The Tolerance Of Focal Cerebral Ischemic And Astrocyte Reaction In Rats

Now it is believed that when exposed to a brief sublethal ischemia /hypoxia can be regarded as a injurious stress response ,most living organisms can mobilize the self-protective mechanisms to protect brain from the subsequent lethal ischemia , that is the induction of cerebral ischemia preconditioning (IPC) and ischemic tolerance (IT). Preconditioning is to give various kind interventions study before serious ischemic and can induce subsequent ischemia tolerance obviously. Astrocyte participate this neural protection but the underlying mechanism of it is still not fully undersood. There is less research on the express of GDNF and it's receptor in MCAO and report. The paper explore this mechanism of IT and responde of Astrocyte mechanism through MCAO model established by Wistar rats. Part 1. Evaluation the establish of animal model and the investigation of neural protective effect of preconditioning. MCAO was induced using filament method in this study with a modification on the tip of the nylon suture .Different time ischemic preconditioning was performed 24h before MCAO. Praxiology changes and neurologic deficit were examined for the evaluation on utility of this animal model. Infarction volume was calculated by HE staining and MAP2,immunohistochemical staining were used to investigate the histopathology changes. It was shown that the MCAO model in our experiment was resemble to the clinic symptoms and histopathology change of cerebral ischemia diseases. Ischemic preconditioning(10min before MCAO ) can produce protective effect on subsequent MCAO by reducing infarct volume by approximately 34.74%, and decreasing the neurologic deficit when compared with control. The histopathological injuries of rats were lightened we found by HE staining. It is proved that Ischemic preconditioning can induce the ischemia tolerance and has protective effect to the brain. The model was useful for its stability and easy to be duplicated and it can regarded as a ideal model for studying ischemic preconditioning. Part 2. GFAP is the main fiber of interstitial substance which has abundantly express only and more in active Aastrocyte .Widespread and seriously physiopathologic damage could exciting mature Astrocyte synthesize GFAP. The process of neuroglia activing was a particular reaction to any serious damage of brain and characteristic by proliferation and swelled cell which keeping on any damaged location. The proliferation extent of Astrocyte and infarct can evaluate by express of GFAP. It was shown that the strengthen expressed GFAP at the penumbral region and manifest after 24h than 6h in focal cerebral ischemic by immunochemical method. Deformed and complete Astrocyte alternating each other with overgrowth and protuberant Astrocyte could be seen in dyeing .This changing manifest accompany with the lasting of ischemic time but decreased in ischemic center. IPC can strengthen the express of GFAP at penumbral region and has significant difference with MCAO group we can see from our study. It could be seen a possible reaction to non-fatal ischemic and protect the neuron. Part 3. It is known that ischemic preconditioning can induce ischemia tolerance and has protective effect on the brain, but the mechanism and the relationship with Astrocyte is not elucidated. Astrocyte not only a ingredient of C.N.S. and maintain the ionic balance of extracellular fluid but also play an important role on the survival of nerve cell . Glial cell line-derived neurotrophicfactor(GDNF) is discovered recently and gene cloned protein already. Ectogenic GDNF experiment discovered that the protein play a powerful protection in cerebral ischemic,but it can not through blood brain barrier. However, ischemia tolerance induced by IPC maybe induce the generation of endogenous GDNF. Research have found that astrocyte activated widespread and existing express of GDNF at peripheral cortex in ischemic preconditioning group which maybe strengthen the function of astrocyte and play an important effect on the survival of neuron. It have thinness GDNF express at control group but have positive express at cortex,coxopodite neuron at MCAO and the color is buffy. MCAO 3h, positive express begin to enhanced at penumbral region but no express at ischemic core .GDNF positive cell dereasing at perimeter with MCAO time and enhanced too at 3d. GDNF positive cells is higher than MCAO group obviously in PC+MCAO group and have significant difference. The express of GDNF have two time course peak amplitude:the first at 3 hour after cerebral ischemic and 72 hour the second from this study which confirmed by research on GDNFmRNA. We have observed the GDNF express at striatum,basal and hippocampus nuclei besides cortex which indicate the function on other brain injured and regression pathology changes. The study research GFRα1,c-RetmRNA express intervent by IPC through hybridition in situ method and the result show that there have thinness express in control and no in ischemic core area but high express in infart border. Express local in survival and complete shape neuron but none in pyknosis and necrosis neuron. There have obviously difference with MCAO group at 6h,12h and 1d in IPC+MCAO group. The express time of c-RetmRNA same as...