Receptor mediation of the stimulus properties of cholecystokinin.

Recently, Melton, Kopman, and Riley (20) reported the rapid acquisition of drug discrimination learning using the sulfated form of cholecystokinin (CCK) within the conditioned taste aversion baseline of drug discrimination learning. The present study was designed to explore the receptor mediation of the stimulus properties of CCK within this procedure. Every fourth day, experimental subjects were given CCK-saccharin-LiCl pairings, and on the intervening recovery days, saccharin alone. Once discriminative control was established, doses of the CCK receptor antagonists devazepide (CCK-type A receptor subtype) and L-365,260 (CCK-type B receptor subtype) were administered in combination with the training dose of CCK. Unlike L-365,260 (1-1000 micrograms/kg), devazepide (1 microgram/kg) blocked the CCK stimulus, suggesting that within this design CCK's stimulus properties are mediated by the CCK-type A receptor subtype.