Biogenic amine alterations in limbic brain regions of muricidal rats

Endogenous levels of serotonin, 5-hydroxyindoleacetic acid (5-HIAA), dopamine, 3-4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were measured in eight brain regions of muricidal (mouse killing) and non-muricidal rats. The regions studied were: the frontal cortex, caudate nucleus, septal area, hypothalamus, thalamus, amygdalae with pyriform cortex, anterior hippocampal formation, and brain stem. Serotonergic systems showed significant differences in discrete brain regions of muricidal rats as compared to those of non-muricidal rats. The differences were: significantly higher serotonin levels in the amygdalae and significantly higher 5-HIAA levels in the hippocampus of the muricidal rats. Serotonin levels were also higher in the hypothalamus of the muricidal rats, but the difference reached only borderline significance. Dopaminergic systems also showed significant differences in the septum of muricidal rats, where DOPAC levels were significantly lower than those of non-muricidal rats. The hippocampus of muricidal rats showed significantly higher dopamine levels. HVA levels in the hippocampus of muricidal rats were also higher but reached only borderline significance. These data suggest both central serotonergic and central dopaminergic involvements in rat muricidal behavior. The discrete brain regions which showed differences further suggest a limbic involvement.