Avoidance performance, cue and response-choice discrimination after neuroleptic treatment

The effects of pimozide on discriminated avoidance performance in a Y-maze were evaluated in mice. Relatively low doses of pimozide (0.4 mg/kg) retarded acquisition of an active avoidance response. The avoidance deficit induced by this dosage was largely eliminated among mice that had received either 1 or 2 previous avoidance training sessions, but was still evident in mice treated with a higher drug dosage (0.8 mg/kg). If mice were initially trained in the drug condition, the disruptive effects were still evident in a later test conducted in the absence of the drug treatment. In contrast to the avoidance deficits, pimozide did not disrupt the acquisition or the performance of a cue- or response-choice discrimination. That is, once a running response was initiated (on avoidance trials) pimozide treated animals appeared capable of appropriately directing the response. It is suggested that at the dosages used pimozide did not affect S-S learning or learning response-outcome contingencies, but rather hindered performance owing to deficits in response initiation processes. Moreover, within a task involving aversive motivation pimozide did not appear to reduce the reinforcement derived for correct responding.