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 studyAsian 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 MethodsSpinal 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 μg 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.ResultsIntrathecal 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.ConclusionThe present study demonstrates that BmK AS is capable of producing remarkable anti-nociceptive effects not only in periphery but also in spinal cord.