急性重复缺氧对大鼠海马电活动的影响

EFFECTS OF ACUTE REPEATEDHYPOXIA ON ELECTRICAL ACTIVITY OF HIPPOCAMPUS

本实验以大鼠喘呼吸的出现为重复缺氧时每次缺氧耐受极限（下次缺氧开始的标志），观察重复缺氧对海马ＣＡ１、ＣＡ３区群锋电位（ｐｏｐｕｌａｔｉｏｎｓｐｉｋｅ，ＰＳ）及海马脑电图的影响。结果表明，首次缺氧早期，刺激同侧隔区所诱发ＣＡ１和ＣＡ３的ＰＳ幅值无明显变化。随着缺氧程度的加深，ＣＡ１和ＣＡ３的ＰＳ幅值逐渐降低，ＣＡ１－ＰＳ于缺氧８ｍｉｎ时消失，此时ＣＡ３－ＰＳ为缺氧前的６０％；海马脑电图θ慢波的波幅和频率也随着缺氧的加深而降低。随着缺氧重复次数的增加，耐受时间逐次延长，ＣＡ１－ＰＳ和ＣＡ３－ＰＳ幅度均逐次降低，到第４次缺氧时，维持在很低水平。ＣＡ１－ＰＳ于缺氧１４ｍｉｎ时消失，此时ＣＡ３的ＰＳ为缺氧前的５％，缺氧１６─１８ｍｉｎ时ＣＡ３－ＰＳ才消失；ＣＡｌ区海马脑电图经常表现为自发性放电，而ＣＡ３区则表现低幅低频慢波。结果提示，重复缺氧时缺氧耐受性的逐次增高与海马电活动逐次抑制相关，重复缺氧使海马ＣＡ１、ＣＡ３区缺氧耐受性差异增大。

Population spike(PS)and electroencephalogram(EEG)in hippocampal CAl and CA3 re-gions were monitored and recorded during acute repeated hypoxia.The appearance of gaspingbreath was taken as the limit of tolerance to hypoxia and next run of the hypoxic exposure wasstarted accordingly.As exposure went on,tolerance time increased and both amplitude ofhippocampal activity and frequency of EEG were reduced.Difference in tolerance time betweenCA1-PS and CA3-PS in the 4th run is longer than that in first run.Seizure-like discharge oftenappeared in CA1 region,while low-amplitude and low-frequency waves were shown in CA3zone.These results indicate that adaptation to hypoxia is related to supprssion of hippocampalevoked potentials and reduction of electrical activity.The difference in tolerance time betweenCA1 and CA3 regions become greater during repetitive exposure to hypoxia.