Gelsenicine from Gelsemium elegans Attenuates Neuropathic and Inflammatory Pain in Mice

Gelsemium elegans BENTH and its crude extract are widely used to treat pain in China despite its apparent toxicity. The analgesic effects of gelsenicine, an active component of G. elegans, however, have not been reported. The current study examined potential analgesic effects of subcutaneously injected gelsenicine using acetic acid-induced writhing, formalin-induced nociceptive behavior, and thermal hyperalgesia caused by chronic constriction injury (CCI) in mice. Gelsenicine produced dose-dependent analgesic effects in both inflammatory and neuropathic pain models. The ED50, for either the inflammatory pain (10.4 mu g/kg for writhing test, 7.4 mu g/kg for formalin test) or neuropathic pain (9.8 mu g/kg for thermal hyperalgesia caused by CCI model), was far below the LD50 (95% confidence interval at 100-200 mu g/kg). Repeated subcutaneous injections of gelsenicine in CCI mice led to sustained attenuation of neuropathic pain after drug discontinuation. These results revealed that gelsenicine could be used safely to attenuate both inflammatory and neuropathic pain.