Anti-nociceptive effects induced by intrathecal injection of BmK AS, a polypeptide from the venom of Chinese-scorpion Buthus martensi Karsch, in rat formalin test

Aim of the study: Asian scorpion Buthus martensi Karsch (BmK) is widely used to treat neurological symptoms, especially chronic pain, in traditional Chinese medicine for thousands of years. BmK AS, a polypeptide from BmK venom, could produce peripheral potent anti-nociceptive effects in rats. In the present study, spinal anti-nociceptive effects of BmK AS were investigated in rat formalin test. Materials and Methods: Spinal anti-nociceptive activity of BmK AS was studied using formalin test in rats. BmK AS in doses of 0.02, 0.1 and 0.5 mu g was administered intrathecally before formalin injection 10 min. The suppression by intrathecal injection of BmK AS on formalin-induced spontaneous nociceptive behaviors and spinal c-Fos expression were investigated. Results: Intrathecal injection of BmK AS markedly reduced formalin-evoked biphasic spontaneous nociceptive behaviors in a dose-dependent manner. Formalin-induced c-Fos expression could be dose-dependently inhibited by BmK AS in superficial (I-II), the nucleus proprius (III and IV) and deep (V-VI) dorsal horn laminae, but not in the ventral gray laminae (VII-X) of lumbar spinal cord. The suppression by BmK AS on c-Fos expression in superficial laminaes was much stronger than that in deep laminaes. Conclusion: The present study demonstrates that BmK AS is capable of producing remarkable anti-nociceptive effects not only in periphery but also in spinal cord. (C) 2008 Elsevier Ireland Ltd. All rights reserved.