Anxiety level and body weight changes in rats living in overpopulated cages.

Behavioral indicators of anxiety and body weight dynamics were compared in rats kept under standard conditions (4-5 animals per cage) and in overpopulated cages (17 rats per cage). The behavior of rats exposed to overcrowding for a short and long period was evaluated in the open field, light-darkness, and elevated plus-maze tests. The anxiety parameters of animals increased only in the light-darkness test during the acute period of overcrowding and in all tests during chronic overcrowding. Behavioral tests had a negative impact on body weight gain in controls and rats living in overpopulated cages. If the behavioral tests were carried out at the beginning of the experiment, body weight ceased to increase in animals exposed to overcrowding and continued to increase in the controls. Overcrowding without behavioral tests had no effects on the body weight dynamics. The model of chronic (but not acute) overcrowding may be used for evaluation of anxiolytic effects of drugs.