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Martínez-Aguirre C, Carmona-Cruz F, Velasco AL, Velasco F, Aguado-Carrillo G, Cuéllar-Herrera M, Rocha L. Cannabidiol Acts at 5-HT 1A Receptors in the Human Brain: Relevance for Treating Temporal Lobe Epilepsy. Front Behav Neurosci 2020; 14:611278. [PMID: 33384591 PMCID: PMC7770178 DOI: 10.3389/fnbeh.2020.611278] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 11/23/2020] [Indexed: 12/29/2022] Open
Abstract
Experimental evidence indicates that cannabidiol (CBD) induces anxiolytic and antiepileptic effects through the activation of 5-HT1A receptors. These receptors are coupled to Gi/o proteins and induce inhibitory effects. At present, the interaction of CBD with 5-HT1A receptors in the human brain is unknown. The aim of this study focused on evaluating the interaction between CBD and 5-HT1A receptors in cell membranes obtained from the hippocampus and temporal neocortex of autopsies and patients with drug-resistant mesial temporal lobe epilepsy (DR-MTLE). Cell membranes were isolated from the hippocampus and temporal neocortex of a group of patients with DR-MTLE who were submitted to epilepsy surgery (n = 11) and from a group of autopsies (n = 11). The [3H]-8-OH-DPAT binding assay was used to determine the pharmacological interaction of CBD with 5-HT1A receptors. The [35S]-GTPγS assay was used to investigate the CBD-induced activation of Gi/o proteins through its action on 5-HT1A receptors.The CBD affinity (pK i) for 5-HT1A receptors was similar for autopsies and patients with DR-MTLE (hippocampus: 4.29 and 4.47, respectively; temporal neocortex: 4.67 and 4.74, respectively). Concerning the [35S]-GTPγS assay, no statistically significant changes were observed for both hippocampal and neocortical tissue (p > 0.05) at low CBD concentrations (1 pM to 10 μM). In contrast, at high concentrations (100 μM), CBD reduced the constitutive activity of Gi/o proteins of autopsies and DR-MTLE patients (hippocampus: 39.2% and 39.6%, respectively; temporal neocortex: 35.2% and 24.4%, respectively). These changes were partially reversed in the presence of WAY-100635, an antagonist of 5-HT1A receptors, in the autopsy group (hippocampus, 59.8%, p < 0.0001; temporal neocortex, 71.5%, p < 0.0001) and the group of patients with DR-MTLE (hippocampus, 53.7%, p < 0.0001; temporal neocortex, 68.5%, p < 0.001). Our results show that CBD interacts with human 5-HT1A receptors of the hippocampus and temporal neocortex. At low concentrations, the effect of CBD upon Gi/o protein activation is limited. However, at high concentrations, CBD acts as an inverse agonist of 5-HT1A receptors. This effect could modify neuronal excitation and epileptic seizures in patients with DR-MTLE.
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Affiliation(s)
| | - Francia Carmona-Cruz
- Department of Pharmacobiology, Center for Research and Advanced Studies, Mexico City, Mexico
| | - Ana Luisa Velasco
- Epilepsy Clinic, Hospital General de México Dr. Eduardo Liceaga, Mexico City, Mexico
| | - Francisco Velasco
- Epilepsy Clinic, Hospital General de México Dr. Eduardo Liceaga, Mexico City, Mexico
| | | | | | - Luisa Rocha
- Department of Pharmacobiology, Center for Research and Advanced Studies, Mexico City, Mexico
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García-Pedraza JÁ, Hernández-Abreu O, García M, Morán A, Villalón CM. Chronic 5-HT 2 receptor blockade unmasks the role of 5-HT 1F receptors in the inhibition of rat cardioaccelerator sympathetic outflow. Can J Physiol Pharmacol 2018; 96:328-336. [PMID: 28886249 DOI: 10.1139/cjpp-2017-0191] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Abstract
Serotonin (5-hydroxytryptamine; 5-HT) inhibits the rat cardioaccelerator sympathetic outflow by 5-HT1B/1D/5 receptors. Because chronic blockade of sympatho-excitatory 5-HT2 receptors is beneficial in several cardiovascular pathologies, this study investigated whether sarpogrelate (a 5-HT2 receptor antagonist) alters the pharmacological profile of the above sympatho-inhibition. Rats were pretreated for 2 weeks with sarpogrelate in drinking water (30 mg/kg per day; sarpogrelate-treated group) or equivalent volumes of drinking water (control group). Animals were pithed and prepared for spinal stimulation (C7-T1) of the cardioaccelerator sympathetic outflow or for intravenous (i.v.) bolus injections of noradrenaline. Both procedures produced tachycardic responses remaining unaltered after saline. Continuous i.v. infusions of 5-HT induced a cardiac sympatho-inhibition that was mimicked by the 5-HT receptor agonists 5-carboxamidotryptamine (5-CT; 5-HT1/5A), CP 93,129 (5-HT1B), or PNU 142633 (5-HT1D), but not by indorenate (5-HT1A) in both groups; whereas LY344864 (5-HT1F) mimicked 5-HT only in sarpogrelate-treated rats. In sarpogrelate-treated animals, i.v. GR 127935 (310 μg/kg; 5-HT1B/1D/1F receptor antagonist) attenuated 5-CT-induced sympatho-inhibition and abolished LY344864-induced sympatho-inhibition; while GR 127935 plus SB 699551 (1 mg/kg; 5-HT5A receptor antagonist) abolished 5-CT-induced inhibition. These results confirm the cardiac sympatho-inhibitory role of 5-HT1B, 5-HT1D, and 5-HT5A receptors in both groups; nevertheless, sarpogrelate treatment specifically unmasked a cardiac sympatho-inhibition mediated by 5-HT1F receptors.
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Affiliation(s)
- José Ángel García-Pedraza
- a Department of Pharmacobiology, Cinvestav-Coapa, Czda. Tenorios 235, Col. Granjas-Coapa, Deleg. Tlalpan, C.P. 14330, Mexico City, Mexico
- b Laboratory of Pharmacology, Department of Physiology and Pharmacology, Faculty of Pharmacy, University of Salamanca, Biomedical Research Institute of Salamanca (IBSAL), Salamanca 37007, Spain
| | - Oswaldo Hernández-Abreu
- a Department of Pharmacobiology, Cinvestav-Coapa, Czda. Tenorios 235, Col. Granjas-Coapa, Deleg. Tlalpan, C.P. 14330, Mexico City, Mexico
| | - Mónica García
- b Laboratory of Pharmacology, Department of Physiology and Pharmacology, Faculty of Pharmacy, University of Salamanca, Biomedical Research Institute of Salamanca (IBSAL), Salamanca 37007, Spain
| | - Asunción Morán
- b Laboratory of Pharmacology, Department of Physiology and Pharmacology, Faculty of Pharmacy, University of Salamanca, Biomedical Research Institute of Salamanca (IBSAL), Salamanca 37007, Spain
| | - Carlos M Villalón
- a Department of Pharmacobiology, Cinvestav-Coapa, Czda. Tenorios 235, Col. Granjas-Coapa, Deleg. Tlalpan, C.P. 14330, Mexico City, Mexico
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Vidal-Cantú GC, Jiménez-Hernández M, Rocha-González HI, Villalón CM, Granados-Soto V, Muñoz-Islas E. Role of 5-HT5A and 5-HT1B/1D receptors in the antinociception produced by ergotamine and valerenic acid in the rat formalin test. Eur J Pharmacol 2016; 781:109-16. [PMID: 27068146 DOI: 10.1016/j.ejphar.2016.04.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 03/30/2016] [Accepted: 04/07/2016] [Indexed: 12/29/2022]
Abstract
Sumatriptan, dihydroergotamine and methysergide inhibit 1% formalin-induced nociception by activation of peripheral 5-HT1B/1D receptors. This study set out to investigate the pharmacological profile of the antinociception produced by intrathecal and intraplantar administration of ergotamine (a 5-HT1B/1D and 5-HT5A/5B receptor agonist) and valerenic acid (a partial agonist at 5-HT5A receptors). Intraplantar injection of 1% formalin in the right hind paw resulted in spontaneous flinching behavior of the injected hindpaw of female Wistar rats. Intrathecal ergotamine (15nmol) or valerenic acid (1 nmol) blocked in a dose dependent manner formalin-induced nociception. The antinociception by intrathecal ergotamine (15nmol) or valerenic acid (1nmol) was partly or completely blocked by intrathecal administration of the antagonists: (i) methiothepin (non-selective 5-HT5A/5B; 0.01-0.1nmol); (ii) SB-699551 (selective 5-HT5A; up to 10nmol); (iii) anti-5-HT5A antibody; (iv) SB-224289 (selective 5-HT1B; 0.1-1nmol); or (v) BRL-15572 (selective 5-HT1D; 0.1-1nmol). Likewise, antinociception by intraplantar ergotamine (15nmol) and valerenic acid (10nmol) was: (i) partially blocked by methiothepin (1nmol), SB-699551 (10nmol) or SB-224289 (1nmol); and (ii) abolished by BRL-15572 (1nmol). The above doses of antagonists (which did not affect per se the formalin-induced nociception) were high enough to completely block their respective receptors. Our results suggest that ergotamine and valerenic acid produce antinociception via 5-HT5A and 5-HT1B/1D receptors located at both spinal and peripheral sites. This provides new evidence for understanding the modulation of nociceptive pathways in inflammatory pain.
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Affiliation(s)
- Guadalupe C Vidal-Cantú
- Laboratories of Neurobiology of Pain and Cardiovascular Pharmacology, Departamento de Farmacobiología, Cinvestav, Sede Sur, México D.F., México
| | | | - Héctor I Rocha-González
- Sección de Estudios de Posgrado e Investigación. Escuela Superior de Medicina, Instituto Politécnico Nacional, México D.F., México
| | - Carlos M Villalón
- Laboratories of Neurobiology of Pain and Cardiovascular Pharmacology, Departamento de Farmacobiología, Cinvestav, Sede Sur, México D.F., México
| | - Vinicio Granados-Soto
- Laboratories of Neurobiology of Pain and Cardiovascular Pharmacology, Departamento de Farmacobiología, Cinvestav, Sede Sur, México D.F., México
| | - Enriqueta Muñoz-Islas
- Departamento de Biología Celular, Instituto Nacional de Perinatología, Secretaría de Salud, Montes Urales 800, Col. Lomas Virreyes, 11000 México D.F., México; Unidad Académica Multidisciplinaria Reynosa-Aztlán, Universidad Autónoma de Tamaulipas, Reynosa, Tamaulipas, México.
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Endogenously released 5-HT inhibits A and C fiber-evoked synaptic transmission in the rat spinal cord by the facilitation of GABA/glycine and 5-HT release via 5-HT(2A) and 5-HT(3) receptors. Eur J Pharmacol 2013; 702:149-57. [PMID: 23399761 DOI: 10.1016/j.ejphar.2013.01.058] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Revised: 01/08/2013] [Accepted: 01/16/2013] [Indexed: 01/06/2023]
Abstract
Serotonin (5-HT) released from descending fibers plays important roles in spinal functions such as locomotion and nociception. 5-HT2A and 5-HT3 receptors are suggested to contribute to spinal antinociception, although their activation also contributes to neuronal excitation. In the neonatal spinal cord, DL-p-chloroamphetamine (pCA), a 5-HT releaser, inhibited both A fiber-evoked monosynaptic reflex potential (MSR) and C fiber-evoked slow ventral root potential (sVRP). The pCA-mediated inhibition was reversed by ketanserin (a 5-HT2A receptor antagonist) and tropisetron (a 5-HT3 receptor antagonist). Bath-applied 5-HT also inhibited MSR and sVRP; in this case, the actions of 5-HT were antagonized by ketanserin, but not by tropisetron. The pCA-evoked inhibition of sVRP was reduced by bicuculline (a GABAA receptor antagonist) and strychnine (a glycine receptor antagonist). Furthermore, ketanserin inhibited the pCA-evoked release of gamma-aminobutyric acid (GABA) and glycine, while tropisetron inhibited the pCA-evoked release of 5-HT. These results suggest that 5-HT released by pCA activates 5-HT2A receptors, which in turn stimulates the release of GABA/glycine and thereby blocks the spinal nociceptive pathway. 5-HT3 receptors may be involved in the facilitation of 5-HT release via a positive feedback process.
