Although paclitaxel is an effective anti-malignant tumor drug for female genital organ cancers, it often has the adverse effect of inducing peripheral neuropathy. We prepared a paclitaxel-induced sciatic neuropathy model, and investigated the efficacy of orally administered Glutamic acid (GA), Dexamethasone (DX), Mexiletine hydrochloride (MX), Angelica keiskei Koidzumi (AK), Shakuyakukanzoto (SK), and Goshajinkigan (GJ), which have been reported effective against paclitaxel-induced peripheral neuropathy. The efficacy was evaluated using cold-allodynia, mechano-allodynia, and mechano-hyperalgesia as indices before preparation of the paclitaxel model, and 7, 14, and 21 days after surgery. The acetone spray test was used for evaluating cold allodynia, the von Frey hair test for mechano-allodynia, and the pin-prick test for mechano-hyperalgesia. Results of the acetone spray test in the GJ group showed that the only difference between the normal and treated groups was that the development of cold-allodynia was inhibited in the latter. Cold-allodynia was not inhibited in any other group. The von Frey hair test results indicated that development of hypoesthesia was not inhibited in any of the treatment groups. The pin-prick test showed mixed results for development of mechano-hyperalgesia and hypoalgesia in all groups. However, the disorders tended to improve in the GJ and SK treated groups. We discussed the mechanism for the favorable effect of GJ on the neuropathy model. GJ increases blood flow by producing NO and exhibits an analgesic effect via opioid receptors. It has been reported that these effects may be involved in the improvement of peripheral neuropathy. Inhibition of cold-allodynia by GJ may have resulted from a combination of these effects and it may be effective for treatment of neuropathic pain.
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