Role of dopamine receptors in the regulation of aggression in mice; relationship to genotype

The interline differences in the manifestation of aggression evoked by stimulation was studied in mice of eight inbred lines, and the role of different types of dopamine (DA) receptors in its manifestation was investigated. Aggression was assessed in a test involving the effect of a weak electrical stimulation through the floor of the cage. A significant relationship to the animals' genotype was demonstrated, and low-aggression (C3h/He, DD, BALB/c, and AKR) and high-aggression (CBA, DBA/2, and CC57Br) lines could be distinguished on the basis of the level of aggressivity. The mixed agonist of DA receptors, apomorphine, in a one-time administration activated aggressivity in the low-aggression mice. The selective stimulation of D₂-receptors with bromocriptine substantially increased the evoked aggressivity in the low-aggression mice; the blockade of D₂-receptors by sulpiride decreased or prevented the manifestation of aggressivity in the high-aggression lines. At the same time, the selective D₁.agonist SKF 38393 and the selective D₁-antagonist SCH 23390 did not exert a substantial influence on evoked aggressivity. Evidently the D₂-receptors play a key role in the control of aggression evoked by stimulation, which constitutes a model of affective aggression.