"EFFECT OF APAMIN ON TOLERANCE TO COCAINE-INDUCED LOCOMOTOR ACTIVITY IN MICE"

In the present study, the effect of apamin (potassium channel blocker) on tolerance to cocaine-induced locomotor activity in mice has been investigated. Locomotor activity was measured by locomotor activity meter, Animax, type S (LKB, Farrad). Intraperitoneal (IP) injection of different doses of cocaine (2.5, 5, 10 and 15 mg/kg) produced dose-dependent locomotor activity in mice.Animals were treated with a dose of cocaine (60 mg/kg, IP) once daily, for 2, 3 or 4 days in order to produce tolerance to cocaine-induced locomotion. Twenty-four hours after the last dose of cocaine, locomotor activity induced by a test dose of cocaine (10 mg/kg) was assessed. Animals pretreated with apamin (0.1 mg/kg) 30 min before the test dose of cocaine had a decreased cocaine response. However, daily treatment of animals with apamin (0.1 mg/kg), 30 min after cocaine (60 mg/kg) for 3 days (during development of tolerance to cocaine-induced locomotion), did not alter the cocaine effect. Single administration of apamin to mice did not cause any response. It is concluded that, apamin as a potassium channels blocker may decrease tolerance to cocaine-induced locomotion due to blockade of potassium channels.