Small intestinal capsaicin-sensitive afferents mediate feedback inhibition of gastric emptying in rats.

Functional studies have implied the existence of small intestinal receptive mechanisms for components of chyme to mediate feedback inhibition of gastric function. However, it is not known if the sensors are in the wall of the small intestine or located at another site. The present studies evaluated the localization of receptive mechanisms mediating intestinal feedback inhibition of gastric emptying by functional ablation of intestinal capsaicin-sensitive afferents. Perfusion of the small intestine of conscious rats with hydrochloric acid (0.1 N; total amount 50 meq), glucose (1 M; total amount 90 mg), or a lipid emulsion (Intralipid 10%; total amount 50 mg) inhibited gastric emptying. One to 7 days after perfusion of the intestine with capsaicin (3.6 mumol), feedback inhibition of gastric emptying produced by acid, glucose, or lipid was inhibited 100, 59, and 42%, respectively. We conclude that acid-induced inhibition of gastric emptying is mediated entirely by small intestinal capsaicin-sensitive afferent neurons and that a major portion of the glucose-induced inhibition of gastric emptying is mediated by small intestinal afferents. However, only a minor part of the response to lipid is mediated by this pathway.