Specific involvement of striatal D1 and D2 dopamine receptors in the neuroleptic catalepsy in rats.

Since highly specific antagonists of D1 (SCH 39166) and D2 (raclopride) dopamine receptors have recently become available, we decided to investigate the role of striatal populations of these receptors in catalepsy - an animal model of neuroleptic-induced parkinsonism in humans. Injections of raclopride (2.5, 5 and 10 micrograms/0.5 microliters) into the ventro-rostral part of the striatum induced a strong, dose-dependent and long-lasting catalepsy. Intrastriatal injections of SCH 39166 (1.5 and 3.6 micrograms/ 0.5 microliters) also evoked a dose-dependent, but short-lasting catalepsy. The present results suggest, that neuroleptic side-effects are specifically dependent on the blockade of D2 and D1 dopamine receptors in the striatum.