Divergent effects of cholecystokinin, bombesin, and lithium on rat exploratory behaviors

Cholecystokinin induces a reduction in exploratory behaviors which could reflect an underlying behavioral state of either satiety or malaise. To investigate these alternative hypotheses, the effects of CCK were compared to the effects of (a) consumption of an extra quantity of palatable food, of (b) bombesin at doses known to inhibit food consumption, and of (c) lithium chloride, at doses known to produce taste aversion. Parameters of exploration of a novel arena surface and investigation of a novel object placed in the center of the arena were analyzed by an automated video-tracking computer-assisted animal behavior monitor. Cholecystokinin reduced all parameters of exploration. Ingestion of at least one gram of chocolate chip cookie also reduced all exploratory parameters. Bombesin reduced only parameters of approach to the novel object and the center of the arena. Lithium chloride reduced only parameters of approach to the novel object and the center of the arena. CCK may influence exploratory behaviors through mechanisms similar to those produced by ingestion of palatable food, but somewhat different from those produced by lithium and bombesin.