Catecholamine correlates of isolation-induced aggression in mice.

Drugs differentially affecting catecholaminergic neurotransmission mechanisms were injected into isolated mice to assess effects on aggression. L-DOPA in combination with a peripheral decarboxylase inhibitor produced a dose-dependent decrease in the number of fights and average fight durations accompanied by an increase in attack latencies. Central dopamine levels were increased whilst brain noradrenaline and 5-hydroxytryptamine were reduced. Virtually identical effects on aggression were observed after apomorphine. Pimozide decreased fighting, but neither attack latencies nor average fight durations were effected. All doses of disulfiram virtually abolished all components of aggressive responses. The effect of D-amphetamine on number of fights was biphasic; lower doses potentiated aggression, but higher doses reduced fighting accompanied by increased attack latencies and reduced average fight durations. We conclude that catecholamines may be intimately involved in mediating certain components of aggressive responses but that balance relationships among various putative neurotransmitters may be a more meaningful correlate of this behavior.