In K562 human erythroleukemia cells, knockdown of LPA2 enhanced erythropoiesis, whereas knockdown of LPA3 inhibited RBC differentiation. In CD34+ human hematopoietic stem cells (hHSC) and K526 cells, the LPA3 agonist 1-oleoyl-2-methyl-sn-glycero-3-phosphothionate (2S-OMPT) promoted erythropoiesis, whereas the LPA2 agonist dodecyl monophosphate (DMP) and the nonlipid specific agonist GRI977143 (GRI) suppressed this process. In zebrafish embryos, hemoglobin expression was significantly increased by 2S-OMPT treatment but was inhibited by GRI. Furthermore, GRI treatment decreased, whereas 2S-OMPT treatment increased RBC counts and amount of hemoglobin level in adult BALB/c mice. These results indicate that LPA2 and LPA3 play opposing roles during RBC differentiation. The pharmacological activation of LPA receptor subtypes represent a novel strategies for augmenting or inhibiting erythropoiesis. PMID:27244685

  20. Discovery of novel protease activated receptors 1 antagonists with potent antithrombotic activity in vivo.

    PubMed

    Perez, Michel; Lamothe, Marie; Maraval, Catherine; Mirabel, Etienne; Loubat, Chantal; Planty, Bruno; Horn, Clemens; Michaux, Julien; Marrot, Sebastien; Letienne, Robert; Pignier, Christophe; Bocquet, Arnaud; Nadal-Wollbold, Florence; Cussac, Didier; de Vries, Luc; Le Grand, Bruno

    2009-10-08

    Protease activated receptors (PARs) or thrombin receptors constitute a class of G-protein-coupled receptors (GPCRs) implicated in the activation of many physiological mechanisms. Thus, thrombin activates many cell types such as vascular smooth muscle cells, leukocytes, endothelial cells, and platelets via activation of these receptors. In humans, thrombin-induced platelet aggregation is mediated by one subtype of these receptors, termed PAR1. This article describes the discovery of new antagonists of these receptors and more specifically two compounds: 2-[5-oxo-5-(4-pyridin-2-ylpiperazin-1-yl)penta-1,3-dienyl]benzonitrile 36 (F 16618) and 3-(2-chlorophenyl)-1-[4-(4-fluorobenzyl)piperazin-1-yl]propenone 39 (F 16357), obtained after optimization. Both compounds are able to inhibit SFLLR-induced human platelet aggregation and display antithrombotic activity in an arteriovenous shunt model in the rat after iv or oral administration. Furthermore, these compounds are devoid of bleeding side effects often observed with other types of antiplatelet drugs, which constitutes a promising advantage for this new class of antithrombotic agents.

  1. Ultrastructural and biochemical analysis of fibrinogen receptors on activated thrombocytes

    SciTech Connect

    O'Toole, E.T.

    1989-01-01

    The present studies have been concerned with the role of fibrinogen and its receptor, GP IIb/IIIa, during the activation and early aggregation of pigeon thrombocytes. Thrombocytes were surface labeled with {sup 125}I then separated on SDS-PAGE. Analysis by gel autoradiography revealed major bands at MW 145 kd and 98 kd, which corresponded to human GPIIb and GPIIIa. Immunologic similarity of the pigeon and human receptor components was established by dot blot analysis using polyclonal antibodies directed against human GPIIb and GPIIIa. Pigeon fibrinogen, isolated by plasma precipitation with PEG-1000 and purified over Sepharose 4B, was used to study receptor-ligand interaction. Separation of pigeon fibrinogen on SDS-PAGE resulted in three peptides having apparent MW of 62kd, 55kd, and 47kd which are comparable to human fibrinogen. Further similarity of human and pigeon fibrinogen was verified by immonodiffusion against an antibody specific for the human protein. The role of fibrinogen and its receptor in thrombocyte function was established by turbidimetric aggregation using thrombin as an agonist under conditions requiring Ca++ and fibrinogen.

  2. Peroxisome proliferator-activated receptors and the control of inflammation.

    PubMed

    Cabrero, A; Laguna, J C; Vázquez, M

    2002-09-01

    Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors which form a subfamily of the nuclear receptor gene family. This subfamily consists of three isotypes, alpha (NR1C1), gamma (NR1C3), and beta/delta (NRC1C2) with a differential tissue distribution. PPARalpha is expressed primarily in tissues with a high level of fatty acid catabolism such as liver, brown fat, kidney, heart and skeletal muscle. PPARbeta is ubiquitously expressed, and PPARgamma has a restricted pattern of expression, mainly in white and brown adipose tissues, whereas other tissues such as skeletal muscle and heart contain limited amounts. Furthermore, PPARalpha and gamma isotypes are expressed in vascular cells including endothelial and smooth muscle cells and macrophages/foam cells. PPARs are activated by ligands, such as naturally occurring fatty acids, which are activators of all three PPAR isotypes. In addition to fatty acids, several synthetic compounds, such as fibrates and thiazolidinediones, bind and activate PPARalpha and PPARgamma, respectively. In order to be transcriptionally active, PPARs need to heterodimerize with the retinoid-X-receptor (RXR). Upon activation, PPAR-RXR heterodimers bind to DNA specific sequences called peroxisome proliferator-response elements (PPRE) and stimulate transcription of target genes. PPARs play a critical role in lipid and glucose homeostasis, but lately they have been implicated as regulators of inflammatory responses. The first evidence of the involvement of PPARs in the control of inflammation came from the PPARalpha null mice, which showed a prolonged inflammatory response. PPARalpha activation results in the repression of NF-kappaB signaling and inflammatory cytokine production in different cell-types. A role for PPARgamma in inflammation has also been reported in monocyte/macrophages, where ligands of this receptor inhibited the activation of macrophages and the production of inflammatory cytokines (TNFalpha

