MUSCARINIC CHOLINERGIC STIMULATION INCREASES CYCLIC GMP LEVELS IN RAT HIPPOCAMPUS¹

Abstract

Abstract— Muscarinic cholinergic agonists increase cyclic GMP levels in a number of neural tissues. Since the rat hippocampus receives a cholinergic innervation from the septum, we decided to test whether cyclic GMP levels of the rat hippocampus are increased by bethanechol, a muscarinic cholinergic agonist. Incubation of rat hippocampi with varying concentrations of bethanechol showed that the increase in cyclic GMP levels is concentration‐dependent, 500 pwbethanechol producing a maximum increase of 490% over control values. The bethanechol‐evoked increases were blocked by the muscarinic antagonist atropine, and were calcium‐dependent. It is concluded that at least some of the cells projecting to the rat hippocampus form muscarinic cholinergic synapses which act via a cyclic GMP‐dependent mechanism.