Effect of surgical trauma on cognitive function and activation of microglias in hippocampus in rats of different ages / 中华麻醉学杂志

ABSTRACT

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 3-4months,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 performed 1 day after surgery to evaluate the space and fear memory abilities.The animals were sacrificed on 1st,3rd and 7th days after surgery and hippocampi were removed for measurement of OX42 expression in microglias by immunohistochemistry.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 1st 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 memory ability in adult rats.Surgical trauma decreases the space and fear memory abilities in aged rats,which maybe related to activation of microglias in hippocampus.