EFFECTS OF INTRAVENOUS VASOACTIVE-INTESTINAL-PEPTIDE INJECTION ON JEJUNAL ALANINE ABSORPTION AND GASTRIC-ACID SECRETION IN RATS

The effect of intravenous vasoactive intestinal polypeptide (VIP) inje ction on jejunal L-alanine absorption and gastric acid secretion in th e rat was investigated. Continuous intravenous VIP infusion (11.2 ng/k g per min) throughout the experimental period (160 min) produced 60% d ecrease in alanine absorption and 40% decrease in gastric acid secreti on during the second hour of the experiment. Subdiaphragmatic vagotomy reduced alanine absorption to 91% (P > 0.05) and 71.3% (P < 0.05) of control value during the first and second hours of perfusion, respecti vely. VIP infusion following vagotomy elicited a reduced effect when c ompared to that produced by similar injections in normal rats. Gastric secretion in vagotomized rats was reduced by 40 % (P < 0.05) below co ntrol. VIP infusion in vagotomized rats exerted a significant decrease (P < 0.05) of gastric acid secretion. Moreover, water absorption was decreased by almost 10% (P < 0.05) after i.v. injection of VIP and was increased by 20-24% above control value following vagotomy. However, i,v. administration of VIP following vagotomy did not elicit any furth er change in water absorption. It can be concluded that VIP inhibits a lanine absorption and gastric acid secretion in the rat and that these inhibitory effects might be partially mediated by the vagus nerve.