Aggression and the brain monoamines: what are the answers, but of more importance what are the questions...?

Experiments involving three models of aggression (shock-induced fighting, ranacide and septal lesion-induced hyperirritability) are employed to demonstrate classically different sub-types of aggressive behavior. These categories are shown to be distinct entities when compared on the basis of hormonal dependency, central anatomical and peripheral autonomic involvement and inhibition or enhancement through pharmacological manipulations. Investigations into brain monoamine functioning (norepinephrine, dopamine and serotonin) demonstrate the heterogeneity of correlations which may exist between aggressive behaviors and brain amines. Data are analyzed on the basis of individual amine alterations and changes in monoaminergic neuronal balances. Thus, higher levels of shock-induced aggressive behavior is associated with higher NE/5-HT and DA/K-HT ratioes whereas similar alterations in these biochemical indices occur without observable changes in ranacide behavior. Septal lesion induced hyperirritability is correlated with precisely opposite aminergic changes, namely, decreases in NE/5-HT ratioes. These results demonstrate the necessity of precise aggressive model evaluation prior to attempts at biochemical mechanism elucidation.