Involvement of dopaminergic neurons in mouse-killing aggression in rats.

Abstract

The sites associated with dopamine neurons which produce mouse-killing aggression (muricide) were examined in the rat brain. Muricide appeared in 60-80% of rats after being fed a thiamine-deficient diet for 28 days. Microinjection of dopamine (500 ng/rat) into the olfactory bulb (OB) significantly suppressed muricide, whereas injection into other brain areas failed to do so. The incidence of muricide after dopamine injection was 40% at 5 min and 20% at 15-30 min. When 6-hydroxydopamine (8 micrograms/0.5 microliter), following pretreatment with desmethylimipramine (25 mg/kg i.p.), was injected twice into the ventral tegmental area (VTA) or the olfactory bulb (OB) in nonkiller rats during thiamine-deficient feeding, the occurrence of muricide gradually increased over time. The present results suggest that degeneration of dopamine neurons projecting from the VTA to the OB may be related to mouse-killing aggression in rats.