Acetylcholine stimulates GTP binding to G proteins in rat striatum

To evaluate the role of G proteins in acetylcholine (ACh)-mediated signal transduction, a novel assay to measure [35S]GTP gamma S binding to rat striatal membranes was standardized. ACh and carbamylcholine (CCh) stimulated the high affinity [35S]GTP gamma S binding to striatal membranes by up to 45% in a concentration-dependent manner. A time course study revealed that 0.1 microM CCh stimulated [35S]GTP gamma S binding by 26% at 4 min and 20% at 15 min. CCh-stimulated [35S]GTP gamma S binding was inhibited by atropine, N-methylscopolamine and pirenzepine. Oxotremorine (1 microM), a partial muscarinic agonist, maximally stimulated the binding to striatal membranes by only 25%.