Research On Excitatory Amino Acid Transporter's MRNA Regulation After Infrasonic Injury Of Brain

Part I. Establish Infrasonic brain injured model of ratObjective :An infrasonic brain injured model is to be established to form a foundation for molecular pathological mechanism research in central nervous system injury. In this study, we aimed to form a convenient, reliable and easy-conducted infrasonic brain injured model of rat .Methods :Eighty SD rats were randomly divided into four groups:control, 1-time, 7-time and 14-time infrasonic damage groups. The infrasonic apparatus was made by the Fourth military medical university and the 41 station of aerospace industry. Rats (280±15)g were exposed to 8Hz 130 dB infrasound as designed, each time for two hours.We used the neurological severity score(NSS) and pathological method to observe the results of injury. Results:Ten rats were randomly selected from each experiment group.Every groups's NSS evaluation was carried out after infrasonic injury was finished at 1h, 24h, 48h.Statistics analysis indicated that 1-time group's score was not significantly different compared with that of the control group.7-time and 14-time groups'score was significantly different compared with that of the control group(P<0.01).14-time group's score was much higher than that of the 7-time group(P<0.05).Light microscope indicated that in 1-time group cortical neuron was not found apparently damaged.Cellularity was integrity.But cortical neuron was injured in 7-time and 14-time groups.It included nuclear condense, endochylema anachromasis and cellularity unclear. Damaged neuron was extensively distributed in cortex. The number of damaged neuron have no difference between 1-time group and control group, but the number of damaged neuron in 7-time and 14-time was significantly higher than that of the control group(P<0.01). Addtionally, the damaged neurons in 14-time group was also higher than that of the 7-time group (P<0.01).The brain tissue also was observed under the transmission electron microsope.In 1-time group, the surroundings of capillary vessel was lightly dropsy. Part of the neurons was dyed lightly. Plasma membrane had minimal changes. Endoplasmic reticulum had little ectasy. Groundsubstance of Golgi fused gently.The quantity of mitochondria was normal,but the shap of it became larger than before.A small quantity mitochondria in neuraxis had the changes like vacuole.In 7-time group ,the exudation was severer than that of 1-time group.The shape of Nucleolus of neuron was irregular. Part of neuron appeared chromatin margination and karyopycnosis. Endochylema had a great quatitiy of microfilament. The sum of cell organ grew down obviously. Mitochondria became swelling. The cristae was collapse and the sum of cristae was decreased . The medullary shell of axon was disaggregation. The injury of 14-time group was more severe and more extensive than that of 7-time group.Conclusion :In our study, infrasonic brain injury were successfully developed. This simple and effective infrasonic brain injured model of neurons is convenient for the study of morphology, molecular pathology and therapeutics after infrasonic brain injury.Part II. The changes of excitatory amino acid transporter (EAAT) mRNA regulation after infrasonic brain injuryObjective : To investigate the significance of changes of the excitatory amino acid transporter1(EAAT) mRNA in brain after infrasonic damage in rats.At the same time ,to find out the different function among all subtypes. Methods: On the base of infrasonic brain injury model, hybridization in situ and realtime PCR methods were adopted to detect the changes of the mRNA.Results :EAAT1 and EAAT2,mRNA have tendency of up-regulation after infrasonic damage.It was showed that in 1-time group EAAT1mRNA and EAAT2mRNA were up regulation compared with that of control group.In 7-time group, the up regulation of EAAT1mRNA and EAAT2mRNA were more severe than that of control group.Conclusion :Glutamate cumulated in ectocytic may be concerned with the down regulation of EAAT1 and EAAT2 after infrasonic brain damages,which may lead to the disorder of glutamate's reabsorbtion and result in secondary brain damages. Therefore the up-regulation of EAAT1 mRNA and EAAT2 mRNA may have protection for the brain after infrasonic damage.