Acute and chronic effects of psychotropic drugs on maternal aggression in mice.

The present study investigated the acute and chronic effects of psychotropic drugs on maternal aggression in mice. All female mice had been singly housed since the end of the 4-day mating period. Behavioral testing for acute drug effects was carried out on postpartum days 5 and 7. Chronic drug treatment was started immediately after removal of the partner male, and was terminated on the 3rd postpartum day; behavioral testing was done on the 5th postpartum day. Acute administration of chlordiazepoxide (CDP; 5, 10 and 15 mg/kg, IP) showed a biphasic effect on maternal aggression; 10 mg/kg CDP significantly increased the frequency of bites, while 15 mg/kg CDP significantly decreased it. Imipramine (IMP; 5, 10 and 15 mg/kg, IP) decreased the frequency of bites in a dose-dependent manner. Haloperidol (HAL; 0.1, 0.2 and 0.4 mg/kg, IP) also decreased the frequency of bites dose dependently, but 0.2 and 0.4 mg/kg HAL decreased both the frequency and duration of locomotion. Chronic treatment with either CDP (5 and 10 mg/kg, IP) or HAL (0.1 and 0.2 mg/kg, IP) failed to alter the frequency of bites. This evidence indicates that the antidepressant imipramine has a specific action in alleviating postpartum female aggression, and suggests that female aggression in mice is a useful tool for differentiating the actions of psychotropic drugs.