D1- and D2-receptor antagonists induce catalepsy via different efferent striatal pathways [corrected].

The D1- and D2-receptor antagonists SCH 23390 and raclopride produced a dose-dependent catalepsy as studied by a vertical grid test in the male rat. The benzodiazepine antagonist Ro 15-1788 antagonized catalepsy induced by the D2-receptor antagonist raclopride while it failed to block the action of SCH 23390. The antimuscarinic drug scopolamine reduced and the gamma-aminobutyric acid (GABA) agonist muscimol enhanced catalepsy induced by both SCH 23390 and raclopride. The results suggest that D2-antagonist-induced catalepsy is mainly mediated via activation of the strio-pallidal GABA pathways whereas D1-receptor antagonist induced catalepsy is mainly mediated via increased activity in the nigrothalamic GABA pathways.