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Masson J, Emerit MB, Hamon M, Darmon M. Serotonergic signaling: multiple effectors and pleiotropic effects. ACTA ACUST UNITED AC 2012. [DOI: 10.1002/wmts.50] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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6
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González-Hernández A, Manrique-Maldonado G, Lozano-Cuenca J, Muñoz-Islas E, Centurión D, Maassen VanDenBrink A, Villalón CM. The 5-HT(1) receptors inhibiting the rat vasodepressor sensory CGRPergic outflow: further involvement of 5-HT(1F), but not 5-HT(1A) or 5-HT(1D), subtypes. Eur J Pharmacol 2011; 659:233-43. [PMID: 21473863 DOI: 10.1016/j.ejphar.2011.03.035] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Revised: 03/01/2011] [Accepted: 03/21/2011] [Indexed: 11/20/2022]
Abstract
We have previously shown that 5-HT(1B) receptors inhibit prejunctionally the rat vasodepressor CGRPergic sensory outflow. Since 5-HT(1) receptors comprise 5-HT(1A), 5-HT(1B), 5-HT(1D) and 5-HT(1F) functional subtypes, this study has further investigated the role of 5-HT(1A), 5-HT(1D) and 5-HT(1F) receptor subtypes in the inhibition of the above vasodepressor sensory outflow. Pithed rats were pretreated with i.v. continuous infusions of hexamethonium and methoxamine, followed by 5-HT(1) receptor agonists. Then electrical spinal stimulation (T(9)-T(12)) or i.v. bolus injections of exogenous α-CGRP produced frequency-dependent or dose-dependent vasodepressor responses. The electrically-induced vasodepressor responses remained unchanged during infusions of the 5-HT(1A) receptor agonists 8-OH-DPAT and NN-DP-5-CT. In contrast, these responses were inhibited by the agonists sumatriptan (5-HT(1A/1B/1D/1F)), indorenate (5-HT(1A)), PNU-142633 (5-HT(1D)) or LY344864 (5-HT(1F)), which did not affect the vasodepressor responses to exogenous CGRP (implying a prejunctional sensory-inhibition). When analysing the effects of antagonists: (i) 310 μg/kg (but not 100 μg/kg) GR127935 (5-HT(1A/1B/1D/1F)) abolished the inhibition to sumatriptan, indorenate, PNU-142633 or LY344864; (ii) 310 μg/kg SB224289 (5-HT(1B)) or BRL15572 (5-HT(1D)) failed to block the inhibition to sumatriptan or PNU-142633, whereas SB224289+BRL15572 partly blocked the inhibition to sumatriptan; and (iii) 10 μg/kg WAY100635 (5-HT(1A)) failed to block the inhibition to indorenate. These results suggest that 5-HT(1F), but not 5-HT(1A) or 5-HT(1D), receptor subtypes inhibit the vasodepressor sensory CGRPergic outflow although, admittedly, no selective 5-HT(1F) receptor agonist is available yet. The pharmacological profile of these receptors resembles that shown in rat dorsal root ganglia by molecular biology techniques.
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MESH Headings
- Animals
- Calcitonin Gene-Related Peptide/metabolism
- Calcitonin Gene-Related Peptide/pharmacology
- Electric Stimulation
- Hemodynamics/drug effects
- Ligands
- Male
- Rats
- Rats, Wistar
- Receptor, Serotonin, 5-HT1A/metabolism
- Receptor, Serotonin, 5-HT1D/metabolism
- Receptors, Serotonin/metabolism
- Receptors, Serotonin, 5-HT1/metabolism
- Serotonin 5-HT1 Receptor Agonists/administration & dosage
- Serotonin 5-HT1 Receptor Agonists/pharmacology
- Serotonin 5-HT1 Receptor Antagonists/pharmacology
- Vasodilation/drug effects
- Receptor, Serotonin, 5-HT1F
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Affiliation(s)
- Abimael González-Hernández
- Departamento de Farmacobiología, Cinvestav-Coapa, Czda. de los Tenorios 235, Col. Granjas-Coapa, Deleg. Tlalpan, 14330 México D.F., Mexico
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7
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Masuda H, de Gannes FP, Haro E, Billaudel B, Ruffié G, Lagroye I, Veyret B. Lack of effect of 50-Hz magnetic field exposure on the binding affinity of serotonin for the 5-HT 1B receptor subtype. Brain Res 2010; 1368:44-51. [PMID: 21047499 DOI: 10.1016/j.brainres.2010.10.103] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2010] [Revised: 10/26/2010] [Accepted: 10/27/2010] [Indexed: 10/18/2022]
Abstract
There is some concern that exposure to extremely low-frequency magnetic fields (MF) causes adverse health effects via signal transduction pathways. Two previous studies reported that exposure to 50-Hz MF decreased the binding affinity of the 1B receptor subtype of serotonin (5-HT) in rat brain membranes. The aim of this study was to investigate whether the exposure to MF affects binding to the 5-HT(1B) receptor and a physiological function associated with 5-HT(1B) receptor activation. Rat brain crude membrane fractions, including 5-HT(1B) receptor and C6-glial cells transfected with human 5-HT(1B) receptor gene, were exposed to 50-Hz MF at 1 mT using Merritt coils under temperature-regulated conditions. In the rat crude membrane, there was no significant difference in the affinity constant of [(3)H]-5-HT between exposed (K(d): 0.92±0.38 nM) and sham-exposed (K(d): 1.00±0.32 nM). The lack of affinity change after exposure was also confirmed using a chemical agonist of the 5-HT receptor, [(3)H]-5-carboxytryptamine (K(d): 0.59±0.06 nM for exposed and 0.71±0.08 nM for sham). Similar negative results in terms of affinity constant were obtained on the human 5-HT(1B) receptor in C6-glial cells. In addition, forskolin-stimulated cAMP production was inhibited by 5-HT administration in a dose-dependent manner in C6-glial cells, but exposure did not modify the inhibitory response. This study thus failed to confirm the previous results and findings suggest that exposure to MF below the current occupational limit does not affect the physiological function involved in 5-HT(1B) receptor subtypes.
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Affiliation(s)
- Hiroshi Masuda
- University of Bordeaux, IMS laboratory, ENSCBP, 16 av. Pey-Berland, 33607 Pessac, France.
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8
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Granados-Soto V, Argüelles CF, Rocha-González HI, Godínez-Chaparro B, Flores-Murrieta FJ, Villalón CM. The role of peripheral 5-HT1A, 5-HT1B, 5-HT1D, 5-HT1E and 5-HT1F serotonergic receptors in the reduction of nociception in rats. Neuroscience 2010; 165:561-8. [PMID: 19837141 DOI: 10.1016/j.neuroscience.2009.10.020] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2009] [Revised: 10/08/2009] [Accepted: 10/13/2009] [Indexed: 12/13/2022]
Abstract
This study assessed the possible antinociceptive role of peripheral 5-HT(1) receptor subtypes in the rat formalin test. Rats were injected into the dorsum of the hind paw with 50 microl of diluted formalin (1%). Nociceptive behavior was quantified as the number of flinches of the injected paw. Reduction of flinching was considered as antinociception. Ipsilateral, but not contralateral, peripheral administration of the 5-HT(1) receptor agonists R(+)-UH-301 (5-HT(1A); 0.1-3 microg/paw), CGS-12066A (5-HT(1B); 0.01-0.3 microg/paw), GR46611 (5-HT(1B/1D); 0.3-10 microg/paw), BRL54443 (5-HT(1E/1F); 3-300 microg/paw) or LY344864 (5-HT(1F); 3-300 microg/paw) significantly reduced formalin-induced flinching. The corresponding vehicle was devoid of any effect by itself. The local antinociceptive effect of R(+)-UH-301 (0.3 microg/paw) was significantly reduced by WAY-100635 (30-100 microg/paw; a 5-HT(1A) receptor antagonist). Moreover, the antagonists GR55562 (30-100 microg/paw; 5-HT(1B/D)) or SB224289 (30-100 microg/paw; 5-HT(1B)) dose-dependently reduced the antinociceptive effect of CGS-12066A (0.3 microg/paw) whereas GR55562 (30-100 microg/paw) or BRL15572 (30-100 microg/paw, 5-HT(1D)) reduced the antinociceptive effect of GR46611 (0.3 microg/paw). Interestingly, the effects of BRL54443 and LY344864 (300 microg/paw each) were partially reduced by methiothepin, but not by the highest doses of WAY-100635, SB224289 or BRL15572. The above antagonists did not produce any effect by themselves. These results suggest that peripheral activation of the 5-HT(1A,) 5-HT(1B), 5-HT(1D), 5-HT(1F) and, probably, 5-HT(1E) receptor subtypes leads to antinociception in the rat formalin test. Thus, the use of selective 5-HT(1) receptor agonists could be a therapeutic strategy to reduce inflammatory pain.
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MESH Headings
- Animals
- Dose-Response Relationship, Drug
- Female
- Formaldehyde
- Functional Laterality
- Hindlimb/drug effects
- Hindlimb/metabolism
- Pain/chemically induced
- Pain/drug therapy
- Pain/metabolism
- Pain Measurement
- Peripheral Nerves/drug effects
- Peripheral Nerves/metabolism
- Rats
- Rats, Wistar
- Receptor, Serotonin, 5-HT1A/metabolism
- Receptor, Serotonin, 5-HT1B/metabolism
- Receptor, Serotonin, 5-HT1D/metabolism
- Receptors, Serotonin/metabolism
- Serotonin 5-HT1 Receptor Agonists
- Serotonin Receptor Agonists/administration & dosage
- Serotonin Receptor Agonists/pharmacology
- Receptor, Serotonin, 5-HT1F
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Affiliation(s)
- V Granados-Soto
- Departamento de Farmacobiología, Cinvestav, Sede Sur, Calzada Tenorios 235, México, DF, Mexico.
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Mehrotra S, Gupta S, Centurión D, Villalón CM, Saxena PR, VandenBrink AM. A61603-induced contractions of the porcine meningeal artery are mediated by alpha1- and alpha2-adrenoceptors. Basic Clin Pharmacol Toxicol 2007; 100:279-85. [PMID: 17371533 DOI: 10.1111/j.1742-7843.2007.00050.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
It has recently been shown that A61603 (N-[5-(4,5-dihydro-1H-imidazol-2yl)-2-hydroxy-5,6,7,8-tetrahydro-naphthalen-1-yl]methane sulphonamide), a potent alpha(1A)-adrenoceptor agonist, decreased carotid artery conductance in anaesthetized pigs by a novel non-adrenergic mechanism. In this study, we set out to pharmacologically characterize A61603-induced contractions of the porcine isolated meningeal artery. While the maximum contractile responses of the artery were similar, A61603 (E(max): 183 +/- 23% of 100 mM KCl; pEC(50): 7.25 +/- 0.18) was more potent than noradrenaline (E(max): 156 +/- 16%; pEC(50): 5.75 +/- 0.17) or phenylephrine (E(max): 163 +/- 20%; pEC(50): 5.63 +/- 0.02). Prazosin (pA(2): 9.36 +/- 0.23) and, to a lesser extent, rauwolscine (pK(b): 6.36 +/- 0.38) and yohimbine (pK(b): 7.30 +/- 0.15) antagonised the contractions to A61603. The 5-HT(1B) (GR127935; N-[4-methoxy-3-(4-methyl-1-piperazinyl) phenyl]-2'-methyl-4'-(5-methyl-1,2,4-oxadiazol-3-yl)[1,1-biphenyl]-4-carboxamide) and 5-HT(2) (ritanserin) receptor antagonists failed to affect the responses to A61603, but methiothepin, which, in addition, has a high affinity for alpha-adrenoceptors, proved an effective antagonist. The A61603-induced responses were suppressed by the cAMP stimulator forskolin, but not by the protein kinase C inhibitor chelerythrine. Our results suggest that the contraction of porcine isolated meningeal artery by A61603 is mediated via mainly alpha(1)-(probably alpha(1A)) and, to a lesser extent, alpha(2)-adrenoceptors, involving the adenylyl cyclase, but not the diacylglycerol pathway.
