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Involvement of dopaminergic neurons in mouse-killing aggression in rats
1Department of Pharmacology, Tohoku College of Pharmacy, Sendai, Japan.
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.
Insights
Dopamine neuron degeneration in the rat olfactory bulb (OB) may trigger mouse-killing aggression (muricide). Suppressing muricide involves dopamine injection into the OB, suggesting a key role for this pathway.
Area of Science:
- Neuroscience
- Animal Behavior
Background:
- Mouse-killing aggression (muricide) is a complex behavior observed in rats.
- Thiamine deficiency is known to induce muricide in a significant percentage of rats.
- The neural circuits underlying muricide are not fully understood.
Purpose of the Study:
- To investigate the role of dopamine neurons in the induction of muricide.
- To identify specific brain regions involved in dopamine-mediated regulation of muricide.
Main Methods:
- Induction of muricide using a thiamine-deficient diet in rats.
- Microinjection of dopamine into various brain regions, including the olfactory bulb (OB).
- Lesioning of dopamine neurons using 6-hydroxydopamine in the ventral tegmental area (VTA) and OB.
Main Results:
- Muricide occurred in 60-80% of rats on a thiamine-deficient diet.
- Dopamine microinjection into the OB significantly suppressed muricide.
- Dopamine neuron lesions in the VTA or OB increased the incidence of muricide.
Conclusions:
- Dopamine neurons projecting from the VTA to the OB are implicated in the regulation of muricide.
- Degeneration of this specific dopamine pathway may contribute to the development of mouse-killing aggression.