  3. 3-Methylcholanthrene and other aryl hydrocarbon receptor agonists directly activate estrogen receptor alpha.

    PubMed

    Abdelrahim, Maen; Ariazi, Eric; Kim, Kyounghyun; Khan, Shaheen; Barhoumi, Rola; Burghardt, Robert; Liu, Shengxi; Hill, Denise; Finnell, Richard; Wlodarczyk, Bogdan; Jordan, V Craig; Safe, Stephen

    2006-02-15

    3-Methylcholanthrene (3MC) is an aryl hydrocarbon receptor (AhR) agonist, and it has been reported that 3MC induces estrogenic activity through AhR-estrogen receptor alpha (ER alpha) interactions. In this study, we used 3MC and 3,3',4,4',5-pentachlorobiphenyl (PCB) as prototypical AhR ligands, and both compounds activated estrogen-responsive reporter genes/gene products (cathepsin D) in MCF-7 breast cancer cells. The estrogenic responses induced by these AhR ligands were inhibited by the antiestrogen ICI 182780 and by the transfection of a small inhibitory RNA for ER alpha but were not affected by the small inhibitory RNA for AhR. These results suggest that 3MC and PCB directly activate ER alpha, and this was confirmed in a competitive ER alpha binding assay and in a fluorescence resonance energy transfer experiment in which PCB and 3MC induced CFP-ER alpha/YFP-ER alpha interactions. In a chromatin immunoprecipitation assay, PCB and 3MC enhanced ER alpha (but not AhR) association with the estrogen-responsive region of the pS2 gene promoter. Moreover, in AhR knockout mice, 3MC increased uterine weights and induced expression of cyclin D1 mRNA levels. These results show that PCB and 3MC directly activate ER alpha-dependent transactivation and extend the number of ligands that activate both AhR and ER alpha.

  4. Cinnamaldehyde suppresses toll-like receptor 4 activation mediated through the inhibition of receptor oligomerization.

    PubMed

    Youn, Hyung S; Lee, Jun K; Choi, Yong J; Saitoh, Shin I; Miyake, Kensuke; Hwang, Daniel H; Lee, Joo Y

    2008-01-15

    Toll-like receptors (TLRs) play a critical role in induction of innate immune and inflammatory responses by recognizing invading pathogens or non-microbial endogenous molecules. TLRs have two major downstream signaling pathways, MyD88- and TRIF-dependent pathways leading to the activation of NFkappaB and IRF3 and the expression of inflammatory mediators. Deregulation of TLR activation is known to be closely linked to the increased risk of many chronic diseases. Cinnamaldehyde (3-phenyl-2-propenal) has been reported to inhibit NFkappaB activation induced by pro-inflammatory stimuli and to exert anti-inflammatory and anti-bacterial effects. However, the underlying mechanism has not been clearly identified. Our results showed that cinnamaldehyde suppressed the activation of NFkappaB and IRF3 induced by LPS, a TLR4 agonist, leading to the decreased expression of target genes such as COX-2 and IFNbeta in macrophages (RAW264.7). Cinnamaldehyde did not inhibit the activation of NFkappaB or IRF3 induced by MyD88-dependent (MyD88, IKKbeta) or TRIF-dependent (TRIF, TBK1) downstream signaling components. However, oligomerization of TLR4 induced by LPS was suppressed by cinnamaldehyde resulting in the downregulation of NFkappaB activation. Further, cinnamaldehyde inhibited ligand-independent NFkappaB activation induced by constitutively active TLR4 or wild-type TLR4. Our results demonstrated that the molecular target of cinnamaldehyde in TLR4 signaling is oligomerization process of receptor, but not downstream signaling molecules suggesting a novel mechanism for anti-inflammatory activity of cinnamaldehyde.

  5. Transgenic silkworms expressing human insulin receptors for evaluation of therapeutically active insulin receptor agonists.

