Differential discrimination of G-protein coupling of serotonin<SUB>1A</SUB> receptors from bovine hippocampus by an agonist and an antagonist

We have studied the effect of guanosine-5'-O-(3-thiotriphosphate) (GTP-&#947; -S), a non-hydrolyzable analogue of GTP, on agonist and antagonist binding to bovine hippocampal 5-hydroxytryptamine (5-HT)1A receptor in native membranes. Our results show that the specific binding of the agonist is inhibited with increasing concentrations of GTP-&#947; -S along with a reduction in binding affinity. In sharp contrast to this, antagonist binding to 5-HT1A receptor shows no significant reduction and remains invariant over a large range of GTP-&#947; -S concentrations. The binding affinity of the antagonist also remains unaltered. This shows that the agonist and the antagonist differentially discriminate G-protein coupling of 5-HT1A receptors from bovine hippocampus