Effect of different time of ischemia on the intensity of spinal cord injury in rabbits

AIM:To observe the intensity of spinal cord ischemic injuries induced by different time of ischemia in rabbits and identify a more sensitive model for the evaluation of neuropretective drugs.METHODS:Thirty New Zealand rabbits were divided into 5 groups:animals in the ischemia groups went through spinal cord ischemia for 10 min(I10),20 min(I20),30 min(I30) or 40 min(I40),while animals in the sham group just had their aorta dissected without cross clamped(SHAM).Neurologic function evaluation was done at 4,8,12,24 and 48 h after reperfusion according to the modified Tarlov criteria.The lumbar spinal cords were collected after the evaluation and stained with HE and TUNEL to appraise morphological and apoptotic changes under microscope.RESULTS:① All animals in I40 group showed absolute paraplegia in all time points after reperfusion(Score 0).All animals but one in group I10 showed normal hind limb motor function.And the Tarlov score of animals in group I20 and group I30 were between that of group I10 and group I40.② The HE staining showed that the spinal cord of rabbits in group I40 exhibited severe spinal cord injury with extensive vacuolation of gray matter while the rabbits in group I10 showed slight injury;the intensity of injury in I20 and I30 groups was between I10 and I40 groups.③ The number of TUNEL positive neurons in the spinal cord of group I20 was significantly more than that of group I40 and the SHAM group.There were no differences with that of group I10 and group I30.CONCLUSION:Twenty min of spinal cord ischemia could produce moderate injury that might be the most sensitive and appropriate model for the evaluation of neuroprotective drugs for spinal cord ischemic injury.