Reduced anxious behavior in mice lacking the CCK2 receptor gene

Cholecystokinin 2 (CCK2) receptors have been implicated as mediators of anxiety in standard mouse models such as exploratory behavior both in black and white test boxes and in elevated plus-mazes. We investigated the role of the CCK2 receptor in anxiety by evaluating the behavior of mice lacking the gene for this receptor in these standard anxiety models (i.e., exploratory behavior in a black and white test box and exploratory behavior in an elevated plus-maze). In the black and white test box, mice lacking the CCK2 receptor gene showed significantly increased numbers of transitions between the boxes compared to control mice. In the elevated plus-maze, mice lacking the CCK2 receptor gene displayed significantly more head dips than control mice. These results suggest that mice lacking the CCK2 receptor gene are less anxious than normal mice. (C) 2003 Elsevier B.V./ECNP. All rights reserved.