Effect of nitric oxide synthase inhibition on plasma motilin release in fasted dogs

Inhibition of nitric oxide (NO) synthase on plasma motilin concentrations is not known. The aim of this study was to examine the effect of NO synthesis inhibitor on gastrointestinal motility and motilin release in conscious dogs. Dogs fitted with force transducers were given N-omega-nitro-L-arginine (L-NNA) after the termination of phase III contractions. Blood samples were taken for measurement of motilin concentrations. L-NNA induced phase III-Iike contractions in the stomach and duodenum in association with a significant increase in motilin level. Atropine or hexamethonium significantly inhibited L-NNA-induced phase III-like contractions and the increase in motilin level. Ondansetron markedly inhibited gastric, but not duodenal, phase III-Iike contractions without affecting the increase in motilin level caused by L-NNA. Vagotomy affected neither the occurrence of phase III-like contractions nor the increase in motilin level produced by L-NNA. We conclude that inhibition of NO synthesis stimulates motilin release via cholinergic pathways independent of the vagus, and induces phase III-like contractions in the stomach and duodenum. Phase III-like contractions induced by L-NNA are mediated through the activation of 5-HT3 receptors. (C) 1997 Elsevier Science B.V.