Yohimbine potentiates the anticataleptic action of clonidine against perphenazine-induced catalepsy in rats.

The modulatory role of clonidine and yohimbine on the perphenazine-induced catalepsy was studied in rats. Perphenazine (5 mg/kg) produced severe catalepsy which lasted for more than 4 hr. Clonidine (50 micrograms/kg), an alpha 2-agonist, pretreatment offered protection against perphenazine-induced catalepsy. On the other hand yohimbine (5 mg/kg), an alpha 2-antagonist, pretreatment not only showed per se protective action but also potentiated the effects of clonidine against perphenazine-induced catalepsy. Yohimbine also potentiated the protective action of quipazine, a serotonin agonist. The protective effect of yohimbine is explained on the basis of its serotoninergic action.