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Affiliation(s)
- Suneet Mehrotra
- Department of Pharmacology, Erasmus MC, University Medical Center Rotterdam, Rotterdam, The Netherlands
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10
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Assié MB, Lomenech H, Ravailhe V, Faucillon V, Newman-Tancredi A. Rapid desensitization of somatodendritic 5-HT1A receptors by chronic administration of the high-efficacy 5-HT1A agonist, F13714: a microdialysis study in the rat. Br J Pharmacol 2006; 149:170-8. [PMID: 16921393 PMCID: PMC2013794 DOI: 10.1038/sj.bjp.0706859] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2006] [Accepted: 07/04/2006] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE Desensitization of somatodendritic 5-HT(1A) receptors is involved in the mechanism of action of several antidepressants, but the rapidity of this effect and the amount of agonist stimulation needed are unclear. We evaluated the capacity of the high-efficacy 5-HT(1A) agonist, F13714 (3-chloro-4-fluorophenyl-(4-fluoro-4-{[(5-methyl-6-methylamino-pyridin-2-ylmethyl)-amino]-methyl}-piperidin-1-yl-methanone) and of the partial agonist, flesinoxan, to desensitize somatodendritic 5-HT(1A) receptors involved in the control of 5-HT release. EXPERIMENTAL APPROACH Intracerebral microdialysis in the hippocampus of freely moving rats was used to examine the acute and chronic effects of the two compounds (administered by osmotic pumps for 3, 7 or 14 days) on extracellular 5-HT levels, measured by HPLC with electrochemical detection. KEY RESULTS When given acutely, F13714, flesinoxan and the low-efficacy 5-HT(1A) agonist, buspirone, dose-dependently decreased extracellular 5-HT concentrations (ED(50) values: 0.04, 0.77 and 5.6 mg kg(-1), respectively). The selective 5-HT(1A) antagonist WAY100635 inhibited the effects of the three compounds. F13714 (2.5 mg kg(-1) per day for 3, 7 or 14 days and 0.63 mg kg(-1) for 7 days) significantly attenuated the inhibition of 5-HT release induced by buspirone (10 mg kg(-1)). In contrast, flesinoxan (10 mg kg(-1) per day) failed to alter the response to buspirone at any of the treatment durations. CONCLUSIONS AND IMPLICATIONS Rat somatodendritic 5-HT(1A) receptors controlling hippocampal 5-HT release were rapidly desensitized by chronic activation with a high-efficacy 5-HT(1A) agonist, but not by chronic activation with a partial agonist. Thus, rapid 5-HT(1A) autoreceptor desensitization by high-efficacy agonists may accelerate the onset of the therapeutic effects of antidepressants.
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Affiliation(s)
- M-B Assié
- Centre de Recherche Pierre Fabre, Castres Cedex, France.
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11
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Wyman PA, Marshall HR, Flynn ST, King RJ, Thompson M, Smith PW, Hadley MS, Price GW, Scott CM, Dawson LA. Identification of a potent and selective 5-HT1B receptor antagonist. Bioorg Med Chem Lett 2005; 15:4708-12. [PMID: 16153839 DOI: 10.1016/j.bmcl.2005.07.085] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2005] [Revised: 07/19/2005] [Accepted: 07/27/2005] [Indexed: 11/22/2022]
Abstract
An SAR study around the mixed 5-HT1ABD receptor antagonist SB-272183 found that introduction of cis-2,6-dimethyl substitution onto the piperazine ring was a key structural change, which imparted a combination of both excellent selectivity over the 5-HT1A and 5-HT1D receptors and low intrinsic activity. This led to the identification of the selective 5-HT1B receptor antagonist SB-616234.
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Affiliation(s)
- Paul A Wyman
- Psychiatry CEDD, New Frontiers Science Park, GlaxoSmithKline, Third Avenue, Harlow, Essex CM19 5AW, UK.
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12
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Knight PJK, Grigliatti TA. Chimeric G proteins extend the range of insect cell-based functional assays for human G protein-coupled receptors. J Recept Signal Transduct Res 2005; 24:241-56. [PMID: 15648445 DOI: 10.1081/rrs-200035217] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
We previously described a functional assay for G protein-coupled receptors (GPCRs) based on stably transformed insect cells and using the promiscuous G protein Galpha16. We now show that, compared with Galpha16, the use of chimeric Galphaq subunits with C-terminal modifications (qi5-HA, qo5-HA, or qz5-HA) significantly enhances the ability of insect cells to redirect Gi-coupled GPCRs into a Gq-type signal transduction pathway. We coexpressed human Gi-coupled GPCRs, G protein alpha subunits (either a chimeric Galphaq or Galpha16), and the calcium-sensitive reporter protein aequorin in Sf9 cells using a nonlytic protein expression system, and measured agonist-induced intracellular calcium flux using a luminometer. Three of the GPCRs (serotonin 1A, 1D, and dopamine D2) were functionally redirected into a Gq-type pathway when coexpressed with the chimeric G proteins, compared with only one (serotonin 1A) with Galpha16. We determined agonist concentration-response relationships for all three receptors, which yielded EC50 values comparable with those achieved in mammalian cell-based assay systems. However, three other Gi-coupled GPCRs (the opioid kappa1 and delta1 receptors, and serotonin 1E) were not coupled to calcium flux by either the G protein chimeras or Galpha16. Possible reasons and solutions for this result are discussed.
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Affiliation(s)
- Peter J K Knight
- Department of Biochemistry, University of Cambridge, Cambridge, Cambs, UK
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13
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Honda M, Imaida K, Tanabe M, Ono H. Endogenously released 5-hydroxytryptamine depresses the spinal monosynaptic reflex via 5-HT1D receptors. Eur J Pharmacol 2005; 503:55-61. [PMID: 15496296 DOI: 10.1016/j.ejphar.2004.09.045] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2004] [Revised: 09/06/2004] [Accepted: 09/10/2004] [Indexed: 10/26/2022]
Abstract
In the spinal cord, various 5-hydroxytryptamine (5-HT) receptor subtypes are involved in the modulation of motor output. Previously, we have shown that 5-HT1B receptors mediate the monosynaptic reflex depression induced by exogenously applied 5-HT that was formed from the precursor L-5-hydroxytryptophan in spinalized rats. In this study, we determined the effects of endogenous 5-HT, which was released from serotonergic terminals by DL-p-chloroamphetamine, on spinal reflexes. DL-p-chloroamphetamine depressed the monosynaptic reflex and increased the polysynaptic reflex. The depletion of 5-HT abolished the monosynaptic reflex depression, but the increase in polysynaptic reflexes was maintained, suggesting that endogenous 5-HT released by DL-p-chloroamphetamine mediates depression of the monosynaptic reflex in the spinal cord. The depression of the monosynaptic reflex was antagonized by GR127935 (N-[methoxy-3-(4-methyl-l-piperazinyl)phenyl]-2'-methyl-4'-(5-methyl-1,2,4-oxadiazol-3-yl)[1,1-biphenyl]-4-carboxamide; 5-HT1B/1D receptor antagonist) and BRL15572 (3-[4-(4-chlorophenyl)piperazin-1-yl]-1,1-diphenyl-2-propanol; 5-HT1D receptor antagonist) but not by isamoltane (5-HT(1B) receptor antagonist). These results suggest that 5-HT released from serotonergic terminals depresses monosynaptic reflex transmission via 5-HT1D receptors.
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Affiliation(s)
- Motoko Honda
- Laboratory of CNS Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya 467-8603, Japan.
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14
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Honda M, Tanabe M, Ono H. Serotonergic depression of spinal monosynaptic transmission is mediated by 5-HT1B receptors. Eur J Pharmacol 2003; 482:155-61. [PMID: 14660017 DOI: 10.1016/j.ejphar.2003.09.070] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In the spinal cord, various subtypes of serotonin (5-hydroxytryptamine; 5-HT) receptors are involved in the modulation of motor output. Although the excitatory role of 5-HT(2) receptors is known, the receptor subtypes mediating the inhibitory effect of 5-HT on monosynaptic reflex transmission remain unclear. In this study, segmental spinal reflexes were recorded to examine the receptor subtypes underlying 5-HT-mediated inhibition of monosynaptic reflex transmission in spinalized rats. Under conditions of monoamine oxidase blockade with clorgyline, the 5-HT precursor L-5-hydroxytryptophan depressed the monosynaptic reflex. 3-Hydroxybenzylhydrazine dihydrochloride (NSD-1015), a centrally active decarboxylase inhibitor, abolished this inhibition, confirming that the depression of the monosynaptic reflex by L-5-hydroxytryptophan was due to 5-HT. In the presence of GR127935 or isamoltane, which show high affinity for 5-HT(1B) receptors, L-5-hydroxytryptophan did not suppress the monosynaptic reflex, whereas 5-HT(1A), 5-HT(1D), 5-HT(2) and 5-HT(7) receptor antagonists did not alter the inhibitory effect of L-5-hydroxytryptophan. These results suggest that serotonergic depression of monosynaptic reflex transmission is mediated by 5-HT(1B) receptors.
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Affiliation(s)
- Motoko Honda
- Laboratory of CNS Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho, Nagoya 467-8603, Japan.
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15
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Sánchez-López A, Centurión D, Vázquez E, Arulmani U, Saxena PR, Villalón CM. Pharmacological profile of the 5-HT-induced inhibition of cardioaccelerator sympathetic outflow in pithed rats: correlation with 5-HT1 and putative 5-ht5A/5B receptors. Br J Pharmacol 2003; 140:725-35. [PMID: 14504136 PMCID: PMC1574076 DOI: 10.1038/sj.bjp.0705489] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Continuous infusions of 5-hydroxytryptamine (5-HT) inhibit the tachycardiac responses to preganglionic (C7-T1) sympathetic stimulation in pithed rats pretreated with desipramine. The present study identified the pharmacological profile of this inhibitory action of 5-HT. The inhibition induced by intravenous (i.v.) continuous infusions of 5-HT (5.6 microg x kg-1x min-1) on sympathetically induced tachycardiac responses remained unaltered after i.v. treatment with saline or the antagonists GR 127935 (5-HT1B/1D), the combination of WAY 100635 (5-HT1A) plus GR 127935, ritanserin (5-HT2), tropisetron (5-HT3/4), LY215840 (5-HT7) or a cocktail of antagonists/inhibitors consisting of yohimbine (alpha2), prazosin (alpha1), ritanserin, GR 127935, WAY 100635 and indomethacin (cyclooxygenase), but was abolished by methiothepin (5-HT1/2/6/7 and recombinant 5-ht5A/5B). These drugs, used in doses high enough to block their respective receptors/mechanisms, did not modify the sympathetically induced tachycardiac responses per se. I.v. continuous infusions of the agonists 5-carboxamidotryptamine (5-CT; 5-HT1/7 and recombinant 5-ht5A/5B), CP 93129 (r5-HT1B), sumatriptan (5-HT1B/1D), PNU-142633 (5-HT1D) and ergotamine (5-HT1B/1D and recombinant 5-ht5A/5B) mimicked the above sympatho-inhibition to 5-HT. In contrast, the agonists indorenate (5-HT1A) and LY344864 (5-ht1F) were inactive. Interestingly, 5-CT-induced cardiac sympatho-inhibition was abolished by methiothepin, the cocktail of antagonists/inhibitors, GR 127935 or the combination of SB224289 (5-HT1B) plus BRL15572 (5-HT1D), but remained unchanged when SB224289 or BRL15572 were given separately. Therefore, 5-HT-induced cardiac sympatho-inhibition, being unrelated to 5-HT2, 5-HT3, 5-HT4, 5-ht6, 5-HT7 receptors, alpha1/2-adrenoceptor or prostaglandin synthesis, seems to be primarily mediated by (i). 5-HT1 (probably 5-HT1B/1D) receptors and (ii). a novel mechanism antagonized by methiothepin that, most likely, involves putative 5-ht5A/5B receptors.
