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

1. 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 conditioned place preference and biphasic changes in motor activity induced by morphine (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. 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 blockers affected morphine-induced hypoactivity, but both K +- channel blockers prevented morphine-induced secondary hyperactivity. 3. 3. These results suggest the involvement of quinine-sensitive but not 4-aminopyridine-sensitive K +-channels in morphine reward. It is also suggested that the blockade of K +-channels sensitive to these blockers is not sufficient to prevent morphine-induced hypoactivity whereas morphine- induced hyperactivity seems to be connected to both quinine- and 4-aminopyridine-sensitive K +-channels.