    PubMed

    Matsumoto, Yasuhiko; Ishii, Masaki; Ishii, Kenichi; Miyaguchi, Wataru; Horie, Ryo; Inagaki, Yoshinori; Hamamoto, Hiroshi; Tatematsu, Ken-ichiro; Uchino, Keiro; Tamura, Toshiki; Sezutsu, Hideki; Sekimizu, Kazuhisa

    2014-12-12

    We established a transgenic silkworm strain expressing the human insulin receptor (hIR) using the GAL4/UAS system. Administration of human insulin to transgenic silkworms expressing hIR decreased hemolymph sugar levels and facilitated Akt phosphorylation in the fat body. The decrease in hemolymph sugar levels induced by injection of human insulin in the transgenic silkworms expressing hIR was blocked by co-injection of wortmannin, a phosphoinositide 3-kinase inhibitor. Administration of bovine insulin, an hIR ligand, also effectively decreased sugar levels in the transgenic silkworms. These findings indicate that functional hIRs that respond to human insulin were successfully induced in the transgenic silkworms. We propose that the humanized silkworm expressing hIR is useful for in vivo evaluation of the therapeutic activities of insulin receptor agonists.

  6. Type-1 cannabinoid receptor activity during Alzheimer's disease progression.

    PubMed

    Manuel, Iván; González de San Román, Estíbaliz; Giralt, M Teresa; Ferrer, Isidro; Rodríguez-Puertas, Rafael

    2014-01-01

    The activity of CB1 cannabinoid receptors was studied in postmortem brain samples of Alzheimer's disease (AD) patients during clinical deterioration. CB1 activity was higher at earlier AD stages in limited hippocampal areas and internal layers of frontal cortex, but a decrease was observed at the advanced stages. The pattern of modification appears to indicate initial hyperactivity of the endocannabinoid system in brain areas that lack classical histopathological markers at earlier stages of AD, indicating an attempt to compensate for the initial synaptic impairment, which is then surpassed by disease progression. These results suggest that initial CB1 stimulation might have therapeutic relevance.

  7. Activation of glycine receptors modulates spontaneous epileptiform activity in the immature rat hippocampus

    PubMed Central

    Chen, Rongqing; Okabe, Akihito; Sun, Haiyan; Sharopov, Salim; Hanganu-Opatz, Ileana L; Kolbaev, Sergei N; Fukuda, Atsuo; Luhmann, Heiko J; Kilb, Werner

    2014-01-01

    While the expression of glycine receptors in the immature hippocampus has been shown, no information about the role of glycine receptors in controlling the excitability in the immature CNS is available. Therefore, we examined the effect of glycinergic agonists and antagonists in the CA3 region of an intact corticohippocampal preparation of the immature (postnatal days 4–7) rat using field potential recordings. Bath application of 100 μm taurine or 10 μm glycine enhanced the occurrence of recurrent epileptiform activity induced by 20 μm 4-aminopyridine in low Mg2+ solution. This proconvulsive effect was prevented by 3 μm strychnine or after incubation with the loop diuretic bumetanide (10 μm), suggesting that it required glycine receptors and an active NKCC1-dependent Cl− accumulation. Application of higher doses of taurine (≥1 mm) or glycine (100 μm) attenuated recurrent epileptiform discharges. The anticonvulsive effect of taurine was also observed in the presence of the GABAA receptor antagonist gabazine and was attenuated by strychnine, suggesting that it was partially mediated by glycine receptors. Bath application of the glycinergic antagonist strychnine (0.3 μm) induced epileptiform discharges. We conclude from these results that in the immature hippocampus, activation of glycine receptors can mediate both pro- and anticonvulsive effects, but that a persistent activation of glycine receptors is required to suppress epileptiform activity. In summary, our study elucidated the important role of glycine receptors in the control of neuronal excitability in the immature hippocampus. PMID:24665103

  8. Cholecystokinin 1 receptor modulates the MEKK1-induced c-Jun trans-activation: structural requirements of the receptor

    PubMed Central

    Ibarz, Géraldine; Oiry, Catherine; Carnazzi, Eric; Crespy, Philippe; Escrieut, Chantal; Fourmy, Daniel; Galleyrand, Jean Claude; Gagne, Didier; Martinez, Jean

    2006-01-01

    In cells overexpressing active MEKK1 to enhance c-Jun trans-activation, expression of rat cholecystokinin 1 receptor increased the activity of c-Jun while in the same experimental conditions overexpression of mouse cholecystokinin 1 receptor repressed it. This differential trans-activation is specific, since it was not observed for either the other overexpressed kinases (MEK, PKA) or for other transcription factors (ATF2, ELK-1, CREB). This differential behaviour was also detected in a human colon adenocarcinoma cell-line naturally producing high levels of endogenous MEKK1. This differential behaviour between the two receptors on the MEKK1-induced c-Jun trans-activation was independent of the activation state of JNK, of the phosphorylation level of c-Jun and of its ability to bind its specific DNA responsive elements. Two amino acids (Val43 and Phe50 in the mouse cholecystokinin 1 receptor, replaced by Leu43 and Ileu50 in the rat cholecystokinin 1 receptor) localized in the first transmembrane domain were found to play a crucial role in this differential behaviour. MEKK1 probably activates a transcriptional partner of c-Jun whose activity is maintained or increased in the presence of the rat cholecystokinin 1 receptor but repressed in the presence of the mouse cholecystokinin 1 receptor. PMID:16491099

  9. Cholecystokinin 1 receptor modulates the MEKK1-induced c-Jun trans-activation: structural requirements of the receptor.