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MESH Headings
- Animals
- Autonomic Fibers, Preganglionic/drug effects
- Autonomic Fibers, Preganglionic/physiology
- Blood Pressure/drug effects
- Decerebrate State/physiopathology
- Desipramine/administration & dosage
- Desipramine/pharmacokinetics
- Disease Models, Animal
- Drug Therapy, Combination
- Electric Stimulation/methods
- Ergotamine/administration & dosage
- Ergotamine/pharmacokinetics
- Infusions, Intravenous
- Injections, Intravenous
- Male
- Oxadiazoles/administration & dosage
- Oxadiazoles/pharmacokinetics
- Piperazines/administration & dosage
- Piperazines/pharmacokinetics
- Pyridines/administration & dosage
- Pyridines/pharmacokinetics
- Rats
- Rats, Wistar
- Receptors, Serotonin/classification
- Receptors, Serotonin/drug effects
- Receptors, Serotonin/physiology
- Receptors, Serotonin, 5-HT1/classification
- Receptors, Serotonin, 5-HT1/drug effects
- Receptors, Serotonin, 5-HT1/physiology
- Serotonin/administration & dosage
- Serotonin/analogs & derivatives
- Serotonin/pharmacokinetics
- Serotonin Antagonists/administration & dosage
- Serotonin Antagonists/pharmacokinetics
- Serotonin Receptor Agonists/administration & dosage
- Serotonin Receptor Agonists/pharmacokinetics
- Sympathetic Nervous System/drug effects
- Sympathetic Nervous System/physiopathology
- Tachycardia/drug therapy
- Tachycardia/physiopathology
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Affiliation(s)
- Araceli Sánchez-López
- Departamento de Farmacobiología, CINVESTAV-IPN, Czda. de los Tenorios 235, Col. Granjas-Coapa, Deleg. Tlalpan, C.P. 14330, México D.F., México
| | - David Centurión
- Departamento de Farmacobiología, CINVESTAV-IPN, Czda. de los Tenorios 235, Col. Granjas-Coapa, Deleg. Tlalpan, C.P. 14330, México D.F., México
| | - Erika Vázquez
- Departamento de Farmacobiología, CINVESTAV-IPN, Czda. de los Tenorios 235, Col. Granjas-Coapa, Deleg. Tlalpan, C.P. 14330, México D.F., México
| | - Udayasankar Arulmani
- Department of Pharmacology, Cardiovascular Research Institute ‘COEUR', Erasmus MC, University Medical Center Rotterdam, PO Box 1738, Rotterdam 3000 DR, The Netherlands
| | - Pramod R Saxena
- Department of Pharmacology, Cardiovascular Research Institute ‘COEUR', Erasmus MC, University Medical Center Rotterdam, PO Box 1738, Rotterdam 3000 DR, The Netherlands
| | - Carlos M Villalón
- Departamento de Farmacobiología, CINVESTAV-IPN, Czda. de los Tenorios 235, Col. Granjas-Coapa, Deleg. Tlalpan, C.P. 14330, México D.F., México
- Author for correspondence:
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16
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Clitherow JW, King FD, Middlemiss DN, Wyman PA. The discovery and development of 5-HT-terminal autoreceptor antagonists. PROGRESS IN MEDICINAL CHEMISTRY 2003; 41:129-65. [PMID: 12774693 DOI: 10.1016/s0079-6468(02)41004-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
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17
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Bhalla P, Sharma HS, Wurch T, Pauwels PJ, Saxena PR. Molecular cloning and expression of the porcine trigeminal ganglion cDNA encoding a 5-ht(1F) receptor. Eur J Pharmacol 2002; 436:23-33. [PMID: 11834243 DOI: 10.1016/s0014-2999(01)01605-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Using a combination of reverse transcription polymerase chain reaction (RT-PCR) and inverse-PCR techniques, we amplified, cloned and sequenced a full-length porcine 5-hydroxytryptamine 1F (5-ht(1F)) receptor complementary DNA (cDNA) derived from porcine trigeminal ganglion. Sequence analysis revealed 1101 base pairs (bp) encoding an open reading frame of 366 amino acids showing a high similarity (>90%) with the 5-ht(1F) receptor sequences from other species, including human. The recombinant porcine 5-ht(1F) receptor was expressed in African green monkey kidney cell lines (COS-7 cells) and its ligand binding profile was determined using [3H]5-HT. The affinities of several agonists (LY334370 (5-(4-fluorobenzoyl)amino-3-(1-methylpiperidin-4-yl)-1H-indole fumarate)>CP122638 (N-methyl-3 [pyrrolidin 2(R)-yl methyl]-1H-indol-5-ylmethyl sulphonamide)=naratriptan =5HT>eletriptan>sumatriptan>frovatriptan =avitriptan>dihydroergotamine>zolmitriptan>5-carboxamidotryptamine>rizatriptan>alniditan=donitriptan>L694247 (2-[5-[3-(4-methylsulphonylamino)benzyl-1,2,4-oxadiazol-5-yl]-1H-indole-3-yl] ethylamine) and putative antagonists (methiothepin>GR127935 (N-[4-methoxy-3-(4-methyl-1-piperazinyl) phenyl]-2'-methyl 4'-(5-methyl-1,2,4-oxadiazol-3-yl) [1,1-biphenyl]-4-carboxamide hydrochloride)>ritanserin>SB224289 (2,3,6,7-tetrahydro-1'-methyl-5-[2'-methyl-4'(5-methyl-1,2,4-oxadiazol-3-yl) biphenyl-4-carbonyl] furo [2,3-f] indole-3-spiro-4'-piperidine hydrochloride)>BRL155572 ([1-(3-chlorophenyl)-4-[3,3-diphenyl (2-(S,R) hydroxypropanyl)piperazine] hydrochloride)>ketanserin=pindolol) correlated highly with those described for the recombinant human 5-ht(1F) receptor (Spearman correlation coefficient; r(s)=0.942). Nevertheless, as compared to the human homologue, some triptans (i.e. sumatriptan, zolmitriptan and rizatriptan) displayed a 10- to 15-fold lower affinity for the porcine 5-ht(1F) receptor. Using RT-PCR technique, the expression of porcine 5-ht(1F) receptor mRNA was observed in cerebral cortex, trigeminal ganglion and several blood vessels, but not in skeletal muscles. In conclusion, we have cloned and established the amino acid sequence and ligand binding profile of the porcine 5-ht(1F) receptor as well as the distribution of its mRNA. This information may be helpful in exploring the role of 5-ht(1F) receptor in physiological processes and diseases, such as migraine.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Binding, Competitive
- COS Cells
- Cloning, Molecular
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- Gene Expression
- Humans
- Molecular Sequence Data
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Serotonin/genetics
- Receptors, Serotonin/metabolism
- Recombinant Proteins/metabolism
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Sequence Homology, Nucleic Acid
- Serotonin Antagonists/metabolism
- Serotonin Receptor Agonists/metabolism
- Swine
- Trigeminal Ganglion/metabolism
- Receptor, Serotonin, 5-HT1F
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Affiliation(s)
- Pankaj Bhalla
- Department of Pharmacology, Erasmus University Medical Centre Rotterdam, Post Box 1738, 3000 DR, Rotterdam, The Netherlands
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18
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Raymond JR, Mukhin YV, Gelasco A, Turner J, Collinsworth G, Gettys TW, Grewal JS, Garnovskaya MN. Multiplicity of mechanisms of serotonin receptor signal transduction. Pharmacol Ther 2001; 92:179-212. [PMID: 11916537 DOI: 10.1016/s0163-7258(01)00169-3] [Citation(s) in RCA: 333] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The serotonin (5-hydroxytryptamine, 5-HT) receptors have been divided into 7 subfamilies by convention, 6 of which include 13 different genes for G-protein-coupled receptors. Those subfamilies have been characterized by overlapping pharmacological properties, amino acid sequences, gene organization, and second messenger coupling pathways. Post-genomic modifications, such as alternative mRNA splicing or mRNA editing, creates at least 20 more G-protein-coupled 5-HT receptors, such that there are at least 30 distinct 5-HT receptors that signal through G-proteins. This review will focus on what is known about the signaling linkages of the G-protein-linked 5-HT receptors, and will highlight some fascinating new insights into 5-HT receptor signaling.
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Affiliation(s)
- J R Raymond
- The Research Service of the Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC 29401, USA.
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19
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Wurch T, Matsumoto A, Pauwels PJ. Agonist-independent and -dependent oligomerization of dopamine D(2) receptors by fusion to fluorescent proteins. FEBS Lett 2001; 507:109-13. [PMID: 11682068 DOI: 10.1016/s0014-5793(01)02969-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Oligomerization of the short (D(2S)) and long (D(2L)) isoforms of the dopamine D(2) receptor was explored in transfected Cos-7 cells by their C-terminal fusion to either an enhanced cyan or enhanced yellow fluorescent protein (ECFP or EYFP) and the fluorescent fusion protein interaction was monitored by a fluorescence resonance energy transfer (FRET) assay. The pharmacological properties of the fluorescent fusion proteins, as measured by both displacement of [(3)H]nemonapride binding and agonist-mediated stimulation of [(35)S]GTPgammaS binding upon co-expression with a G(alphao)Cys(351)Ile protein, were not different from the respective wild-type D(2S) and D(2L) receptors. Co-expression of D2S:ECFP+D2S:EYFP in a 1:1 ratio and D2L:ECFP+D2L:EYFP in a 27:1 ratio resulted, respectively, in an increase of 26% and 16% in the EYFP-specific fluorescent signal. These data are consistent with a close proximity of both D(2S) and D(2L) receptor pairs of fluorescent fusion proteins in the absence of ligand. The agonist-independent D(2S) receptor oligomerization could be attenuated by co-expression with either a wild-type, non-fluorescent D(2S) or D(2L) receptor subtype, but not with a distinct beta(2)-adrenoceptor. Incubation with the agonist (-)-norpropylapomorphine dose-dependently (EC(50): 0.23+/-0.06 nM) increased the FRET signal for the co-expression of D2S:ECFP and D2S:EYFP, in support of agonist-dependent D(2S) receptor oligomerization. In conclusion, our data strongly suggest the occurrence of dopamine D(2) receptor oligomers in intact Cos-7 cells.
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Affiliation(s)
- T Wurch
- Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, 17 avenue Jean Moulin, 81106 Cedex, Castres, France.
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20
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Pauwels PJ, Tardif S, Colpaert FC. Differential signalling of both wild-type and Thr(343)Arg dopamine D(2short) receptor by partial agonists in a G-protein-dependent manner. Biochem Pharmacol 2001; 62:723-32. [PMID: 11551517 DOI: 10.1016/s0006-2952(01)00717-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
G-protein activation and Ca(2+) responses by the wild-type D(2short) receptor and a mutation Thr(343)Arg, in the distal BBXXB motif of its third intracellular loop, were investigated in CHO-K1 cells in terms of ligand:receptor:G-protein interactions. No evidence was obtained for constitutive, agonist-independent receptor activation, but differences in the ligand-mediated activation profiles of both the wild-type and mutant Thr(343)Arg D(2short) receptor were observed. Most of the partial agonists, but not bromocriptine, displayed an enhanced response at the mutant D(2short) receptor, suggesting that the mutation brings the receptor in a more active state. This enhancement was apparent both at the level of G-protein activation ([35S]GTPgammaS binding) and at the effector (Ca(2+) response) and occurred with different G(alpha)-proteins. Partial agonists were also found to act differently via the wild-type D(2short) receptor depending on the involved G(alpha)-protein. Compared with higher efficacy agonists, partial agonists displayed Ca(2+) responses with slower and dissimilar kinetic properties. Lisuride and in particular bromocriptine produced a more potent response in the co-presence of a G(alphao) protein instead of a chimeric G(alphaq/o)- or a promiscuous G(alpha15)-protein. S(+)-propylnorapomorphine showed a similar partial response irrespective of the combined G(alpha)-protein. Bromerguride and (+)-UH 232 induced weak (16 to 21% versus dopamine) intrinsic activity in the co-presence of a G(alphaq/o)-protein in contrast to their silent properties with a G(alpha15)- or a G(alphao)Cys(351)Ile-protein. In conclusion, the present data strongly suggest that multiple activation binding sites are involved with these ligands at the D(2short) receptor, and that their activation may be unravelled by either the mutation or co-expressed G(alpha)-proteins being investigated.
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Affiliation(s)
- P J Pauwels
- Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, 17 Avenue Jean Moulin, F-81106, Castres, France.
