The influence of antidepressants on aggressive behavior in stressed rats: the role of dopamine.

Abstract

The influence of dopamine (DA) receptor blockers (haloperidol, sulpiride) on electric footshock-induced fighting behavior and on the effect of antidepressants (imipramine, clomipramine, nomifensine, mianserine) was investigated in chronically stressed male Wistar rats. Exploratory activity in an open field was measured in the same groups of animals. The effect of chronic stress and antidepressants on DA utilization in the brain was also investigated. It was shown that 48 h after the last session of repeated stress (various unpredictable stressors over 16 days) the number of fighting attacks was significantly reduced. However in stressed rats treated chronically (for 14 days) with antidepressants the intensity of fighting was restored to control value. On the contrary, when the stressed rats, receiving antidepressants chronically, were pretreated with DA receptor blockers: haloperidol (0.5 mg/kg) or sulpiride (50 mg/kg) but also alpha 1-adrenergic receptor blocker - prazosin (3 mg/kg) the effect of antidepressants was abolished. Exploratory activity was not significantly reduced under influence of stress. Neither antidepressants nor sulpiride modified exploratory activity of stressed rats. Haloperidol and prazosin but not sulpiride decreased this activity of normal, stressed and antidepressant-treated rats. It is concluded that prolonged treatment with antidepressants counteracts the decrease in aggression induced by chronic stress and that DA mechanism participate in this effect of antidepressant drugs.