阿片受体在肢体远程缺血后处理对脊髓保护中的作用

Roles of opioid receptors in the protective effect of limb remote ischemic postconditioning on spinal cord

目的研究肢体远程缺血后处理对脊髓缺血再灌注损伤的保护作用,并探讨阿片受体在此机制中的可能作用。方法新西兰大白兔24只,随机分为4组,每组6只。缺血组(SCII组):阻断肾下腹主动脉25 min后再灌注;远程缺血后处理组(RIP组):脊髓缺血操作同SCII组,在开放腹主动脉前2 min予3个循环双下肢缺血后处理;吗啡组(MOR组)及纳洛酮组(NAL组):脊髓缺血前经耳缘静脉分别给予吗啡、纳洛酮1 mg/kg,余操作同RIP组。分别于再灌注4、12、24、48 h对所有动物行后肢运动功能评分;再灌注48 h后行脊髓组织病理学观察并计数脊髓前角正常运动神经元;行再灌注48 h神经功能评分与脊髓前角正常运动神经元计数之间相关性分析。结果 RIP组再灌注4、12、24、48 h神经功能评分及脊髓前角正常运动神经元计数均明显高于SCII组(P<0.05);再灌注4 h MOR组神经功能评分高于RIP组(P<0.05),而再灌注12、24、48 h神经功能评分及脊髓前角正常运动神经元计数二者差异无统计学意义(P>0.05);NAL组再灌后4、12、24、48 h神经功能评分及脊髓前角正常运动神经元计数均明显低于RIP组(P<0.05);再灌注48 h神经功能评分与脊髓前角正常神经元计数之间等级相关系数r_S=0.882(P<0.001),二者之间具有良好的相关性。结论肢体远程缺血后处理对兔脊髓缺血损伤具有保护作用;该保护作用可被纳洛酮阻断,提示阿片受体参与肢体远程缺血后处理的脊髓保护作用机制。

Objective To investigate mechanism of opioid receptor mediating the protective effects of limb remote ischemic preconditioning on spinal cord in rabbits. Methods Twenty-four New Zealand rabbits were randomly divided into 4 groups（ n = 6 per group）. Spinal cord ischemia group（ SCI） ： spinal cord ischemia was induced by an infrarenal aorta clamping for 25 min. Remote ischemia postconditioning group（ RIP） ： postconditioning was induced by 3 conditioning cycles of 5 minutes of ischemia and reperfusion on both hind limbs at 2 min before infrarenal reperfusion. MOR group（ MOR） and NAL group（ NAL） ： morphine（ 1 mg/kg） and naloxone（ 1 mg/kg） were given,respectively before reperfusion. The neural status was scored with the Tarlov criteria 4,12,24 and 48 hours after reperfusion. All the animals were sacrificed 48 hours after reperfusion and the spinal cords were harvested immediately for histopathological study. The correlation between neurological function after reperfusion（ 48 h） and the number of normal neurons in anterior spinal cord was analyzed. Results Tarlov scores and the number of normal motor neurons in spinal cord anterior horn of RIP group were significantly higher than SCII group 4 h,12 h,24 h,48 h after reperfusion（ P 〈 0. 05）. Tarlov score at 4 h of MOR group was significantly higher than RIP group（ P 〈 0. 05）,but no statistical significance in Tarlov scores at 12 h,24 h,48 h and the number of normal motor neurons in spinal cord anterior horn between the two groups. Tarlov scores and the number of normal motor neurons in spinal cord anterior horn of NAL group were significantly lower than RIP group 4 h,12 h,24 h and 48 h after reperfusion（ P 〈 0. 05）. There was a strong correlation between the final neural function scores and the number of normal motor neurons in the anterior horn of spinal cord（ r_S= 0. 882,P 〈 0. 001）. Conclusion Limb remote ischemic postconditioning has neuroprotective effects on spinal cord ischemia reperfusion injury in rabbit. The neuroprotection can be restrained by naloxone,implying opioid relates with the mechanism of limb remote ischemic postconditioning against spinal cord ischemic reperfusion injury.