Adult Neural Regeneration And AxonoPathy Following Transient Focal Cerebral Ischemia In Rats

Stress is one of the most potent inhibitors of adult hippocampal neurogenesis, and has been demonstrated in multiple mammalian species, including the mouse, rat, tree shrew, and marmoset. Although the antineurogenic effects of stress in the hippocampus are well known, the underlying mechanisms remain ill defined.The present study explored the possible changes and regulation of glucocorticoid receptors in adult rats neurogenesis subjected to transient unilateral middle cerebral artery (MCA) suture occlusion, which is a focal cerebral ischemic model commonly used in experimental stroke studies.Firstly Nine to ten weeks old male Wistar rats were subjected to 0.5 hour of middle cerebral artery occlusion by the monofilament method. Rats received repeated intraperitoneal injections of the cell proliferation-specific marker 5-bromodeoxyuridine (BrdU) after ischemia induction. Then To collect serum samples for quantitative assay of corticosterone that were imbibed before rats were perfused. Finally Brain sections were processed for immunohistochemistry with an avidin-biotin complex-alkaline phosphatase and/or-peroxidase method. Brain sections processed with GR immune staining and single/double immune staining for newly generated nerve cells.This study demonstrated Corticosterone level of normal rats keeped stable and only a small amount of BrdU, Nestin, and DCX single/double labeling positive cells can be observed in the cortex, SVZ, and hippocampus. Corticosterone level gradually increased after middle cerebral artery occlusion, which arrived at summit in 3 weeks.meanwhile the number of GR positive cells also decreased to the minimum. in the first and second week following MCAO, the number of BrdU, Nestin, and DCX single/double labeling positive cells obviously increased. to the third week, the number of BrdU, Nestin, and DCX single/double labeling positive cells obviously decreased. Four weeks later after middle cerebral artery occlusion, BrdU positive cells mainly existed in the ischemic Cortex and SVZ. Corticosterone level quickly increased after sham operation and subsequently decreased step by step, till the third week, corticosterone level gradually recovered for stabilization. In the first and second week, GR positive cells normally distributed to the brains. Amount of BrdU, Nestin, and DCX single/double labeling positive cells existed in the cortex, SVZ, and hippocampus. To the third week, although GR positive cells decreased, a large number of BrdU, Nestin, and DCX single/double labeling positive cells still existed both in the cortex, SVZ, and hippocampus.Corticosterone that is a kind of stress hormone in rat gradually increased after middle cerebral artery occlusion, meanwhile the number of GR positive cells decreased and neural regeneration impaired.which demonstrated it is the key point that GR influences neurogenesis regulated negatively to GC levels. In sham operation, Although corticosterone level increased quickly but the number and distribution of GR positive cells seemed no influences. At the same time, amount of neural stem cells /progenitors still existed in adult rat's brain. It maybe hinted that one or more mechanisms participated in regulation or inhibition of high corticosterone level, which impaired neurogenesis.By means of BDA tracing, this study also observed sequential neural axonopathy characterized of swelling axon and varicosity after MCAO, which revealed main pathological changes of cerebral ischemia. ALL the wistar rats that cerebral ischemia successfully induced, were decapitated respectively in the 2nd hour,6th hour,24th hour, first to fourth week, in vitro tracing rats were intracerebral injection of BDA before 72h on operation, and in vivo rats were quickly took the brains out that further being proceeded for axonal transportation recovery. Both in vitro and vivo,3 rats that were noraml rats without cerebral ischemia were distributed to each groups. Serial coronal brain-sections were processed for immunohistochemistry with an avidin-biotin complex-alkaline phosphatase and/or-peroxidase method. This study demonstrated axonopathy sequentially appeared after MCAO, which mainly showed swelling axons and varicosities and related to timing of injury, meanwhile control rats were without axonopathy.To try for having a clear knowledge to the relations between space frequency of stimulation mode, amplitude of P100 and regeneration repair after optic nerve injury. The experiment firstly determined space frequency of stimulation mode and amplitude of P100 as examining targets, then took these cooperative volunteers'visions as references and recorded all experimental results of being examined eyes. On the basis of the above, This study analyzed the Relations between VEP changes and regeneration repair on different time stage after optic nerve injury. A certain space frequency of stimulation mode and the optic nerve regeneration displayed the consistency; amplitude of P100 and present vision level was related. In the first three months after optic nerve injury, VEP results showed dynamic changes, which optic nerves were under the circumstances of regeneration repair. It indicated regeneration repair for the better that the visual acuity recovered, space frequency of stimulation mode reduced and amplitude of P100 increased. If the visual acuity fallen, the space frequency of stimulation mode increased (or had no change) and the amplitude of P100 reduced (or had no change), it indicated that there was not obvious regeneration repair after serious optic nerve injury.