Effects of M1 AChR expression in hippocampus on learning and memory of rats exposed to plateau hypoxia
Objective To investigate the effects of the expression of muscarinic acetylcholine receptor M1(M1 AChR)in hippocampus on learning and memory of male rats exposed to plateau hypoxia.Methods The rats were randomly divided into normoxic control group(NC group),normoxic group(N group),hypoxia group(H group)and hypoxia+TAK-071 group(HT group).Their learning and spatial memory abilities were investigated by place navigation test and spatial probe test respectively.Hematoxylin-eosin staining(H&E)technique was used to observe the morphology of frontal lobe and hippocampus of rats.Immunohistochemical staining(IHC)and western blot(WB)were adopted to detect the protein expression level of M1 AchR in rat hippocampus.Fluorescence quan-titative PCR(qPCR)was used to detect the gene expression levels of M1 AchR and forkhead box protein P2(FOXP2)in rat hippocampus.Results After morris water maze(MWM)training,the overall expression level of M1 AChR protein in rat hippocampus decreased significantly(P<0.05),while increased significantly in hippocampus CA1 and CA3 areas(P<0.05).Hypoxia environment significantly altered the performance of rats in place naviga-tion test,i.e.an increase in escape latency duration.Besides,it significantly altered the performance of rats in spatial probe test,i.e.reduced residence time in the target quadrant(P<0.05).After activating M1 AChR,M1 AChR in-creased due to hypoxia in rat hippocampus decreased significantly(P<0.05).Conclusion Activating M1 AChR can improve the memory impairment of male rats caused by plateau hypoxia and slow down the process of memory decline.It has no effect on learning improvement.It is speculated that the role of M1 AChR in the cognitive function of male rats may be the preservation of existing memories.
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