慢性间歇低氧诱导小鼠学习记忆障碍的实验研究

目的 探讨慢性间歇低氧（CIH）诱导小鼠空间学习记忆能力的变化及CIH对认知功能损伤的可能机制.方法 60只ICR雄性幼鼠随机分为常氧对照组（UC组）和间歇低氧组（CIH组）,每组30只;CIH组小鼠置于低氧舱内,通过吹入氮气及压缩空气,每60s做一次缺氧/再氧合循环,使氧浓度波动在6％～8％和20％～ 21％之间,每天8h.CIH组根据低氧造模时间分为3d（A组）、1周（B组）、2周（C组）、4周（E组）、6周（F组）,以及造模结束后常氧饲养1月的10周组（G组）,共6组,每组5只小鼠,同期设6组对照,每组5只小鼠.在慢性间歇低氧3d、1周、2周及6周终点,采用Morris水迷宫的方法测定CIH组和UC组空间学习记忆功能的变化;Western blot法分别测各组海马N-甲基-D-天冬氨酸受体（NMDAR）亚单位1（NR1）蛋白表达的变化;采用免疫荧光标记测定海马Caspase-3表达情况.结果 ①CIH组小鼠在间歇低氧3d时,水迷宫逃避潜伏期较对照组有所延长,但无统计学差异（P＞0.05）;随着间歇低氧时间的延长,逃避潜伏期较对照组逐渐延长（P＜0.05）;低氧6周后,CIH组逃避潜伏期（68.64±26.52）s]较对照组（21.36±14.14）s]明显延长（P＜0.01）.低氧6周后,CIH组穿越平台次数（4.58±2.58）次]较对照组（8.06±2.74）次]明显减少（P＜0.01）;②与对照组比较,CIH组B、C、E、F及G组小鼠海马神经元NR1蛋白表达均降低（P＜0.叭）,C、E组降至最低水平（P＜0.01）;复氧1月后的G组NR1蛋白与F组相仿,仍较对照组降低（P＜0.01）.CIH各组海马Caspase-3表达均明显升高,并成时间-效应关系,除A组外,其余各组与对照组相比,差异均有统计学意义（P均＜0.01）,CIH组组内指标比较无显著差异（P＞0.05）.结论 慢性间歇低氧诱导小鼠空间学习记忆障碍,且随低氧暴露时间延长学习记忆功能损害加重,这可能与海马神经元NR1蛋白表达下调以及与Caspase-3介导的海?

Experimental study on the impairment of spatial learning and memory in the mice exposed to chronic intermittent hypoxia

Objective To investigate the possible mechanism on spatial learning and memory impairment in the mice model of chronic intermittent hypoxia （CIH）.Methods Male ICR mice （n =60）were randomly assigned to two treatments：normoxic control （UC） and CIH （CIH）,CIH exposure was generated by cycling O2 concentration between 6％ ～ 8％ and 20％ ～ 21％ every 60 s during 8 h of day time.Each group were divided into 3 d （group A）,1 week （group B）,2 weeks（group C）,4weeks （group E） and 6weeks （group F）,after 6 weeks,animals were kept in room air for additional 4 weeks of recovery （group G）.Neurobehavioral assessments （Morris water maze） were performed at 3 d,1 week,2 weeks and 6 weeks.Hippocampal expression levels of Caspase-3 expression were evaluated by immunofluorescence,N-methyl-D-aspartate receptor （NMDAR） subunit 1 （NR1） protein expression was detected by Western blotting.Results ①Compared with the time-matched control animals in UC group,the CIH mice displayed longer mean escape latency in place navigation test starting as early as 3 d （group A）,followed by statistically significant progressive prolongation in group B,C and F.At 6 week,the mean ± SD escape latency was （68.64 ± 26.52）s in CIH mice compared to （21.36 ± 14.14） s in UC mice （P ＜ 0.01）.The number of times of crossing the platform in spatial probe test was also significantly reduced in CIH mice （CIH 4.58 ± 2.58 vs.UC 8.06 ± 2.74） at 6 weeks,（P ＜0.01）; ②Compared with the UC animals,CIH group B,C,E,and F,the hippocampal expression of NR1 proteins decreased significantly （P ＜ 0.01）,group C and E dropped to the lowest level （P ＜0.01）.NR1 expression persisted in group G mice after 4 weeks normoxic recovery （P ＜0.01）.The expression levels of caspase-3 in hippocampus in CIH mice were significantly higher than UC mice at all time points during the 6 weeks exposure of CIH （P ＜ 0.01）,except group A in 3 d.Conclusions Experimental mice CIH model demonst