Figure 1. Effect of 30 micro gram intrathecal N omega-nitro-L- arginine (L-NA) and 100 micro gram intrathecal N omega-nitro-L-arginine methyl ester hydrochloride (L-NAME) on the development of thermal hyperesthesia induced by a nerve constriction injury in the pretreatment study. The vehicle group is presented for comparison. Each point represents the mean plus/minus SEM of ten rats. Ordinate difference score (DS); abscissa - days after the nerve constriction injury. *P < 0.05 compared with presurgery (day-0) value in the same group. #P < 0.05 compared with the vehicle group 3, 7, and 14 days after the nerve injury.