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21
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Bhalla P, Sharma HS, Ma X, Wurch T, Pauwels PJ, Saxena PR. Molecular cloning, pharmacological properties and tissue distribution of the porcine 5-HT(1B) receptor. Br J Pharmacol 2001; 133:891-901. [PMID: 11454663 PMCID: PMC1572856 DOI: 10.1038/sj.bjp.0704150] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Using a combination of RT - PCR and inverse-PCR techniques, we amplified, cloned and sequenced a full-length porcine 5-HT(1B) receptor cDNA derived from porcine cerebral cortex. Sequence analysis revealed 1170 bp encoding an open reading frame of 390 amino acids showing a 95% similarity with the human 5-HT(1B) receptor. The recombinant porcine 5-HT(1B) cDNA was expressed in monkey Cos-7 cells and its pharmacological profile was determined by radioligand binding assay using [(3)H]-GR125743. The affinities of several agonists (L694247>ergotamine > or =5-carboxamidotryptamine=dihydroergotamine=5-HT>CP122638=zolmitriptan>sumatriptan) and putative antagonists (GR127935>methiothepin>SB224289>>ritanserin>ketanserin > or =BRL15572) correlated highly with those described for the recombinant human 5-HT(1B) receptor. In membranes obtained from cells co-expressing the porcine 5-HT(1B) receptor and a mutant G(alphao)Cys(351)Ile protein, 5-HT and zolmitriptan increased, while the 5-HT(1B) receptor antagonist SB224289 decreased basal [(35)S]-GTPgammaS binding, thus showing inverse agonism. The potency of zolmitriptan in the [(35)S]-GTPgammaS binding assay (pEC(50): 7.64+/-0.04) agreed with its affinity in displacing the antagonist [(3)H]-GR125743 (pK(i): 7.36+/-0.07). The 5-HT(1B) receptor mRNA was observed by RT-PCR in several blood vessels, cerebral cortex, cerebellum and trigeminal ganglion. In situ hybridization performed in frontal cerebral cortex sections revealed the expression of 5-HT(1B) receptor mRNA in pyramidal cells. In conclusion, we have cloned and established the amino acid sequence, ligand binding profile and location of the porcine 5-HT(1B) receptor. This information may be useful in exploring the role of 5-HT(1B) receptor in pathophysiological processes relevant for novel drug discovery in diseases such as migraine.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Benzamides/metabolism
- Binding, Competitive/drug effects
- COS Cells
- Cerebral Cortex/metabolism
- Cloning, Molecular
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- Dose-Response Relationship, Drug
- Gene Expression
- Guanosine 5'-O-(3-Thiotriphosphate)/metabolism
- In Situ Hybridization
- Molecular Sequence Data
- Pyridines/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Radioligand Assay
- Receptor, Serotonin, 5-HT1B
- Receptors, Serotonin/drug effects
- Receptors, Serotonin/genetics
- Receptors, Serotonin/metabolism
- Recombinant Proteins/drug effects
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Sequence Homology, Nucleic Acid
- Serotonin Antagonists/pharmacology
- Serotonin Receptor Agonists/pharmacology
- Sulfur Radioisotopes
- Swine
- Tissue Distribution
- Tritium
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Affiliation(s)
- Pankaj Bhalla
- Department of Pharmacology, Erasmus University Medical Centre Rotterdam, Rotterdam, The Netherlands
| | - Hari S Sharma
- Department of Pharmacology, Erasmus University Medical Centre Rotterdam, Rotterdam, The Netherlands
| | - Xiaoqian Ma
- Department of Pharmacology, Erasmus University Medical Centre Rotterdam, Rotterdam, The Netherlands
| | - Thierry Wurch
- Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, Castres Cédex, France
| | - Petrus J Pauwels
- Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, Castres Cédex, France
| | - Pramod R Saxena
- Department of Pharmacology, Erasmus University Medical Centre Rotterdam, Rotterdam, The Netherlands
- Author for correspondence:
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Koek W, Vacher B, Cosi C, Assié MB, Patoiseau JF, Pauwels PJ, Colpaert FC. 5-HT1A receptor activation and antidepressant-like effects: F 13714 has high efficacy and marked antidepressant potential. Eur J Pharmacol 2001; 420:103-12. [PMID: 11408031 DOI: 10.1016/s0014-2999(01)01011-1] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To examine further the hypothesis that the magnitude of the intrinsic activity of agonists at 5-HT1A receptors determines the magnitude of their psychotropic activity, we studied the relationship between the maximal receptor activation produced by various 5-HT1A receptor ligands and their antidepressant-like effects (i.e., decreased immobility in the forced swimming test in rats). Using three different in vitro assays suitable to measure differences among high, intermediate, and low efficacy 5-HT1A receptor agonists, ligands were identified with intrinsic activities ranging from low-negative (i.e., the inverse agonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexane-carboxamide (WAY 100635)) to high-positive (i.e., 3-chloro-4-fluorophenyl-(4-fluoro-4-[[(5-methyl-6-methylamino-pyridin-2-ylmethyl)-amino]-methyl]-piperidin-1-yl-methanone (F 13714)). In addition, novel compounds with intermediate intrinsic activity, like buspirone, but with high selectivity for 5-HT1A receptors, unlike buspirone, were identified. The maximal effects of the 5-HT1A receptor ligands in the forced swimming test correlated positively (rS=0.91, P<0.005) with the rank order of their intrinsic activity at 5-HT1A receptors. This relationship constitutes evidence that the magnitude of the psychotropic activity of 5-HT1A receptor ligands is a positive function of their intrinsic activity at the receptor, and suggests that F 13714, which had maximal effects in the forced swimming test significantly larger than any of the other compounds examined here, did so because of its higher intrinsic activity at 5-HT1A receptors.
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Affiliation(s)
- W Koek
- Centre de Recherche Pierre Fabre, 17 Ave. Jean Moulin, 81106 Cedex, Castres, France.
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23
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Bhalla P, Sharma HS, Wurch T, Pauwels PJ, Saxena PR. Molecular cloning, sequence analysis and pharmacological properties of the porcine 5-HT(1D) receptor. Br J Pharmacol 2000; 131:949-57. [PMID: 11053216 PMCID: PMC1572407 DOI: 10.1038/sj.bjp.0703645] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2000] [Revised: 07/31/2000] [Accepted: 08/08/2000] [Indexed: 11/08/2022] Open
Abstract
A cDNA encoding the full-length 5-HT(1D) receptor derived from porcine cerebral cortex was amplified, cloned and sequenced, using guinea-pig 5-HT(1D) receptor coding sequence oligonucleotide primers in reverse transcription-polymerase chain reaction (RT - PCR). The 5' and 3' ends of the porcine 5-HT(1D) receptor cDNA were verified by inverse PCR. Sequence analysis of porcine 5-HT(1D) receptor cDNA revealed an open reading frame of 1134 nucleotides encoding a polypeptide of 377 amino acids having 92% homology with the human 5-HT(1D) receptor and 88 - 90% homology with other species homologues. The porcine 5-HT(1D) receptor cDNA was further subcloned into a mammalian expression vector pcDNA3 and expressed in monkey Cos-7 cells. Radioligand binding assays using either [(3)H]-5-CT or [(3)H]-GR125743 on Cos-7 cell membranes showed that pK(i) values of 14 serotonin ligands were highly correlated with those obtained with the human 5-HT(1D) receptor. Nonetheless, a selective antagonist at the human 5-HT(1D) receptor, BRL15572, only poorly recognized the porcine homologue. Using membranes from cells co-expressing the porcine 5-HT(1D) receptor and rat G(alphail)Cys(351) Ile protein, it was shown that 5-HT and zolmitriptan increased, while ketanserin decreased basal [(35)S]-GTPgammaS binding. The potency of zolmitriptan in the [(35)S]-GTPgammaS binding assay (pEC(50): 8. 46+/-0.08) agreed with its affinity in displacing the radioligands [(3)H]-5-CT and [(3)H]-GR125743 (pK(i): 8.38+/-0.15 and 8.67+/-0.08, respectively). In conclusion, we have established the cDNA sequence and pharmacology of the cloned porcine 5-HT(1D) receptor. This information would be useful in exploring the role of divergent amino acid residues in the receptor-ligand interaction as well as the role of 5-HT(1D) receptor in pathophysiological processes relevant for novel drug discovery in diseases such as migraine.
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Affiliation(s)
- Pankaj Bhalla
- Department of Pharmacology, Erasmus University Medical Centre Rotterdam, Rotterdam, The Netherlands
| | - Hari S Sharma
- Department of Pharmacology, Erasmus University Medical Centre Rotterdam, Rotterdam, The Netherlands
| | - Thierry Wurch
- Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, Castres Cédex, France
| | - Petrus J Pauwels
- Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, Castres Cédex, France
| | - Pramod R Saxena
- Department of Pharmacology, Erasmus University Medical Centre Rotterdam, Rotterdam, The Netherlands
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24
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Pauwels PJ, Colpaert FC. Heterogeneous ligand-mediated Ca(++) responses at wt and mutant alpha(2A)-adrenoceptors suggest multiple ligand activation binding sites at the alpha(2A)-adrenoceptor. Neuropharmacology 2000; 39:2101-11. [PMID: 10963753 DOI: 10.1016/s0028-3908(00)00040-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Ligand:receptor interactions were analysed at wild-type, Asp(79)Asn and Thr(373)Lys alpha(2A) AR by measuring Ca(++) responses in the co-presence of a G(alpha 15) protein in CHO-K1 cells. (-)-Adrenaline displayed a time-dependent Ca(++) response with the following magnitude: wt alpha(2A) AR>Thr(373)Lys alpha(2A) AR>Asp(79)Asn alpha(2A) AR. The maximal amplitude of activation by d-medetomidine and clonidine versus that of (-)-adrenaline was not affected by the Asp(79)Asn mutation, whereas it was significantly lower for both UK 14304 (-42%) and oxymetazoline (-35%). BHT 920 induced a higher Ca(++) response (+19%) at the Asp(79)Asn alpha(2A) AR. Some (atipamezole>BRL 44408=idazoxan approximately SKF 86466>dexefaroxan) but not all (RX 811059 and RS 15385) of the putative alpha(2) AR antagonists tested also displayed partial agonist properties at the Asp(79)Asn alpha(2A) AR. At the Thr(373)Lys alpha(2A) AR, high-efficacy responses were produced by each of the agonists, whereas the putative antagonists showed the following rank order of maximal responses: BRL 44408>SKF 86466>atipamezole approximately idazoxan>dexefaroxan. The observed heterogeneity of Ca(++) responses produced by different ligands at wt and mutant alpha(2A) AR may be explained by assuming the existence of multiple ligand activation binding sites at the alpha(2A) AR.
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Affiliation(s)
- P J Pauwels
- Centre de Recherche Pierre Fabre, Department of Cellular and Molecular Biology, 17, avenue Jean Moulin, 81106 Castres Cédex, France.
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25
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Rauly I, Ailhaud M, Wurch T, Pauwels PJ. alpha(2A)-adrenoceptor: G(alphai1) protein-mediated pertussis toxin-resistant attenuation of G(s) coupling to the cyclic AMP pathway. Biochem Pharmacol 2000; 59:1531-8. [PMID: 10799649 DOI: 10.1016/s0006-2952(00)00276-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
Fusion proteins were constructed between a recombinant human alpha(2A)-adrenoceptor and either a rat wild-type G(alphai1) or putative pertussis toxin-resistant form of the G(alphai1) protein (G(alphai1)Cys(351)Gly). [(3)H]2-[2-(2-Methoxy-1, 4-benzodioxanyl)]imidazoline hydrochloride (RX 821002) saturation binding experiments demonstrated that both fusion proteins were expressed at a similar level as the alpha(2A)-adrenoceptor co-expressed with either a wild-type G(alphai1) or mutant G(alphai1)Cys(351)Gly protein in COS-7 cells, and displayed a ligand binding profile similar to that for the alpha(2A)-adrenoceptor protein. In alpha(2A)-adrenoceptor-transfected COS-7 cells, 5-bromo-6-(2-imidazolin-2-yl-amino) quinoxaline tartrate (brimonidine, 10 microM) induced stimulation (151 +/- 28%) of adenosine 3',5'-cyclic monophosphate (cAMP) formation which was prevented by cholera toxin treatment, demonstrating a direct coupling of the alpha(2A)-adrenoceptor to an endogenous G(alphas) protein in COS-7 cells. Expression of either the wild-type G(alphai1) or mutant G(alphai1)Cys(351)Gly protein in co-expression or fusion with the alpha(2A)-adrenoceptor in COS-7 cells suppressed the brimonidine-induced stimulation of cAMP formation, both in the presence and absence of pertussis toxin pretreatment. Hence, the G(alphai1) protein apparently blocks the G(s)-coupled alpha(2A)-adrenoceptor-mediated pathway in a pertussis toxin-non-sensitive way.
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Affiliation(s)
- I Rauly
- Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, 81106, Castres, France.
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26
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Le Grand B, Panissié A, Perez M, Pauwels PJ, John GW. Zolmitriptan stimulates a Ca(2+)-dependent K(+) current in C6 glioma cells stably expressing recombinant human 5-HT(1B) receptors. Eur J Pharmacol 2000; 397:297-302. [PMID: 10844127 DOI: 10.1016/s0014-2999(00)00284-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Stimulation of a Ca(2+)-dependent K(+) current by zolmitriptan, a 5-HT(1B/1D) receptor partial agonist, was investigated in C6 glioma cells stably expressing recombinant human 5-HT(1B) receptors. Outward K(+) currents (I(K)) were examined in non-transfected C6 glioma cells and in cells expressing cloned human 5-HT(1B) receptors using the patch-clamp technique in the whole-cell configuration. In C6 glioma cells expressing recombinant human 5-HT(1B) receptor, zolmitriptan increased I(K) in a concentration-dependent manner (maximum increase 16.3+/-7.8%, n=5, p<0.001) with a pD(2) value (geometric mean with 95% confidence intervals) of 7.03 (7.90-6.10). Zolmitriptan failed to elicit increases in I(K) in non-transfected C6 cells. In the presence of the mixed 5-HT(1B/1D) receptor antagonist, N-[4-methoxy-3-(4-methyl-1-piperazinyl)phenyl]-2(-methyl-4(5-methyl-1 ,2,4)-oxadiazol-3-yl)[1,1-biphenyl]-4-carboxamide 2HCl (GR 127935, 0. 1 mcM), zolmitriptan (1 mcM) failed to significantly increase I(K) in C6 cells expressing human 5-HT(1B) receptors confirming that zolmitriptan-evoked responses were indeed mediated by human 5-HT(1B) receptors. In C6 cells expressing cloned human 5-HT(1B) receptors, zolmitriptan-induced increases in I(K) were prevented by the calcium chelator, EGTA (5 mM) when included in the patch pipette (maximum increase -3.3+/-4.2%, n=4, P=NS). The Ca(2+)-dependent K(+) channel blockers, iberiotoxin (0.1 mcM) and tetraethylammonium (TEA, 1 mM), abolished zolmitriptan-induced increases in I(K) (4.5+/-7.3%, n=4 and -0.8+/-1.7%, n=4, respectively, P=NS in each case) in C6 cells expressing human 5-HT(1B) receptors, confirming the involvement of Ca(2+)-dependent K(+) channels. In conclusion, the 5-HT(1B/1D) receptor partial agonist, zolmitriptan, stimulates I(K/Ca) in C6 glioma cells stably transfected with human 5-HT(1B) receptors suggesting an increase of hyperpolarizing current.
