Experimental Research Of Reperfusion Time Window After Brainstem Ischemia Reperfusion Of Rat

Objective: The key to treatment of patients with acute cerebralischemic disease is rapid recovery of ischemia surrounding penumbraarea of blood flow in short time, Nerve cell can survive and restorefunctions. The establishment of the brainstem isehemic reperfusionmodel，it not only can reflect the mechanisms of brainstem isehemicdamage and reperfusion,but also provide the experimental basis forestablishing effective and safe therapeutic time window for clinical.Butthe persistence of brainstem ischemia model in China and abroad moreseen as a barometer of the measure,and more concentrated in thepathophysioiogy,electrophysiological of large animals. At present，thereare few reports about this model in China and abroad. In this study,theestablishment of rat brainstem ischemia reperfusion model,To beobservation of brainstem ischemia and ischemia reperfusion differenttime pionts BAEP changes.Determinnaton of SOD activity and MDAcontent in brainstem tissue.Further explore the brainstem ischemiareperfusion time window and reperfusion injury mechanism.Provide theexperimental basis for clinical treatment.Methods:100adult male SDrats were divided into three group:sham-operative group（20rats）,ischemia group（40rats） and ischemia reperfusion group（40rats）. ischemia group has five subgroup according to different ischemia time ofI₁、I₂、I₃、I₄、I₆. ischemia reperfusion group has five subgroup accordingto different ischemia and reperfusion time of I₁R₇、I₂R₆、I₃R₅、I₄R₄、I₆R₂.every subgroup has6rats.Two minisize artery clips clamped thebasilar artery（BA） on both the first no-ramus section and the secondno-ramus section, and after some time open the BA to establish thebrainstem ischemia reperfusion model: ischemia group were clamped alsobut not opening; and sham-operative group only diseovered BA.Neuralsymptoms were observed after BA occlusion.Coverage and degree ofischemia were defined with TTC stain. To investigate the change of peaklatency（PL） and inter-peak latency（IPL） of brainstem auditory evokedpotential（BAEP） of the th three group is rats. The activities of SOD,andMDA contents at various subgroups were measured in the brainstem withspectrophotometry. The brainstem tissue at various stages was observedby light microscope. Results:1.The neural symptoms disapeared at thesham-operative group; ischemia group rats and ischemia reperfusiongroup rats,They were dilation of pupils，bluntness of lightre flex，irregularbreathing，eonvulsion，singultus，nystagmus，extremities paralysis andstupor. After vascular recanalization, neuroligical symptoms haveabated.2. TTC:The brainstem tissues was coloured by TTC, all brainstemtissues were red in the sham-operative group; ischemia1h and ischemia1h reperfusion7h subgroup brainstem tissues were red.The coverage of ischemia mainly located in pons and part of superior medulla stained withTTC.3. Light mieroseope: The sham-operative group after occlusion hadno ischemie tissue，lh after occlusion had no ischemie tissue aslo, butsurround of vessel stain light，after reperfusion occurred obvious vesselexpanding and hemorrhage of blood vessel;2h after occlusion normaltissue define with the ischemic tissue，neurnal nuclear stain deepen, cellbody shrinkage, Nissl body decrease;:after reperfusion ischemic rangeoccurred obvious hemorrhage and red blood cell filling in vessel;3h afterocclusion，some degenerated necrotic foci,after reperfusion all theseexhibitions were lighten，hemorrhage of blood vessel were also observed.4h and6h after occlusion，ischemic range increased obviously，at thecenter of ischemic tissue neuronal nuclear karyopyknosis，cell body missand lysis were observed，at edge of ischemic tissue cell body shrinkageand Nissl body decrease，after reperfusion all these exhibitions were moresevere，occur leucocytes soakage.4. BAEP: The PL of Ⅲ,Ⅴ,IPL ofI-III,I-V,III-V were prolonged in schemia group and ischemia reperfusiongroup（except ischemia1h reperfusion7h group）than the sham-operativegroup （P<0.05）. The PL of Ⅲ, Ⅴ,IPL of I-III,I-V,III-V at varioussubgroups in ischemia1h reperfusion7h, ischemia2h reperfusion6h,ischemia3h reperfusion5h group were shorten than those in ischemia1h,ischemia2h, ischemia3h group （P<0.05）.5．SOD,MDA:The activities ofSOD at various subgroups in ischemia group and ischemia reperfusion group were lower than those in sham operation group（P<0.05）, Theactivities of SOD at various subgroups in ischemia1h reperfusion7h,ischemia2h reperfusion6h, ischemia3h reperfusion5h group weresignificantly higher than those in ischemia1h, ischemia2h, ischemia3hgroup（P<0.05）. The contents of MDA at various subgroups in ischemiagroup and ischemia reperfusion group were higher than those in shamoperation group（P<0.05）, The contents of MDA at various subgroups inischemia1h reperfusion7h, ischemia2h reperfusion6h, ischemia3hreperfusion5h group were significantly lower than those in ischemia1h,ischemia2h, ischemia3h group（P<0.05）. Conclusion:1. They are similarto the symptoms due to brainstem infarction in clinical patients. Thismodel simulates some course of clinical pathology.2. Observed results ofpathology showed that ultra-early changes of pathological due to thebrainstem isehemic reperfusion was correlative to the time of occlusion.This experiment reflected that the reperfusion time window is four hour.3. The changes of BAEP and SOD、MDA prompted that the damage ofthe brainstem ischemia tissue and the ability to scavenge oxygen freeradicals.Explain that after the brainstem ischemia4h reperfusion mayexacerbate brain damage.