Noradrenergic denervation attenuates desipramine enhancement of aggressive behavior in isolated mice

The effects of denervation of central noradrenergic system on the desipramine-induced enhancement of aggressive behavior were examined in long-term isolated mice. Consistent with previous reports, desipramine (10 mg/kg, IP) significantly increased the duration of aggressive behavior in isolated mice. Pretreatment of isolated mice with DSP-4, a selective noradrenaline neurotoxin, significantly attenuated the enhancing effect of desipramine on aggressive behavior without affecting the basal aggressive responses. This effect appeared concomitant with decrease of noradrenaline levels in the cortex, hippocampus, cerebellum and hypothalamus (78%, 75%, 57%, and 17%, respectively). DSP-4 did not significantly affect dopamine or 5-HT levels in these regions. These results suggest that noradrenergic terminals originating mainly from the locus coeruleus play an important role in the desipramine enhancement of aggressive behavior, but not in the basal aggressive behavior of isolated mice.