Changes of brain monoamine contents in three models of experimentally induced muricide in rats

Monoamine levels were measured by high performance liquid chromatography with electrochemical detection in seven brain regions of three models of experimentally-induced muricide (mouse-killing behavior) in rats (bilateral olfactory bulbectomized rats: OB rats, midbrain raphe nuclei lesioned rats: Raphe rats and nucleus accumbens lesioned rats: Acc rats). Noradrenaline (NA) levels in the lateral hypothalamus (LH) and ventromedial hypothalamus (VMH), 3,4-dihydroxyphenylacetic acid (DOPAC) levels in LH and homovanillic acid (HVA) levels in the frontal cortex (FC) were increased in all three muricide models. In LH, serotonin (5-HT) levels increased in Acc rats and the 5-hydroxyindoleacetic acid (5-HIAA)/5-HT ratio was reduced in OB rats. But in VMH an increase in NA level was not accompanied by any changes of other amines in three muricide models except for 5-HT and 5-HIAA in Raphe rats. In the mamillary body (MB), NA level was increased and 5-HIAA/5-HT ratio was decreased in both OB and Acc rats. Monoamine changes in the amygdaloid nuclei were different in three muricide models, suggesting that the role of monoamines in various nuclei of the amygdala may be different in each muricide model. The present findings suggest that both noradrenergic (LH and VMH) and serotonergic function (LH and MB) may play an important role in exhibiting muricide of OB, Raphe and Acc rats, while dopaminergic function (LH and FC) may be related rather to hyperirritability elicited in these three muricide models.