The effects of quinine and 4-aminopyridine on conditioned place preferenceand chances in motor activity induced by morphine in rats

1. The effects of two unselective potassium (K+-) channel blockers, quinine (12.5, 25 and 50 mg/kg) and 4-aminopyridine (1 and 2 mg/kg), on conditione d place preference and biphasic changes in motor activity induced by morphi ne (10 mg/kg) were tested in Wistar rats. Quinine is known to block voltage -, calcium- and ATP-sensitive K+-channels while 4-aminopyridine is known to block voltage-sensitive K+-channels. 2. In the counterbalanced method, quinine attenuated morphine-induced place preference, whereas 4-aminopyridine was ineffective. In the motor activity test measured with an Animex-activity meter neither of the K+-channel bloc kers affected morphine-induced hypoactivity, but both K+-channel blockers p revented morphine-induced secondary hyperactivity. 3. These results suggest the involvement of quinine-sensitive but not 4-ami nopyridine-sensitive K+-channels in morphine reward. It is also suggested t hat the blockade of K+-channels sensitive, to these blockers is not suffici ent to prevent morphine-induced hypoactivity whereas morphine-induced hyper activity seems to be connected to both quinine- and 4-aminopyridine-sensiti ve K+-channels.