Effects of pimozide on escape and discrimination performance in a water-escape task

The effects of pimozide (0.2 and 0.4 mg/kg) on discrimination learning were evaluated by a water-escape paradigm in which the degree of motor difficulty was manipulated by varying water temperature. Treatment with the drug marginally affected escape latencies in relatively warm water (25 degrees C) but markedly disrupted escape latencies when the task was more demanding (e.g., 15 degrees C and 20 degrees C water). The escape deficits, however, were not accompanied by disturbances in the acquisition of a position discrimination response or of a cue discrimination response when mice were required to make the highly prepared response of swimming to light or the contraprepared response of swimming to dark. These data were taken to suggest that in tasks involving aversive motivation pimozide influences performance through its effects on response maintenance but does not appear to affect either associative or motivational processes.