Enhancement of apomorphine-induced climbing in mice by reversible and irreversible narcotic antagonist drugs

Apomorphine produced a characteristic climbing syndrome in mice. Pretreatment of mice with increasing doses of the reversible narcotic antagonist naloxone resulted in a dose-related enhancement of this activity. Central microinjection of mice with the irreversible narcotic antagonist drug chlornaltrexamine also resulted in significant potentiation of apomorphine-induced climbing for up to fourteen days following pretreatment. These data indicate that narcotic antagonist drugs of both reversible and irreversible types are capable of enhancing this dopaminergic drug effect in mice.