DUODENAL LIPID INHIBITS GASTRIC-ACID SECRETION BY VAGAL, CAPSAICIN-SENSITIVE AFFERENT PATHWAYS IN RATS

Neural and endocrine pathways mediate the inhibitory effects of intest inal fat on gastric acid secretion. To study whether vagal and/or spin al afferent nerves contribute to the neural component of the enterogas tric reflex, the sensory neurotoxin capsaicin was applied topically ei ther to the vagus nerves bilaterally or to the celiac-superior mesente ric ganglia in rats with chronic gastric and duodenal fistulas. In lig htly restrained, awake rats acid secretion was stimulated for 2 h by c ontinuous intragastric perfusion with 8% peptone and was measured by e xtragastric titration to pH 5.5. Duodenal lipid perfusion (0-20%) duri ng the 2nd h caused inhibition of peptone-stimulated acid output. Acid output was inhibited by 81% during 5% lipid perfusion of the duodenum and was restored after capsaicin treatment of the vagus nerves. In co ntrast, capsaicin treatment of the celiac ganglion did not alter the a cid inhibitory response to any dose of intestinal lipid. Basal and max imum acid outputs were not significantly different among rats treated by either method with capsaicin. The neural component of the enterogas tric reflex in awake rats is mediated in part by a capsaicin-sensitive , vagal-afferent neural reflex.