Duration of catalepsy correlates with increased intrastriatal sulpiride

To investigate the mechanism underlying sulpiride-induced catalepsy, we simultaneously examined cataleptic behavior and the kinetics of the dopamine receptor antagonist, sulpiride of dopamine, and the dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC), using in vivo voltammetry. After intrastriatal administration of sulpiride to freely moving rats, the levels increased, peaked at 20 min, and remained elevated for more than 3 h. Sulpiride-induced cataleptic behavior also continued for 3 h. Levels of DOPAC peaked 180 min after the injection and did not return to baseline within the experimental period. Thus, the time-course of cataleptic behavior correlated better with elevated extracellular levels of sulpiride than with that of DOPAC. These findings suggest that sulpiride induces catalepsy via a direct action.