七氟烷对衰老模型大鼠认知功能及海马α7nAChR的影响

Effects of sevoflurane on the cognitive function and the quantity of alpha 7 nicotinicacetycholine receptors in the hippocampus of elderly model rats

目的研究发现α7nAChR与认知功能的改变有密切的关系,而老年患者由于其年龄特殊性成为了术后认知功能障碍发生的高危群体,文章探讨了七氟烷对衰老模型大鼠认知功能及海马内α7nAChR的影响。方法成年健康雄性SD大鼠共72只,连续6周头颈部皮下注射D-半乳糖,复制衰老模型大鼠。模型大鼠随机分为:对照组(n=18)予以运载气体(2 L/min Air+2 L/min O2)6 h;七氟烷组(Sev组,n=18)予以体积分数为3.2%七氟烷+运载气体6 h;七氟烷+α7nAChR拮抗剂组(Sev+M组,n=18):注射拮抗剂24 h后,处理同Sev组;七氟烷+α7nAChR激动剂组(Sev+P组,n=18):注射激动剂24 h后,处理同Sev组。各组大鼠分别于麻醉苏醒后2 h、1周、4周后,以水迷宫法做行为学检测;每周期行为学检测结束后,腹腔注射麻醉取大鼠海马组织,RT-qPCR法测定海马内α7nAChR mRNA表达;Western blot法测定海马α7nAChR蛋白表达。结果苏醒后2 h,Sev组、Sev+M组、Sev+P组大鼠工作记忆逃避潜伏期[(17.1±1.5、18.2±1.6、8.0±1.3)s]均较对照组[(4.2±1.3)s]对应时间延长(P<0.05),Sev+P组较Sev组及Sev+M组明显缩短(P<0.05);苏醒后1周Sev组及Sev+M组[(15.3±2.5、23.3±1.8)s]较对照组[(10.9±1.3)s]明显延长(P<0.05)。各组大鼠麻醉苏醒后2 h,Sev组大鼠平台穿越次数、有效区域穿越次数及平台象限穿越次数与Con比较均明显下降(P<0.05);Sev+M组平台象限穿越次数,有效区域穿越次数及平台象限穿越次数百分比较对照组明显下降(P<0.05);麻醉苏醒后1周,Sev组大鼠平台象限穿越次数与对照组比较明显下降(P<0.05);Sev+P组大鼠有效区域穿越次数及平台象限穿越次数较Sev+M组明显升高(P<0.05)。与对照组比较,其余各组苏醒后2 h及1周α7nAChR mRNA和蛋白表达均下调(P<0.05);4周α7nAChR mRNA和蛋白表达均上调(P<0.05)。结论吸入3.2%七氟烷6 h可引起衰老模型大鼠海马内α7nAChR代谢紊乱并导致大鼠短期内(1周)学习记忆能力下降,但这种影响具有可逆性。而α7nAChR激动剂PNU-282987能够缓解七氟烷引起的短暂性的学习记忆能力下降。

Objective Some studies reported thatα7nAChR is closely related to the cognitive function.However,the elderly patients have become a high-risk group of postoperative cognitive dysfunction.The aim of this study was to explore the effect of sevoflurane inhalation on the cognitive function and the quantity of alpha 7nicotinic acetycholine receptors in the hippocampus of elderly model rats.Methods Adult male Sprague-Dawley rats(N=72)were given subcutaneous injection of D-galactose on the neck for 6 weeks to establish elderly models.The model rats were divided into 4 groups randomly:control group(group Con,n=18)with 6h exposure carrier gas(2L/min Air+2L/min O 2);Sevoflurane group(group Sev,n=18)with 6 h exposure to 3.2% sevoflurane through carrier gas.Sev+α7nAChR antagonist group(group Sev+M)injected with methyllycaconitine,after 24 h inhaled of 3.2% sevoflurane and carrier gas for 6 h.Sev+α7nAChR agonist group(group Sev+P,n=18)injected with PNU-282987,after 24 h inhaled of 3.2% sevoflurane and carrier gas for 6 h.Morris water maze experiments were conducted on 6 rats in each group 2 h,1 week and 4 weeks after treatments,respectively.Every cycle after the behavioral test,the hippocampi were taken out.RT-qPCR method was used to detectα7nAChR mRNA expression.Western blotting was used to detectα7nAChR proteins expression.Results Behavioral test:compared with Con group at 2 h after awakening,indicators of working memory and spatial probe test in Sev group and Sev+M group decreased significantly(P<0.05).Compared with Con group,the working memory of rats in Sev group and Sev+M group continued to decrease after awakening(P<0.05).There was no significant difference in behavioral test between groups at 4 w after awakening(P>0.05).RT-qPCR:compared with Con group at 2 h and 1 w after awakening,the expression of alpha 7nAChR mRNA in the other groups was down-regulated,while at 4 w it was up-regulated(P<0.05).Western blot:protein expression of alpha 7nAChR was down-regulated in the 2 h,1 w Sev group and the Sev+M group after awakening,and up-regulated in the 4 w group after awakening(P<0.05).Conclusion Inhalation of 3.2%sevoflurane for 6 h can cause 7nAChR metabolic disturbance in hippocampus of aging model rats and lead to a short-term(1 w)decline in learning and memory ability of the rats,but this effect is reversible.The PNU-282987 agonist can alleviate the temporary decrease of learning and memory caused by sevoflurane.