新生期小鼠多次氯胺酮麻醉对远期认知功能的影响及其机制研究

Effect of neonatal repeated anesthesia with ketamine on the longterm cognitive function in mice and its mechanisms

目的研究多次氯胺酮麻醉是否影响新生期小鼠学龄期及成年后认知功能,并进一步探讨小胶质细胞及其特异性受体CX3CR1相关信号通路在该过程中发挥的作用。方法将出生后6 d(P6)的同窝昆明小鼠随机分为对照组和氯胺酮组,每组20只。氯胺酮组连续5 d腹腔注射氯胺酮80 mg/(kg·d),对照组注射同等体积生理盐水;给药1个月和2个月后分别行Morris水迷宫实验,检测学龄期及成年后两组小鼠的空间学习记忆能力;观察海马齿状回小胶质细胞数的变化,检测双侧海马组织CX3CR1蛋白相对表达量。结果氯胺酮组与对照组学龄期和成年小鼠训练前第1天、第2天、第3天、第4天、第5天逃避潜伏期比较,采用重复测量设计的方差分析,结果:(1)不同时间点学龄期和成年小鼠逃避潜伏期有差异(F=34.213和41.527,均P=0.000)。(2)氯胺酮组与对照组学龄期和成年小鼠逃避潜伏期有差异(F=19.856和21.365,均P=0.000);氯胺酮组与对照组相比逃避潜伏期较长(P<0.05)。(3)两组学龄期和成年小鼠逃避潜伏期变化趋势有差异(F=12.436和17.548,均P=0.000)。对照组学龄期和成年小鼠60 s内穿台次数、目的象限活动时间占比多或高于氯胺酮组(P<0.05)。对照组P11、P16、P21、P35、P67小鼠海马齿状回小胶质细胞数、CX3CR1蛋白相对表达量多或高于氯胺酮组(P<0.05)。结论新生期小鼠多次氯胺酮麻醉可致其远期认知功能障碍,且海马齿状回小胶质细胞和海马区CX3CR1蛋白相对表达量减少对其有促进作用。

Objective To investigate whether the long-term cognitive function will be affected by neonatal repeated anesthesia with ketamine in mice,and to explore the potential role of microglia and CX3CR1 signaling pathway in the process.Methods The postnatal day 6(P6)littermates were randomly divided into the control group and the ketamine group.The ketamine group received intraperitoneal injection of 80 mg/kg ketamine once a day for five consecutive days,whereas the control animals were injected with an equal volume of saline.After one month and two months of administration,the Morris water maze test was performed respectively to reflect the spatial learning and memory abilities of the school-age and adult mice.The alterations in the number of microglia in the dentate gyrus of hippocampus were observed and the expression of CX3CR1 protein in bilateral hippocampal tissues was detected.Results The escape latency as detected in the Morris water maze test was significantly different among the distinct time points(1 st,2 nd,3 rd,4 th and 5 th day before training)in school-age and adult mice(F=34.213 and 41.527,both P<0.001).The escape latency of school-age and adult mice was different between the ketamine group and the control group(F=19.856 and 21.365,both P<0.001),and was even greater in the ketamine group(P<0.05).In addition,the change trend of the escape latency of school-age and adult mice was also different between the ketamine group and the control group(F=12.436 and 17.548,both P<0.001).The number of platform crossing within 60 s was greater,and the time spent in the target quadrant was longer in the control group relative to the ketamine group(P<0.05).The number of microglia and the level of CX3CR1 protein in hippocampal dentate gyrus at P11,P16,P21,P35 and P67 were higher in the control groups than those in the ketamine group(P<0.05).Conclusions Neonatal repeated anesthesia with ketamine leads to long-term cognitive dysfunction in mice,which may be associated with the decrease in the number of microglia and the expression of CX3CR1 protein in the hippocampus.