The Effect Of Chronic Intermittent Hypoxia On Hippocampus Relating Learning And Memory

AimTo investigate the effects of chronic intermittent hypoxia (CIH) on the hippocampus relating learning and memory of rats, exploring the underlying mechanism.To study the changes of oxidative stress and inflammatory factors in CIH rats.MethodsThere are 2 parts of this research. The first part is,14 SD rats were randomly divided into chronic intermittent hypoxia group (CIH) group, which given intermittent hypoxia treatment for 8 hours everyday, and control group with normoxia, to study the behaviors of rats and the immunohistochemistry of hippocampus. At 8 week, all rats in both groups would perform the Spatial memory with Morris Water Maze, conditional learning and memory with passive avoidance test. Then the hippocampucal lobes of these rats were remain to study the expression of synaptophysin, muscarinic acetylcholine receptor M1 (CHRM1) in hippocampucal dentate gyrus regions. The second part is,36 SD rats were randomly divided into CIH group (n=18) and control group (n=18) with normoxia for the study about CIH on oxidative stress and Inflammatory factors; In every group, six rats were killed to get serum for SOD,POD,hsCRP,IL-1β,and TNF-αat the time point of the second, the fourth and the eighth week.ResultsThere were no significant differences in Morris Water Maze test and the next day after the training in passive avoidance test between the control rats and CIH ones. The latency time of control rats was longer at the 8th day after the training in passive avoidance test, than those CIH ones. Compared to control rats, CIH rats showed increased optical density values of synaptophysin and CHRM1 in hippocampucal dentate gyrus region(P<0.05). The serum levels of POD in CIH rats were decreased at the time point of the second and the fourth week comparing with those in control rats (P<0.05), but at the 8th week, there was no differences between both groups (P>0.05). No significant differences were observed in serum levels of hsCRP,IL-1β,TNF-αand SOD between the control rats and CIH rats (P>0.05)ConclusionSD rats with chronic intermittent hypoxia(CIH) for 8 weeks had deficit in memory retrieval and recall, but no significant impairment in spatial memory. Immunohistochemistry test showed that CIH increase the synaptophysin and CHRM1 in hippocampus loci, which probably the compensative mechanism to protect the spatial memory of SD rats against CIH. Oxidative stress level in SD rats was relatively higher at the early stage of CIH, and then may return to the normal levels with time. On the other hand, CIH maybe have less influences on the expression of inflammatory factor.