Objective:To investigate the effects of ischemic postconditioning and controlled low-pressure reperfusion on ischemia and reperfusion-induced spinal cord injury.Methods: Spinal cord ischemia was induced by occlusion of the descending thoracic aorta combined with maintaining systemic hypotension (40 mmHg,1 mmHg=0.133 kPa) in rats.Rats were randomly divided into three groups (n=103),namely,control group,postconditioning group (Post-con group) and low-pressure reperfusion group (LR group).Rats in control group underwent an abrupt increase to 100 mmHg in mean arterial pressure (MAP) after reperfusion.Those in the Post-con group underwent 3 cycles of 30-second reperfusion and 30-second occlusion after 30-second full reperfusion with MAP of 100 mmHg.The MAP maintained 40 mmHg for the initial 3 min of reperfusion in the animals of the LR group,then increased to 100 mmHg.The relative spinal cord blood flow (rSCBF) was monitored simultaneously during the ischemia and 30 min after reperfusion.The activities of superoxide dismutase (SOD),catalase (CAT) and myeloperoxidase (MPO) and malondialdehyde (MDA) content in lumbar spinal cord tissue were measured at 1,4,12 and 24 h after reperfusion,and the neurologic function of hind-limb was also evaluated at the same time.The samples of lumbar spinal cord were collected in all groups at the end of observation for histological examination.Results: Postconditioning and low-pressure reperfusion both improved the hyperperfusion after reperfusion.In Post-con group the activities of SOD and CAT was markedly increased 1 and 4 h after reperfusion (P<0.01) compared with control group,and no marked increase in MDA and MPO was observed.The MDA in the spinal tissue of LR group was significantly lower than that of the control group (P<0.01),but no significant increases were observed in the activities of SOD and CAT.The MPO activity in LR group peaked from the 1st to 4th hour of reperfusion and then gradually reduced.Postconditioning and low-pressure reperfusion both improved the neurologic function during reperfusion,but behavioral scores of animals in LR group were lower than that in the Post-con group.The pathological results had a similar pattern to the behavioral scores in all 3 groups 24 h after reperfusion.Conclusion: Ischemic postconditioning and controlled low-pressure reperfusion can both attenuate ischemia and reperfusion injury in spinal cord,and the neuroprotection of ischemic postconditioning is superior to controlled low-pressure reperfusion,probably because postconditioning can enhance activities of antioxidant enzymes and decrease neutrophil accumulation.