Cholecystokinin attenuates incentive learning in rats.

The hypothesis that endogenous cholecystokinin (CCK) reduces the incentive value assigned to food was examined by training undeprived rats to lever press and chain pull, with one action earning food pellets and the other maltodextrin solution. All animals were then food deprived and reexposed to one outcome after an injection of CCK-8 and the other after an injection of vehicle (VEH). When maintained food deprived and given a choice between the lever and chain in an extinction test, the rats performed fewer of the action trained with the outcome that was reexposed under CCK whether tested under CCK or VEH. In a subsequent experiment, this preference was attenuated by coadministration of the 5-hydroxytryptamine1A (5-HT1A) agonist 8-hydroxy-2(di-n-propylamino)tetralin during reexposure, suggesting that CCK interacts with 5-HT to modify incentive value.