AGE-DEPENDENT EFFECTS OF CCK AND DEVAZEPIDE IN MALE AND FEMALE RATS

Peripheral administration of the brain/gut peptide cholecystokinin (CC K) has been demonstrated to inhibit food intake in a variety of specie s, and administration of the specific type A CCK receptor antagonist d evazepide increases food intake in a variety of experimental paradigms . The potency of CCK to inhibit intake depends upon a variety of facto rs, but CCK is generally less potent under conditions of elevated food intake. At different developmental stages, rats' intake requirements differ as growth rates change. To determine whether CCK plays a variab le role in the control of intake in rats of different ages, we examine d the feeding-inhibitory effect of various doses of CCK and the feedin g-enhancing potential of various doses of devazepide on glucose consum ption (0.5 kcal/ml) in male and female rats at 45-70 and 110-130 days of age. CCK was more potent in older male and female rats than in youn ger rats, and inhibited intake in a dose-related fashion. In younger r ats, the efficacy of CCK was attenuated and the inhibition was not dos e related. Administration of devazepide had no effect on intake in you nger rats of either sex, but significantly increased glucose consumpti on in the older rats. These data suggest that during a period of rapid growth and high levels of food intake relative to body weight, adoles cent rats are relatively insensitive to exogenous CCK and endogenous C CK does not appear to play a significant role in controlling their int ake.