    PubMed

    Ibarz, Géraldine; Oiry, Catherine; Carnazzi, Eric; Crespy, Philippe; Escrieut, Chantal; Fourmy, Daniel; Galleyrand, Jean Claude; Gagne, Didier; Martinez, Jean

    2006-04-01

    In cells overexpressing active MEKK1 to enhance c-Jun trans-activation, expression of rat cholecystokinin 1 receptor increased the activity of c-Jun while in the same experimental conditions overexpression of mouse cholecystokinin 1 receptor repressed it. This differential trans-activation is specific, since it was not observed for either the other overexpressed kinases (MEK, PKA) or for other transcription factors (ATF2, ELK-1, CREB). This differential behaviour was also detected in a human colon adenocarcinoma cell-line naturally producing high levels of endogenous MEKK1. This differential behaviour between the two receptors on the MEKK1-induced c-Jun trans-activation was independent of the activation state of JNK, of the phosphorylation level of c-Jun and of its ability to bind its specific DNA responsive elements. Two amino acids (Val43 and Phe50 in the mouse cholecystokinin 1 receptor, replaced by Leu43 and Ileu50 in the rat cholecystokinin 1 receptor) localized in the first transmembrane domain were found to play a crucial role in this differential behaviour. MEKK1 probably activates a transcriptional partner of c-Jun whose activity is maintained or increased in the presence of the rat cholecystokinin 1 receptor but repressed in the presence of the mouse cholecystokinin 1 receptor.

  10. Persistently active cannabinoid receptors mute a subpopulation of hippocampal interneurons.

    PubMed

    Losonczy, Attila; Biró, Agota A; Nusser, Zoltan

    2004-02-03

    Cortical information processing requires an orchestrated interaction between a large number of pyramidal cells and albeit fewer, but highly diverse GABAergic interneurons (INs). The diversity of INs is thought to reflect functional and structural specializations evolved to control distinct network operations. Consequently, specific cortical functions may be selectively modified by altering the input-output relationship of unique IN populations. Here, we report that persistently active cannabinoid receptors, the site of action of endocannabinoids, and the psychostimulants marijuana and hashish, switch off the output (mute) of a unique class of hippocampal INs. In paired recordings between cholecystokinin-immunopositive, mossy fiber-associated INs, and their target CA3 pyramidal cells, no postsynaptic currents could be evoked with single presynaptic action potentials or with repetitive stimulations at frequencies <25 Hz. Cannabinoid receptor antagonists converted these "mute" synapses into high-fidelity ones. The selective muting of specific GABAergic INs, achieved by persistent presynaptic cannabinoid receptor activation, provides a state-dependent switch in cortical networks.

  11. Structural rearrangement of the intracellular domains during AMPA receptor activation

    PubMed Central

    Zachariassen, Linda G.; Katchan, Ljudmila; Jensen, Anna G.; Pickering, Darryl S.; Plested, Andrew J. R.

    2016-01-01

    α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are ligand-gated ion channels that mediate the majority of fast excitatory neurotransmission in the central nervous system. Despite recent advances in structural studies of AMPARs, information about the specific conformational changes that underlie receptor function is lacking. Here, we used single and dual insertion of GFP variants at various positions in AMPAR subunits to enable measurements of conformational changes using fluorescence resonance energy transfer (FRET) in live cells. We produced dual CFP/YFP-tagged GluA2 subunit constructs that had normal activity and displayed intrareceptor FRET. We used fluorescence lifetime imaging microscopy (FLIM) in live HEK293 cells to determine distinct steady-state FRET efficiencies in the presence of different ligands, suggesting a dynamic picture of the resting state. Patch-clamp fluorometry of the double- and single-insert constructs showed that both the intracellular C-terminal domain (CTD) and the loop region between the M1 and M2 helices move during activation and the CTD is detached from the membrane. Our time-resolved measurements revealed unexpectedly complex fluorescence changes within these intracellular domains, providing clues as to how posttranslational modifications and receptor function interact. PMID:27313205

  12. Identification of intracellular receptor proteins for activated protein kinase C.

    PubMed Central

    Mochly-Rosen, D; Khaner, H; Lopez, J

    1991-01-01

    Protein kinase C (PKC) translocates from the cytosol to the particulate fraction on activation. This activation-induced translocation of PKC is thought to reflect PKC binding to the membrane lipids. However, immunological and biochemical data suggest that PKC may bind to proteins in the cytoskeletal elements in the particulate fraction and in the nuclei. Here we describe evidence for the presence of intracellular receptor proteins that bind activated PKC. Several proteins from the detergent-insoluble material of the particulate fraction bound PKC in the presence of phosphatidylserine and calcium; binding was further increased with the addition of diacylglycerol. Binding of PKC to two of these proteins was concentration-dependent, saturable, and specific, suggesting that these binding proteins are receptors for activated C-kinase, termed here "RACKs." PKC binds to RACKs via a site on PKC distinct from the substrate binding site. We suggest that binding to RACKs may play a role in activation-induced translocation of PKC. Images PMID:1850844

