The inhibition of feeding produced by direct intraintestinal infusion of glucose: is this satiety?

The food intake of two male rhesus monkeys (Macaca mulatta) trained to a daily four hour feeding period and prepared with intragastric and intraintestinal cannulas, was studied under three different experimental conditions intended to place glucose into the small intestine. In the first experiment, the monkeys drank 150 ml of 1 kcal/ml glucose which was then emptied from the stomach after 5 min. In this experiment, a mean of 21.6 kcal of glucose passed into the intestine. In the second experiment, 150 ml of 1 kcal/ml glucose was infused into the stomach, left for 5 min and again removed. In this experiment, a mean of 26.4 kcal of glucose passed the pylorus. In the third experiment, loads of glucose matching those passed through the pylorus on the first experiment were infused directly into the intestine. The feeding of the monkeys was monitored in 10 min intervals over a subsequent four hour meal period. While the glucose passed naturally from the stomach in the ingested or intragastric infusion situations did not affect feeding, glucose infused directly into the intestine significantly inhibited feeding throughout the first 60 min of the feeding period. These results suggest that some aspect of direct intraintestinal nutrient infusions produces an excessively powerful inhibitory signal on feeding.