Effects Of Sciatic Nerve Compression On Spinal Neuron And Glial Cell Flow An Experimental Study In Rats

Objective: To investigate the effect of peripheral nerve compression on the ultrastructural changes and the number of neurons and observe the changes of glial cell in rats.Methods: A chronic nerve compression animal model was made according the method described by Machinnonic, the animals were anesthetized using an abdominal injection of sodium thiopental (0.3ml/100g). The procedures were conducted using a surgical microscope under 10 magnifications and by the same person. The left sciatic nerve was exposed and identified, a 10mm length of silastic tub with an internal diameter of 1.2mm was cut longitudinally and placed around the nerve. The cut of tub was sewn closed with 9-0 sutures and the tub was reconstituted to its original diameter. The procedures were conducted on the left side, the right side served as a within -subject control. The rats were randomly sacrificed in 12,18,24,30 and 36 weeks after operation .The animals were anesthetized again at different interval after sciatic nerve compression and spinals (L4-6) were cut from thebackhand and stained respectively. The ultrastructural changes and the number of neuron and glial cell of the corresponding spinal segments were observed under light microscope and transmission electron microscope, The number of neurons were counted to calculate the percentage by comparing the experimental side with the control side,Results: light microscope: After sciatic nerve compression of 12 weeks, the number of neurons were no obviously decrease while after sciatic nerve compression of 18,24,30 and 36 weeks ,the number of neurons were decreased 7.46 %> 12.24 %, 16.83 %> 20.98 % respectively. Satellitosis was observed after sciatic nerve compression of 18 weeks in the sections stained with hematoxylin-eosion. The number of neurons locating lamina Ix is decreased significant comparing the group of control side. Trasmission electron microscope: After sciatic nerve compression of 12 weeks the swelled mitochondrion and dilatation endoplasmic was seen, the nucleolus is clear, the chromatin is distributed proportionate. After sciatic nerve compression of 18 weeks, the mitochondrion became more and more swell and the endoplasmic enlarged further more the lysosme has vanished, chromatin margination was seen and heterochromation formed. After sciatic nerve compression of 24,30 and 36 weeks The mitochordrion and endoplasmic decreased gradually, the nucleus becamesmaller, dark stained and some of them were condensed. The nerve cell became cavitation, the perinuclear membrane became indistinct and even the death might occur.Conclusions: The experimental results showed as following: After the sciatic nerve were compressed, the number of neuron and ultrastructure of neurons might undergo changes and even the death might occur. These changes might be aggravated as the time of compression was prolonged and the compression force was increased. It was conclude that for nerve compression decompression should be done as early as possible in order to avoid or minimize the ultrastructural changes of the neuron. In the meantime we should recognize the repair function of glial cell in early stage of nerve lesion. What is the condition that the repair function of glial cells transform inhibition barrier and how to prolong the stage of its repair function, which need make further study.