The Change Of Muscle Tissue Of Spastic Rat With Spinal Cord Injury In Morphology And Function

[Objective:]To establish a spastic rat model of spinal cord injury, observed the changes in nerve electrophysiology, morphology and AChE in motor end plates of gastrocnemius, in order to provide the experimental basis for the further explore to the mechanism of spasticity with spinal cord injure; And by studying the correlation between spasticity with neurophysiological examination, to establish an objective evaluation method of spasm, and provide the basis for the following experimental study, as a foundation for the clinical application of neural electrophysiological examination for the patients with spasm. At the same time, by studying the changes of spastic rat with spinal cord injury in Morphology and AchE in motor end plate of gastrocnemius, to provide the basis for the treatment of spasticity with spinal cord injure, and to improve the methods.[Methods] 56 healthy adult female Sprague-Dawley (SD) rats, weighing 200-250g, were randomly divided into experimental and control group; The experimental group that spastic rat model group with spinal cord injure was divided into spastic 1 week,2 weeks 3 weeks,4 weeks,6 weeks, and 8 weeks; Totally were divided into 7 groups, n=8; The experimental group, Allen's method was applied to make the spastic rat model with spinal cord injury, while normal control group without any treatment; Before and after surgery, the behavioral assessment, Ashworth grade and neural electrophysiology examination were made out. And then take the normal control group and model group rats at different time points for one side of the gastrocnemius for electron microscope observation, the other side for the acetylcholinesterase staining observation. [Results] After 3-7 days more in the experimental group appeared in both lower limbs and tail spasticity,1-2 weeks after the animals Ashworth score more in the 1-2 grade,3-4 weeks after surgery and more in the 2-4 level, spasm after 4 weeks began to be reduced,6-8 weeks after there was spasticity in tail muscle only.1. The differences of Ashworth score between model group at each time point and the normal control group were statistically significant (p<0.05); 3 week group and 4 week group Ashworth are the highest, and there is no significant difference between the two groups (p>0.05); Followed by 1 week group,2 week group and 6 week group, differences among the three groups was not significant (p> 0.05).2. Neural electrophysiology:SEP latency after 1 week and 2 week of experimental group was significantly longer than the control group (p<0.05), SEP latency after 4 weeks compared with the control group was no significant difference (p>0.05); F wave minimum latency of the two groups after 1 week was no significant difference, after 2 weeks,3 weeks and 4 weeks the experimental group F wave minimum latency were shorter than the control group (p<0.05), the shortest latency of F wave of the experimental group after 6 weeks and after 8 weeks is no significant difference with the normal control group (p>0.05), the experimental group, the F wave minimum latenc among after 2 weeks,3 weeks and 4 weeksy was no significant difference (p>0.05); The shortest F wave latency and Ashworth score was negatively correlated; Experimental group, the rate of H reflex increased faster than the control group. Hmax/Mmax, the experimental group after 1 week,2 weeks,3 weeks,4 weeks increased than the control group (p<0.05), the experimental group after 3 weeks and 4 weeks increased than after 1 week and 2 weeks (p<0.05), the experimental group after 1 week and 2 weeks after surgery showed no significant difference (p> 0.05), experimental group after 6 weeks and 8 weeks after surgery, there was the no significant difference compared with the normal control group (p> 0.05); Hmax/Mmax and the Ashworth score was positively correlated.3. Acetylcholinesterase staining:the experimental group after 1 week and 2 weeks, the average optical density of AChE staining positive parts was no significant difference with the control group showed (P> 0.05); After 3 weeks,4 weeks compared with the control group the mean optical density significantly decreased (P<0.05), experimental group, after6 weeks the mean optical density increased compared with 3 weeks after (P<0.05), however, the experimental group after 6 weeks the average optical density value decreased than in the control group, (P<0.05), after 8 weeks there was no significant difference in both groups of light transmission (P>0.05).4. Electron microscopy:electron microscopy after the formation of spastic model results showed that:sarcomere was significantly shorter, myofilament derangement, H-zoo shortened, mitochondrial was concentrated after 1-4 weeks and 4 weeks after the swelling of mitochondria, vacuoles; Glycogen was reducted. Model group from 1 week after sarcomere length was shorter than the normal group (p <0.05), after 4 weeks sarcomere length was the shortest. Sarcomere length and Ashworth score negatively correlatied[Conclusion] 1. SEP can be made in the model as the assessment criteria of spinal cord injury and restore the integrity; Neuronal excitability increased in the spastic rat with spinal cord injury; F wave latency and Hmax/Mmax ratio have a good correlation with Ashworth scores of animals, and can be used as a quantitative assessment standards of spasticity.2. Activity and the concentration of AChE in the motor end plate of spastic rat with spinal cord injure decreased with time gradually, and then increased later, there is degeneration and repair process in motor end plates. 3. The sarcomere of spastic rats with spinal cord injury was shorter than the normal group, the fourth week after was the shortest, is the peak period of cramps.