  13. Detection of Neu1 sialidase activity in regulating Toll-like receptor activation.

    PubMed

    Amith, Schammim R; Jayanth, Preethi; Finlay, Trisha; Franchuk, Susan; Gilmour, Alanna; Abdulkhalek, Samar; Szewczuk, Myron R

    2010-09-07

    Mammalian Toll-like receptors (TLRs) are a family of receptors that recognize pathogen-associated molecular patterns. Not only are TLRs crucial sensors of microbial (e.g., viruses, bacteria and parasite) infections, they also play an important role in the pathophysiology of infectious diseases, inflammatory diseases, and possibly in autoimmune diseases. Thus, the intensity and duration of TLR responses against infectious diseases must be tightly controlled. It follows that understanding the structural integrity of sensor receptors, their ligand interactions and signaling components is essential for subsequent immunological protection. It would also provide important opportunities for disease modification through sensor manipulation. Although the signaling pathways of TLR sensors are well characterized, the parameters controlling interactions between the sensors and their ligands still remain poorly defined. We have recently identified a novel mechanism of TLR activation by its natural ligand, which has not been previously observed. It suggests that ligand-induced TLR activation is tightly controlled by Neu1 sialidase activation. We have also reported that Neu1 tightly regulates neurotrophin receptors like TrkA and TrkB, which involve Neu1 and matrix metalloproteinase-9 (MMP-9) cross-talk in complex with the receptors. The sialidase assay has been initially use to find a novel ligand, thymoquinone, in the activation of Neu4 sialidase on the cell surface of macrophages, dendritic cells and fibroblast cells via GPCR Gαi proteins and MMP-9. For TLR receptors, our data indicate that Neu1 sialidase is already in complex with TLR-2, -3 and -4 receptors, and is induced upon ligand binding to either receptor. Activated Neu1 sialidase hydrolyzes sialyl α-2,3-linked β-galactosyl residues distant from ligand binding to remove steric hinderance to TLR-4 dimerization, MyD88/TLR4 complex recruitment, NFkB activation and pro-inflammatory cell responses. In a collaborative

  14. AF-2 activity and recruitment of steroid receptor coactivator 1 to the estrogen receptor depend on a lysine residue conserved in nuclear receptors.

    PubMed Central

    Henttu, P M; Kalkhoven, E; Parker, M G

    1997-01-01

    Hormone-dependent transcriptional activation by nuclear receptors depends on the presence of a conserved C-terminal amphipathic alpha-helix (helix 12) in the ligand-binding domain. Here we show that a lysine residue, which is conserved in most nuclear receptors in the predicted helix 3, is also required for estrogen-dependent transactivation. The replacement of lysine 366 with alanine appreciably reduced activation function 2 (AF-2) activity without affecting steroid- or DNA-binding activity in the mouse estrogen receptor. The mutation dramatically reduced the ability of the receptor to bind steroid receptor coactivator 1 (SRC-1) but had no effect on receptor-interacting protein 140 (RIP-140) binding, indicating that while their sites of interaction overlap, they are not entirely consistent and in keeping with the proposal that the recruitment of coactivators, such as SRC-1, is required for AF-2 activity. Although the function of RIP-140 remains to be established, RIP-140 appears to be capable of recruiting the basal transcription machinery, since overexpression of the protein markedly increased the transcriptional activity of the mutant receptor. Since the lysine residue is conserved, we propose that it is required, together with residues in helix 12, to form the surface by which members of the nuclear receptor family interact with coactivators. PMID:9121431

  15. Identification of Modulators of the Nuclear Receptor Peroxisome Proliferator-Activated Receptor α (PPARα) in a Mouse Liver Gene Expression Compendium

    EPA Science Inventory

    The nuclear receptor family member peroxisome proliferator-activated receptor α (PPARα) is activated by therapeutic hypolipidemic drugs and environmentally-relevant chemicals to regulate genes involved in lipid transport and catabolism. Chronic activation of PPARα in rodents inc...

  16. The prostaglandin EP1 receptor potentiates kainate receptor activation via a protein kinase C pathway and exacerbates status epilepticus

    PubMed Central

    Rojas, Asheebo; Gueorguieva, Paoula; Lelutiu, Nadia; Quan, Yi; Shaw, Renee; Dingledine, Raymond

    2014-01-01

    Prostaglandin E2 (PGE2) regulates membrane excitability, synaptic transmission, plasticity, and neuronal survival. The consequences of PGE2 release following seizures has been the subject of much study. Here we demonstrate that the prostaglandin E2 receptor 1 (EP1, or Ptger1) modulates native kainate receptors, a family of ionotropic glutamate receptors widely expressed throughout the central nervous system. Global ablation of the EP1 gene in mice (EP1-KO) had no effect on seizure threshold after kainate injection but reduced the likelihood to enter status epilepticus. EP1-KO mice that did experience typical status epilepticus had reduced hippocampal neurodegeneration and a blunted inflammatory response. Further studies with native prostanoid and kainate receptors in cultured cortical neurons, as well as with recombinant prostanoid and kainate receptors expressed in Xenopus oocytes, demonstrated that EP1 receptor activation potentiates heteromeric but not homomeric kainate receptors via a second messenger cascade involving phospholipase C, calcium and protein kinase C. Three critical GluK5 C-terminal serines underlie the potentiation of the GluK2/GluK5 receptor by EP1 activation. Taken together, these results indicate that EP1 receptor activation during seizures, through a protein kinase C pathway, increases the probability of kainic acid induced status epilepticus, and independently promotes hippocampal neurodegeneration and a broad inflammatory response. PMID:24952362