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Affiliation(s)
- B Le Grand
- Division of Cardiovascular Diseases, Centre de Recherche Pierre Fabre, 17 Av. Jean Moulin, 81106 Cedex, Castres, France
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27
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Wurch T, Palmier C, Pauwels PJ. Induction of a high-affinity ketanserin binding site at the 5-Hydroxytryptamine(1B) receptor by modification of its carboxy-terminal intracellular portion. Biochem Pharmacol 2000; 59:1117-21. [PMID: 10704941 DOI: 10.1016/s0006-2952(99)00416-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Two chimeric 5-hydroxytryptamine (5-HT) receptors were constructed by exchanging the C-terminal portion of the human (h) 5-HT(1B) receptor with the equivalent domain of the h 5-HT(2A) receptor (5-HT(1B/2A)) or with this domain truncated from its last 44 amino acids (5-HT(1B/2ADelta44)). The equilibrium dissociation constant of the radioligand [(3)H]GR 125743 was similar for both chimera compared to the wild-type (wt) h 5-HT(1B) receptor upon transient expression in COS-7 cells. Ketanserin binding affinity was 21-fold increased from pK(i): 5.79 (wt h 5-HT(1B) receptor) to pK(i): 7.11 at the 5-HT(1B/2A) chimeric receptor, this latter value being close to that of the wt h 5-HT(1D) receptor (pK(i): 7.62). This enhanced ketanserin binding affinity was lost when the last 44 C-terminal amino acids of the 5-HT(2A) receptor were deleted in the chimera 5-HT(1B/2ADelta44) (pK(i): 5.80). The binding affinities of the 5-HT antagonists ritanserin, GR 125743, and SB-224289 were not modified at either chimeric 5-HT receptor. The agonists F 11356, 5-HT, zolmitriptan, and sumatriptan yielded slightly increased (2- to 6-fold) binding affinities at both chimera as compared to the wt h 5-HT(1B) receptor. The present data suggest a role for the C-terminal intracellular receptor domain in modifying ketanserin/5-HT(1B) receptor interactions.
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Affiliation(s)
- T Wurch
- Department of Cellular and Molecular Biology, Centre De Recherche Pierre Fabre, 81106, Castres, France
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28
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Abstract
It is now nearly 5 years since the last of the currently recognised 5-HT receptors was identified in terms of its cDNA sequence. Over this period, much effort has been directed towards understanding the function attributable to individual 5-HT receptors in the brain. This has been helped, in part, by the synthesis of a number of compounds that selectively interact with individual 5-HT receptor subtypes--although some 5-HT receptors still lack any selective ligands (e.g. 5-ht1E, 5-ht5A and 5-ht5B receptors). The present review provides background information for each 5-HT receptor subtype and subsequently reviews in more detail the functional responses attributed to each receptor in the brain. Clearly this latter area has moved forward in recent years and this progression is likely to continue given the level of interest associated with the actions of 5-HT. This interest is stimulated by the belief that pharmacological manipulation of the central 5-HT system will have therapeutic potential. In support of which, a number of 5-HT receptor ligands are currently utilised, or are in clinical development, to reduce the symptoms of CNS dysfunction.
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Affiliation(s)
- N M Barnes
- Department of Pharmacology, The Medical School, University of Birmingham, Edgbaston, UK.
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29
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Marcoli M, Maura G, Munari C, Ruelle A, Raiteri M. Pharmacological diversity between native human 5-HT1B and 5-HT1D receptors sited on different neurons and involved in different functions. Br J Pharmacol 1999; 126:607-12. [PMID: 10188970 PMCID: PMC1565844 DOI: 10.1038/sj.bjp.0702336] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The releases of [3H]5-hydroxytryptamine ([3H]5-HT) and of endogenous glutamic acid and their modulation through presynaptic h5-HT1B autoreceptors and h5-HT1D heteroreceptors have been investigated in synaptosomal preparations from fresh neocortical samples obtained from patients undergoing neurosurgery. The inhibition by 5-HT of the K+ (15 mM)-evoked overflow of [3H]5-HT was antagonized by the 5-HT1B/5-HT1D receptor ligand GR 127935, which was ineffective on its own; this drug was previously found to behave as a full agonist at the h5-HT1D heteroreceptor regulating glutamate release. The recently proposed selective h5-HT1B receptor ligand SB-224289 also prevented the effect of 5-HT at the autoreceptor, being inactive on its own; in contrast, SB-224289, at 1 microM, was unable to interact with the h5-HT1D heteroreceptor. The inhibitory effect of 5-HT on the K+-evoked overflow of glutamate was antagonized by the h5-HT1D receptor ligand BRL-15572; added in the absence of 5-HT the compound was without effect. BRL-15572 (1 microM) was unable to modify the effect of 5-HT at the autoreceptor regulating [3H]5-HT release. The selective 5-HT1A receptor antagonist (+)-WAY 100135, previously found to be an agonist at the h5-HT1D heteroreceptor regulating glutamate release, could not interact with the h5-HT1B autoreceptor when added at 1 microM. It is concluded that native h5-HT1B and h5-HT1D receptors exhibit a hitherto unexpected pharmacological diversity.
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Affiliation(s)
- M Marcoli
- Dipartimento di Medicina Sperimentale, Sezione di Farmacologia e Tossicologia, Università di Genova, Italy
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30
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Wurch T, Colpaert FC, Pauwels PJ. G-protein activation by putative antagonists at mutant Thr373Lys alpha2A adrenergic receptors. Br J Pharmacol 1999; 126:939-48. [PMID: 10193774 PMCID: PMC1571221 DOI: 10.1038/sj.bjp.0702379] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. Replacement of a threonine by a lysine at position 373 in the C-terminal portion of the third intracellular loop of the human alpha2A-adrenergic receptor (alpha2A AR) has been reported to generate a constitutively active mutant receptor in analogy with similar mutations in the alpha1B and beta2 AR (Ren et al., 1993). In the present study, the mutant Thr373Lys alpha2A AR receptor was investigated by measuring the formation of inositol phosphates in either the absence or presence of mouse G(alpha)15 protein in Cos-7 cells. 2. Increased affinity, potency and/or efficacy for the agonists [(-)-adrenaline, UK 14304, clonidine, guanabenz and oxymetazoline] was observed, consistent with a precoupled mutant alpha2A AR: G-protein state. The basal inositol phosphates response was similar at the wild-type (wt) and mutant alpha2A AR, but was enhanced at the mutant alpha2A AR upon co-expression with the mouse G(alpha)15 protein. This enhanced response could not be attenuated in the presence of any of the tested alpha2 AR antagonists (10 microM), suggesting that inverse agonist activity did not occur at the mutant alpha2A AR. 3. Ligands that so far have been identified as antagonists at the wt alpha2A AR demonstrated either no intrinsic activity (MK 912, WB 4101, RS 15385, RX 811059 and RX 821002) or positive efficacy [Emax, % vs. 1 microM UK 14304: dexefaroxan (27+/-7), idazoxan (34+/-9), atipamezole (27+/-4), BRL 44408 (59+/-5) and SKF 86466 (54+/-9)] at the mutant alpha2A AR, but only in the presence of the mouse G(alpha)15 protein. The ligand potencies corresponded with their respective pKi values at the mutant alpha2A AR receptor. 4. The partial agonist effect of SKF 86466 was resistant to pertussis toxin treatment (100 ng ml(-1)) and not affected by co-expression of the rat G(alpha)i1 protein. It was virtually absent in the presence of 10 microM RS 15385. SKF 86466 was without intrinsic activity upon co-expression of the mouse G(alpha)q protein. 5. Some putative alpha2 AR antagonists exerted a partial agonist activity that was highly dependent on the presence of specific G-protein alpha-subunits, suggesting that these ligands cause selective G-protein activation at the mutant alpha2A AR.
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Affiliation(s)
- T Wurch
- Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, 17, avenue Jean Moulin–81106 Castres Cédex–France
| | - F C Colpaert
- Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, 17, avenue Jean Moulin–81106 Castres Cédex–France
| | - P J Pauwels
- Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, 17, avenue Jean Moulin–81106 Castres Cédex–France
- Author for correspondence:
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31
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Wurch T, Colpaert FC, Pauwels PJ. Chimeric receptor analysis of the ketanserin binding site in the human 5-Hydroxytryptamine1D receptor: importance of the second extracellular loop and fifth transmembrane domain in antagonist binding. Mol Pharmacol 1998; 54:1088-96. [PMID: 9855638 DOI: 10.1124/mol.54.6.1088] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The 5-hydroxytryptamine (5-HT)1B/1D receptor subtypes are involved in the regulation of 5-HT release and have gained particular interest because of their apparent role in migraine. Although selective antagonists for both receptor subtypes recently have been developed, the receptor domains involved in the pharmacological specificity of these antagonists are defined poorly. This was investigated with a chimeric 5-HT1B/1D receptor analysis and using ketanserin as a selective antagonist of h5-HT1D (h5-HT1D) Ki = 24-27 nM) as opposed to h5-HT1B (Ki = 2193-2902 nM) receptors. A domain of the h5-HT1D receptor encompassing the second extracellular loop and the fifth transmembrane domain is necessary and sufficient to promote higher affinity binding (Ki = 65-115 nM) for ketanserin to the h5-HT1B receptor. The same domain of the h5-HT1B receptor, when exchanged in the h5-HT1D receptor, abolished high affinity binding of ketanserin (Ki = 364-1265 nM). A similar observation was made with the antagonist ritanserin and seems specific because besides the unmodified binding affinities for 5-HT and zolmitriptan, only minor modifications (2-4-fold) were observed for the agonists L 694247 and sumatriptan and the antagonists GR 127935 and SB 224289. Generating point mutations of divergent amino acids compared with the h5-HT1B receptor did not demonstrate a smaller peptide region related to a significant modification of ketanserin binding. The antagonists ketanserin and ritanserin are likely to bind the h5-HT1D receptor by its second extracellular loop, near the exofacial surface of the fifth transmembrane domain, or both.
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Affiliation(s)
- T Wurch
- Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, 81106 Castres Cédex, France
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32
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Perez M, Jorand-Lebrun C, Pauwels PJ, Pallard I, Halazy S. Dimers of 5HT1 ligands preferentially bind to 5HT1B/1D receptor subtypes. Bioorg Med Chem Lett 1998; 8:1407-12. [PMID: 9871775 DOI: 10.1016/s0960-894x(98)00222-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
New dimers of known 5HT1 ligands (5HT, 1-NP or 8-OH-DPAT) have been prepared and evaluated at human cloned 5HT1B, 5HT1D and 5HT1A receptors. Binding experiments show that all these dimers have better affinities at 5HT1B/1D receptors than their corresponding monomeric ligands. Studies of inhibition of the forskolin-stimulated c-AMP formation mediated by the human 5HT1B receptor show that hetero-bivalent ligands [combining an agonist (5HT) with an antagonist (1-NP)] behave as partial agonists while the intrinsic activity of bivalent antagonists (combining two 1-NP residues) was found to be spacer dependent. Surprisingly enough, the dimer of 8-OH-DPAT 6 binds to 5HT1A, 5HT1B and 5HT1D receptors with similar high affinity.
