The potentiation of motor activity caused by ephedrine (Eph) in mice was inhibited by prazosin but not by sulpiride. This potentiation effect caused by apomorphine (Apo) was not inhibited by prazosin. Apo produced stereotyped behavior (including sniffing, licking, and biting) in rodents, but Eph was ineffective except at the toxic dose (400 mg.kg-1 in mice, 200 mg.kg-1 in rats). Apo antagonized haloperidol-induced catalepsy in mice whereas Eph had no such effect. Severe vomiting was evoked by Apo in dogs, but not by Eph even when lethal dose (20 mg.kg-1) was used. Palpebral ptosis induced by prazosin was abolished by intracerebroventricular injection of Eph in mice, but not affected by Apo. The results suggest that the central stimulating action of Eph is mediated by alpha 1-adrenoceptors and not by dopamine receptors.