  17. Vortioxetine, but not escitalopram or duloxetine, reverses memory impairment induced by central 5-HT depletion in rats: evidence for direct 5-HT receptor modulation.

    PubMed

    Jensen, Jesper Bornø; du Jardin, Kristian Gaarn; Song, Dekun; Budac, David; Smagin, Gennady; Sanchez, Connie; Pehrson, Alan Lars

    2014-01-01

    Depressed patients suffer from cognitive dysfunction, including memory deficits. Acute serotonin (5-HT) depletion impairs memory and mood in vulnerable patients. The investigational multimodal acting antidepressant vortioxetine is a 5-HT3, 5-HT7 and 5-HT1D receptor antagonist, 5-HT1B receptor partial agonist, 5-HT1A receptor agonist and 5-HT transporter (SERT) inhibitor that enhances memory in normal rats in novel object recognition (NOR) and conditioned fear (Mørk et al., 2013). We hypothesized that vortioxetine's 5-HT receptor mechanisms are involved in its memory effects, and therefore investigated these effects in 5-HT depleted rats. Four injections of the irreversible tryptophan hydroxylase inhibitor 4-chloro-dl-phenylalanine methyl ester hydrochloride (PCPA, 86mg/kg, s.c.) induced 5-HT depletion, as measured in hippocampal homogenate and microdialysate. The effects of acute challenge with vortioxetine or the 5-HT releaser fenfluramine on extracellular 5-HT were measured in PCPA-treated and control rats. PCPA's effects on NOR and spontaneous alternation (SA) performance were assessed along with the effects of acute treatment with 5-hydroxy-l-tryptophan (5-HTP), vortioxetine, the selective 5-HT reuptake inhibitor escitalopram, or the 5-HT norepinephrine reuptake inhibitor duloxetine. SERT occupancies were estimated by ex vivo autoradiography. PCPA depleted central 5-HT by >90% in tissue and microdialysate, and impaired NOR and SA performance. Restoring central 5-HT with 5-HTP reversed these deficits. At similar SERT occupancies (>90%) vortioxetine, but not escitalopram or duloxetine, restored memory performance. Acute fenfluramine significantly increased extracellular 5-HT in control and PCPA-treated rats, while vortioxetine did so only in control rats. Thus, vortioxetine restores 5-HT depletion impaired memory performance in rats through one or more of its receptor activities.

  18. The aryl hydrocarbon receptor and glucocorticoid receptor interact to activate human metallothionein 2A.

    PubMed

    Sato, Shoko; Shirakawa, Hitoshi; Tomita, Shuhei; Tohkin, Masahiro; Gonzalez, Frank J; Komai, Michio

    2013-11-15

    Although the aryl hydrocarbon receptor (AHR) and glucocorticoid receptor (GR) play essential roles in mammalian development, stress responses, and other physiological events, crosstalk between these receptors has been the subject of much debate. Metallothioneins are classic glucocorticoid-inducible genes that were reported to increase upon treatment with AHR agonists in rodent tissues and cultured human cells. In this study, the mechanism of human metallothionein 2A (MT2A) gene transcription activation by AHR was investigated. Cotreatment with 3-methylcholanthrene and dexamethasone, agonists of AHR and GR respectively, synergistically increased MT2A mRNA levels in HepG2 cells. MT2A induction was suppressed by RNA interference against AHR or GR. Coimmunoprecipitation experiments revealed a physical interaction between AHR and GR proteins. Moreover, chromatin immunoprecipitation assays indicated that AHR was recruited to the glucocorticoid response element in the MT2A promoter. Thus, we provide a novel mechanism whereby AHR modulates expression of human MT2A via the glucocorticoid response element and protein-protein interactions with GR.

  19. Analysis of Ah receptor pathway activation by brominated flame retardants.

    PubMed

    Brown, David J; Van Overmeire, Ilse; Goeyens, Leo; Denison, Michael S; De Vito, Michael J; Clark, George C

