| ObjectiveWe set up an intermittent hypoxia animal model by simulating the features of OSAHS(obstructive sleep apnea-hypopnea syndrome) to observe the learning and memory changes and the ultrastructure in CA1 region of the hippocampus exposed to 5%IH.Our purpose is that providing a theoretical basis of cognitive impairment for OSAHS patients.MethodsExperiments were performed on 48 mature male Wistar rats,they were randomly assigned to three experimental groups(n=6/group weight 170±10g):5% intermittent hypoxia group(5%IH) and unhandled control group (UC). Rats in every group were raised normally, and then those in IH groups suffered 8 hours intermittent hypoxia everyday, the duration of experiment was respectively 2,4,6 and 8 weeks. The compressed air was given to the UC group. The learning and memory ability of rats in each group were assessed with the Morris water maze(MWM) test at the end of the experiments,and then we observed the ultramicrostructural changes in the hippocampus of rats with electromicroscope and light microscope.Results1,Morris water maze test learning scores:①place navigation:The escape latency period was shorted gradually during the place navigation in all groups and there were signifcant statistically differences among different days(P<0.05).There were trends that the escape latency period of IH groups prolonged with hypoxia time increased. The escape latency period was apparently different between 5% IH and UC groups. Within-subjects contrasts: The escape latency period in 5%IH2w was shorter than5%IH6w,8w groups.The ELP in 5%IH8w was much longer than that in 5%IH4w(P<0.05).The contrast had not sharply differences among other IH groups.②spatial probe :⒈frequency of crossing the platform : Using nonparametric tests, the number of times of crossing the platform in different exposure time were not incompletely same.With the prolongation of exposure time, the numbers of crossing the platform decreased( P<0.01).⒉crossing the target quardant time:The time spent on crossing the target quardant to the total swimming time had gradually degressive trends with the extension of hypoxia time in IH groups.There was notable distinction between IH groups and UC group(P<0.05). 5%IH2w group was different with 5%IH4w,6w,8w groups.2,the change of hippocampus structure under the light microscopeWith the extention of intermittent hypoxia, each stage apoptosis could be seen in neuron cells.The phenomenon was observed that nuclear chromatin buildup under the nuclear envelope at the nonage.Nuclear fragmentation were observed at advanced stage. Tigroid body became blur gradually and generated dosaggregation. The quantity of neuron diminished along with the extention of intermittent hypoxia. Besides we also observed oncootic neurons which showed vacuolization and the raise of lucency ,but the composition of kytoplasm did not clear.3,We could observe that chromatospherite is clear, caryoplasm displayed uniform distribution caryotheca was smooth and glossy, and cell organ was abundant and integrated. With the extention of exposure time,hippocampus neurons displayed that the reduction of glycogen granule and lower-grade damage in intermittent hypoxia groups.The fissura of cellular nucelus emerged and became deeply with the extention of exposure time. The quantity of cell organ diminished, apart from this chondrosome showed vacuolization and emerged allotype. The phenomenon of degranulation in the surface of Rough endoplasmic reticulum became serious. With the extention of exposure time, synaptic vesicle greaten,Frame became indefinite and synaptic cleft widen.The following appearance,including chromatin margination and the formation of the decrease of neuron, happened at the later stage. Demyelinate reached the peak when the rats exposured to six weeks.Blood vessel showed different degree oedema at each stage.Conclusion1,Chronic intermittent hypoxia can make the function of learning and memory in rats drop. With the extention of exposure time , the function of learning and memory presents the gradually aggravating trend. The rats have presented obvious cognitive impairment when the chronic intermittent hypoxia reaches certain time.2,The injury of hippocampus neurons could be resulted in by chronic intermittent hypoxia. With the extention of exposure time , the injury of hippocampus neurons became serious.
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