To explore the relationship of mieroglia activation,motoneuronal loss in the ventral horn of spinal cord and sciatic nerve regen-eration after the sciatic nerve injury,Sprague-Dawley rats were prepared a modal of the fight sciatic nerve crash injury.The immunoreactiv-ity(-ir)ofmicroglia and number of the motoneurons inthe ventral horn of spinal cord were detected at 3 and7 days,light and electron mi-croscopic detection of sciatic nerve degeneration and regeneration were performed at 4 weeks after the nerve injury.The results showed:(1)At 3 days after the sciatic nerve injury,OX-42-irinthe ventral horn of spinal cord begantoincrease significantly(P<0.05);(2)The number ratio of motoneurons in ventral horn of spinal cord in ipsilateral to contralateral for injury decreased markedly(P<0.05),in-dicating the numbers of ipsilateral motoneuroanl survival decreased;(3)Histological assessment showed the poor regeneration of the in-jured nerves;(4)Simvastatin(an inhibitor of cholesterol biosynthesis,having potential immunomodulatory capacities)facilitated the mi-eroglial activation.the motoneuronal survival and sciatic nerve regeneration were better than non-simvastatin-treated vehicle rats.The pres-ent results suggest that mieroglia activation in the ventral horns ofthe spinal cord may play an important protective role in the nerve regener-ation after peripheral nerve injury of the rat.