| Objective Postoperative cognitive dysfunction is one of the common central nervous system complications after surgery, which the elderly patients are more likely to happen. Research shows that whether sevoflurane can result in POCD, the sevoflurane concentration that causes POCD and its mechanism is unclear. PI3K pathway controls a variety of neuronal responses. In addition to its role in neuronal survival, PI3K has been implicated in dendritic morphogenesis, neuronal polarity and growth, synaptic plasticity and memory formation. But we have not found reports about the impact of sevoflurane on the activity of PI3K. AMPA receptor is made up of four different genes encoding subunits of GluRl-4four submits. It traffics in the postsynaptic membrane rapidly. Transporting to the cytoplasm is mainly mediated by GluR2. Research shows that the inhibition GluR2AMPA receptor internalization in hippocampus is important to improve cognitive function. But whether sevoflurane regulates AMPA receptor GluR2trafficking has not been reported. This study to investigate the cognitive function that different concentrations of sevoflurane anesthesia induce and the role of PI3K-AMPA receptor GluR2submit signaling in hippocampus in it.Methods Two hundred and sixty-four healthy male Wistar rats, aged18-20months, weighting600-650g.Part1:Ninety-six rats were equally and randomly divided into6groups(n=16each):control group (group C), propofol group(group P), propofol+surgery group(group PS),1MAC sevoflurane+surgery group(group1MAC),1.3MAC sevoflurane+surgery group(group1.3MAC),1.5MAC sevoflurane+surgery group(group1.5MAC). Group C inhaled30%O2for2h. Rats in group P were infused with propofol at a rate of0.6+0.1mg·kg-1·min-1for2h. In group PS, open tibial fracture surgery was performed when propofol was infused at a rate of0.6±0.1mg·kg-1·min-1for2h. In group1MAC,1.3MAC and1.5MAC, open tibial fracture surgery was performed when rats were exposed to2.4%,3.1%and3.6%sevoflurane in30%O2for2h respectively. Rats in group P and PS also inhaled30%O2for2h. Eight rats in each group were chosen to perform fear conditioning training one day before surgery and to be tested on days1,3and7after surgery. Eight rats left in each group were chosen to perform Y maze test on days1,3and7after surgery. Through fear conditioning text and Y maze test, the sevoflurane concentration that could induce POCD in aged rats was determined.Part2:According to the results of part1, group1.5MAC was choosed as the sevoflurane concentration that could induce POCD in aged rats. Another one hundred and sixty-eight rats were randomly divided into4groups:group C、group P、group PS and group1.5MAC. Six rats in each group were chosen at6h after surgery for the determination of the expression of GluR2in hippocampus by RT-PCR. Another6rats of each were chosen on days1,3and7after surgery to detect the expression of PI3K, pAkt, Akt, pGSK3β,GSK3β, total protein of GluR2and cell membrane GluR2in hippocampus by western blot. Remaining6rats of each group were chosen on days1,3and7after surgery to detect the expression of PI3K-GIuR2submit complex by co-immunoprecipiation and western blot.ResultsPart1:Compared with group C, the percentage freezing time of contextual test and tone cued test and spontaneous alternation were decreased on days1～7after surgery in group P, PS,1MAC,1.3MAC and1.5MAC (P<0.05). Compared with group PS, the percentage freezing time of contextual text on day1after surgery and tone cued test on days1～7after surgery and spontaneous alteration on days1and3were decreased in group1.5MAC (P<0.05).Part2:No significant change in the expression of GluR2mRNA at6h after surgery and total protein of GluR2on days1～7after surgery were found in each group (P>0.05). Compared with group C, the expression of cell membrane GluR2 and PI3K-AMPA receptor GluR2complex in hippocampus was decreased on days1-7after surgery in group PS and1.5MAC (P<0.05). Compared with group PS, the expression of cell membrane GluR2and PI3K-AMPA receptor GluR2complex were decreased on days1and3after surgery in group1.5MAC (P<0.05). Compared with group C, the expression of PI3K、pAk、pGSK3β(3on days1～7after surgery were decreased in group PS and1.5MAC (P<0.05). Compared with group PS, the expression of PI3K、pAkt、pGSK3β on days1and3after surgery were decreased in group1.5MAC (P<0.05). No significant change in the expression of Akt and pGSK3β on days1～7after surgery were found in each group (P>0.05).Conclusion Anesthesia with1.5MAC sevoflurane can induce the impairment of fear memory and work memory in aged rats possibly through decrease of PI3K activity and PI3K-GluR2complex in hippocampus, thus inhibiting AMPA receptor GluR2subunit trafficking from cytoplasm to cell membrane. |
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