Sulpiride has an antiaggressive effect in mice without markedly depressing motor activity

The atypical neuroleptic, sulpiride is a selective D2 antagonist, having a preferential action on mesolimbic regions. The effects of acute and chronic treatment with sulpiride on aggressive behaviour in male mice were studied using an ethologically based analysis. It was hypothesized that sulpiride would diminish "threat" and "attack" but would not produce marked "immobility", because of the mesolimbic effect referred to above. Isolated albino male mice (experimental animals) were confronted by "standard opponents". Acutely-treated experimental animals received an intraperitoneal injection of sulpiride (20, 50 or 100 mg/kg) 30 min before testing. Chronically-treated animals received sulpiride (10, 20 or 50 mg/kg) once a day for 7 or 14 consecutive days. Acute treatment with sulpiride had an obvious antiaggressive effect, with significantly decreased time devoted to "attack" and "threat" behaviour. Although time spent in "immobility" was modestly increased, the time devoted to other motor behaviour was also increased. Chronic treatment for 1 or 2 weeks did not change any behavioural category, except "immobility". The antiaggressive action of acutely administered sulpiride is interpreted as a relatively specific dopaminergic antagonist effect and not as merely a non-specific correlate of its disruptive action on motor behaviour. The possible anxiolytic action of sulpiride is also discussed.