Effect of 6-OHDA injected into the locus coeruleus on apomorphine-induced aggression.

Bilateral microinjections of 6-hydroxydopamine (6-OHDA) into the nuclei loci coerulei (LC) of male Wistar rats resulted in significant depletion of mesencephalic and striatal norepinephrine, accompanied by a small reduction in dopamine content only in the striatum. Apomorphine (2.5 mg/kg IP) induced marked aggression consisting of prolonged posturing, vocalization and attacks only in 6-OHDA lesioned animals. Biochemical analysis revealed that 6-OHDA antagonized the ability of apomorphine to raise the serotonin concentration in the striatum. It is concluded that the LC neurons play an inhibitory role in apomorphine-induced aggressiveness and the involvement of serotonergic neurons is suggested.