Effects of alpha- and beta-adrenergic agents and dopamine on gastric motor activity stimulated by acetylcholine or physostigmine.

The inhibitory actions of phenylephrine, adrenaline, isoprenaline and dopamine on the antral and fundic pressure responses to exogenous acetylcholine or physostigmine were tested on isolated whole guinea-pig stomachs. Phenylephrine, adrenaline and dopamine markedly inhibited pressure responses to physostigmine, while the responses to acetylcholine were impaired to a less extent. The antral inhibition was more pronounced than the fundic. Isoprenaline was significantly less potent, but like the former inhibited physostigmine more than acetylcholine in the antrum. It may be concluded that adrenergic agents and dopamine exert their inhibition of gastric motor activity partly on intramural cholinergic neural pathways. Dopaminergic as well as alpha-adrenergic influence appear to be more effective than beta-adrenergic. The pronounced effect on phasic antral activity indicates principal inhibitory actions on propulsive motility and gastric emptying.