Effects of pimozide on accuracy of performance and distribution of correct responding on a simultaneous discrimination task in the rat.

After training rats in a simultaneous discrimination problem, pimozide, a dopamine receptor blocker, was administered to determine whether accuracy of performance would be disrupted. Each animal received five doses of pimozide (vehicle, 0.05, 0.10, 0.30, and 0.60 mg/kg) delivered in a Latin Square sequence with five non-drug days between injections. Pimozide did not disrupt well established discrimination behavior at any of the doses even though a decrease in rate of responding was observed at the two higher doses. These results provide additional evidence that DA neutrons are not essential in the mediation of previously learned associations.