| Cerebral ischemia-reperfusion injury(IRI)is a common pathophysiological process in many medical events such as brain trauma,perioperative stroke and cardiopulmonary resuscitation(CPR)etc.Because neurons can not tolerate ischemia/hypoxia,patients often suffer a irreversible central nervous system disorder,or even death due to cerebral IRI.So treatment and prevention of cerebral IRI are still vital and difficult.Recent studies have reported that pre-conditioning or post-conditioning of inhalation anesthetics,such as sevoflurane,isoflurane,desflurane and so on,have neuroprotective effect to some extent at different levels include treated brain cells in vitro,brain slices and mice with incomplete cerebral ischemia and hypoxia model.This mechanism may be related to promote the functional recovery of neurons surrounding the cerebral ischemia.However,it has not been confirmed in large animals and human being.The structure of central nerve and cerebrovascular in large animals such as rabbit,dog and primate is more similar to human.To determine translational potential,it is necessary to explore the neuroprotection of volatile anesthetic post-conditioning in large animal.Thus,we designed this study to determine whether isoflurane post-conditioning induced neuroprotection in rabbits after an embolic stroke model.Objective:To further test its translational potential,this study was designed to determine whether isoflurane post-conditioning(IPC)induced neuroprotection in rabbits after embolic stroke.More importantly,a highly clinical relevant stroke model was used to test this neuroprotection.Methods:1.Emboli preparationBlood was drawn from one rabbit.After self-solidifying,blood clots was dried,grinded.Then the dried clots were filtered through a 240-um2 and then 100-um2 nylon net.The particles of clot bigger than 100-um2 were weighed,packed and sterilized by epoxy ethane.2.Embolic strokeAfter being anesthetized,all rabbits' right external carotid artery(ECA)and common carotid artery(CCA)were ligated.An arterial puncture needle was inserted into the right CCA distal to the ligation site.The catheter was filled with heparinized saline(25 units/m L)and plugged with an injection cap.Animals were recovered from anesthesia for 3 h and then received 1 m L sterile saline containing the intended amount of blood clots through the catheter.Rabbits in embolic stroke group were received 2.5,5,7.5,10,12.5,15 and 17.5 mg blood clots respectively,while those in control group were received equivalent of normal saline.3.Isoflurane post-conditioningIn the dose-response study,rabbits in embolic stroke group were recived 2.5,5,7.5,10,12.5 and 15 mg blood clots,while rabbits in IPC group were selected using 5,7.5,10,12.5,15 and 17.5 mg clots.In the second experiment,rabbits received 5 mg clots for the both groups.Five minutes after receiving intra-carotid injection with clots,rabbits in the post-conditioning group were treated with 2.5% isoflurane that was about 1.2 minimum alveolar concentrations for rabbits in pure oxygen for 1 h.Those in embolic stroke group were exposed to 100% oxygen for 1 h.Results:1.Rabbit stroke model(1)The dry blood clots with same size(100 ~ 240 ? m2)and same form,were well-distributed and undissolved after dilution.(2)There was observed no abnormality in control group,the success rate of infarction in embolic stroke group was 90.5%.2,3,5-triphenyltetrazolium chloride staining slices showed that cerebral infarcts of 80% animals in 2.5~7.5mg groups were located in right cerebral cortex,while bilateral cerebral cortex had infarcts in 10-15 mg groups.(3)The mortality,neurological score and cerebral infarction volume of each dose groups were positive correlation with clot weight,especially from 5mg to 12.5 mg group which had the significant correlation with clot weight(R>0.8);When blood clots were up to 17.5mg,all the rabbits died.(4)The neurological deficit scores at 72 h post-emboli were lower in 2.5mg,5mg,7.5mg groups than that in 2h post-emboli,it manifested that the damage of brain had partly recoveried after 72 h.In 10 mg,12.5mg,15 mg groups,the the neurological deficit scores at 72 h post-emboli were increased,the damage of brain had been worsen,it meant that the process was irreversible.2.Outcomes of rabbit stroke after IPC(1)In the dose-response study,IPC increased the tolerance of rabbits in according to the amount of clots.(2)In the second experiment,IPC also reduced brain infarct volumes,plasma S100 B and improved neurological deficit scores after the stroke for 72 h.Conclusions:1.The rabbit dry blood clot embolic stroke model is simple,successful and stable.5~7.5mg and 10~15mg can establish unilateral and bilateral cerebral infarcts,respectively.Our research shows that this kind of rabbit cerebral occlusion model can be used as a reliable utility for pre-clinical treatment and research of cerebral infarction.2.Isoflurane post-conditioning improves neurological outcomes in rabbits after embolic stroke.It can contribute to the clinical study of volatile anesthetics in cerebral protection. |
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