The duration of the effects of a single administration of dopamine antagonists on ambulatory activity and motor coordination

Pimozide, cis(Z)-flupenthixol, SCH 23390 and sulpiride were administered to male rats. Each subject received a single drug injection, and tests for ambulatory activity and motor coordination were performed 1, 24, 48 and 72hrs later. All drugs reduced ambulatory activity at the test 1hr postinjection. Pimozide and SCH 23390 continued to reduce ambulatory activity at the test 24hrs after injection. All drugs impaired motor coordination 1hr after injection and, with the exception of SCH 23390, were also effective at the 24hrs test. Flupenthixol, 2mg/kg, continued to impair motor coordination also at the 48hrs test. These data show that effects of dopamine antagonists on motor functions may persist for much longer than is generally believed. That should be important to take into account in experimental designs where repeated drug administration is employed.