Sympatho-adrenomedullary system mediation of the bombesin-induced central inhibition of gastric acid secretion

Abstract

Possible mechanisms of the inhibitory effect of bombesin on gastric acid secretion were examined in rats anesthetized with urethane. Intracerebroventricular (i.c.v.) administration of bombesin (0.1–3 nmol) dose dependently inhibited the increase in gastric acid secretion induced by both intravenous (i.v.) administration of 2-deoxy-D-glucose 60 mg/kg and electrical stimulation of the vagus nerve (1 mA, 0.5 ms, 3 Hz), but not increase due to i.v. infusion of bethanechol (10 μg/kg per min). Such an inhibitory effect of bombesin on the gastric response was markedly reduced by bilateral cutting of the greater splanchnic nerves. The inhibitory effect of bombesin on gastric acid secretion induced by stimulation of the vagus nerve was not modified either by chemical sympathectomy with 6-hydroxydopamine or by bilateral adrenalectomy alone. However, this inhibitory effect of bombesin was abolished under conditions of combined chemical sympathectomy and adrenalectomy. These results suggest that bombesin (i.c.v.) probably excites the sympatho-adrenomedullary system and thus induces inhibition of gastric acid secretion. Furthermore, a dysfunction of the sympathetic or of the adrenomedullary system may well be functionally compensated for by the system with unaltered function.