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Affiliation(s)
- M Perez
- Medicinal Chemistry Division, Centre de Recherche Pierre FABRE, Castres, France
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33
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Dupuis DS, Colpaert FC, Pauwels PJ. G-protein activation at 5-HT1A receptors by the 5-ht1F ligand LY334370 in guinea-pig brain sections and recombinant cell lines. Br J Pharmacol 1998; 124:283-90. [PMID: 9641544 PMCID: PMC1565387 DOI: 10.1038/sj.bjp.0701832] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
1. G-protein activation by the 5-ht1F receptor agonist 5-(4-fluorobenzoyl)amino-3-(1-methylpiperidin-4-yl)-1H-indole fumarate (LY334370) was investigated by use of autoradiography of receptor-activated G-proteins in guinea-pig brain sections and [35S]-GTPgammaS binding responses in cell lines stably expressing human 5-HT1A (h 5-HT1A) receptors. 2. LY334370 (10 microM) caused little or no stimulation of [35S]-GTPgammaS binding in guinea-pig brain regions enriched in 5-ht1F binding sites (e.g., claustrum, caudate/putamen and thalamic nuclei), as identified by labelling with 10 nM [3H]-sumatriptan plus 10 nM 5-carboxamidotryptamine (5-CT). 3. Application of LY334370 (10 microM) to guinea-pig brain sections resulted in an increase of [35S]-GTPgammaS binding in hippocampus (123+/-17%), lateral septum (58+/-14%), dorsal raphe (57+/-10%), entorhinal (37+/-11%) and cingulate cortex (28+/-10%). This distribution fits with the G-protein activation mediated by 5-HT1A receptors as found with lisuride (10 microM), and labelling of 5-HT1A receptors by 140 pM [125I]-4-(2'-methoxy-phenyl)- -[2'-(n-2"-pyridinyl)-p-iodobenzamido]-ethyl-piperazine (p-MPPI). 4. The LY334370-mediated [35S]-GTPgammaS response was antagonized by the selective, silent 5-HT1A receptor antagonist N-[2-[4-(2-methoxyphenyl)1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohex anecarboxa-mide (WAY100635, 1 microM) in each of the brain structures investigated. The distribution pattern of the [35S]-GTPgammaS binding response and the antagonist profile suggest that the LY334370-induced response in guinea-pig brain is mediated by 5-HT1A receptors. 5. The maximal LY334370-induced [35S]-GTPgammaS binding response (83 to 94%) in membranes of recombinant C6-glial/h 5-HT1A and HeLa/h 5-HT1A cells was close to that of 5-HT, suggesting LY334370 to exert high intrinsic activity at h 5-HT1A receptors. 6. In conclusion, in guinea-pig brain sections and recombinant cell lines the 5-ht1F receptor agonist LY334370 causes G-protein activation that is mediated by 5-HT1A receptors. Caution should be taken when employing this ligand as a putative selective 5-ht1F agonist.
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Affiliation(s)
- D S Dupuis
- Department of Cellular and Molecular Biology, Centre de Recherche Pierre Fabre, Castres, France
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34
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Maura G, Marcoli M, Tortarolo M, Andrioli GC, Raiteri M. Glutamate release in human cerebral cortex and its modulation by 5-hydroxytryptamine acting at h 5-HT1D receptors. Br J Pharmacol 1998; 123:45-50. [PMID: 9484853 PMCID: PMC1565139 DOI: 10.1038/sj.bjp.0701581] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
1. The release of glutamic acid and its modulation by 5-hydroxytryptamine (5-HT) in the human brain has been investigated in synaptosomal preparations from fresh neocortical samples obtained from patients undergoing neurosurgery to reach deeply sited tumours. 2. The Ca2+-dependent K+ (15 mM)-evoked overflow of glutamate was inhibited by 5-HT in a concentration-dependent manner (EC50 = 2.9 nM; maximal effect approximately 50%). The inhibition caused by 5-HT was antagonized by the 5-HT1/5-HT2 receptor antagonist methiothepin. The 5-HT1B/5-HT1D receptor agonist sumatriptan mimicked 5-HT (EC50 = 6.4 nM; maximal effect approximately 50%); the effect of sumatriptan was also methiothepin-sensitive. Selective 5-HT1A receptor antagonists could not prevent the inhibition of glutamate release by 5-HT. 3. The 5-HT1B/5-HT1D receptor ligand GR 127935 and the 5-HT2C/5-HT1B/5-HT1D receptor ligand metergoline were unable to prevent the 5-HT effect; instead they inhibited glutamate release, their effects being abolished by methiothepin. Some 5-HT1A receptor antagonists also displayed intrinsic agonist activity. 4. The effect of sumatriptan was prevented by ketanserin, a drug known to display much higher affinity for recombinant h 5-HT1D than for h 5-HT1B receptors. 5. We propose that neocortical glutamatergic nerve terminals in human brain cortex possess release-inhibiting presynaptic heteroreceptors that appear to belong to the h 5-HT1D subtype.
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Affiliation(s)
- G Maura
- Institute of Pharmacology and Toxicology, University of Genova, Italy
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Pauwels PJ, Wurch T, Palmier C, Colpaert FC. Pharmacological analysis of G-protein activation mediated by guinea-pig recombinant 5-HT1B receptors in C6-glial cells: similarities with the human 5-HT1B receptor. Br J Pharmacol 1998; 123:51-62. [PMID: 9484854 PMCID: PMC1565141 DOI: 10.1038/sj.bjp.0701584] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
1. The guinea-pig recombinant 5-hydroxytryptamine1B (gp 5-HT1B) receptor stably transfected in rat C6-glial cells was characterized by monitoring G-protein activation in a membrane preparation with agonist-stimulated [35S]-GTPgammaS binding. The intrinsic activity of 5-HT receptor ligands was compared with that determined previously at the human recombinant 5-HT1B (h 5-HT1B) receptor under similar experimental conditions. 2. Membrane preparations of C6-glial/gp 5-HT1B cells exhibited [3H]-5-carboxamidotryptamine (5-CT) and [3H]-N-[4-methoxy-3,4-methylpiperazin-1-yl) phenyl]-3-methyl-4-(4-pyridinyl)benzamide (GR 125743) binding sites with a pKd of 9.62 to 9.85 and a Bmax between 2.1 to 6.4 fmol mg(-1) protein. The binding affinities of a series of 5-HT receptor ligands determined with [3H]-5-CT and [3H]-GR 125743 were similar. Ligand affinities were comparable to and correlated (r2: 0.74, P<0.001) with those determined at the recombinant h 5-HT1B receptor. 3. [35S]-GTPgammaS binding to membrane preparations of C6-glial/gp 5-HT1B cells was stimulated by the 5-HT receptor agonists that were being investigated. The maximal responses of naratriptan, zolmitriptan, sumatriptan, N-methyl-3-[pyrrolidin-2(R)-ylmethyl]-1H-indol-5-ylmethyl sulphonamide (CP 122638), rizatriptan and dihydroergotamine were between 0.76 and 0.85 compared to 5-HT. The potency of these agonists showed a positive correlation (r2: 0.72, P=0.015) with their potency at the recombinant h 5-HT1B receptor. 1-naphthylpiperazine, (+/-)-cyanopindolol and (2'-methyl-4'-(5-methyl[1,2,4] oxadiazole-3-yl)biphenyl-4-carboxylic acid [4-methoxy-3-(4-methylpiperazin-1-yl)phenyl]amide (GR 127935) elicited an even smaller response (Emax: 0.32 to 0.63). 4. The ligands 1'-methyl-5-(2'-methyl-4'-(5-methyl-1,2,4-oxadiazole-3-yl) biphenyl-4-carbonyl)-2,3,6,7tetrahydrospiro [furo[2,3-f]indole-3-spiro-4'-piperidine] (SB224289), methiothepin and ritanserin displayed inhibition of basal [35S]-GTPgammaS binding at concentrations relevant to their binding affinity for the gp 5-HT1B receptor. Methiothepin and SB224289 behaved as competitive antagonists at gp 5-HT1B receptors; pA2 values were 9.74 and 8.73, respectively when 5-HT was used as an agonist. These estimates accorded with the potencies measured in antagonism of zolmitriptan-mediated inhibition of forskolin-stimulated cyclic AMP formation. Ketanserin acted as a weak antagonist (pK(B): 5.87) at gp 5-HT1B receptors. 5. In conclusion, the recombinant gp 5-HT1B receptor shares important pharmacological similarities with the recombinant h 5-HT1B receptor. The finding that negative activity occurs at these receptors further suggests that SB224289, methiothepin and ritanserin are likely to be inverse agonists.
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Affiliation(s)
- P J Pauwels
- Centre de Recherche Pierre Fabre, Department of Cellular & Molecular Biology, Castres, France
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Jorand-Lebrun C, Pauwels P, Palmier C, Chopin P, Moret C, Marien M, Halazy S. Arylpiperazide derivatives of phenylpiperazines as a new class of potent and selective 5-HT1B receptor antagonists. Bioorg Med Chem Lett 1997. [DOI: 10.1016/s0960-894x(97)10164-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Jorand-Lebrun C, Pauwels PJ, Palmier C, Moret C, Chopin P, Perez M, Marien M, Halazy S. 5-HT1B receptor antagonist properties of novel arylpiperazide derivatives of 1-naphthylpiperazine. J Med Chem 1997; 40:3974-8. [PMID: 9397179 DOI: 10.1021/jm9703552] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A new series of arylpiperazide derivatives of 1-naphthylpiperazine of general formula 4 has been prepared and evaluated as 5-HT1B antagonists. Binding experiments at cloned human 5-HT1A, 5-HT1B, and 5-HT1D receptors show that these derivatives are potent and selective ligands for 5-HT1B/1D subtypes with increased binding selectivity versus the 5-HT1A receptor when compared to 1-naphthylpiperazine (1-NP). Studies of inhibition of the forskolin-stimulated cAMP formation mediated by the human 5-HT1B receptor demonstrate that the nature of the arylpiperazide substituent modulates the intrinsic activity of these 1-NP derivatives. Among them, 2-[[8-(4-methylpiperazin-1-yl)naphthalen-2-yl]oxy] -1-(4-o-tolylpiperazin-1-yl)ethanone (4a) was identified as a potent neutral 5-HT1B antagonist able to antagonize the inhibition of 5-HT release induced by 5-CT (5-carbamoyltryptamine) in guinea pig hypothalamus slices. Moreover, 4a was found to potently antagonize the hypothermia induced by a selective 5-HT1B/1D agonist in vivo in the guinea pig following oral administration (ED50 = 0.13 mg/kg).
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Affiliation(s)
- C Jorand-Lebrun
- Department of Cellular and Molecular Biology, Centre de Recherche Pierre FABRE, Castres, France
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Moret C, Briley M. 5-HT autoreceptors in the regulation of 5-HT release from guinea pig raphe nucleus and hypothalamus. Neuropharmacology 1997; 36:1713-23. [PMID: 9517443 DOI: 10.1016/s0028-3908(97)00145-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
5-HT autoreceptors involved in the regulation of 5-HT release in the guinea pig dorsal raphe nucleus have been studied in comparison with those in the hypothalamus. In vitro release was measured in slices of raphe and hypothalamus prelabelled with [3H]5-HT, superfused with Krebs solution and depolarized electrically. The non-selective 5-HT receptor agonist, 5-carboxamidotryptamine (5-CT) (0.1-10 nM for raphe: 1-100 nM for hypothalamus) and antagonist, methiothepin (10-1000nM), decreased and increased, respectively, the release of [3H]5-HT evoked by electrical stimulation in either of these regions when given alone. The selective 5-HT1B/D receptor antagonist, GR127935 (100-1000 nM), and the 5-HT1D receptor antagonist, ketanserin (300-1000 nM), had no significant effect on this release in either of these regions. Methiothepin and GR127935 (100-1000 nM) shifted to the right the concentration-effect curve of 5-CT in both the raphe and the hypothalamus. At 300 nM, ketanserin shifted to the right the concentration-effect curve of 5-CT in the raphe but did not modify the 5-CT curve in the hypothalamus. In microdialysis experiments ketanserin, applied locally at 10 microM, increased the extracellular levels of 5-HT in the dorsal raphe nucleus of the freely moving guinea pig, whereas 5-HT levels were unchanged in the hypothalamus. Ketanserin at 1 microM did not affect the decrease in 5-HT output induced by the selective 5-HT1B/D receptor agonist, naratriptan (used at 10 microM in raphe and 0.1 microM in hypothalamus), in the raphe or the hypothalamus. In the raphe, WAY100635, a 5-HT1A receptor antagonist, at 1 microM, did not prevent naratriptan (10 microM) from reducing the extracellular levels of 5-HT. These results suggest that, in the conditions used in this study, the release of 5-HT in the dorsal raphe nucleus is possibly modulated in part by 5-HT1B receptors but essentially the control is through 5-HT receptors whose subtype is still to be determined. In the hypothalamus, however, it is clear that only 5-HT1B receptors are involved in the modulation of 5-HT neurotransmission.
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Affiliation(s)
- C Moret
- Pierre Fabre Research Center, Castres, France
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Pauwels PJ. Competitive and silent antagonism of recombinant 5-HT1B receptors by amiloride. GENERAL PHARMACOLOGY 1997; 29:749-51. [PMID: 9347320 DOI: 10.1016/s0306-3623(97)00008-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
1. The cyclic adenosine monophosphate (cAMP) response of the diuretic amiloride was compared with sumatriptan at recombinant human 5-HT1B (h5-HT1B) receptor sites in stably transfected Chinese hamster ovary (CHO-K1) cells. 2. Amiloride, free of intrinsic activity (pEC50 < 3.0), competitively antagonized the sumatriptan-mediated inhibition (pEC50: 7.37) of 100 microM forskolin-induced cAMP formation with a pA2 value of 4.46. 3. The antagonist feature was not shared by the amiloride derivative ethylisopropylamiloride, notwithstanding a slightly higher 5-HT1B receptor-binding affinity (pKi: 4.87) than that of amiloride (pKi: 4.70).
