Inhibitory effects of magnolol on voltage-gated Na+ and K+ channels of NG108-15 cells

Abstract

Magnolol, a polyphenolic compound isolated from Houpu, a Chinese herb from the bark of Magnolia officinalis, has been reported to have in vitro and in vivo neuroprotective effects. In spite of these reported beneficial effects, studies on the direct impact of magnolol on neuronal ion channels have been scarce. Whether magnolol affects voltage-gated Na+ channels (VGSC) and voltage-gated K+ (Kv) channels is unknown. Using the whole-cell voltage-clamp method, we studied the effects of magnolol on voltage-gated ion channels in neuronal NG108-15 cells. Magnolol inhibited VGSC channels with mild state-dependence (IC50 of 15 and 30μM, at holding potentials of −70 and −100mV, respectively). No frequency-dependence was observed in magnolol block. Magnolol caused a left-shift of 18mV in the steady-state inactivation curve but did not affect the voltage-dependence of activation. Magnolol inhibited Kv channels with an IC50 of 21μM, and it caused a 20-mV left-shift in the steady-state inactivation curve without affecting the voltage-dependence of activation. In conclusion, magnolol is an inhibitor of both VGSC and Kv channels and these inhibitory effects may in part contribute to some of the reported neuroprotective effects of magnolol.