Down-reglation Of ET-1 Expression By Pre-treadmill Training Improve Cerebral Blood Flow In Stroke Rat

BackgroudSudden reduction or interruption of cerebral blood flow induce stroke.The cerebral blood flow after stroke changes directly affect the prognosis of stroke.The mechanism of pre-treadmill training as an primary prevention affect on ischemic stroke via cerebral blood flow will be an interesting research.Endothelin-1,as the strongest vasoconstrictor factor,plays an important role in regulation of blood flow.ObjectiveIn this study,we use laser speckle imaging(LSI)to observe the developing of cerebral blood flow,aiming to study the impact of pre-treadmill training on cerebral blood flow after cerebral ischemia/reperfusion.Furthermore,we detect its regulation on endothelin-1 to explore the molecular mechanism between pre-treadmill training and cerebral blood flow on stroke rat.MethodsMale Sprague-Dawley(SD)rats,weighing 250-280 g,were randomly divided into 3 equal groups:the pre-treadmill group,the ischemic group,and the sham group.Rats in the pre-treadmill group started training on an electric treadmill machine 2 weeks,5 days per week before ischemia.Rats in the sham and ischemic groups were not exposed to the treadmill before sham or MCAO surgery,but remained in their home cages for 2 weeks.The three groups of rats,respectively,at the point of prior to surgery(baseline),occlude MCA(middle cerebral artery)90min(MCAO time point),and 1,2,3,24 hour after reperfusion(Rep-1h,Rep-2h,Rep-3h,Rep-24h)to be detected the changes of blood flow velocity in the rat cerebral cortex by laser speckle imaging(LSI).After reperfusion at time point Oh,3h,24h,we collected blood samples from jugular vein and detected plasma ET-1 concentrations by ELISA;neurological functions and infarct volume will be measured at 24h after ischemic/reperfusion.Results1.Cerebral cortical blood flow(CBF)results(n=8)1.1 Capillaries relative perfusion:compared with baseline period,the capillaries relative perfusion after ischemic 90min,the pre-treadmill training and ischemic groups capillaries relative perfusion rate decreased more than 60%(P<0.05).Compared with the ischemic group,capillaries relative perfusion of the pre-treadmill group decline(P>0.05)at Rep-1h,Rep-2h,Rep-3h,but at Rep-24h,the capillaries relative perfusion speed increase(P<0.05):1.2 Artery relative speed ratio:compared with the ischemic group,artery relative blood flow velocity of the pre-treadmill group decreased at Rep-lh(P<0.05),Rep-2h(P<0.05),Rep-3h(P<0.05)and Rep-24h(P>0.05).But compared to the Rep-lh,the artery relative blood flow velocity of ischemic group decreased at Rep-2h(P<0.05),Rep-3h(P<0.05)and Rep-24h(P>0.05),while artery relative blood flow velocity of the pre-treadmill group decreased at Rep-2h(P>0.05),Rep-3h(P>0.05)and increased at Rep-24h(P>0.05).1.3 Vein relative speed ratio:compared with the ischemic group,vein blood flow relative velocity of the pre-treadmill group decreased at Rep-lh(P<0.05),Rep-2h(P<0.05),Rep-3h(P<0.05)and Rep-24h(P>0.05).When compared to the Rep-1h,the vein blood flow relative velocity of ischemic group decreased at Rep-2h(P>0.05),Rep-3h(P>0.05)and Rep-24h(P>0.05),while vein blood flow relative velocity of the pre-treadmill group decreased at Rep-2h(P>0.05),Rep-3h(P>0.05)and increased at Rep-24h(P>0.05).2.ET-1 concentration(n=6)Compared with sham group,plasma concentration of ET-1 in pre-treadmill group decreased at 0 h,3 h,24 h after ischemic/reperfusion(Rep-Oh,Rep-3h,Rep-24h)(P<0.01),while the plasma concentration of ET-1 in ischemic group decreased at Rep-Oh,Rep-24h(P<0.01)and at Rep-3h(P>0.05).Compared with ischemic group,the plasma concentration of ET-1 in pre-treadmill group decreased at Rep-Oh(P<0.01),Rep-3h(P<0.01)and Rep-24h(P<0.01).Respectively,compared with the plasma of ET-1 concentration at Rep-Oh,the plasma of ET-1 concentration of ischemic group rose at Rep-3h(P<0.01)and declined at Rep-24h(P<0.05),while the plasma concentration of ET-1 in pre-treadmill group rose at Rep-3h(P>0.05)and declined at Rep-24h(P>0.05).3.Neurobehavioral ScoreThe neurobehavioral score was assessed after 24 h of ischemia.The neurobehavioral score was 3.33 ± 0.21 in the ischemic group and 2.33 ± 0.21 in the pre-treadmill group,indicating significant improvement(n=8,P<0.01)following pre-ischemic treadmill training.4.Cerebral Infarct VolumeRats were sacrificed after neurobehavioral scoring and variations in infarct volume were investigated.The cerebral infarct volume in the pre-treadmill group was 138.8 ±11.75 mm3,significantly lower than that observed in the ischemic group 180.8 ± 5.25 mm3(n=8,P<0.05).No significant ischemic injury(0.0 ± 0.0 mm3)was observed in the sham group.Conclusion1.Pre-treadmill training can improve cerebral blood flow after reperfusion 24 hour via stabilized cerebral blood flow on acute phase,which is highly possibly to be the direct reason of amelioration the ischemic/reperfusion injury.2.The improvement of pre-treadmill on cerebral blood flow may attribute to the reduction of the ET-1 expression.