title: Activation of Gq proteins coupled with 5-HT2 receptors in rat cerebral cortical membranes assessed by antibody-capture scintillation proximity assay/[S]GTPγS binding.
abstract: OBJECTIVE
  Functional activation of Gq coupled with 5-HT2 receptors was investigated in rat cerebral cortical membranes.
  
  
  METHODS
  Antibody-capture scintillation proximity assay (SPA)/[(35)S]GTPγS binding with anti-Gαq antibody was performed.
  
  
  RESULTS
  The specific [(35)S]GTPγS binding to Gαq was increased by 5-hydroxytryptamine (5-HT) in a concentration-dependent but unsaturable manner. The increase elicited by micromolar concentrations of 5-HT was inhibited completely by ketanserin, whereas it inhibited the response by submillimolar to millimolar concentrations of 5-HT only partially. Analysis of the concentration-dependent increases by 5-HT in the absence and presence of ketanserin, methiothepin, WAY100635, and pirenzepine clearly indicates that there are two distinct components of 5-HT-stimulated [(35)S]GTPγS binding, one of which is a pharmacologically relevant increase elicited by lower concentrations (-30 μmol/l) of 5-HT mediated through 5-HT2 receptors and the other is pharmacologically undefined stimulation by higher concentrations of 5-HT. When 5-HT and carbachol were added simultaneously, there was apparently lack of additivity.
  
  
  CONCLUSIONS
  It is concluded that by means of antibody-capture SPA/[(35)S]GTPγS binding it is possible to detect two distinct components of 5-HT-elicited activation of Gq shared by M1 muscarinic receptors, one of which is mediated through 5-HT2 receptors and the other is derived from unknown origin in rat cerebral cortical membranes.
authors.affiliation: Department of Psychiatry, Faculty of Medicine, Saitama Medical University, Saitama, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Odagaki
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Toyoshima
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology; D001681:Biological Assay; D002217:Carbachol / Q000494:pharmacology; D002540:Cerebral Cortex / Q000378:metabolism*; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000276:immunology / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D044348:Receptors, Serotonin, 5-HT2 / Q000378:metabolism*; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013462:Sulfur Radioisotopes
chemical_list: D000906:Antibodies; D044348:Receptors, Serotonin, 5-HT2; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D013462:Sulfur Radioisotopes; D012701:Serotonin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002217:Carbachol; D043802:GTP-Binding Protein alpha Subunits, Gq-G11