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

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