Protective Effect And Mechanism Research Of Limb Ischemic Postconditioning After Spinal Cord Ischemia In Rabbits

Background and Objective:Ischemia-reperfusion injury of the spinal cord can result spinal cord nerve dysfunction,and even leading to paraplegia which is very difficult to reverse. Therefore, it is a need to be resolved instantly problem to prevent and reduce the Ischemia-reperfusion injury of spinal cord. Recently, many studies has been demonstrated that limb remote ischemic postconditioning is able to protect many vital organs from Ischemia-reperfusion injury,but the report about protection of limb ischemic postconditioning in spinal cord ischemia/reperfusion injury is less relatively.The study intends to discuss whether limb ischemic postconditioning can prevent neurologic injury of the spinal cord after ischemic reperfusion on spinal cord ischemia reperfusion injury mode in rabbit.And we test the hypothesis that the mechanisms of remote limb ischemic postconditioning involves activation of the opioid receptor and opening of the mitochondria KATP channel in our futher study. Method:Forty-two New Zealand rabbits were randomly divided into seven groups (n=6per group):sham operated control(Sham), spinal cord ischemia(SCI), remote ischemia postconditioning (RIPostC), Glibenclamide(GLI), Diazoxide(DIA), Naloxone(NAL), Morphine(MOR). Spinal cord ischemia/reperfusion injury model was copied in rabbits by infrarenal aorta occlusion for25 minutes. Control animals underwent no additional intervention. RIPostC group was induced by3conditioning cycles of5minutes of ischemia and reperfusion on both hind limbs at2min before infrarenal aorta reperfusion. Glibenclamide(lmg/kg), diazoxide(3mg/kg), naloxone (lmg/kg) and morphine(lmg/kg), were given10min,30min,10min,10min before infrarenal aorta occlusion respectively in GLI group, DIA group, NAL group, MOR group, and each group received limb remote ischemic postconditioning at2min before reperfusion. Hind-limb motor function was assessed at4h,12h,24h,48h after reperfusion using the modified Tarlov criteria. Histologic examination of the lumbar spinal cord was performed at48h after reperfusion, and the number of normal motor neurons in spinal cord anterior horn was counted under light microscope. Results:1. Neurobehavioral scores:The hind limbs motor function of all animals are normal preoperatively, and the Tarlov score are4points.(1) Comparison among groups:Hind limbs motor function scores at4h after spinal cord ischemia reperfusion:there was no statistical significance between Sham group and MOR group (p>0.05); SCII group, GLI group, DIA group, NAL group were significantly lower than Sham group (p<0.05); The scores between SCII group,GLI group, and NAL group; NAL group and RIPostC group, DIA group and NAL group were no statistical significance (p>0.05); The difference between the rest groups were statistically significant (p<0.05). Hind limbs motor function scores at12h,24h and48h after reperfusion:Sham group, MOR group,DIA group, RIPostC group were significantly higher than NAL group, GLI group, SCII group (p<0.05); NAL group and GLI group were higher than SCII group (p<0.05); The difference between Sham group, MOR group,DIA group and RIPostC group, between NAL group and GLI group were no statistical significance (p>0.05); But the scores of NAL group were higher than GLI group at24h after reperfusion.(2) Comparison in the group:results of hind limbs motor function scores compared Sham group with MOR group, there were no significant difference in different time point (p>0.05); The scores of SCII group and GLI group at12h after reperfusion were significantly higher than other different time points (p<0.05),and there were no significant difference in rest time point(p>0.05). The scores of RIPostC group and DIA group at4h after reperfusion were significantly lower than other different time points(p<0.05),and there were no significant difference in rest time point(p>0.05). The scores of NAL group at4h after reperfusion were significantly lower than12h (p<0.05), and there were no significant difference in rest time point (p>0.05).2. The number of normal motor neurons in spinal cord anterior horn:the number of normal motor neurons at48h after reperfusion in SCII group, RIPostC group, GLI group, DIA group, NAL group, MOR group were significantly lower than Sham group (p<0.05).The number between SCII group and GLI group, between RIPostC group, DIA group and MOR group were no significant difference(p<0.05), and there were no significant difference in other group(p>0.05). Conclusion:(1) Limb remote ischemic postconditioning has neuroprotective role to spinal cord ischemia-reperfusion injury in rabbit.(2) The K-ATP channel and opioid receptor take part in the mechanisms of protective effect that limb remote ischemic postconditioning has to spinal cord ischemia-reperfusion injury in rabbit, their agonists diazoxide and morphine are unable to enhance the protective effect, but their antagonists glibenclamide and naloxone are able to weaken the protection, and there is no difference in weakening extents between the two.