Delta-9-tetrahydrocannabinol differently affects striatal c-Fos expression following haloperidol or clozapine administration.

It was previously shown that haloperidol, but not clozapine, induced intense rat catalepsy when co-administered with delta-9-tetrahydrocannabinol. The presentstudy investigated whether similar alterations could be observed on striatalc-Fos immunoreactivity after administration of the same drug combinations.Western Blot and immunocytochemistry stereological analyses indicated thatdelta-9-tetrahydrocannabinol (0.5 mg/kg) increased striatal c-Fosimmunoreactivity induced by haloperidol (0.1 mg/kg). Conversely, no significantalterations of striatal c-Fos immunoreactivity were observed after injections of clozapine (10 mg/kg)+vehicle, clozapine+delta-9-tetrahydrocannabinol orvehicle+delta-9-tetrahydrocannabinol. The present results indicate that thebehavioral effects induced by delta-9-tetrahydrocannabinol in haloperidol- andclozapine-treated rats are associated with different striatal c-Fos expressions.