Experiment Study Of Ischemic Tolerance Induced By Cortical Spreading Depression In Rats

Part IEstablishment of cortical spreading depression model in catsfor study in vivoObjective: To establish an animal model of cortical spreading depression(CSD) in rats by application of kcl and needling and valuate the opticalintrinsic signal imaging(OIIS ) and electrophysiological characteristics in vivo and for the father study. Methods: 25 Spangue-Dawley rats were divided into three groups. Inducing and obervating windows were drilled by bur drill and CSD was evoked by needling (group 1, n=10) and applying 5M KC1 cotton dap (group 2, n=10) in cortex. Five rats (group 3, n=5) were served as controls with applying 0.9% saline solution in the cortex. CSD waves were recorded by optical images and electrophysiology and analysised. Results: CSD waves were observed to spread out, in all dirctions, from the region stumulated by Optical Imaging with the characteristics of interval shading bracket-shaped waves and depolarizational potential were recored with the CSD waves both in group 1 and group 2. However, this phenomenon was not found in group 3. The multiple CSD waves induced - kcl were extending away, while the single CSD wave was spreading away when acupuncturing the cortex of the rats once. Conclusion: The rat CSD model was made easily using this technic.The course of the CSD waves was obersved directly by the OIIS Systems In accordence with the depolarizational potential recorded by recording apparatus. This animal model is suitable to study in vivo and for the farther study of the mechanism and the possible function of the CSD.Part IIStudy of cortical spreading depression preconditioning protecting against brain ischemic injury in vivo in ratObjective: To study cortical spreading depression (CSD) induced-kcl preconditioning affecting cerebral blood flow and infarct volume after middle cerebral artery occlusion (MCAO) in rat and examine wether CSD can protect brain agaist ischemic injury.Methods: 24 Sprague-Dawley rats were divided into experimental group(n=12) and control group group(n=12).CSD was induced by applying 5mKCl cotton pad on the cortex thrugh the pinhole of rats' skull, replacing one time every 20 min and contuning 2 hours. The rat cerebral focal ischemic model after middle cerebral artery occlusion was made by the intraluminal suture method three days later in the CSD preconditioning rats. Opitcal imaging technology of laser speckle imaging was used to monitor the cerebral blood flow (CBF) for 2h after MACO and cortical and subcortical infarct volumes were measured 7 days later. Control group was treated as the experimental group only applying Nacl instead of kcl. To compare infarct volume and the hemodynamic changes of the experimental group with control group. Results: CSD preconditioning group significantly improved CBF during MCAO than control group. CSD preconditioning group reduced the hemispheric and neocortical volume of infarction than control group group. There was no difference between the two groups in the subcortical infarct volume. Conclusion: Opitcal imaging technology of laser speckle imaging can be used to monitor the cerebral blood flow (CBF) in vivo. CSD preconditioning can improve the cortical cerebral blood flow significantly and reduced the hemispheric and neocortical volume of infarction. We conclude that CSD preconditioning can protect ischemic brain impairment.Part IIIEffects of Neurogenesis after focal cerebral ischemia with cortical spreading depression preconditioning in ratsObjective: To study the influence of Neurogenesis after focal cerebral ischemia with cortical spreading depression preconditioning in rats and to explore the mechanism of CSD preconditioning inducing brain protection after ischemic brain injury.Methods: CSD was induced by kcl and the model of the middle cerebral artery occlusion (MCOA)was made by the intraluminal suture method in 72 major Spangue-Dawley rats, who were divided averagely randomly into six group: group I: noischemic rats with only CSD; group II: ischemic rats with CSD preconditioning by kcl; group III: MCOA with vehicle(saline) preconditioning; group IV: ischemic rats with CSD abolished by the NMDA receptor antagonist, MK-801, which inhibits the propagation of CSD; group V: Only ischemic rats; group VI: blank control: no CSD and no ischemic rats with sham operation. Immunohistochemistry method was used to observe the number of BrdU expression positive cells on the 1st, 3th, 7th and 14th days after ischemia.Results:There were BrdU positive cells in the cortex, hippocampal dentate gyrus (DG)and striatum at different time points after cerebral ischemia, and the number of BrdU positive cells in various brain regions were increased significantly on the 7th day (p < 0. 05 ) .It was also found that the number of BrdU positive cells in group II was significantly more than that in the other model groups and the number of BrdU positive cells in group I was increased significantly compared with the groupVI on d7 and d14 (p < 0. 05).Conclusion: CSD could induce BrdU expression positive cells in some brain regions in normal rats and in rats suffering focal cerebral ischemia and could stimulate the potency of neurogenesis after focal cerebral ischemia. It reveals that CSD stimulating neurofenesis could be the important mechanisms of CSD inducing focal cerebral ischeimic protect.