[Changes in voltage-gated potassium currents in the trigeminal neurons after a chronic constriction of infraorbital nerve.].

The purpose of this study was to establish a model of trigeminal neuralgia (TN) through an approach from lower edge of cheekbone and to observe the functional changes in the voltage-gated potassium currents in the cultured trigeminal ganglion (TG) neurons. Thirty Sprague-Dawley male rats were divided into two groups, the sham-operated (sham) group and the operated group. The TN model was carried out by using a chronic constriction injury of the infraorbital nerve (ION-CCI) from lower edge of cheekbone. Peripheral pain threshold test and whole-cell patch clamp recording were used to determine the difference between sham and ION-CCI rats. The withdrawal threshold of whisker pad in operated side of ION-CCI rat was decreased significantly from 6 d after operation and then maintained until 21 d, with the lowest on the 15th day. The threshold of whisker pad in non-operated side of operated rats was also decreased significantly compared with that in the sham group. Delayed rectifier potassium current (I(K)) in cultured ION-CCI TG neurons was decreased significantly compared with that in the sham group. Transient outward potassium currents (I(A)) in both operated and non-operated sides of TG neurons from ION-CCI rats were also reduced significantly compared with that in the sham group. The present study provided a new method of ION-CCI. In this model, the decrease of I(A) and I(K) might contribute, at least in part, to the decrease in mechanical pain threshold of whisker pad and the subsequent hyperalgia.