Effects of duodenal and distal ileal infusions of glucose and oleic acid on meal patterns in rats.

The mechanisms mediating the anorexic effects of nutrients in the proximal and distal small intestine are not clearly understood. We determined the dose-dependent effects of duodenal and distal ileal infusions of glucose and oleic acid on meal patterns in ad libitum feeding rats. Rats with cannulas in both the duodenum and ileum received a 2-h infusion of glucose (0, 800, 1,600, 3,200, 6,400, or 12,800 mumol/h) or oleic acid (0, 48, 240, 640, or 1,280 mumol/h) into the duodenum or ileum at the start of the dark period, and meal patterns were monitored for 4 h. Cumulative food intake was inhibited dose dependently by ileal as well as duodenal infusion of both glucose and oleic acid. Ileal glucose was more inhibitory than duodenal glucose, whereas duodenal oleic acid was more inhibitory than ileal oleic acid. Duodenal glucose and oleic acid inhibited feeding by decreasing meal frequency; ileal oleic acid decreased only meal size, whereas ileal glucose reduced both meal size and frequency. We interpret these results to suggest that ileal oleic acid and glucose suppress feeding by different mechanisms and that these mechanisms differ from those mediating the anorexic responses to oleic acid and glucose in the duodenum.