title: In vitro autoradiographic localization of 5-HT1A receptor-activated G-proteins in the rat brain.
abstract: Serotonin 5-HT1A receptors belong to the superfamily of G-protein-coupled receptors. Receptor activation of G-proteins can be determined by agonist-stimulated [35S]GTPgammaS binding in the presence of excess GDP, and in vitro autoradiographic adaptation of this technique allows visualization of receptor-activated G-proteins in tissue sections. The present study was performed to examine 5-HT1A receptor activation of G-proteins using 8-OH-DPAT-stimulated [35S]GTPgammaS binding in membranes and brain sections. In hippocampal membranes, 8-OH-DPAT stimulated [35S]GTPgammaS binding by twofold, with an ED50 value of 25 nM. 5-HT1 antagonists, but not 5-HT2 antagonists, increased the ED50 of 8-OH-DPAT in a manner consistent with competitive antagonists. Scatchard analysis of [35S]GTPgammaS binding showed that 8-OH-DPAT induced the formation of high affinity [35S]GTPgammaS binding sites with a KD for GTPgammaS of 3.2 nM. [35S]GTPgammaS autoradiography, performed in brain sections with the 5-HT1A agonist 8-OH-DPAT, revealed high levels of 5-HT1A-stimulated [35S]GTPgammaS binding in the hippocampus, lateral septum, prelimbic cortex, entorhinal cortex, and dorsal raphe nucleus. 5-HT1A-stimulated [35S]GTPgammaS binding in sections was blocked by the addition of the 5-HT1 antagonist methiothepin. These results show that the use of agonist-stimulated [35S]GTPgammaS autoradiography for the 5-HT1A receptor system should provide new information regarding signal transduction in specific brain regions.
authors.affiliation: Department of Physiology and Pharmacology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC 27157, USA.
authors.forename: L J
authors.initials: LJ
authors.lastname: Sim
authors.forename: R
authors.initials: R
authors.lastname: Xiao
authors.forename: S R
authors.initials: SR
authors.lastname: Childers
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000378:metabolism* / Q000502:physiology; D001931:Brain Mapping; D004305:Dose-Response Relationship, Drug; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000378:metabolism*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology
chemical_list: D011985:Receptors, Serotonin; D017366:Serotonin Receptor Agonists; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins