| Traumatic brain injury is a disease with high inception rate, mortality and morbidity, which often cause sequels, seriously affecting the quality of life in some degrees. With the development of the global economy, high-speed transport and the building industry, the incidence of traumatic brain injury increased dramatically year by year. The specific mechanism of traumatic brain injury is not entirely clear. At present, there is no effective treatment method to resolve the trauma caused by the loss of function and therefore further clarifies nerve repair and function of compensatory mechanism. How to effectively improve the neural plasticity and the reduction or elimination injury dysfunction has become the important subjects of neuroscience research. In the past, the ultra structure of the brain injury research mostly concentrated on the nuclei of neurons and axons, but there is few research study the change of the synapses.In this study, subjects wistar rats were randomly divided into normal control group, the sham control group and the injury group. Put the injury group under the lateral impact of different hydraulic pressure to produce mild, moderate and severe brain injury animal model .With the use of transmission electron microscopy techniques, we analysis the brain injury after injury around the cortex and hippocampal CA1 synapses change and shape parameter changes.Objective: To discuss the post-traumatic changes in the ultra structure and the changes in parameters in the different periods, parts, providing a theoretical basis for further research on the brain injury after synaptic remodeling.Methods:130 adult male wistar rats were involved in this study, which were weighted 300-350 g. The rats were randomly grouped; five rats were reserved to measure the stability to hydraulic device, and determine the relationship between the pressure and the impact of local pressure. Normal control group (5), the sham control group (30), injury (90). After craniotomy the sham control group rats, we use the bone wax to closed bone hole and sue the wound with the commissioner cranial suture.The injury group is divided into light (100 kPa), (200 kPa), weight (300 kPa) three groups based on the pressure of the brain tissue. We collected the samples from each group on the 4th h, 8thh, 24thh, 3rdd, 5thd, and the 7thd after injury, fixed the perfusions around from rat brain cortex and hippocampus injury site, after we finished the antero-fixed, postero- fixation, dehydration series, embedded, sliced, we radiography observed synaptic ultra structural changes. The application of methods depending on the synaptic AMD parameters of the structure of semi-quantitative analysis, numerical from each group to mean±standard deviation ( x±s), using SPSS11.0 statistical analysis package, compared to the number of teams are in the homogeneity of variance determined after a single factor variance analysis, if significant difference between group with q test.Results:1. Ultra structural changes in synaptic after the hydraulic impactWith increasing degree of injury and the time of injury on the hydraulic attacked rats, damage surrounding cortex and hippocampal CA1 neurons carpet gradual reduction in the number of synapses, on the 3rdd to reach the minimum level, and then began to increased significantly on the 5th d , then basically return to normal on the 7thd. during 4th h to 3rdd after the combat, There are various degrees of degeneration and pyknosis in the neurons, as appeared that dark cells increased, irregular-shaped nucleus, mitochondrial structure with varying degrees of swelling, ridge fault. After the 5th d, these changes begun to elevated. After the 7th d, these changes disappeared and basic resume to the normal structure.2. Parameters changes of the ultra structure of the synaptic after the hydraulic impact2.1 synaptic density (Nv value) change2.1.1 After the hydraulic impact, the injury around rat cortex and hippocampus were in the CA1 region, the Nv value began to reduction on the 4th h, continued to decrease next 24th h, on the 3rd d it reach the minimum level, on the 5th d it began to increase and on the 7th d it basically return to normal. There was significant differences between subgroups on the 24thh, 3rdd and the subgroups on the4th h, 8thh, 5thd, 7thd about the Nv value (p<0.05). The subgroups on the 7thd about Nv value was significantly higher than that of other subgroups, there were significant differences (p<0.05).2.1.2 Comparison among the subgroups on the same stage about the light, medium and severe injury group: The Nv value of the moderate and severe injury group is lower than the mild injury group (p <0.05); the value of 4th h, 8thh, 24thh, 3rdd subgroups of the injury group were significantly lower than that of the normal control group and sham group at the same stage (p<0.05). There was no significant difference among the 7thd subgroup and the corresponding subgroups control group and sham-operated group (P>0.05).2.2 synaptic density (Sv value) change2.2.1 Sv values began to decrease on the 4th h in the injury cortex hippocampus CA1 of the rats, the values continued to decrease in the next 24th h, reach the minimum level on the 3rd d, on the 5th d it began to increase and on the 7th d it basically return to normal. Sv value of the subgroups on the 24th, 3rdd were less than that of 4th h, 8thh, 5thd, 7thd (p<0.05). The value of subgroup on the 7thd was significantly higher than that of the other subgroups, there were significant differences (p <0.05).2.2.2 Comparison of the subgroups of the light, medium and severe injury group at the same period: Sv value of the moderate damage group and severe injury group is lower than that of the mild injury group, the difference was significant (p<0.05); the subgroups of each injury group on 4th h, 8thh, 24thh , 3rdd were significantly lower than that of the normal control group and sham group at the same period, there were significant differences (p<0.05). There was no significant difference compared the value of the subgroup on the 7thd and the corresponding subgroups of the control group and sham- operated group (P> 0.05).Conclusion:1. The hydraulic shocked animal model of brain injury in rats were successfully established2. After the brain was injured by the fluid percussion, synaptic density of the injured areas around the cortex and hippocampal CA1 region was decrease. Moreover, there were morphological changes as well, which were associated with the changes of the central nervous system repair, the regeneration.3. There were certain time sequence of post injury synaptic density and surface density of synapses. It appeared that the value reduced on the 4th h , reach the minimum level on the 3rd d, basically return to the normal level on the 7th d after the injury.4. As time goes by, after the fluid percussion injury to the brain, the number of synapses gradually increase, and even returned to normal, synaptic structure is gradually improving as well. All these indicated that the injured central nervous system have the certain capability of plasticity. |
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