L-655,708对丙泊酚麻醉大鼠海马磷酸化Tau蛋白表达及认知功能的影响

Effects of L-655,708 on Tau phosphorylation in hippocampus and cognitive function in rats anesthetizedby propofol

目的研究L-655，708对丙泊酚麻醉大鼠海马磷酸化Tau蛋白表达及认知功能的影响。方法2月龄雄性Wistar大鼠30只，体重180～220g，随机分为六组（n=5）：生理盐水组（C组）、L-655，708＋生理盐水组（LC组）、丙泊酚麻醉1h组（P1组）、L-655，708＋丙泊酚麻醉1h组（LP1组）、丙泊酚麻醉24h组（P24组）和L-655，708＋丙泊酚麻醉24h组（LP24组）。于用药前及用药后1h（C组、LC组、P1组和LP1组）、24h（P24组和LP24组）用Morris水迷宫测试大鼠认知功能，随后处死大鼠，取脑组织，分别采用HE染色和尼氏体染色观察海马区神经细胞及尼氏体形态学变化、免疫组化法测定海马区磷酸化Tau蛋白（Tau-pSer^355）表达阳性细胞数及平均灰度值。结果与用药前比较，用药后P1组、LP1组、P24组潜伏期明显延长（P〈0．05）。与C组比较，用药后P1组、P24组潜伏期明显延长，海马区Tau-pSer^356表达阳性细胞数增加、平均灰度值明显升高（P〈0．05）。与LC组比较，用药后LP1组潜伏期明显延长，海马组织Tau-pSer^356表达阳性细胞数明显增加（P〈0．05）。与P1组比较，用药后LP1组、P24组潜伏期明显缩短，海马区Tau-pSera^356表达阳性细胞数明显减少、平均灰度值明显降低（P〈0．05）。与P24组比较，用药后LP24组潜伏期明显缩短，海马区Tau-pSer^356表达阳性细胞数减少、平均灰度值明显降低（P〈0．05）。六组原平台区域进入次数差异无统计学意义。C组、LC组海马区神经细胞形态结构完整，尼氏体深染并广泛分布于胞浆和树突；其余四组神经细胞出现核固缩、核碎裂及核溶解，尼氏体淡染。结论L-655，708可下调丙泊酚麻醉大鼠海马磷酸化Tau蛋白表达，减轻大鼠认知功能损害；丙泊酚麻醉后大鼠出现的认知功能障碍可能与海马磷酸化Tau蛋白高表达、神经细胞及尼氏体损伤有关。

Objective To investigate the effects of L-655,708 on the expression of phosphoryl- ated tau in hippoeampus and cognitive function in rats anesthetized by propofol. Methods Thirty male two-month-old Wistar rats, weight 180-220 g, were randomly divided into 6 groups： normal saline groups （group C）; group L-655,708＋normal saline （group LC）; 1 hour after propofol anesthesia group （group Pl）; group L-655,708 ＋ P1 （group LP1）; 24 hours after propofol anesthesia group （group P24） ; group L-655,708＋P24（group LP24）. Morris water maze tests were used to assess the cognitive function of rats before and 1 h （groups C, LC,P1,LP1） or 24 h （groups P24,LP24） after anesthesia. The rats were sacrificed at the end of Morris water maze tests and their brains were removed for detection of the phospho-Tau expression （by immuno-histochemistry） in hippocampus and the morphologie changes of hippocampal neurons and Nissl body （by HE staining and Nissl staining）. Results The latency prolonged in groups P1, LP1, and P24 after drug administration（P〈0. 05）. Compared with group C, the latency prolonged, the phospho-Tau expression was up-regulated, and the average grey value was increased in groups P1 and P24 （P〈0.05）. Compared with group LC, the latency prolonged and the phospho-Tau expression was up-regulated in group LP1 （P〈0. 05）. Compared with group Pl, the latency was shorter, the phosphc-Tau expression was down-regulated, and the average grey value was decreased in groups LP1 and P24 （P〈0. 05）. Compared with group P24, the latency was shorter and the phospho-Tau expression was down-regulated, and the average grey value was decreased in group LP24 （P〈0.05）. The frequency of passing the original platform had no significant difference among the six groups. In groups C and LC, the morphology and structure of neurons were integrated, and the nissl body was dark staining and widely distributed in the cytoplasm and dendrites, whereas in groups P1, LP1, P24, and LP24, the cell nuclear karyopyknosis, fragmentation and solution were observed, and the nissl body was light staining or no staining and decreased in the cytoplasm and dendrites. Conclusion L-655,708 down-regulates the expression of phospho-tau in hippocampus and improves the cognitive function in rats anesthetized with propofol. The high-expression of phospho-Tau and the damage of the neurons and Nissl body may be involved in the cognitive impairment after propofol anesthesia.