Cholecystokinin elicits the complete behavioral sequence of satiety in rats

The behavior of intact rats and rats with chronic gastric fistulas was observed and scored during a 60-min test period when they were offered liquid diet after 17 hr of food deprivation. Intact rats and rats with closed fistulas displayed a specific behavioral sequence at the end of each meal: They stopped eating, engaged in grooming and exploration for a short time, and then rested or slept. Thus, a fixed behavioral sequence characterizes satiety in the rat. Although the behavioral sequence of satiety was fixed, the cessation of feeding was not a sufficient condition for the appearance of the rest of the sequence: Quinine adulteration of the liquid diet stopped sham feeding but did not elicit the complete sequence. Intraperitoneal injection of the intestinal hormone cholecystokinin during sham feeding, however, elicited the complete sequence of satiety. The observation that cholecystokinin not only stops feeding but elicits the complete sequence of satiety supports our hypothesis that endogenous cholecystokinin is a satiety signal for the rat.