Cholinergic mediation of gamma-aminobutyric acid-induced gastrin and somatostatin release from rat antrum.

Addition of gamma-aminobutyric acid (GABA) to antral mucosal fragments in short-term incubation results in dose-dependent and bicuculline-sensitive stimulation of gastrin release and inhibition of somatostatin release, respectively. These effects of GABA on antral gastrin and somatostatin release closely resembled the actions of cholinergic agonists on G- and D-cell function. The present study examines the possibility that the effects of GABA on antral peptide release may be mediated, in part, through stimulation of antral cholinergic neurons. Inclusion of either atropine or pirenzepine in incubation medium prevented GABA-induced stimulation of gastrin release and inhibition of somatostatin release. Addition of the acetylcholinesterase inhibitor, physostigmine, caused a leftward shift in the GABA dose-response curve and increased by 10-fold the sensitivity of the antral preparation to GABA stimulation. Studies with tetrodotoxin suggest that GABA-stimulated gastrin release is mediated through activation of neurons contained within the antral mucosal/submucosal fragments. Hexamethonium, the ganglionic nicotinic receptor antagonist, did not affect GABA-induced gastrin release. These results indicate that GABA affects antral gastrin and somatostatin release through stimulation of antral postganglionic cholinergic neurons.