Effects of electroconvulsive shock on mouse-killing behavior (muricide) in olfactory bulbectomized rats.

We investigated the influence of electroconvulsive shock (ECS), regarded to possess an antidepressant effect clinically, on muricide in olfactory bulbectomized rats (OB rats). Muricide in these rats was markedly inhibited by ECS treatment. Five and 10 min after the termination of ECS-induced convulsions, muricide was inhibited by 100%. Even after intervals of 20 and 60 min, inhibition rates of 80% and 30% were obtained, respectively. ECS-induced muricide inhibition was remarkably antagonized by pretreatment with the alpha-blocker phenoxybenzamine but not by pretreatment with the beta-blocker sotalol. ECS-induced suppression of muricide was potentiated by repeated ECS treatment once daily for 10 days. After several applications of ECS treatment, muricide was inhibited in muricide tests done 24 hours after ECS treatment; this state persisted for up to 10 days thereafter. The results of this experiment demonstrated that ECS treatment specifically inhibited muricide in OB rats and further suggested that the cerebral noradrenergic alpha-receptor system plays an important role in this ECS-induced inhibition of muricide. Similar findings in the case of antidepressant administration, inhibition of muricide was potentiated by chronic ECS treatment. Specific inhibition of muricide in OB rats by antidepressants indicated that this phenomenon may serve as an animal model for the evaluation of antidepressant activity. Our results reiterate the usefulness of muricide in OB rats as an excellent experimental model for the assessment of antidepressant activity.