Inhibitory Effects of Honokiol on the Voltage-Gated Potassium Channels in Freshly Isolated Mouse Dorsal Root Ganglion Neurons.

Voltage-gated potassium (KV ) currents, subdivided into rapidly inactivating A-type currents (I A ) and slowly inactivating delayed rectifier currents (I K ), play a fundamental role in modulating pain by controlling neuronal excitability. The effects of Honokiol (Hon), a natural biphenolic compound derived from Magnolia officinalis, on KV currents were investigated in freshly isolated mouse dorsal root ganglion neurons using the whole-cell patch clamp technique. Results showed that Hon inhibited I A and I K in concentration-dependent manner. The IC50 values for block of I A and I K were 30.5 and 25.7 µM, respectively. Hon (30 µM) shifted the steady-state activation curves of I A and I K to positive potentials by 17.6 and 16.7 mV, whereas inactivation and recovery from the inactivated state of I A were unaffected. These results suggest that Hon preferentially interacts with the active states of the I A and I K channels, and has no effect on the resting state and inactivated state of the I A channel. Blockade on K+ channels by Hon may contribute to its antinociceptive effect, especially anti-inflammatory pain.