Effects of Imipramine on Anxiety, Depressive-like Behavior and Body Weight Gain in Rats Housed in Overcrowded Conditions

Long-term crowding in rats can lead to anxiety-depressivedisorders. Antidepressants, including imipramine, are used in clinicaland experimental settings to correct such states. The aim of thisstudy was to test whether Imipramine has an antidepressant and/oranxiolytic effect on the behavior of rats kept in overcrowded conditions.The effect of daily (4 days before and 10 days during crowding) intraperitonealinjections of imipramine (10 mg/kg) on the behavior of male Wistarrats housed in overcrowded (16 rats per cage) and standard (4–5rats per cage) conditions was studied in the open field, light–darkand elevated plus maze tests for anxiety, as well as in the forcedswim test, after imipramine withdrawal (days 12 and 15 of overcrowding).In addition, body weight gain on days 8 and 12 of overcrowding andplasma corticosterone levels on day 16 of overcrowding were assessedin the same groups of rats. In standard housing conditions, imipraminedid not alter rat behavior in all tests. Overcrowding led to theactivation of behavioral responses in the light–dark and elevatedplus maze tests, which was not reduced by imipramine (except forthree indices), indicative of no significant corrective effect ofthis drug in these tests on the behavior of rats kept in overcrowdedconditions. In the forced swim test, overcrowding led to increasedimmobility, while imipramine corrected this disorder. Body weightgain decreased after imipramine treatment in both standard and overcrowded(to a greater extent) conditions, suggesting a negative side effectof this antidepressant. Plasma corticosterone levels did not differin rats kept in either overcrowded or standard conditions and werenot altered by imipramine. Thus, imipramine had a therapeutic effecton increased immobility in overcrowded rats in the forced swim test,suggesting that the behavioral changes observed in this test inrats under overcrowded conditions are depressive-like behavioraldisorders, i.e., imipramine exerted a pronounced antidepressanteffect on rats in the forced swim test.