| Part I the correlation between surgical trauma and postoperative cognitive dysfunction (POCD) in elderly miceObjective:Mouse model of POCD was constructed through left lateral hepatic lobectomy in elderly C57BL/6 mice, to investigate the effect of surgical trauma on postoperative cognitive function of elderly mice.Methods:Using a random number table,80 healthy 15-month-old C57BL/6 mice were randomly divided into 4 groups:the blank control group, the anesthesia group, the sham group, and the operation group. The mice were trained to find a hidden fixed platform in the first 5 days before operation,3 times each day. Then, their spatial memory capacity was evaluated on day 1,3 and 7 after surgery through the "space exploration experiment", and times crossing the platform and percentage of time spend in the target quadrant were recorded.Results:In the space exploration experiment, the elderly C57BL/6 mice of each group significantly improved as the training extended (P<0.05), but no significant difference was detected between the groups. In the Morris water maze test, times crossing the platform and percentage of time spend in the target quadrant had no significant difference between the control group and the anesthesia group, those of the sham group had a decrease on Day 1 and 3(P<0.05) but not Day 7, while those of the operation group decreased at all three points even when compared to the sham group (P<0.05). Test results of the control and sham group showed no significant difference among the 3 days; test results of the sham group gradually recovered on Day 3 and 7, compared to those of Day 1 (P<0.05), roughly to normal; while for the operation group, despite some recovery on Day 3 and 7, the value is still significantly lower than normal (P<0.05).Conclusion:the mouse model of POCD was successfully constructed through left lateral hepatic lobectomy in elderly C57BL/6 mice, and spatially memory capacity of these mice was more severely damaged compared to mice that received only sham operation.Part II the correlation between POCD and the NMDA receptor-NF-Kappa B-nNOS signaling pathway Experiment IObjective:Stress response of the elderly C57BL/6 mice was inhibited through analgesia and sedation during the operation, to investigate the role of NMDA receptor-NF-Kappa B-nNOS signaling pathway in central nervous POCD.Methods:Using a random number table,80 healthy 15-month-old C57BL/6 mice were randomly divided into 4 groups:the blank control group, the anesthesia group, the sham group, and the operation group. Mice of each group were sacrificed on Day 1,3, and 7 after operation,8 mice each day. The brain was obtained, using the left brain, NMDA receptor, nNOS, NF-κB, and NOS levels in the left hippocampus were determined by ELISA, and NO content was measured, and the right brain was used for analysis of synaptophysin and PSD-95 mRNA by RT-PCR.Results:The test results demonstrated no significant differences in NMDA receptor, nNOS, NF-κB, NOS protein levels and NO content between the anesthesia group and control group, while these indicators significantly decreased in the sham group compared to the control group on Day 1 and 3 (P<0.05) but not Day 7, while those of the operation group significantly decreased even when compared to the sham group at all three time points (P<0.05). These indicators of the sham group gradually returned to normal till Day 7 (P<0.05); while those of the operation group went down all the way (P<0.05).Conclusion:after construction of the POCD model, the elderly C57BL/6 mouse showed progressive decrease in NMDA receptor, nNOS, and NF-κB proteins in hippocampus, which was consistent with changes in synaptophysin and PSD-95 protein expression, suggesting that changes in NMDA receptor, nNOS, and NF-κB protein levels in hippocampus may be a link to POCD in elderly mice.Experiment IIObjective:Stress response of the elderly C57BL/6 mice was inhibited through analgesia and sedation during the operation as in Experiment I, but NMDA receptor agonists (15mg/ kg NMDA) was administered before operation to verify the presence of activation of the NMDA receptor-NFFκB-nNOS signaling pathway during the process of POCD in elderly mice.Methods:56 healthy 15-month-old C57BL/6 mice were randomly divided into 4 groups using a random number table:the blank control group, the anesthesia group, the sham group, and the operation group. NMDA receptor agonists (15mg/kg NMDA) was administered through intraperitoneal injection.1 hour before operation. Mice of each group were sacrificed on Day 1,3, and 7 after operation,8 each day, to obtain the brain, NMDA receptor, nNOS, NF-κB, and NOS levels in the left hippocampus were determined by ELISA, and NO content was measured, and the right brain was used for analysis of synaptophysin and PSD-95 mRNA by RT-PCR.Results:The test results demonstrated that NMDA receptor, nNOS, NF-κB, NOS protein levels and NO content of the sham group showed no significant difference compared to those of the control group, while those of the operation group significantly decrease compared to the control group at all tested time points (P<0.05). The results of the operation group at Day 3 and 7 significantly decreased compared to those on Day 1 (P<0.05), but no significant difference was detected between Day 3 and 7 (P>0.05). As for synaptophysin and PSD-95 mRNA, their levels in the sham group decreased on Day 1 after operation compared to the control group, but no difference on Day 3 and 7; while their levels in the operation group significantly decreased at all three time points (P<0.05). The results of the operation group significantly decreased on Day 3 and 7 compared to those on Day 1 (P<0.05), but no significant difference was detected between Day 3 and 7 (P>0.05).Conclusion:Decrease of NMDA receptor, nNOS, NF-κB, NOS protein levels and NO content after operation was alleviated by intraperitoneal administration of NMDA receptor agonist, and these indicators showed no further decrease on Day 7 compared to those on Day 3, which were consistent with changes in synaptophysin and PSD-95 mRNA levels. These results suggest that changes in NMDA receptor, nNOS, and NF-κB protein levels in hippocampus may be a link to POCD in elderly mice, providing a new approach to treat POCD. |
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