Chronic treatment with antidepressant drugs: potentiation of apomorphine-induced aggressive behaviour in rats.

Chronic (14 days) but not acute treatment with antidepressants (amitriptyline, imipramine, desipramine, clomipramine, mianserin, danitracen, iprindole) potentiated the aggressive behaviour induced by apomorphine (APO) in rats. The APO stereotypy was not changed. A similar potentiation was caused by chronic treatment with phentolamine or thioridazine but not with spiperone or deazepam. In rats treated chronically with amitriptyline the APO-induced fighting was antagonized by phenoxybenzamine or spiperone, and not by metergoline. The results allows us to postulate that the chronic treatment with antidepressants potentiates the APO-induced aggressiveness via the noradrenergic mechanism, i.e., through an enhanced response to the endogenous NA.