手术创伤对不同月龄大鼠认知功能及海马小胶质细胞活化的影响

Effect of surgical trauma on cognitive function and activation of microglias in hippocampus in rats of differ- ent ages

目的评价手术创伤对不同月龄大鼠认知功能和海马小胶质细胞活化的影响。方法健康雄性sD大鼠72只，3～4月龄，采用随机数字表法，将其分为2组：成年对照组（n=30）和成年手术组（n=42）。健康雄性sD大鼠72只，18～20月龄，采用随机数字表法，将其分为2组：老年对照组（n=30）和老年手术组（n=42）。手术组腹腔注射5％水合氯醛4～6ml／kg麻醉下行剖腹探查术，对照组腹腔注射生理盐水1ml／kg。于术后1—7d开始行水迷宫实验，术后1d采用条件恐怖适应实验检测大鼠术后空间和恐怖记忆能力，术后第1、3、7天时处死大鼠，取海马，采用免疫组化法检测小胶质细胞07（42表达。结果与成年对照组比较，成年手术组大鼠僵直时间占总时间百分比降低，术后第1天海马小胶质细胞OX42表达上调（P〈0．05），逃避潜伏期及穿过原平台次数差异无统计学意义（P〉0．05）；与老年对照组比较，老年手术组大鼠逃避潜伏期延长，穿过原平台次数减少，僵直时间占总时间百分比降低，术后第1和3天海马小胶质细胞0X42表达上调（P〈0．05）。结论手术创伤可降低成年大鼠恐怖记忆能力，但对空间记忆能力影响不明显；手术创伤可降低老年大鼠空间及恐怖记忆能力，与海马小胶质细胞活化有关。

Objective To investigate the effect of surgical trauma on the cognitive function and activation of microglias in hippocampus in rats of different ages.Methods Seventy-two male Sprague-Dawley rats, aged 3-4 months, were randomly allocated into 2 groups： adult control group （ n = 30） and adult surgery group （ n = 42）. Seventy-two male Sprague-Dawley rats, aged 18-20 months, were randomly allocated into 2 groups： aged control group （ n = 30） and aged surgery group （ n = 42）. The rats were anesthetized with 5% chloral hydrate 4-6 ml/kg and underwent exploratory laparotomy in surgery groups, while normal saline 1 ml/kg was injected intraperitoneally in control groups. Morris water maze test was performed at 1-7 days after surgery. Fear conditioning test was per- formed 1 day after surgery to evaluate the space and fear memory abilities. The animals were sacrificed on ist, 3rd and 7th days after surgery and hippocampi were removed for measurement of OX42 expression in microglias by im- munohistochemistry. Results Compared with adult control group, the percentage of freezing time in total time was significantly decreased, and OX42 expression in microglias was up-regulated on 1 st day after surgery （P 〈 0.05 ）, and no significant change was found in the escape latency and the number of crossing the original platform in adult surgery group （ P 〉 0.05）. Compared with aged control group, the escape latency was significantly prolonged, the number of crossing the original platform was decreased, the percentage of freezing time in total time was decreased, and OX42 expression in microglias was up-regulated on 1st and 3rd days after surgery in aged surgery group （ P 〈 0.05）. Conclusion Surgical trauma decreases fear memory ability, but exerts no effect on the space memoryability in adult rats. Surgical trauma decreases the space and fear memory abilities in aged rats, which maybe re- lated to activation of microglias in hippocampus.