Effect Of The Combination Of Propofol And Sevoflurane On GABA_A Receptor α1/α2 Subunits Protein Proteostasis And Depressive State In MCI Rats

Objective:To evaluate the effect of the combination of propofol and sevoflurane on GABA_Areceptor（GABA_AR）α1/α2 subunits protein homeostasis and depressive state to hippocampal neurons of rats with mild cognitive impairment（MCI）,so as to provide clinical guidance and basis for optimizing anesthesia management and maintaining brain health in patients with MCI who are at high risk of Alzheimer’s disease（AD）.Method:In this experiment,the healthy male SD rats aged 16-18 months were randomly divided into 5 groups（n=24/group）:normal control group（C group）,sham operation group（Sham group）,propofol group（P group）,sevoflurane group（S group）and propofol combined with sevoflurane group（SP group）.In addition to C group,MCI model was established by ligating bilateral common carotid arteries of the other four groups.After 30 days of modeling,Morris Water Maze test was used to screen the model rats to select the MCI rats.On the 36th day after modeling,the rats inhaled1.3 MAC sevoflurane in S group.Propofol 40mg·kg^-1·h^-1was infused intravenously in P group.The rats inhaled 0.7 MAC sevoflurane,and infused propofol20mg·kg^-1·h^-1intravenously in SP group.The anesthesia time of each group was controlled at 3h.During anesthesia,open reduction and internal fixation（ORIF）was performed for tibial fractures in rats.At the beginning of the ORIF,the index was the disappearance of eyelash reflex.The rats in Sham group were only sutured skin incision under local anesthesia without surgery.A 4-day sugar-water preference test was conducted on the 11^thday after operation to evaluate the depressive state.At the day 14 postoperatively,the Y maze test was used to test the spatial recognition and memory ability.After the behavioral experiment,the expression of KCC2,NKCC1,GABA_ARα1 and GABA_ARα2 subunits m RNA and protein in hippocampal neurons were detected by real-time Polymerase Chain Reaction（PCR）and western blot.Results:In Y maze test and the sugar-water preference test,compared with C group,the ratio of sugar-water consumption and the rate of time spend in N-arm were reduced in Sham group（P<0.05）.In real-time PCR,compared with C group,the m RNA level of KCC2 and GABA_ARα1 subunit were decreased（P<0.05）,and the m RNA level of NKCC1 was higher（P<0.05）and the m RNA level of GABA_ARα2subunit was extremely increased（P<0.01）in Sham group.Compared with Sham group,the m RNA level of KCC2 and GABA_ARα1 subunit were significantly decreased（P<0.01）,the m RNA level of NKCC1 was extremely increased（P<0.01）and the m RNA level of GABA_ARα2 subunit was increased（P<0.05）in S group.There were no statistical differences of the above indexes in real-time PCR between SP group and Sham group（P>0.05）.In western blot,compared with C group,the expression of KCC2 was decreased（P<0.05）,the expression of GABA_ARα1 subunit was extremely decreased（P<0.01）,but the expression of NKCC1 and GABA_ARα2subunit were increased（P<0.05）in Sham group.Compared with Sham group,the expression of KCC2 and GABA_ARα1 subunit were extremely decreased（P<0.01）,the expression of NKCC1 was increased（P<0.05）,and the expression of GABA_ARα2subunit was significantly increased（P<0.01）in S group.No significant changes were found in the parameters mentioned above between Sham group and SP group（P>0.05）.Conclusion:The results showed that cognitive impairment was accompanied by depression symptoms in MCI rats.The decrease of KCC2/NKCC1 ratio and the imbalance of GABA_ARα1/α2 subunits protein homeostasis was one of the mechanisms that 1.3MAC sevoflurane or 40mg·kg^-1·h^-1propofol aggravated the degree of cognitive impairment in MCI rats.In this study,we further verified that20mg·kg^-1·h^-1propofol combined with 0.7 MAC sevoflurane had the least effect on GABA_ARα1/α2 subunits protein homeostasis,postoperative cognitive function and depressive state in MCI rats.