Continuous infusion of cholecystokinin and meal pattern in the rat.

Purified natural cholecystokinin (CCK-33) was infused continuously for two days at a rate of 5.9 micrograms/hr in two rats trained to bar-press for food (Noyes pellet 45 mg) on a fixed ratio of five bar presses to obtain one pellet. The animals also received control surgery and were tested in the operant chamber for two days, one prior to and the other following the CCK-33 treatment. CCK-33 suppressed the number of meals, the total amount of food eaten, and the total duration of time spent eating. However, the size of each meal and the rate of intake were not affected. The CCK effect did not interact with the light-dark phases of diurnal cycle. It appears that a major effect of continuous systemic elevation of CCK-33 is to reduce food intake by prolonging the satiety period rather than by decreasing the individual meal size.