Abstract: Aim To observe the effect of infiltration of Methylprednisolone on injured spinal nerve root and the protective function of Methylprednisolone to non-impressed spinal nerve root lesion. Methods The spinal nerve roots were injured in 20 rabbits.Three days later local Methylprednisolone infiltration of spinal nerve root profromed in rabbits in experiment group? while rabbits in the control roup received equal amount of 0 9% natiiichloridi instead. The conduct velocity of spinal nerve root was measured one week after operation. The histological change of spinal nerve root and immunohistochemical stain of posterior horn of spine were observed by microscope. Results The conduct velocity was recovered obviously in experiment group. In observation of spinal nerve we found the edema and hyperaemia of matrix were impaired obviously, the lesion focus was minimized, the amount of inflammatory cells was decreased. The area of substance P positive fiber and its terminus in posterior of spinal was smaller in experiment group remarkably than in control group. Conclusions The local infiltration of Methylprednisolone can relieve inflammation inhibit the transmission of pain and accelerate recovery of spinal nerve root

Key words: Methylprednisolone, spinal nerve root, local infiltration, substance P