Neural Mechanisms in Basal and Meal-Stimulated Ileal Absorption

Abstract

The ingestion of a meal stimulates absorption from the jejunal lumen and is dependent on intact neural pathways. Few studies of ileal absorptive responses to a meal have been performed. This study tested two hypotheses: (1) a meal stimulates ileal glucose, water, and ion absorption, and (2) intact intestinal neurotransmission is necessary to maintain the basal and meal-stimulated absorptive states in the ileum. Absorption studies (n = 50) using 14 C-labeled PEG were performed on six dogs with 25-cm ileal Thiry-Vella fistulas (TVF). Four groups were randomly studied over 4 hr. Intraluminal oxethazaine (2 mg/dl) was administered 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 Groups 1 and 3 after the 1st hour. A 480 kcal meal was ingested at the end of the 2nd hour in groups 3 and 4. Ileal water, ion, and glucose absorption were increased significantly (P < 0.05) by the ingestion of a meal. TVF oxethazaine significantly reduced (P < 0.05) basal water and ion absorption but had no effect on meal-stimulated absorption. Ileal 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 myenteric plexus of the enteric nervous system as the primary modulators of meal-stimulated ileal absorption.