Behavioral profile of CCK2 receptor-deficient mice.

CCK2 receptor-deficient mice were used to investigate in vivo the role of this receptor in behavior. Mutant mice showed a neuromuscular impairment in the traction and rotarod tests but not in the chimney test. Brain cholecystokinin has been shown to participate in stress-related behaviors. However, CCK2 receptor-deficient mice did not show behavioral modifications compared to wild-type mice in the elevated plus maze and in the motility conditioned suppression test, indicating that compensatory mechanisms very likely occur following CCK2 receptor invalidation. On the other hand, a hyperlocomotor activity was observed in actimeter which can be related to an impairment in environmental habituation. Finally, CCK2 receptor-deficient mice showed an impairment of performance in the spontaneous alternation behavior as expected from the opposite effects evoked by CCK2 agonists, supporting the physiological role of CCK2 receptors in attention and/or memory processes. This result is reinforced by the defects observed in these functions after the administration of CCK2 antagonists.