Chemical lesions of the nucleus accumbens septi in rats: effects on muricide and apomorphine-induced aggression.

To assess the influence of monoaminergic neurones in the nucleus accumbens septi (NAS) on muricidal and apomorphine-induced aggression, bilateral intraaccumbens injections of relevant neurotoxins were performed. Neurochemical effects in the mesolimbic area (NAS and tuberculi olfactorii) and striatal tissue were investigated using high performance liquid chromatography. 6-Hydroxydopamine (6-OHDA) with desipramine pretreatment significantly decreased mesolimbic dopamine (DA) metabolism, 5,7-dihydroxytryptamine (5,7-DHT) plus desipramine diminished serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA), while DSP-4 depleted noradrenaline (NA), 5-HT, 5-HIAA and tryptophan in the mesolimbic area. No significant biochemical changes were observed in the striatum. Behaviourally, 6-OHDA-treated rats were markedly more aggressive in the apomorphine-induced fighting test. Similarly, DSP-4 injections into the NAS (10 micrograms/1 microliter) enhanced this type of aggression. The 5,7-DHT lesion did not alter apomorphine-induced fighting. None of the neurotoxins induced muricidal behaviour. It is concluded that dopaminergic postsynaptic receptors in the NAS may be involved in the pro-aggressive effect of apomorphine. The results support the hypothesis that NA-containing neurones play an inhibitory role in apomorphine-induced aggression and suggest that such a DA-NA interaction might occur in the NAS.