Central inhibition of nitric oxide synthase modulates upper gastrointestinal motor activity

We investigated the role of central nitric oxide (NO) synthase inhibition in the modulation of fasting gastrointestinal motor activity and gastric emptying rate of solid nutrient meals in conscious dogs. N(omega)-nitro-L-arginine methyl ester and N(omega)-nitro-L-arginine were infused intracerebroventricularly. Circular muscle contractions were recorded with surgically implanted strain gauge transducers. Gastric emptying was measured by a radiolabeled meal. The inhibition of NO synthase in the brain suppressed phase III activity in the stomach and the duodenum but not in the jejunum or the ileum. However, the central inhibition of NO synthase had no significant effect on the rate of gastric emptying of solid nutrient meals or the duration of postprandial disruption of migrating motor complex cycling. The central actions of NO synthase inhibition were blocked by bilateral truncal vagotomy but not by intravenous administration of propranolol or phentolamine. We conclude that the inhibition of NO synthase in the brain generates a stimulus that selectively inhibits gastric and duodenal phase III activities. This stimulus, however, may not affect the postprandial gastroduodenal motor activity or the rate of gastric emptying of solid nutrient meals.