联合应用缺血后处理、远隔缺血后处理和纳洛酮后处理对大鼠脑缺血-再灌注损伤的影响

Effects of combined ischemic postconditioning, remote ischemic postconditioning and naloxone postconditioning on focal cerebral ischemia-reperfusion injury in rats

目的评价联合应用缺血后处理、远隔缺血后处理和纳洛酮后处理对大鼠局灶性脑缺血－再灌注损伤的影响。方法将110只大鼠随机分为5组（n：22），通过阻塞右侧大脑中动脉90min和再灌注24h实施局灶性脑缺血－再灌注。I组为对照组；Ⅱ组为缺血后处理组，再灌注开始时实施3次30S的缺血和再灌注；Ⅲ组为远隔缺血后处理组，再灌注开始前实施5min的右侧股动脉缺血；Ⅳ组为纳洛酮后处理组，再灌注开始时腹腔注射纳洛酮10mg／kg；Ⅴ组为联合应用组。再灌注2h和24h时测定大鼠的神经功能障碍评分（NDS）；再灌注24h时，测定脑梗死区面积（n=10）、脑组织微管相关蛋白2（MAP2）表达（n=6）和脑组织血浆容量、血管直径和节段长度（n：6）。结果观察期所有时间点的心率和平均动脉压（MAP）组间比较差异均无统计学意义（均P〉0．05）。再灌注24h后，Ⅰ—Ⅴ组的缺血侧脑梗死面积与同侧大脑半球面积的比值（即脑梗死严重程度）分别是43％±6％、31％±4％、32％±5％、28％±6％和21％±7％。与Ⅰ组比较，Ⅱ-Ⅴ组的NDS和脑梗死严重程度均低（均P〈0．05），MAP2表达、血浆容量、血管直径和节段长度均高，但上述指标在Ⅱ组、Ⅲ组和Ⅵ组之间比较差异均无统计学意义（均P〉0．05）。与Ⅰ组、Ⅱ组、Ⅲ组和Ⅳ组比较，Ⅴ组的NDS评分和脑梗死程度均低（均P〈0．05），MAP2表达和血浆容量显著高（均P〈0．05），但是缺血侧脑组织的血管直径和节段长度在Ⅱ组、Ⅲ组Ⅵ组和Ⅴ组之间差异均无统计学意义（均P〉0．05）。结论在局灶性脑缺血-再灌注损伤大鼠，缺血后处理、远隔缺血后处理和纳洛酮后处理均具有明显的神经保护作用，表现为脑梗死严重程度降低和神经功能障碍改善。联合应用3种后处理措施可获得增强的神经保护效应。

Objective To assess the effects of ischemic postconditioning, remote isehemic postconditioning and naloxone postconditioning on focal cerebral ischemia-reperfusion injury in rats. Methods A total of 110 adult SD rats were randomly divided into 5 groups （n = 22 each）. The focal cerebral ischemia-reperfusion injury was induced by a 90-minute occlusion of right middle cerebral artery （MCA） and a 24-hour reperfusion sequentially. Group 1 was of ischemia-reperfusion control; Group 2 ischemic postconditioning induced by three 30-second cycles of MCA occlusion followed by a 30-second reperfusion; Group 3 remote ischemic postconditioning performed via a transient occlusion of right femoralartery at 5 min before the initiation of reperfusion; Group 4 naloxone postconditioning with naloxone 10 mg/kg intraperitoneally injected at the initiation of reperfusion; Group 5 combined ischemic, remote ischemic ＆ naloxone postconditioning performed simultaneously in accordance with the methods used in Groups 2, 3 ＆ 4. The neurologie deficit scores （NDS） were obtained at 2 h ＆ 24 h post-reperfusion. At 24 h post-reperfusion, the anesthetized rat was sacrificed by decapitation and the brain rapidly extracted to assess the size of cerebral infarct （n = 10）, detect the cerebral expression of microtubule-associated protein- 2 （MAP2） （n = 6）, measure the plasma volume of cerebral tissues and quantify the diameter and segment length of cerebral microvessel （ n = 6）. Results There were no significant differences in the heart rate （HR） and mean arterial pressure （MAP） among the above five groups at all observed time points （ P 〉 0. 05）. At 24 h post-reperfusion, the percentage of ischemic cerebral infarct size was 43%±6%, 31%±4% , 32%±5% , 28%±6% ＆ 21%±7% in ipsilateral hemisphere area （i. e. , cerebral infarct severity） in Groups 1 - 5 respectively. Compared with Group 1, the levels of NDS and cerebral infarct severity significantly decreased at ischemic side in Groups 2 - 5 （P 〈 0. 05）. And the cerebral expression of MAP2, plasma volume of cerebral tissues, diameter and segment length of cerebral microvessel significantly increased at the ischemic side （all P 〈 0. 05）. However, there were no significant differences in the above- mentioned parameters at ischemic side among Groups 2, 3 and 4 （all P 〉 0. 05 ）. The parameters of NDS, cerebral infarct severity, cerebral expression of MAP2 and plasma volume of cerebral tissues in the ischemic side significantly increased in Group 5 compared with Groups 1, 2, 3 and 4 （ all P 〈 0. 05 ）. The diameter and segment length of cerebral microvessel at ischemic side were not different among Groups 2, 3, 4 and 5 （all P 〉 0. 05）. Conclusion In focal cerebral ischemia-reperfusion rats, ischemic, remote ischemic and naloxone postconditioning may produce significant neuroprotective effects of reduced cerebral infarct severity and improved neurologic dysfunctions. A combination of three postconditioning approaches enhances the above neuroprotective effects.