Learning and tolerance to the intake suppressive effect of cholecystokinin in rats

Experiments were conducted to evaluate the contribution of conditioning to tolerance to the meal suppressive effect of cholecystokinin (CCK). The results indicate that (a) tolerance was contingent (the rat had to eat in conjunction with drug administration for tolerance to the meal suppressive effect to develop), (b) tolerance was displayed only in the context of environmental cues previously associated with CCK, (c) CCK-tolerant rats overate when presented with cues previously associated with the peptide, and (d) CCK tolerance displayed latent inhibition. The results are consistent with C.X. Poulos and H. Cappell's (1991) homeostatic theory of tolerance, as well as with the results of other experiments indicating that conditioning contributes to tolerance to many effects of a variety of drugs.