NEURAL MECHANISMS IN BASAL AND MEAL-STIMULATED ILEAL ABSORPTION

The ingestion of a meal stimulates absorption from the jejunal lumen a nd is dependent on intact neural pathways, Few studies of ileal absorp tive responses to a meal have been performed. This study tested two hy potheses: (1) a meal stimulates ileal glucose, water, and ion absorpti on, and (2) intact intestinal neurotransmission is necessary to mainta in the basal and meal-stimulated absorptive states in the ileum. Absor ption studies (n = 50) using C-14-labeled PEG were performed on six do gs with 25-cm ileal Thiry-Vella fistulas (TVF), Four groups were rando mly studied over 4 hr. Intraluminal oxethazaine (2 mg/dl) was administ ered to the TVF in Groups 2 and 4 after the 1st hour to produce neural blockade. A control volume of water was administered to the TVF in Gr oups 1 and 3 after the 1st hour. A 480 kcal meal was ingested at the e nd of the 2nd hour in groups 3 and 4. Ileal water, ion, and glucose ab sorption were increased significantly (P < 0.05) by the ingestion of a meal. TVF oxethazaine significantly reduced (P < 0.05) basal water an d ion absorption but had no effect on meal-stimulated absorption. Ilea l absorption of water, ions, and glucose is significantly increased by the ingestion of a meal. Basal ileal absorption appears to be partly dependent upon intact neurotransmission. Postprandial ileal absorption appears to be independent of neural blockade, implicating circulating hormones, paracrine mediators, or neurotransmission within the myente ric plexus of the enteric nervous system as the primary modulators of meal-stimulated ileal absorption. (C) 1995 Academic Press, Inc.