Chronic stress reduces fighting behavior of rats: the effect of antidepressants.

The effect of chronic stress (14 various unpredictable stressors over 16 days) on electric footshock-induced fighting behavior of pairs of male Wistar rats was studied. The influence of antidepressant drugs (imipramine, desmethylimipramine, nomifensine, clomipramine, mianserine and doxepine) administered chronically (1 h before the stressor) on the aggressive behavior was also investigated in control and in stressed rats. Moreover, the effect of chronic stress on noradrenaline (NA) utilization in the brain was estimated in control and in antidepressant-treated rats. It was demonstrated that, in rats submitted to repeated unpredictable stress, the fighting behavior was significantly reduced 48 and 72 h after the last stressor. NA utilization in the brain was decreased 72 h after the stress termination. Prolonged treatment with antidepressant drugs restored the intensity of fighting behavior in stressed rats to control value as well as normalized NA utilization in the brain. It is suggested that antidepressant drugs may counteract the affective aggression deficit induced by chronic stress.