高压氧对缺氧缺血性脑损伤新生大鼠不同时期的影响

Effects of hyperbaric oxygenation on neonatal rats with hypoxic-ischemic brain damage at different stages

目的观察不同时期高压氧(HBO)对大鼠缺氧缺血性脑损伤(HIBD)模型的治疗疗效,分析其机制。方法32只7日龄Wistar大鼠制成HIBD模型,随机分为HIBD组(n=12)、HBO早治组(n=12)、HBO晚治组(n=8),并设假手术组(n=12)。HBO早治组与晚治组分别于造模后4 h1、4 d应用HBO。各组动物(除HBO晚治组)于14日龄治疗结束后各处死6只,余同HBO晚治组喂养至28日龄,避暗法测试学习记忆能力后于30日龄处死。以脑组织海马CA1区形态学及学习记忆能力来判断干预效果。结果(1)HE染色:HIBD组各时间点左侧大脑海马CA1区锥体细胞排列紊乱、疏松,层次不清,与假手术组及HBO早治组差异明显;HBO晚治组与HIBD组相似,但神经元数目较之多。(2)微管相关蛋白(MAP-2)灰度值免疫组化定量:HIBD组不同时间点MAP-2阳性表达不同程度下降,与假手术组及HBO早治组差异显著(P<0.01);HBO晚治组也较假手术组及早治组下降(P<0.01),但较HIBD组表达多(P<0.05)。(3)学习记忆能力测试:HIBD组较假手术组明显下降(P<0.05),而HBO早治组与晚治组均高于HIBD组。结论不论早期或晚期应用HBO治疗均能不同程度地减轻HIBD所致的海马CA1区组织学损伤,改善由HIBD引起的学习记忆能力下降,但早期治疗明显优于晚期治疗。

Objective To evaluate the effect of hyperbaric oxygenation（HBO） on HIBD rats at different stages and investigate its mechanism. Methods Unsexed 7-day-old Wistar rats were used as research subjects, and randomly divided into 4 groups： the HIBD group（ n = 12）, the HBO early-treated group（ n = 12 ）, the HBO late-treated group（ n = 8） and the sham operation group（ n = 12）. HBO treatment was administered from 4h after HI at in HBO early-treated group and 14d after HI in late-treated groups respectively. Eighteen rats from HBO early-treated group, HIBD group, and sham operation group were decapitated 7 days after HBO treated, and the others rats of all groups were bred to 28-day-old and were sacrificed after assessing the learning and memory ability. Brain samples of all groups were collected to evaluate histomorphologic changes by hematoxylin and eosin（HE） staining and immunohistochemical analysis of MAP-2 expression in the hippocampal CA1 subregion. Results （1）HE staining： in different time points of HIBD group, the pyramidal cell layer of cellular demarcation, coagulation necrosis, cytoplasmic eosinophilia and nucleur pyknosis were seen in the hippocampal CA1 subregion, there was significant difference compared with sham operation and HBO earlytreated group. In HBO late-treated group there were similar changes in the left brain but more neurons were preserved in the CA1 subregion compared with HIBD group. （2）Immunohistochemical staining for MAP-2： There was a significant decrease in MAP-2 expression in the HIBD group in different time points compared with sham operation group and HBO early-treated group （P 〈 0.01）. In HBO late-treated group, MAP-2 expression decreased compared with HBO early-treated group and sham operation group , but the degree lightened compared with HIBD group. （3）In the learning and memory ability test, the rate of memory-keeping was lower in HIBD group than that in sham operation group（P 〈 0.05）. It was higher in HBO early-treated group and late-treated group, than that in HIBD group. Conclusion HBO can mitigate the HIBD-induced histomorphologic damage of the hippocampal CA1 subregion and improve the learning and memory disability in different degrees, whether early or late started. The effect is better within 6h than after 14d post-HI, which suggests HBO therapy should be applied early especially.