Intrathecal lemnalol, a natural marine compound obtained from Formosan soft coral, attenuates nociceptive responses and the activity of spinal glial cells in neuropathic rats

The investigators previously found that the administration of lemnalol, a natural marine compound isolated from the Formosan soft coral Lemnalia cervicorni, produced anti-inflammatory and analgesic effects in carrageenan-injected rats. Recently, several studies have demonstrated that the development and maintenance of neuropathic pain are accompanied by releasing of proinflammatory mediators from activated glial cells in the spinal cord. In this study, we investigated the antinociceptive properties of lemnalol, a potential anti-inflammatory compound, on chronic constriction injury (CCI) in a well-established rat model of neuropathic pain. Our results demonstrated that a single intrathecal administration of lemnalol (0.05-10 μg) significantly attenuated CCI-induced thermal hyperalgesia and mechanical allodynia, 14 days postsurgery. Furthermore, immunohistofluorescence analyses showed that lemnalol (10 μg) also significantly inhibits CCI-induced upregulation of microglial and astrocytic immunohistochemical activation markers in the dorsal horn of the lumbar spinal cord. Double immunofluorescent staining demonstrated that intrathecal injection of lemnalol (10 μg) markedly inhibited spinal proinflammatory mediator tumor necrosis factor-α expression in microglial cells and astrocytes in neuropathic rats. Collectively, our results indicate that lemnalol is a potential therapeutic agent for neuropathic pain, and that further exploration of the effects of lemnalol on glial proinflammatory responses is warranted.