Orexin-A has been reported to produce an analgesic effect in the hot plate test and in the inflammatory pain models. In the present study, the authors examined the effect of orexin-A on the mechanical allodynia induced by partial sciatic nerve ligation (a model of neuropathic pain) in the rat. Partial sciatic nerve ligation is created by tight ligation of one-third or one-half of the right sciatic nerve. Orexin-A was administered intrathecally or intracerebroventricularly 7 days after a partial sciatic nerve injury. Either intrathecal or intracerebroventricular injection of orexin-A attenuated the level of mechanical allodynia induced by partial sciatic nerve ligation. These data suggest that either intrathecal or intracerebroventricular injection of orexin-A is a new therapeutic approach to treating mechanical allodynia caused by nerve injury.