5-HT 1A receptor-mediated G protein activation assessed by [ 35S]GTPγS binding in rat cerebral cortex

Abstract

To date, 5-hydroxytryptamine 1A (5-HT 1A) receptor-mediated functional assays (adenylyl cyclase inhibition, high-affinity GTPase activity and [ 35S]guanosine-5′- O-(γ-thio)-triphosphate ([ 35S]GTPγS) binding) have been performed mainly in hippocampal membranes. In the current study, 5-HT-stimulated G protein activation assays were carried out in rat cerebral cortical membranes. High-affinity GTPase activity was stimulated by 5-HT, but not by 8-hydroxy-2-(di- n-propylamino)tetralin (8-OH-DPAT). By contrast, 5-HT- and 8-OH-DPAT-stimulated [ 35S]GTPγS binding displayed sufficient dynamic range enough to warrant further pharmacological analysis. Under standard conditions, which were determined precisely in terms of the concentrations of GDP, MgCl 2 and NaCl, the profile of 5-HT-stimulated [ 35S]GTPγS binding investigated using a series of 5-HT receptor agonists and antagonists clearly indicated the involvement of the 5-HT 1A receptor subtype. There appeared to be no evidence supporting the presence of regional heterogeneity in coupling efficiency between 5-HT 1A and G proteins in the hippocampus or cortex. This method is a useful tool for investigating functional coupling between postsynaptic 5-HT 1A receptors and G proteins in cerebral cortical membranes.