摘要目的 探讨缺血缺氧时间因素对七氟醚后处理减轻新生大鼠缺血缺氧性脑损伤的影响.方法 新生SD大鼠210只,7日龄,体重13～ 17 g,雌雄各半,采用随机数字表法分为7组(n=30):假手术组(Sham组)、缺血缺氧组(HI组)和不同缺血缺氧时间-七氟醚后处理组(P0组、P3组、P6组、P12组、P24组).采用结扎左侧颈总动脉的方法制备新生大鼠缺血缺氧性脑损伤模型.P0组、P3组、P6组、P12组和P24组分别于结扎左颈总动脉即刻、结扎后3、6、12和24 h时吸入含2％七氟醚的湿化混合气体30 min.记录模型制备后7d内大鼠的病死情况.模型制备后7d时,取脑组织,称量左右侧脑半球质量,计算左右侧脑半球质量比值;分离海马CA1区和后扣带回皮层,计算左右侧正常神经元密度比值.结果 与Sham组比较,其余6组左侧大脑半球质量、左右侧脑半球质量比值和海马CA1区和后扣带回皮层正常神经元密度比值降低,病死率升高(P＜0.05);与HI组比较,P0组、P3组和P6组左侧大脑半球质量、左右侧脑半球质量比值和海马CA1区和后扣带回皮层正常神经元密度比值升高(P＜0.05),P12组与P24组上述指标差异无统计学意义(P＞0.05);与P6组比较,P0组和P3组左侧大脑半球质量、左右侧脑半球质量比值和海马CA1区和后扣带回皮层正常神经元密度比值升高(P＜0.05);P0组与P3组上述指标比较差异无统计学意义(P＞0.05).结论 缺血缺氧6h内七氟醚后处理可减轻新生大鼠缺血缺氧性脑损伤,超过12h则无脑保护作用.

abstractsObjective To evaluate the effect of hypoxic-ischemic time on reduction of hypoxic-ischemic brain injury by sevoflurane postconditioning in neonatal rats.Methods Two hundred and ten 7-day-old Sprague-Dawley rats (105 male,105 female),weighing 13-17 g,were randomly divided into 7groups (n=30 each) using a random number table:sham operation group (group Sham),hypoxia-ischemia group (group HI),and sevoflurane postconditioning at different hypoxic-ischemic time point groups (P0,P3,P6,P 12 and P24 groups).Immediately after ligation of the left common carotid artery,and at 3,6,12 and 24 h after ligation,the rats inhaled the mixed gas containing 2％ sevoflurane for 30 min in P0,P3,P6,P13 and P24 groups,respectively.The fatality was recorded within 7 days after establishment of the model.At 7 days after establishment of the model,the rats were sacrificed,the brains were removed,and the right and left cerebral hemispheres were weighed separately,and the left/right cerebral hemisphere weight ratio was calculated.The hippocampal CA1 region and posterior cingulate gyrus were isolated,and the ratio of density of normal neurons in the left to the right was calculated.Results Compared with group Sham,the left cerebral hemisphere weight,left/right cerebral hemisphere weight ratio,and ratio of density of normal neurons were significantly decreased,and the fatality rate was increased in the other six groups (P＜0.05).Compared with group HI,the left cerebral hemisphere weight,left/right cerebral hemisphere weight ratio,and ratio of density of normal ncurons were significantly increased in P0,P3 and P6 groups (P＜0.05),and no significant change was found in the parameters mentioned above in P12 and P24 groups (P＞0.05).Compared with group P6,the left cerebral hemisphere weight,left/right cerebral hemisphere weight ratio,and ratio of density of normal neurons were significantly increased in P0 and P3 groups (P＜ 0.05).There was no significant difference in the parameters mentioned above between group P0 and group P3 (P＞0.05).Conclusion Sevoflurane postconditioning performed within 6 h of hypoxia-ischemia can reduce hypoxic-ischemic brain injury,and it provides no cerebral protection if exceeding 12 h.