Changes Of Secondary Lesion In Motor Neuron Distal To The Damage Site Of Spinal Cord In Rats

objective:To explore the changes of the locomotor function and secondary lesion in motor neuron distal to the damage site of spinal cord in rats.Method:Forty female adult Sprague-Dawley rats were made incomplete spinal cord injury at T10 level by modified Allen's method. Locomotor functioning was evaluated using inclined plane tests,modified Tarlov scores and Basso-Beattie-Bresnahan(BBB)scales before the operation and at 1w,2w,3w,4w,5w post surgery.Histomorphological changes of T10 and L5 were observed through light microscope.Results:(1)Locomotion function: The angles of the inclined plane test, Tarlov scores and BBB scores had decreased significantly at 1, 2, 3, 4 and 5 weeks post- injury compared with those before SCI. The values of these evaluation after SCI of 2,3,4 and 5 weeks had increased significantly than those at 1w after SCI. There was an increasing trend of scores from three to five without obvious differences compared with 2 weeks after operation.(2) Morphology of the distal spinal:At 1week after SCI,neurites and Nissl bodies of the motor neurons decreased. At 2 weeks after SCI,the decrease of neurites and Nissl bodies became more obvious. At 3 weeks,neurites and Nissl bodies had no further decrease. Neuron atrophies and apoptosis were found. From four to five weeks,neurites and Nissl bodies increased significantly. (3)Morphology of the damage site:At 1week after SCI,hemorrhage and inflammation as well as nerve fibers necrosis were observed. At 2 weeks after SCI,astrocytes increased and a few nerve fibers grew at the damage site. At 3 weeks,more nerve fibers and astrocytes were found. From four to five weeks,astrocytes and nerve fibers had no further increase.Conclusions:Locomotor function improved during the spontaneous recovery of SCI.Secondary degeneration and damage, including decrease of neurites and nissl bodies, neuron atrophies and apoptosis may occur in the motorneurons distal to the damaged spinal cord in early stage, which correlated with the change of pathology in local damage site and duration of SCI.