Acute and subchronic effects of pimozide on isolation-induced aggression in male mice

The aim of this study was to examine the effects of pimozide (0.25-1.25 mg/kg), administered acutely or subchronically for 10 days, on agonistic behavior elicited by isolation in male mice. Individually housed mice were exposed to anosmic "standard opponents" 90 min after pimozide injections, and the encounters were videotaped and evaluated using an ethologically based analysis. 3. After acute treatment pimozide did not affect significantly aggression and immobility. However, mice treated subchronically with pimozide (0.75 and 1.25 mg/kg) showed a significant reduction in offensive behaviors (threat and attack) and an increase of immobility (1.25 mg/kg). The antiaggressive and motor actions of pimozide were more marked after subchronic treatment than after acute treatment. It might reflect an accumulation of the drug over time, an effect also described with other neuroleptics such as amisulpride.