Analgesic effects of Huwentoxin-IV on animal models of inflammatory and neuropathic pain.

Huwentoxin-IV (HWTX-IV), a peptide with 35 amino acid residues, was discovered in the venom of spider Ornithoctonus huwena. The peptide had an inhibitory effect on a tetrodotoxin-sensitive (TTX-S) sodium channel with highly sensitive to Nav1.7, an attractive target for pain release therapy. In this study we further demonstrated the analgesic effects of HWTX-IV using mouse and rat as an inflammatory pain model and/or a neuropathic pain models. In the both cases, the analgesic effects of the peptide were dose-dependent, and statistically significant. In the inflammatory model, 100 µg/kg of HWTX-IV produced an efficient reversal of hyperalgesia up to 63.6% after injection of formalin in rats with the efficiency equivalent to that of morphine at 50 µg/kg, and 200 µg/kg of HWTX-IV produced protective effect up to 55.6% after injection of acetic acid with the efficiency equivalent to that of morphine at 100 µg/kg. In the spinal nerve model, the peptide produced the longer and higher reversal effect on allodynia than Mexiletine. These results demonstrated that HWTX-IV released efficiently the acute inflammatory pain and chronic neuropathic pain in these animals, suggesting that HWTX-IV was a potential and efficient candidate for further clinical drug development against inflammatory and neuropathic pain.