Study On The Effects Of Cognitive Function Caused By Hypoxic Injury In The Neonate Rats

Object: Copy the model of chronic intermittent hypoxia(IH) in the neonate rats,using the methods of electrophysiology,behavior and histology to observe the changes in brain neurons and cognitive function caused by hypoxic injury,and to explore the possible mechanism of its occurrence. Hope to provide some experimental basis for the further study of the mechanism of cognitive dysfunction caused by Children with obstructive sleep apnea hypopnea syndrome (OSAHS). Methods:1,Ninety-six adult male Stragu-awley rats (Age 20±2 days) were randomly divided into 6 groups:the unhandled control 2 weeks group, the unhandled control 4 weeks group, the unhandled control 6 weeks group, the intermittent hypoxia 2 weeks group, the intermittent hypoxia 4 weeks group, the intermittent hypoxia 6 weeks group (n=16). Rats in unhandled control (UC) groups were raised normally, and intermittent hypoxia (IH) groups were established as model of intermittent hypoxia. 2,Electrophysiological testing:Randomly selected 10 rats from each group,and record the electrical activity of the frontal cortex with a metal electrode after the model was copied successfully. 3,Behavioral testing:The learning and memory ability of remaining 6 rats in each group were assessed with the Morris water maze test after the model was copied successfully. 4,Morphological testing:The morphologic changes in hippocampal CA1 area were observed through optical microscope after stained with HE at the end of the Electrophysiological testing. Results:1,Electrophysiological testing:After 2-week intermittent hypoxia,the proportion ofδandθwave in rat prefrontal cortex in the UC group was more than that of the normal group,and the proportion ofαandβwave was less than that of the normal group. The difference was significant (P<0.05). However,after 4-week and 6-week intermittent hypoxia,the proportion ofδandθwave in rat prefrontal cortex in the UC group was slightly more than that of the normal group,and the proportion ofαandβwave was slightly less than that of the normal group. The difference was not significant(P>0.05). 2,Morris Water Maze of learning scores( place navigation ):the escape latency was shortened gradually during the place navigation in all groups after 5 days training. Repeated measures analysis of variance showed:(1)the escape latency were significant difference among different days(P< 0.05);(2)Comparison among groups:The escape latency in IH2w group was significantly longer than the UC2w group(P< 0.05);The escape latency in IH4w group was significantly longer than the UC4w group(P< 0.05);The escape latency in IH6w group was significantly longer than the UC6w group(P< 0.05);(3)Comparison among group:With the growth of young rats,the escape latency in UC groups were gradually shortened and significantly different among different ages(P< 0.05);The escape latency in IH2w group was significantly longer than the IH4w and IH6w group(P< 0.05);The IH4w group was longer than the IH6w group,but there was no statistically difference(P>0.05). Morris Water Maze of memory scores (spatial probe):(1)The percentage of crossing the target quadrant time compared with the total swimming time:①Comparison among groups:The IH2w group was significantly less than the UC2w group(P< 0.05);The IH4w group was significantly less than the UC4w group(P< 0.05);The IH6w group was significantly less than the UC6w group(P< 0.05);②Comparison among group:With the growth of young rats,the percentage of crossing the target quadrant time compared with the total swimming time in UC groups were gradually increased and significantly different among different ages(P< 0.05);The percentage of crossing the target quadrant time compared with the total swimming time in IH2w group was significantly less than the IH4w and IH6w group(P< 0.05);The IH4w group was less than the IH6w group,but there was no statistically difference(P>0.05). (2)The number of crossing the platform:①Comparison among groups:The IH2w group was significantly less than the UC2w group(P< 0.05);The IH4w group was significantly less than the UC4w group(P< 0.05);The IH6w group was significantly less than the UC6w group(P< 0.05);②Comparison among group:With the growth of young rats,the number of crossing the platform in UC groups were gradually increased and significantly different among different ages(P< 0.05);The number of crossing the platform in IH2w group was significantly less than the IH4w and IH6w group(P< 0.05);the IH4w group was less than the IH6w group,but there was no statistically difference(P>0.05). 3,Changes in the UC groups of Hippocampal neurons were different from IH groups. Conclusions:1,IH can lead to the changes of the electrical activity of the frontal cortex in neonate rats.2,IH can lead to the impairment of cognitive Function in neonate rats. 3,IH can lead to the changes of the morphologic in hippocampal CA1 area in neonate rats. 4,Neonate rats have a kind of compensatory repair capacity against chronic intermittent hypoxia.