The effect of dopamine on human gastric smooth muscle.

Dopamine had inhibitory effects on contractions of human gastric smooth muscle strips. Inhibition of spontaneous contractions occurred at high concentrations only, the mean maximum inhibition being 17% at a concentration of 4.7 X 10(-4) M. It was unaffected by haloperidol (10(-5) M) or tetrodotoxin (10(-6) M) but was abolished by a combination of phenoxybenzamine (10(-5) M) and propranolol (10(-5) M). Isoprenaline caused a dose-dependent inhibition of spontaneous contractions with mean maximal inhibition at a concentration of 4.6 X 10(-6) M. These results suggest that there are no specific dopamine receptors in human gastric smooth muscle and that dopamine-induced inhibitory effects are due to stimulation of adrenergic receptors.