Abstract
The present study was conducted to investigate the effects of psychotropic drugs on agonistic behavior between resident and intruder mice. The effects of four doses of the following drugs were assessed in either resident or grouphoused intruder mice: chlordiazepoxide (0, 5, 10 and 20 mg/kg, i.p.), haloperidol (0, 0.25, 0.50 and 0.75 mg/kg, i.p.) and imipramine (0, 5, 10 and 20 mg/kg, i.p.). Residents and intruders were drugged on alternate test days, and all animals received different sequences of each of the drug conditions according to a random schedule. The injection-test interval was 30 min. When resident mice were treated with chlordiazepoxide the resident's aggressive episodes (sideways posture, attack bite, tail rattle) were significantly suppressed. Both haloperidol and imipramine also showed a similar suppressive effect on the resident's aggressive episodes, but haloperidol significantly suppressed locomotor activity at all doses. When intruder mice were treated with chlordiazepoxide, attack bites by untreated residents were significantly increased in a dose-dependent manner, and the frequency of defensive upright posture displayed by intruder animals were significantly decreased. Haloperidol and imipramine did not alter resident's behavior and intruder's upright posture when intruders were drugged. The results suggest that chlordiazepoxide has specific effects on both the hostility of the resident and the anxiety of the intruder, differing from haloperidol and imipramine.
