Regional changes in monoamines and metabolites following defensive aggression in the rat

Pharmacological studies have demonstrated that shock-induced defensive fighting is modulated by manipulations of the serotonergic, noradrenergic and dopaminergic neurotransmitter systems. In the present study, regional changes in 5-hydroxytryptamine, norepinephrine, dopamine and their metabolites 5-hydroxyindoleacetic acid, 3-methoxy-4-hydroxyphenylethylene glycol and 3,4-dihydroxyphenylacetic acid were measured following shock-induced fighting using high performance liquid chromatography coupled with electrochemical detection. Fighting produced reductions in the serotonergic, noradrenergic and dopaminergic systems and elevations in the noradrenergic and dopaminergic systems within the brain stem, hypothalamus, hippocampus, caudate and amygdala relative to shocked or non-shocked controls. These data demonstrate that the activities of these neurotransmitters are involved in defensive aggression in rats. The changes in catecholamines may indicate adaptive responses to stress, while the changes in serotonin may indicate a permissive function for serotonin depletion in defensive fighting.