Protective Effects Of Propofol And Midazolam Postconditioning On Cerebral Ischemia Reperfusion Injury In Rats

Objective:Cerebrovascular diseases during the perioperative period,always be focused by anesthesiologists,who have the responsibility for maintaining safety of patients perioperatively.Therefore,one of the important studies is to take effective measures to reduce cerebral ischemia reperfusion injury(CIRI).As this study developed,some of the recent research showed that anesthetics confer preconditioning or postconditioning protection for CIRI.But there has been relatively little research regarding postconditioning protection of the commonly used intravenous anesthetics propofol and midazolam for CIRI.By using rats models of middle cerebral artery occlusion(MCAO),and administrating propofol and midzolam in the early period of reperfusion,we tried to find the appropriate dose and their mechanisms for brain protection.Furthermore we aimed to investigate the effect of PI3K/Akt signaling pathway on intravenous anesthetic postconditioning.This study may help to direct clinical work perioperatively,especially for the patients who have brain ischemic disease.Methods:144 healthy male SD rats weighting 270～320 g were randomly divided into 8 groups(n=18 each):Sham group(group S);focal cerebral ischemia reperfusion group(group I/R);propofol groups(group P₁,P₂,P₃) and midazolam groups(group M₁,M₂,M₃).Focal cerebral ischemia reperfusion(FC I/R) was produced by 2 h MCAO followed by 22 h reperfusion in group I/R,propofol and midazolam groups.In group I/R,2.5 ml saline was infused uniformly through femoral vein from 3 minutes before reperfusion to 5 minutes afterwards;:In propofol and midazolam groups,1,2,5 mg/kg propofol and 0.05,0.1,0.3 mg/kg midazolam diluted with saline to 2.5 ml were administered in the same way.Behavior was assessed by using neurological deficit scores(0=no neurological deficit,4=unable to crawl) at the end of 22 h reperfusion.After that,brains were obtained for determination of(1) cerebral infarct volume(TTC staining);(2) expression of caspase-3 and NF-kB in ischemic cerebral cortex(IHC staining);(3) apoptotic index (TUNEL staining);(4) levels of phosphorylated Akt(western-blotting).Results:FC I/R caused cerebral infarct,significantly increased neurological deficit scores,the expression of NF-κB and caspase-3 and the apoptotic index and decreased the phosphorylation of Akt.In addition,NF-κB in group I/R was significantly translocated from the cytoplasm into the nucleus of the neurons in the ischemic cerebral cortex.Microscopic examination of group I/R showed that there were dying neurons in the core ischemic cortex.And in the ischemic penumbra, neurons were decreased in number and reduced in volume,exhibiting pyknotic nucleus and chromatin margination.There was structure disturbance in hippocampus, and the pyramidal cell layer contained a few neurons and many shrunken cells(P< 0.05).Compared with group I/R,group P₁,P₂,M₂,M₃ significantly reduced the neurological deficit scores,diminished infarct volume,inhibited the translocation of NF-kB,decreased the expression of NF-kB,caspase-3 and apoptotic index,promoted the phosphorylation of Akt,and ameliorated the histologic damage(P<0.05). Compared respectively with group P₁ or M₂,group P₂ or M3 significantly decreased neurological deficit scores,the expression of NF-kB and caspase-3 and the apoptotic index and increased the phosphorylation of Akt.(P<0.05).But there was no significanct difference among group P₃,M₁ and I/R(P>0.05).Conclusion:After 2 h ischemia,administration of propofol 1 mg/kg,2mg/kg or midazolam 0.1 mg/kg,0.3 mg/kg three minutes before reperfusion to five minutes after through femoral vein in uniform speed can provide cerebral protection of ischemic postconditioning.The appropriate dose of propofol is 2 mg/kg and midazolam is 0.3 mg/kg.The possible mechanism of postconditioning protection against CIRI is through down-regulating the expression of caspase-3 and NF-κB, activating the Akt pathway and therefore inhibiting the apoptosis of ischemic neurons.Innovation:1.It was found that propofol and midazolam have the neuroprotective effect of pharmacological postconditioning.2.The PI3K/Akt pathway may play an important role for propofol and midazolam postconditioning of neuroprotection.