Peripheral injections of bombesin and cholecystokinin affect dietary self-selection in rats

Patterns of dietary self-selection were examined in adult female rats following peripheral injections of either bombesin (BBS) (6, 10, 14 and 16 micrograms) or cholecystokinin octapeptide (CCK-8) (0.75, 1.5, 2.25, and 3.0 micrograms). Animals were food deprived for 18 hours and then offered three isocaloric diets (protein, carbohydrate, and fat) following injections of peptides. Each subject received each of 4 doses of both peptides in a within-subjects design. All doses of BBS decreased total food intake and fat intake 30 minutes following injections. Also at this time period the two highest doses suppressed carbohydrate intake, while protein was unaffected. Cumulative intake at one hour revealed that total intake remained suppressed. The two highest doses continued to suppress carbohydrate intake, while only the 14 micrograms dose continued to suppress fat intake. Additionally protein was now significantly suppressed by all doses. The three highest doses of CCK-8 produced a decrease in total food intake and fat intake 30 minutes after injections. By one hour, only total intake remained suppressed but only with administration of the highest dose. Results are interpreted as providing support for the notion that BBS and CCK are physiological satiety signals and that they maintain unique functions in regulating food intake.