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Affiliation(s)
- P J Pauwels
- Centre de Recherche Pierre Fabre, Laboratory of Cellular and Molecular Neurobiology, Castres, France
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40
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Gerhardt CC, van Heerikhuizen H. Functional characteristics of heterologously expressed 5-HT receptors. Eur J Pharmacol 1997; 334:1-23. [PMID: 9346322 DOI: 10.1016/s0014-2999(97)01115-1] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Over the past 10 years, molecular cloning has revealed the presence of 15 serotonin (5-hydroxytryptamine; 5-HT) receptor subtypes, which can be subdivided in seven subfamilies. Except for the 5-HT3 receptors, which are ligand-gated ion channels, all 5-HT receptors belong to the superfamily of G-protein-coupled receptors. The large multiplicity of 5-HT receptor subtypes has been suggested to be a direct result of the evolutionary age of the 5-HT system. Molecular information on G-protein-coupled 5-HT receptors is currently available for several mammalian species as well as for a limited number of invertebrate species (insects, molluscs). The aim of this review is to give an overview of all cloned 5-HT receptor subtypes belonging to the superfamily of G-protein-coupled receptors with specific emphasis on the pharmacological and signaling properties of the receptors upon expression in several heterologous expression systems.
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MESH Headings
- Animals
- Aplysia/chemistry
- Drosophila/chemistry
- Gene Expression Regulation
- Humans
- Lymnaea/chemistry
- Receptor, Serotonin, 5-HT1B
- Receptor, Serotonin, 5-HT1D
- Receptor, Serotonin, 5-HT2A
- Receptor, Serotonin, 5-HT2C
- Receptors, Serotonin/classification
- Receptors, Serotonin/genetics
- Receptors, Serotonin/physiology
- Receptors, Serotonin, 5-HT1
- Receptors, Serotonin, 5-HT4
- Signal Transduction/physiology
- Terminology as Topic
- Receptor, Serotonin, 5-HT1F
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Affiliation(s)
- C C Gerhardt
- Department of Biochemistry and Molecular Biology, Research Institute Neurosciences, Vrije Universteit, Amsterdam, The Netherlands
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41
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Abstract
1. 5-Hydroxytryptamine-1B (5-HT 1B, formerly designated 5-HT 1D beta) and 5-hydroxy-tryptamine-1D (5-HT 1D, formerly designated 5-HT 1D alpha) receptors are distinct molecular entities that mediate serotonergic neurotransmission. Both are G-protein-coupled receptors without introns in their coding region, negatively coupled to adenylate cyclase; their precise function in human beings remains to be defined. In brain, they are highly enriched in the globus pallidus and the substantia nigra. 2. Presynaptic 5-HT 1B/D receptors take part in the control of the release not only of 5-HT itself, but also of other neurotransmitters-for example, acetylcholine, glutamate, dopamine, noradrenaline and gamma-aminobutyric acid. Selective blockade of central 5-HT 1B/D autoreceptors should facilitate 5-HT neurotransmission and may offer a novel approach to antidepressant therapy. Other 5-HT 1B/D receptors are located postsynaptically; those receptors may be supersensitive in the pathophysiology of obsessive-compulsive disorder and may be a potential target for its treatment. 3. Few if any ligands show selectivity for 5-HT 1B or 5-HT 1D receptors or both. Most pharmacological studies have been performed with nonselective antagonists-for example, metergoline, I-naphthylpiperazine, methiothepin, ketanserin and ritanserin. Recently, a novel series of benzanilides have been reported as the first examples of selective 5-HT 1B/D receptor antagonists. GR 127935, a representative compound of this series, displays mixed agonist-antagonist properties both in vitro and in vivo. It induces upon systemic administration in the guinea pig either an opposite (decrease) effect or a small increase (65%, 5 mg/kg) in the concentration of cortical extracellular 5-HT compared with fluoxetine (218%, 10 mg/kg). The importance of blockade of 5-HT 1B/D receptors in the raphé region, their possible interaction with 5-HT 1A receptors, and consequent inhibition of 5-HT release in terminal 5-HT 1B/D receptor-containing regions are discussed. 4. To find out whether the available so-called 5-HT 1B/D receptor antagonists are indeed antagonists and not partial agonists, efficacy was measured at recombinant human 5-HT 1B and 5-HT 1D receptor sites by using a [35S]-GTP gamma S binding assay to membrane preparations of stably transfected rat C6-glial cell lines. Metergoline and the selective 5-HT 1B/D receptor ligands GR 127935 as well as GR 125743 showed significant intrinsic activity (43% to 69%) at the 5-HT 1D receptor subtype, whereas the nonselective ligand 1-naphthylpiperazine yielded less (15% to 19%) intrinsic activity at both receptor subtypes. In contrast, the nonselective ligands methiothepin, ketanserin and ritanserin are inverse agonists because they displayed negative efficacy (-14% to -28%). Differential blockade of 5-HT 1B/D receptors by neutral antagonists and inverse agonists is discussed in relation to the 5-HT tone on 5-HT 1B/D receptors. 5. It can concluded that 5-HT 1B/D receptor ligands modulate 5-HT neurotransmission through a terminal 5-HT 1B/D receptor. Future work should be directed toward the identification of selective 5-HT 1B and 5-HT 1D receptor ligands that display either neutral antagonist or inverse agonist properties to evaluate the therapeutic potential of 5-HT 1B/D receptor blockade.
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Affiliation(s)
- P J Pauwels
- Centre de Recherche Pierre Fabre, Laboratory of Cellular and Molecular Neurobiology, Castres, France.
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Davidson C, Stamford JA. Synergism of 5-HT 1B/D antagonists with paroxetine on serotonin efflux in rat ventral lateral geniculate nucleus slices. Brain Res Bull 1997; 43:405-9. [PMID: 9241443 DOI: 10.1016/s0361-9230(97)00026-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Serotonin (5-HT) efflux in rat ventral lateral geniculate nucleus (vLGN) slices was evoked by electrical stimulation (20 pulses at 100 Hz, 10 mA, 190 ms train) and measured, along with 5-HT uptake, by fast cyclic voltammetry at implanted carbon fibre microelectrodes. Paroxetine (100 nM), a selective serotonin reuptake inhibitor (SSRI), increased stimulated 5-HT efflux to 194 +/- 25% of pre-drug values at maximum (mean +/- SEM, n = 5) and the half-life of uptake to 684 +/- 135%. When given alone, neither the selective 5-HT 1B antagonist isamoltane (1 microM) nor the 5-HT 1D/B antagonist GR 127935 (50 nM), affected 5-HT efflux or uptake under this stimulation paradigm. When added in combination with paroxetine, both isamoltane and GR 127935 significantly potentiated the effect of paroxetine on stimulated 5-HT efflux: isamoltane to 302 +/- 48% at maximum (p < 0.05 vs. paroxetine alone), GR 127935 to 318 +/- 95% (p < 0.05 vs. paroxetine alone) of pre-drug values. Neither isamoltane nor GR 127935 had any effect on 5-HT uptake. The selective 5-HT 1A antagonist WAY 100635 (10 nM) had no effect on 5-HT efflux or uptake, alone or in combination with paroxetine. These data suggest that, under these experimental conditions, paroxetine gives rise to tonic activation of the vLGN terminal 5-HT autoreceptors. Furthermore, these data show that 5-HT 1B and possibly 5-HT 1D antagonists block this inhibitory autoreceptor tone and may thus be a useful addition to SSRI treatment in the clinic.
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Affiliation(s)
- C Davidson
- Royal London School of Medicine and Dentistry, Royal London Hospital, Whitechapel, UK
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Halazy S, Perez M, Fourrier C, Pallard I, Pauwels PJ, Palmier C, John GW, Valentin JP, Bonnafous R, Martinez J. Serotonin dimers: application of the bivalent ligand approach to the design of new potent and selective 5-HT(1B/1D) agonists. J Med Chem 1996; 39:4920-7. [PMID: 8960551 DOI: 10.1021/jm960552l] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A series of serotonin dimers of formula 4 in which two serotonin moeities are linked together through their 5-hydroxyl residue has been prepared and evaluated as 5-HT(1B/1D) receptor agonists. Binding experiments at cloned human 5-HT(1B), 5-HT(1D), and 5-HT(1A) receptors show that all of these dimers are very potent ligands at 5-HT(1B/1D) receptors with increased binding selectivity vs the 5-HT(1A) receptor when compared to serotonin. Studies of inhibition of the forskolin-stimulated c-AMP formation mediated by the human 5-HT(1B) receptor (formerly the 5-HT(1Dbeta) receptor) demonstrate that all of these serotonin dimers behave as full agonists. Among them, the piperazide derivatives of bis-serotonin, 4g,j, were also identified as very potent agonists in contracting the New Zealand white rabbit saphenous vein (pD2 = 7.6 in each case compared to 5.8 for sumatriptan). Results analysis supports the hypothesis that the important increase in potency of the serotonin dimers can be attributed to the presence of two serotonin pharmacophores in the same molecule, while the enhanced selectivity for 5-HT(1B/1D) receptor subtypes may be due to the position of the spacer attachment to serotonin.
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Affiliation(s)
- S Halazy
- Medicinal Chemistry Division, Centre de Recherche Pierre Fabre, Castres, France
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Wurch T, Palmier C, Colpaert FC, Pauwels PJ. Recombinant saphenous vein 5-HT1B receptors of the rabbit: comparative pharmacology with human 5-HT1B receptors. Br J Pharmacol 1996; 120:153-9. [PMID: 9117091 PMCID: PMC1564345 DOI: 10.1038/sj.bjp.0700868] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
1. The rabbit recombinant saphenous vein 5-hydroxytryptamine1B (r 5-HT1B) receptor stably transfected in rat C6-glial cells was characterized by measuring adenosine 3':5'-cyclic monophosphate (cycle AMP) formation upon exposure to various 5-HT receptor ligands. The effects of agonists and antagonists were compared with their effects determined previously at the human cloned 5-HT1B (h 5-HT1B) receptor under similar experimental conditions. 2. Intact C6-glial cells expressing rb HT1B receptors exhibited [3H]-5-carboxamidotryptamine (5-CT) binding sites with a Kd of 0.80 +/- 0.13 nM and a Bmax between 225 to 570 fmol mg-1 protein. The binding affinities of a series of 5-HT receptor ligands determined in a membrane preparation with [3H]-5-CT or [3H]-N-[4-methoxy-3-(4-methylpiperazin-1-yl)phenyl]-3-methyl-4-(-4 -pyridyl) benzamide (GR 125,743) were similar. With the exception of ketanserin, ligand affinities were comparable to those determined at the clones h 5-HT1B receptor site. 3. rb 5-HT1B receptors were negatively coupled to cyclic AMP formation upon stimulation with 5-HT agonists. Of the several 5-HT agonists tested, 5-CT was the most potent, the potency rank order being: 5-CT > 5-HT > zolmitriptan > naratriptan > rizatriptan > sumatriptan > R (+)-8-(hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). The maximal responses of these agonists were similar to those induced by 5-HT. The potency of these agonists showed a positive correlation (r2 = 0.87; P < 0.002) with their potency at the cloned h 5-HT1B receptor subtype. 4. 2'-Methyl-4-(5-methyl-[1,2,4]oxadiazol-3-yl)-biphenyl-4-carboxylic acid [4-methoxy-e-(4-methyl-piperazin-1-yl)-phenyl]-amide (GR 127,935), methiothepin and ketanserin each behaved as silent, competitive antagonists at rb 5HT1B receptors; pKB values were 8.41, 8.32 and 7.05, respectively when naratriptan was used as an agonist. These estimates accorded with their binding affinities and the potencies found on 5-HT and/or sumatriptan-mediated contraction of isolated rabbit saphenous vein segments. 5. In conclusion, the recombinant saphenous vein 5-HT1B receptor of the rabbit shares important pharmacological similarities with the cloned h 5-HT1B receptor. However, ketanserin is a more potent antagonist of rb 5-HT1B receptors.
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Affiliation(s)
- T Wurch
- Centre de Recherche Pierre Fabre, Laboratory of Cellular & Molecular Neurobiology, Castres, France
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45
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Pauwels PJ. Pharmacological Properties of a Putative 5-HT1B/DReceptor Antagonist GR 127,935. CNS DRUG REVIEWS 1996. [DOI: 10.1111/j.1527-3458.1996.tb00309.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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