Premium
An immunocapture/scintillation proximity analysis of Gαq/11 activation by native serotonin (5‐HT) 2A receptors in rat cortex: Blockade by clozapine and mirtazapine
Author(s) -
Mannoury La Cour C.,
Chaput C.,
Touzard M.,
Millan M.J.
Publication year - 2009
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/syn.20587
Subject(s) - ketanserin , 5 ht receptor , agonist , serotonin , receptor , raclopride , mirtazapine , ritanserin , chemistry , clozapine , 5 ht1 receptor , 5 ht2 receptor , pharmacology , antagonist , g protein , gtp' , stimulation , endocrinology , medicine , biology , antidepressant , biochemistry , hippocampus , schizophrenia (object oriented programming) , psychiatry , enzyme
Abstract Though transduction mechanisms recruited by heterologously expressed 5‐HT 2A receptors have been extensively studied, their interaction with specific subtypes of G‐protein remains to be directly evaluated in cerebral tissue. Herein, as shown by an immunocapture/scintillation proximity analysis, 5‐HT, the prototypical 5‐HT 2A agonist, DOI, and Ro60,0175 all enhanced [ 35 S]GTPγS binding to Gαq/11 in rat cortex with pEC 50 values of 6.22, 7.24 and 6.35, respectively. No activation of Go or Gs/olf was seen at equivalent concentrations of DOI. Stimulation of Gαq/11 by 5‐HT (30 μM) and DOI (30 μM) was abolished by the selective 5‐HT 2A vs. 5‐HT 2C /5‐HT 2B antagonists, ketanserin (pK B values of 9.11 and 8.88, respectively) and MDL100,907 (9.82 and 9.68). By contrast, 5‐HT‐induced [ 35 S]GTPγS binding to Gαq/11 was only weakly inhibited by the preferential 5‐HT 2C receptor antagonists, RS102,221 (6.94) and SB242,084 (7.39), and the preferential 5‐HT 2B receptor antagonist, LY266,097 (6.66). The antipsychotic, clozapine, which had marked affinity for 5‐HT 2A receptors, blocked the recruitment of Gαq/11 by 5‐HT and DOI with pK B values of 8.54 and 8.14, respectively. Its actions were mimicked by the “atypical” antidepressant and 5‐HT 2A receptor antagonist, mirtazapine, which likewise blocked 5‐HT and DOI‐induced Gαq/11 protein activation with pK B values of 7.90 and 7.76, respectively. In conclusion, by use of an immunocapture/scintillation proximity strategy, this study shows that native 5‐HT 2A receptors in rat frontal cortex specifically recruit Gαq/11 and that this action is blocked by clozapine and mirtazapine. Quantification of 5‐HT 2A receptor‐mediated Gαq/11 activation in frontal cortex should prove instructive in characterizing the actions of diverse classes of psychotropic agent. Synapse 63:95–105, 2009. © 2008 Wiley‐Liss, Inc.