间歇性缺氧对大鼠认知功能和海马CA1区超微结构的影响

Effects of Intermittent Hypoxia on Cognition and the Ultrastructure in CA1 Region of the Hippocampus in Rats

目的观察间歇性缺氧对大鼠认知功能及海马CA1区神经元超微结构的影响。方法SD雄性大鼠16只,随机分为正常组(UC,n=8)和间歇性缺氧组(IH,n=8)。UC组正常饲养,IH组每日间歇缺氧7 h建立间歇性缺氧大鼠模型,通过Morris水迷宫测试检测其学习和记忆能力,并于灌注固定后应用透射电镜观察海马CA1区超微结构。结果(1)Morris水迷宫学习成绩(定位航行实验):第5 d训练结束时IH组大鼠逃避潜伏期明显长于UC组,两组之间差异有统计学意义(P<0.05)。(2)Morris水迷宫记忆成绩:IH组穿越平台次数[(1.38±0.92)次]较UC组减少[(3.75±1.04)次](P<0.01);IH组跨越目标象限时间占整个游泳时间的百分率[(20.52±3.41)%]也较UC组减少[(39.89±5.63)%](P<0.01)。(3)电镜下可见IH组神经元细胞质的电子密度增加,核染色质浓缩并聚集核膜附近,粗面内质网排列紊乱或扩张并出现脱颗粒现象,线粒体主要表现为肿胀、空泡变性及嵴消失,突触结构分界不清,突触小泡稀疏。UC组无明显病变。结论IH可致大鼠学习记忆障碍和海马神经元超微结构改变,IH所引起的大鼠学习记忆障碍与海马神经元超微结构的改变密切相关。

Objective To study the effects of intermittent hypoxia （IH） on cognitive function in rats and the ultrastructure in CA1 region of the hippocampus. Methods Experiments were performed on 16 three-month-old male Sprague-Dawley rats, Animals were randomly assigned to two experimental groups （n = 8/group）： IH group, unhandled control （UC） group. Rats in UC group were raised normally, and those in IH group suffered 7 h IH everyday, The duration of experiment was 8 weeks. The learning and memory ability of rats in each group were assessed with the Morris water maze test （MWM） at the end of the experiments. The ultrastructure of hippocampal neurons was observed by electron microscope after the completion of the experiment. Results （1） MWM of learning scores （place navigation） after 5 days training, the escape latency in IH rats was significantly longer compared with that in UC rats （P〈0.05） ; （2）MWM of memory scores： the number of times of crossing the platform in IH group （1.38±0.92） was significantly reduced compared with that in UC group （3.75±1.04） （P〈0.01） .The percentage of time spent on crossing the target quadrant to the total swimming time in IH group [ （20.52 ± 3.41） %] was also significantly decreased compared with that in UC group [ （39.89 ±5.63） M, P〈0. 01%]（3） Changes in the ultrastructure of hippocampus neurons and synapses were obvious in IH group as compared with the UC group. Conclusions （1）IH can lead to cognitive impairment of the rats and alterations in the ultrastructure of hippocampal neurons and synapses . （2） There was close correlation between cognitive disorders in rats and the changes in the ultrastructure of hippocampal neurons exposed to IH.