Fos expression in rat spinal cord induced by peripheral injection of BmK I, an α-like scorpion neurotoxin

Abstract In this paper, the central neuronal activities elicited by BmK I, a specific voltage-gated Na + channel modulator, were examined by monitoring the c-Fos expression pattern of rat spinal cord. c-Fos protein in laminae I–II, V–VI, and VII–X could be detected at 0.5 h, increased steadily at 1 h, reached a peak at 2 h, and then decreased rapidly from 4 to 24 h after Bmk I was subcutaneously injected into the rat hind paw. However, c-Fos expression in laminae III–IV was activated to a peak at 0.5 h and then declined gradually from 0.5 to 24 h. Furthermore, c-Fos expression could be induced by BmK I in a dose-dependent manner. In addition, the increase of c-Fos expression in laminae I–II, V–VI, and VII–X induced by BmK I, and not in laminae III–IV, could be partially inhibited by systemic morphine in a dose-dependent manner. The results suggested that peripheral administration of BmK I could evoke a profound change of spinal neuronal activities manifested as specific patterns of c-Fos expression, which may be partially attributed to the selective modulation of BmK I on voltage-gated Na + channels located in peripheral nociceptors.