海马大麻素2型受体在小鼠术后认知功能障碍中的作用
Role of hippocampal cannabinoid receptor 2 in postoperative cognitive dysfunction in mice
目的 探讨海马大麻素2型受体(CB2R)在小鼠术后认知功能障碍(POCD)中的作用.方法 健康雄性C57BL/6小鼠54只,12~16周龄,体重20~ 30 g,采用随机数字表法将其分成3组(n=18):对照组(C组)、POCD组和POCD+CB2R激动剂JWH133组(POCD+J组).吸入1.5%异氟醚麻醉下进行胫骨骨折内固定术以制备POCD模型.POCD+J组麻醉苏醒后腹腔注射JWH133 2mg/kg,总容量10 ml/kg,之后每天腹腔注射1次直至术后第7天.于术前1d、术后1、3、7d时行旷场实验.旷场试验结束后15 min进行条件恐惧实验.行为学测试结束后2h,断头取脑,取海马组织,采用Western blot法检测TNF-α、IL-1β、单核细胞趋化蛋白-1(MCP-1)及CB2R的表达,免疫荧光法检测CD11b的表达.结果 3组各时点旷场实验总探索路程、条件恐惧化训练僵直时间百分比及声音恐惧测试僵直时间百分比差异无统计学意义(P>0.05).与C组比较,S组术后场景恐惧测试僵直时间百分比降低,海马TNF-α、IL-1β、MCP-1、CD11b和CB2R表达上调(P<0.05).与S组比较,S+J组术后场景恐惧测试僵直时间百分比升高,海马TNF-α、IL-1β、MCP-1、CD11b和CB2R表达下调(P<0.05).结论 海马CB2R的激活可能参与了小鼠POCD的内源性保护机制,该机制与抑制海马小胶质细胞活化,减轻中枢炎症反应有关.
更多Objective To investigate the role of hippocampal cannabinoid receptor 2 (CB2R) in postoperative cognitive dysfunction (POCD) in mice.Methods Fifty-four healthy male C57BL/6 mice,aged 12-16 weeks,weighing 20-30 g,were divided into 3 groups (n=18 each) using a random number table:control group (group C),group POCD and POCD plus CB2R agonist JWH133 group (group POCD+J).The mice were subjected to an intramedullary fixation for tibial fracture under 1.5% isoflurane anesthesia to establish POCD model.In group POCD+J,2 mg/kg JWH133 was injected intraperitoneally at a total volume of 10 ml/kg after emergence from anesthesia and then the injection was repeated once a day until the 7th day after surgery.Open field test was carried out on 1 day before surgery and 1,3 and 7 days after surgery to evaluate the locomotor activity.Fear conditioning test was carried out at 15 min after completion of open field test.Mice were sacrificed at 2 h after the end of behavioral test,and the hippocampus was harvested for determination of the expression of tumor necrosis factor-alpha (TNF-α),interleukin-1beta (IL-1β),monocyte chemotactic protein-1 (MCP-1) and CB2R (by Western blot) and expression of CD11b in hippocampal tissues (by immunofluorescence).Results There was no significant difference in the total exploring distance in open field test,percentage of freezing time in contextual fear conditioning test or percentage of freezing time in tone-fear conditioning text at each time point among the three groups (P>0.05).Compared with group C,the percentage of freezing time in contextual fear conditioning test was significantly decreased,and the expression of TNF-α,IL-1β,MCP-1,CD11b and CB2R was up-regulated after surgery in group S (P<0.05).Compared with group S,the percentage of freezing time in contextual fear conditioning test was significantly increased,and the expression of TNF-α,IL-1β,MCP-1,CD11band CB2R was down-regulated after surgery in group S+J (P< 0.05).Conclusion Activation of hippocampal CB2R may be involved in the endogenous protective mechanism of POCD in mice,and the mechanism is related to inhibiting activation of hippocampal microglia and attenuating central inflammatory responses.
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