Study On The Mechanism Of NMDA-NO Pathway Regulated By Subanesthetic Dosage Ketamine In Mice Postoperative Cognitive Dysfunction

Objective: To Study the mechanism of NMDA-NO pathway regulated by subanesthetic dosage ketamine in mice postoperative cognitive dysfunction(POCD).Methods: Thirty Kunming mice were randomly divided into three groups,with10 mice in each group: blank control group(Group A),surgery group(Group B),surgery + subanesthetic dosage ketamine group(Group C).Group A did not do any processing,group B and C were underwent left carotid artery separation,group C was intraperitoneally injected with subanesthetic dosage ketamine0.1mg during the surery.The Morris water maze test was performed on the 1st,3rd,5th and 7th day after operation.The other 30 Kunming mice were treated in the same group and experimentally.The hippocampus were taken after nine hours after surgery and the hippocampus homogenate was collected.The protein levels of N-methyl-D-aspartic acid receptor R1(NMDAR1),N-methyl-D-aspartic acid receptor 2A(NMDAR2A),N-methyl-D-aspartic acid receptor 2B(NMDAR2B)in hippocampus were assayed by Western Blot.Enzyme linked immunosorbent assay(ELISA)was performed to measure theinterleukins(IL-6)and tumor necrosis factor(TNF-α)in the hippocampus homogenate.Immunohistochemical(IHC)analysis the positive expression intensity of NMDAR2 B.The relative activity of nitric oxide synthase(NOS)was measured with a nitric oxide synthase kit.Results: Immunohistochemical results were shown that the NMDAR2 B protein of group A was moderately positive(++),the NMDAR2 B protein of group B was strongly positive(+++),the NMDAR2 B protein of group C was weakly positive(+).In addition,it was observed that NMDAR2 B protein is mainly expressed in the hippocampal CA1 region and the expression is statistically significant difference between the three groups of mice,while the expression in the CA3 region is not significantly different between the three groups of mice.The latency of group B was significantly prolonged on the 1st and 3rd day after operation(63.54±32.25 vs.15.42±7.47,35.37±39.34,51.5±25.36 vs.13.1±6.15,25.8±34.53,both P<0.01).There were no significantly differences in all latency between group B and group C.On the other hand,the percentage of target quadrant in group B was significantly lower than that on the first day(21.94±9.64 vs.37.51±9.52,48.47±20.32,P<0.01).The levels of IL-6 and TNF-αin hippocampus homogenate of group C were significantly decreased[IL-6(ng/ml): 1.95±0.95 vs.2.06±0.46,5.36±0.49,TNF-α(pg/ml):21.84±6.54 vs.25.73±13.84,94.48±35.72,all P<0.05)].Also of Western Blot results suggest:the protein expression of NMDAR1,NMDAR2 A,NMDAR2B and relative activity of NOS in hippocampal homogenate of group C were significantly increased compared with that of blank control group and surgery group.The protein expression of NMDAR1,NMDAR2 A,NMDAR2B were(1.39±0.23),(2.32±3.13),(3.24±0.46)folds of those in surgery group,and the relative activity of NOS was(2.99±1.96)folds of these in surgery group,and(1.11±1.17)folds of these in control group.(all P<0.05).Conclusion: Subanesthesia dosage ketamine can antagonize NMDA receptors,inhibit the relative activity of NOS and reduce the release of inflammatory factors,thereby reducing the incidence of POCD.