    2004-06-01

    Brominated flame-retardants (BFRs) are used as additives in plastics to decrease the rate of combustion of these materials, leading to greater consumer safety. As the use of plastics has increased, the production and use of flame-retardants has also grown. Many BFRs are persistent and have been detected in environmental samples, raising concerns about the biological/toxicological risk associated with their use. Most BFRs appear to be non-toxic, however there is still some concern that these compounds, or possible contaminants in BFRs mixtures could interact with cellular receptors. In this study we have examined the interaction of decabromodiphenyl ether, Firemaster BP4A (tetrabromobisphenol A), Firemaster PHT4 (tetrabromophthalic anhydride), hexabromobenzene, pentabromotoluene, decabromobiphenyl, Firemaster BP-6 (2,2',4,4',5,5'-hexabromobiphenyl) and possible contaminants of BFR mixtures with the Ah receptor. Receptor binding and activation was examined using the Gel Retardation Assay and increased expression of dioxin responsive genes was detected using the reporter gene based CALUX assay. The results demonstrate the ability of BFRs to activate the AhR signal transduction pathway at moderate to high concentrations as assessed using both assays. AhR-dependent activation by BFRs may be due in part to contaminants present in commercial/technical mixtures. This was suggested by our comparative analysis of Firemaster BP-6 versus its primary component 2,2',4,4',5,5'-hexabromobiphenyl. Some technical mixtures of brominated flame-retardants contain brominated biphenyls, dioxins or dibenzofurans as contaminants. When tested in the CALUX assay these compounds were found to be equivalent to, or more active than their chlorinated analogues. Relative effective potency values were determined from dose response curves for these brominated HAHs.

  20. The Pharmacochaperone Activity of Quinine on Bitter Taste Receptors

    PubMed Central

    Upadhyaya, Jasbir D.; Chakraborty, Raja; Shaik, Feroz A.; Jaggupilli, Appalaraju; Bhullar, Rajinder P.; Chelikani, Prashen

    2016-01-01

    Bitter taste is one of the five basic taste sensations which is mediated by 25 bitter taste receptors (T2Rs) in humans. The mechanism of bitter taste signal transduction is not yet elucidated. The cellular processes underlying T2R desensitization including receptor internalization, trafficking and degradation are yet to be studied. Here, using a combination of molecular and pharmacological techniques we show that T2R4 is not internalized upon agonist treatment. Pretreatment with bitter agonist quinine led to a reduction in subsequent quinine-mediated calcium responses to 35 ± 5% compared to the control untreated cells. Interestingly, treatment with different bitter agonists did not cause internalization of T2R4. Instead, quinine treatment led to a 2-fold increase in T2R4 cell surface expression which was sensitive to Brefeldin A, suggesting a novel pharmacochaperone activity of quinine. This phenomenon of chaperone activity of quinine was also observed for T2R7, T2R10, T2R39 and T2R46. Our results suggest that the observed action of quinine for these T2Rs is independent of its agonist activity. This study provides novel insights into the pharmacochaperone activity of quinine and possible mechanism of T2R desensitization, which is of fundamental importance in understanding the mechanism of bitter taste signal transduction. PMID:27223611

  1. Thiophene-Core Estrogen Receptor Ligands Having Superagonist Activity

    PubMed Central

    Min, Jian; Wang, Pengcheng; Srinivasan, Sathish; Nwachukwu, Jerome C.; Guo, Pu; Huang, Minjian; Carlson, Kathryn E.; Katzenellenbogen, John A.; Nettles, Kendall W.; Zhou, Hai-Bing

    2013-01-01

    To probe the importance of the heterocyclic core of estrogen receptor (ER) ligands, we prepared a series of thiophene-core ligands by Suzuki cross-coupling of aryl boronic acids with bromo-thiophenes, and we assessed their receptor binding and cell biological activities. The disposition of the phenol substituents on the thiophene core, at alternate or adjacent sites, and the nature of substituents on these phenols all contribute to binding affinity and subtype selectivity. Most of the bis(hydroxyphenyl)-thiophenes were ERβ selective, whereas the tris(hydroxyphenyl)-thiophenes were ERα selective; analogous furan-core compounds generally have lower affinity and less selectivity. Some diarylthiophenes show distinct superagonist activity in reporter gene assays, giving maximal activities 2–3 times that of estradiol, and modeling suggests that these ligands have a different interaction with a hydrogen-bonding residue in helix-11. Ligand-core modification may be a new strategy for developing ER ligands whose selectivity is based on having transcriptional activity greater than that of estradiol. PMID:23586645

  2. Luminal Cathepsin G and Protease-Activated Receptor 4

    PubMed Central

    Dabek, Marta; Ferrier, Laurent; Roka, Richard; Gecse, Krisztina; Annahazi, Anita; Moreau, Jacques; Escourrou, Jean; Cartier, Christel; Chaumaz, Gilles; Leveque, Mathilde; Ait-Belgnaoui, Afifa; Wittmann, Tibor; Theodorou, Vassilia; Bueno, Lionel

