SMALL-INTESTINAL CAPSAICIN-SENSITIVE AFFERENTS MEDIATE FEEDBACK INHIBITION OF GASTRIC-EMPTYING IN RATS

Functional studies have implied the existence of small intestinal rece ptive mechanisms for components of chyme to mediate feedback inhibitio n 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 presen t studies evaluated the localization of receptive mechanisms mediating intestinal feedback inhibition of gastric emptying by functional abla tion of intestinal capsaicin-sensitive afferents. Perfusion of the sma ll intestine of conscious rats with hydrochloric acid (0.1 N; total am ount 50 meg), 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 mu mol), feedback inhibition of gastric emptying produced by acid, glucose, or lipid was inhibited 100, 59, and 42%, respectively. We conclude that a cid-induced inhibition of gastric emptying is mediated entirely by sma ll intestinal capsaicin-sensitive afferent neurons and that a major po rtion of the glucose-induced inhibition of gastric emptying is mediate d by small intestinal afferents. However, only a minor part of the res ponse to lipid is mediated by this pathway.