Additive Effect of Clonidine and Fluoxetine on Apomorphine-Induced Aggressive Behavior in Adult Male Wistar Rats

Abstract

Background Fluoxetine, a selective serotonin reuptake inhibitor, has been reported to be superior in its antiaggressive properties as compared with other antidepressants. The objective of the study was to investigate whether the effect of a minimal effective dose of fluoxetine could be potentiated by the α2-adrenergic agonist clonidine. Methods Vehicle (1.0 mL/kg), clonidine (0.1 mg/kg), fluoxetine (10 mg/kg), and their combination [clonidine (0.1 mg/kg) plus fluoxetine (10 mg/kg)] were injected into apomorphine-pretreated (1.0 mg/kg, once daily during 12 days) aggressive adult male Wistar rats. Results Repeated apomorphine treatment induced a gradual development of aggressive behavior. Combined clonidine and fluoxetine treatment attenuated the intensity of aggressive behavior, while these drugs alone had only a weak tendency toward reduction of aggression. Latency before the first attack was unchanged. Conclusions Our experiments confirm that combined clonidine and fluoxetine treatment elicits an additive antiaggressive effect on apomorphine-induced aggressive behavior in rats.