Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 42 2 2004 04 15 78 82 H. R. Jamshidi M. Rezayat M. R. Zarrindast 2015 09 28 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. https://acta.tums.ac.ir/index.php/acta/article/view/2695 https://acta.tums.ac.ir/index.php/acta/article/download/2695/2677