Effect of dexamethasone on postoperative cognitive function in rats / 中华麻醉学杂志

ABSTRACT

Objective To investigate the effect of dexamethasone on the postoperative cognitive function in rats.Methods One hundred and eighty Sprague-Dawley rats,aged 18-20 months,weighing 400-600 g,were randomly allocated into 3 groups (n =60 each)∶ control group (C group),surgery group (S group) and dexamethasone group (D group).In groups S and D,the rats were anesthetized with 5％ chloral hydrate 4-6 ml/kg and underwent abdominal surgery.The rats in group D received intraperitoneal injection of dexamethasone 10 mg/kg at the beginning of anesthesia,while the rats in group C underwent no surgery and received intraperitoneal injection of normal saline 1 ml/kg instead.Six rats in each group were chosen at 3 h and 7 days after surgery and sacrificed,and their brains were immediately removed for detection of the expression of OX42 (a specific marker for activation of microglia) in hippocampus.Another 6 rats in each group were chosen at 3 h,and 1,3 and 7 days after surgery and sacrificed,and their brains were immediately removed for detection of the expression of IL-1β mRNA and TNF-α mRNA in hippocampus.Cognitive function was assessed by Morris water maze test and fear conditioning test.Results Compared with group C,the escape latency was prolonged,the frequency of crossing the original platform was decreased,the postoperative freezing time was shortened,and the expression of OX42 after surgery and IL-1β mRNA and TNF-α mRNA at 3 h and 1 and 3 days after surgery was up-regulated in groups S and D (P ＜ 0.05 or 0.01).Compared with group S,the escape latency was shortened,the frequency of crossing the original platform was increased,the postoperative freezing time was prolonged,and the expression of OX42 at 3 h after surgery and IL-1β mRNA and TNF-α mRNA at 3 h and 1 and 3 days after surgery was down-regulated in group D (P ＜ 0.05 or 0.01).Conclusion Dexamethasone can inhibit the over-activation of microglia and reduce the inflammatory response,thus improving cognitive function in rats.