    2009-01-01

    Impairment of the colonic epithelial barrier and neutrophil infiltration are common features of inflammatory bowel disease. Luminal proteases affect colonic permeability through protease-activated receptors (PARs). We evaluated: (i) whether fecal supernatants from patients with ulcerative colitis (UC) trigger alterations of colonic paracellular permeability and inflammation, and (ii) the roles of cathepsin G (Cat-G), a neutrophil serine protease, and its selective receptor, PAR4, in these processes. Expression levels of both PAR4 and Cat-G were determined in colonic biopsies from UC and healthy subjects. The effects of UC fecal supernatants on colonic paracellular permeability were measured in murine colonic strips. Involvement of Cat-G and PAR4 was evaluated using pepducin P4pal-10 and specific Cat-G inhibitor (SCGI), respectively. In addition, the effect of PAR4-activating peptide was assessed. UC fecal supernatants, either untreated or pretreated with SCGI, were infused into mice, and myeloperoxidase activity was determined. PAR4 was found to be overexpressed in UC colonic biopsies. Increased colonic paracellular permeability that was triggered by UC fecal supernatants was blocked by both SCGI (77%) and P4pal-10 (85%). Intracolonic infusion of UC fecal supernatants into mice increased myeloperoxidase activity. This effect was abolished by SCGI. These observations support that both Cat-G and PAR4 play key roles in generating and/or amplifying relapses in UC and provide a rationale for the development of new therapeutic agents in the treatment of this disease. PMID:19528350

  3. FATTY ACIDS MODULATE TOLL-LIKE RECEPTOR 4 ACTIVATION THROUGH REGULATION OF RECEPTOR DIMERIZATION AND RECRUITMENT INTO LIPID RAFTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The saturated fatty acids acylated on Lipid A of lipopolysaccharide (LPS) or bacterial lipoproteins play critical roles in ligand recognition and receptor activation for Toll-like Receptor 4 (TLR4) and TLR2. The results from our previous studies (J Biol Chem 2003, 2004) demonstrated that saturated ...

  4. Dopamine Receptor Activation Increases HIV Entry into Primary Human Macrophages

    PubMed Central

    Gaskill, Peter J.; Yano, Hideaki H.; Kalpana, Ganjam V.; Javitch, Jonathan A.; Berman, Joan W.

    2014-01-01

    Macrophages are the primary cell type infected with HIV in the central nervous system, and infection of these cells is a major component in the development of neuropathogenesis and HIV-associated neurocognitive disorders. Within the brains of drug abusers, macrophages are exposed to increased levels of dopamine, a neurotransmitter that mediates the addictive and reinforcing effects of drugs of abuse such as cocaine and methamphetamine. In this study we examined the effects of dopamine on HIV entry into primary human macrophages. Exposure to dopamine during infection increased the entry of R5 tropic HIV into macrophages, irrespective of the concentration of the viral inoculum. The entry pathway affected was CCR5 dependent, as antagonizing CCR5 with the small molecule inhibitor TAK779 completely blocked entry. The effect was dose-dependent and had a steep threshold, only occurring above 108 M dopamine. The dopamine-mediated increase in entry required dopamine receptor activation, as it was abrogated by the pan-dopamine receptor antagonist flupenthixol, and could be mediated through both subtypes of dopamine receptors. These findings indicate that the effects of dopamine on macrophages may have a significant impact on HIV pathogenesis. They also suggest that drug-induced increases in CNS dopamine may be a common mechanism by which drugs of abuse with distinct modes of action exacerbate neuroinflammation and contribute to HIV-associated neurocognitive disorders in infected drug abusers. PMID:25268786

  5. Glucocorticoid receptor signalling activates YAP in breast cancer

    PubMed Central

    Sorrentino, Giovanni; Ruggeri, Naomi; Zannini, Alessandro; Ingallina, Eleonora; Bertolio, Rebecca; Marotta, Carolina; Neri, Carmelo; Cappuzzello, Elisa; Forcato, Mattia; Rosato, Antonio; Mano, Miguel; Bicciato, Silvio; Del Sal, Giannino

    2017-01-01

    The Hippo pathway is an oncosuppressor signalling cascade that plays a major role in the control of cell growth, tissue homoeostasis and organ size. Dysregulation of the Hippo pathway leads to aberrant activation of the transcription co-activator YAP (Yes-associated protein) that contributes to tumorigenesis in several tissues. Here we identify glucocorticoids (GCs) as hormonal activators of YAP. Stimulation of glucocorticoid receptor (GR) leads to increase of YAP protein levels, nuclear accumulation and transcriptional activity in vitro and in vivo. Mechanistically, we find that GCs increase expression and deposition of fibronectin leading to the focal adhesion-Src pathway stimulation, cytoskeleton-dependent YAP activation and expansion of chemoresistant cancer stem cells. GR activation correlates with YAP activity in human breast cancer and predicts bad prognosis in the basal-like subtype. Our results unveil a novel mechanism of YAP activation in cancer and open the possibility to target GR to prevent cancer stem cells self-renewal and chemoresistance. PMID:28102225

  6. Aryl hydrocarbon receptor-independent activation of estrogen receptor-dependent transcription by 3-methycholanthrene

    SciTech Connect

    Shipley, Jonathan M.; Waxman, David J. . E-mail: djw@bu.edu

    2006-06-01

    Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that stimulates transcription directed by xenobiotic response elements upstream of target genes. Recently, AhR ligands were reported to induce formation of an AhR-estrogen receptor (ER) complex, which can bind to estrogen response elements (EREs) and stimulate transcription of ER target genes. Presently, we investigate the effect of th