Effect Of Hyperbaric Oxygen Preconditioning On Cognitive Function After Sevoflurane Anesthesia In A Rat Model Of The Amnestic Mild Cognitive Impairment

ObjectivesTo observe the effect of hyperbaric oxygen preconditioning on cognitive function after inhalation of sevoflurane in a rat of model of the amnestic mild cognitive impairment and to explore its possible mechanisms.MethodsForty male Sprague-Dawley rats were randomly divided into 4 groups（n=10）:No-treatment control（CON）group,a MCI group,Sevoflurane（SEV）group and Hyperbaric oxygen preconditioning（HBO-PC）group.To establish a MCI rat model,the a MCI group,the SEV group and the HBO-PC group were injected subcutaneously on the nape of the neck with D-galactose 1000mg·kg-1·d-1 for 1 week.Rats in the CON group were injected with an equal amount of normal saline（NS）without D-galactose for one week.After that,the HBO-PC group received hyperbaric oxygen pretreatment for consecutive five days,then rats in the SEV group and the HBO-PC group inhaled3.6%sevoflurane+100%O₂for three hours.The Morris Water Maze was performed in the following day to evaluate the learning and memory ability of all rats.After behavior examination,the pathomorphological changes of hippocampus were observed,and the level of Caspase-3 in hippocampus was determined by immunohistochemical staining;SOD activity,MDA content and inflammatory factor level in hippocampus were measured by Enzyme Linked Immunosorbent Assay,while the relative contents of Cyt C and Caspase-3 in hippocampus were detected by Western Blot.ResultsThere was no difference in weight and swimming speed between all rats（P<0.05）.The results of the Water Maze test showed that compared with the CON group,the escape latency of the a MCI group was significantly longer and the number of crossing platforms was significantly reduced（P<0.05）.Besides,the escape latency of the SEV group was longer than the a MCI group and HBO-PC group,while the number of crossing platforms of the SEV group was significantly reduced when compared with the above two groups（P<0.05）.Hippocampus HE staining showed that,in the a MCI group and HBO-PC group,the pyramidal cells in the hippocampal CA1 area were scattered,some cells were incomplete,and cytoplasmic staining appeared.In the SEV group,the arrangement of pyramidal cells was unclear,and more cells showed pyknosis and deep staining,neuronal apoptosis was more obvious.The results of immunohistochemical analysis were as follows:rare tan granules antigen antibody complexes were found in pyramidal cells and cell membrane in CA1 hippocampus of the CON group;while in the a MCI group,pyramidal cells with diffuse positive expression of caspase-3 were seen,and there were brown-yellow granular cytoplasm staining in the cells;the pyramidal cells in the SEV group were diffusely distributed,and some cells showed strong positive tan granule staining in the cytoplasm;in the HBO-PC group the positive expression area decreased and the staining became shallow.Further statistical analysis showed that the surface density of Caspase-3 in the hippocampal CA1 area of the SEV group was the highest,followed by that of the HBO-PC group and the a MCI group,and the lowest in the CON group（P<0.05）.Biochemical test results showed that compared with the CON group,the hippocampal SOD activity of the a MCI group was significantly reduced and the MDA content of the a MCI group was significantly increased（P<0.05）,and compared with the a MCI group and the HBO-PC group,the hippocampal SOD activity of the SEV group was significantly reduced and the MDA content of the SEV group was increased significantly（P<0.05）.The levels of TNF-α,IL-1β,IL-6,Cyt C and Caspase-3 in the hippocampus of the SEV group were significantly higher than other groups（P<0.05）.ConclusionsHBO preconditioning could significantly mitigate sevoflurane-induced cognitive impairment in a rat model of the amnestic mild cognitive impairment,which is related to inhibiting of oxidative stress level,inflammatory response and neuronal apoptosis in the hippocampus.