不同浓度七氟醚对幼鼠学习记忆及海马NR2BTyrl472磷酸化表达的影响

Effects of different concentrations of sevoflurane on learning and memory ability in infantile rats and on the Tyr1472 phosphorylation of hippocampal NR2B

目的评价不同浓度七氟醚麻醉对幼鼠学习记忆及海马NR2BTyrl472磷酸化表达的影响。方法实验用6SD幼鼠，日龄30～35d，体质量100～110g。行水迷宫训练4d后，随机分为对照（C组）、1％七氟醚（S1组）、2％七氟醚（S2组）和3％七氟醚（s3组）4组。其中，C组单纯吸氧3h，氧流量2．0L·min^-1；S1、S2、S3组在与C组相同吸氧条件下分别吸入1％、2％和3％浓度的七氟醚。实验分两部分完成：①以水迷宫法观察不同浓度七氟醚麻醉1、3、5、7d后对幼鼠学习记忆的影响（n=10）；②用Westernblot法测定不同浓度七氟醚麻醉后幼鼠海马磷酸化NR2BTyrl472的表达（n=6）。结果1．①不同组各时间点比较显示，七氟醚麻醉d1：S2、S3组与c组比较平台象限停留时间（S）和60S内跨过平台次数（次）明显减少（P〈0．05）。②S2及S3组d3、d5、d7较d1平台象限停留时间（S）和60S内跨过平台次数（次）明显增加（P〈0．05）。2．S2组、S3组与c组比较，海马组织NR2BTyrl472的磷酸化水平均明显增强（P〈0．05）；S2、S3组与S1组比较：海马组织NR2BTyrl472的磷酸化水平均明显增强（P〈0．05）。结论吸入低浓度（1％）七氟醚对幼鼠认知功能无影响；吸入高浓度（2％和3％）七氟醚可导致幼鼠认知功能降低，但这种作用是短期的、可逆的；磷酸化NR2BTyrl472的过度表达可能在七氟醚抑制幼年大鼠学习记忆中发挥～定作用。建议临床婴幼儿手术麻醉使用七氟醚尽量选用低浓度，以免造成对婴幼儿认知功能的障碍。

Aim To investigate the effects of different concentrations of sevoflurane on learning and memory in infantile rats and on hippocampal phosphorylated NR2B Tyr1472 （PNR2B Tyr1472） expression. Meth- ods Experimental male SD rats were used, aged from 30 to 35 d, weighing from 100 to 110 g. Experimental animals experienced 4 days of water maze training, and then were randomly divided into 4 groups： control group （Group C）, 1% sevoflurane （ Group S1 ）, 2% sevoflurane （ Group S2 ） and 3 % sevoflurane （ Group $3 ） group. Group C inhaled oxygen for 3 h, with oxy- gen flow rate meter of 23.0 L · min^ -1 Oxygen as the carrier gas, Group S1 , S2, and S3 inhaled 1% , 2% and 3% sevoflurane for 3 h, respectively. The experi- ment was divided into two parts： （1） Regained con- sciousness after 24h, 10 rats for each group were se- lected to assess the ability of learning and memory by using Morris water maze test on 1, 3, 5, and 7 days, respectively. （2） Six rats in each group were scarifiedafter regaining consciousness and the hippocampi re- moved for the determination of pNR2B Tyr1472 expres- sion by Western blot. Results 1. @ On the first day, the time spent in the target quardrant and the number of platform-site crossovers significantly reduced （P 〈 0. 05 ）. There was no significant difference be- tween Group S1 and C （P 〉 0.05）. On the 3 rd, 5 th, and 7 th day, when Group S1, S2, and S3 were com- pared to Group C, they showed no significant differ- ences in the time spent in the target quardrant and the number of platform-site crossovers （P 〉 0.05）. @ For Group S2 and S3, when the 3 rd, 5 th and 7 th day compared to the first day, the time spent in the target quardrant and the number of platform-site crossovers significantly increased （ P 〈 0.05 ）. For Group C and S1, There was no significant difference in the time spent in the target quardrant and the number of plat- form-site crossovers in respective time （ P 〉 0. 05 ）. 2. when Group S 2 and S 3 were compared to Group C,both groups had significantly higher pNR2B Tyr1472 expression in hippocampus （ P 〈 0.05 ）. Group S1 , compared to group C, had similar levels of pNR2B Tyr1472 expression in hippocampus （ P 〉 0. 05 ）. Group S2 and S3, compared to Group S l, both had significantly higher pNR2B Tyr1472 expression in hip- pocampus （P 〈 0.05）. Group S3, compared to Group S2, had a little higher but not significant pNR2B Tyr1472 expression in hippocampus （P 〉 0.05 ）. Conclusions Inhalation of 1% sevoflurane had no effect on cognitive function in infantile rats. Inhalationof 2% and 3% sevoflurane may lead to cognitive de- cline in infantile rats, but the effect was short-term and reversible. Overexpression of pNR2B Tyr1472 might play an important role in sevoflurane induced inhibition of learning and memory in infantile rats. Low concen- trations of sevoflurane to avoid cognitive dysfunction are clinically recommended for anesthesia in infants.