Analgesic and Anti-inflammatory Effects of Neriifolin in Rats with Spinal Nerve Ligation-Induced Neuropathic Pain

. Neriifolin is a cardenolide glycoside abundant in seeds, such as Thevetia ahouai and Thevetia neriifolia, and has been reported to possess anti-inflammatory properties. The present study aimed to investigate the analgesic potential of neriifolin in L5 spinal nerve ligation (SNL)induced peripheral neuropathic pain. Different doses of neriifolin or saline were administered intrathecally once daily for 11 consecutive days. Pain arousal was assessed on day one prior and 7-14 days after surgery in terms of mechanical withdrawal threshold and thermal withdrawal latency. Astrocytic and microglial activation and release of inflammatory mediators were determined on the final day 14 after surgery. The results demonstrated that neriifolin attenuated the mechanical allodynia and thermal hyperalgesia induced by SNL. Furthermore, Neriifolin significantly inhibited SNL-induced activation of glial cells (astrocytes and microglia). Moreover, the unregulated expression of inflammatory mediators in neuropathic pain was significantly inhibited by neriifolin. Our findings suggested that repeated administration of neriifolin may alleviate neuropathic pain, possibly through inhibiting neuroinflammation.