Cholecystokinin receptor antagonists increase the rat pup's preference toward maternal-odor and rug texture

The role of the cholecystokinin (CCK) system in mediating the infant's natural preferences toward maternal-related stimuli was examined by peripheral administration of selective CCK^A and CCK_B receptor antagonists (Devazepide and L-365,260, respectively) to 11-12-day-old rats and presenting them with a 3-minute preference test. In Experiment 1, the choice was between two floor textures, rug and plywood; the time spent on the relatively preferred side (rug) was measured. In Experiment 2, the odor of maternal faces emanated from one end of the test arena; time spent near that end was measured. These sensory, stimuli were chosen as they represent olfactory and tactile aspects of the dam and nest. Compared to controls, both CCK receptor antagonists selectively increased the time spent on the preferred side, in both experiments, without affecting axillary temperature or locomotor activity. The results suggest that CCK may mediate and attenuate the infant's attraction toward naturally preferred stimuli.