麻醉及手术创伤对老年大鼠认知功能及海马突触结构的影响

Effects of ketamine and splenectomy on cognition and synapfic plasticity in hippocampus of senile rats

目的探讨麻醉和手术创伤对老年大鼠认知功能及海马突触结构的影响。方法18月龄SD大鼠56只随机分为3组：对照组（C组，n=8）、麻醉组（A组，n=24）、手术组（0组，n=24），A、0组根据麻醉和手术后1、3和7d分为3个亚组A1、A3、A7组和01、03、07组，每亚组8只。在相应的时间点用Morris水迷宫测试老年大鼠的认知功能，电镜定量测量海马CA3区多形层的突触结构。结果与C组比较，A1、01、03组Morris水迷宫测试潜伏期及游泳距离明显延长（P〈0．05），01、03组通过原平台次数明显减少（P〈0．01）；与A1组比较，O1组潜伏期明显延长（P〈0．05），游泳距离无明显差异。与C组比较，O1、O3组海马CA3区多形层突触间隙宽度加大变宽（P〈0．01）、突触后膜致密物厚度变薄（P〈0．01）、突触活性区长度缩短（P〈0．05）、突触界面曲率减小（P〈0．01）、穿孔性突触百分率亦下降，O7组恢复正常；各麻醉组突触形态改变差异无统计学意义。结论麻醉和手术创伤可损害老年大鼠的认知功能，而海马突触的可塑性可能是术后认知功能障碍的结构基础。

Objective To study the effects of ketamine anesthesia and surgery on cognition and synaptic structure in hippocampus of senile rats. Methods Fifty-six rats aged 18 months were randomly divided into 3 groups ： Groups C （ control group）, A （ ketamine 40 mg/kg, i.p. ） and O （ ketamine anesthesia ＆ splenectomy）. Morris water maze test was used to observe cognition at Days 1, 3 ＆ 7 after ketamine anesthesia or operation respectively. Accordingly Groups A and O were divided into 3 subgroup, i.e. A1, A3, A7 and O1, O3, O7. The time of Morris water maze test was recorded and the synaptic structure was measured in the polymorphic layer of the rat hippoeampal field CA3. Results Compared to Group C, the latency period and swimming distance significantly increased in Groups A1, O1 and O3 （P 〈 0. 05）, and the numbers passing the original platform decreased significantly in Groups O1 and O3 （ P 〈 0. 01 ）. The latency period was significantly longer in Group O1 than that in Group A1 （P 〈0. 05） while the swimming distance was unchanged. Compared to Group C, the width of synaptic cleft （ P 〈 0.01 ） increased, the length and area of postsynaptic densities （ P 〈 0. 05 or P 〈 0. 01 ） as well as synaptie curvature （ P 〈 0. 01 ） decreased in Groups O1 and O3. The percentage of perforated synapses also decreased in Groups O1 and O3. Conclusion Surgical injury can impair cognition of senile rats and the synaptic plasticity might be involved in postoperative cognitive dysfunction.