The inhibitory effects of nifedipine on outward voltage-gated potassium currents in mouse neuroblastoma N2A cells.

ABSTRACT

BACKGROUND: Voltage-gated K(+) (Kv) channels have a pivotal role in tuning the action potential duration and excitability in neuronal cells. Although Ca(2+) channel antagonist nifedipine exhibited an inhibitory effect on cardiac Kv currents, a possible action of nifedipine on neuronal Kv currents has not been fully investigated. METHODS: The effects of nifedipine on elicited Kv currents were characterized using whole-cell recording in mouse neuroblastoma N2A cells. RESULTS: Exposure to nifedipine induced a dose-dependent inhibition of Kv currents with an IC50 value of 22.3±4.2µM and prolonged the time course of activation. The half-maximum activation potential was 1.6±1.7mV in control conditions and became 13.5±1.5mV in 50µM nifedipine. In addition, the decay rate of Kv currents was substantially accelerated by 39.5% at +60mV. For the voltage-dependent inactivation, the half-maximum inactivation potential was -13.8±0.8mV and strongly shifted to the left following treatment with 50µM nifedipine. CONCLUSION: Treatment with nifedipine exerted a strong influence on the activation and inactivation rate of Kv currents as well as an obvious leftward shift in the inactivation curve. These data indicated that nifedipine exerted an inhibitory effect on Kv currents in N2A cells.