【作者】 刘芳；

【导师】 冀秀玲；

【作者基本信息】 东华大学 ， 环境科学， 2012， 硕士

【摘要】 六溴环十二烷(Hexabromocyclododecane, HBCD)作为一种添加型阻燃剂,目前已经成为环境中无处不在的污染物,并且在人体血液甚至儿童体内都可以被检测到。现有的一些研究已证实HBCD具有内分泌干扰作用及神经毒性作用,它可以损害大脑中少突神经胶质细胞的发育,损伤大脑的学习和记忆功能,还会引发异常的自发性行为。尤其是处于脑发育期的儿童更是成为了HBCD暴露和毒性作用的主要人群。为了研究HBCD脑发育期暴露对甲状腺激素受体信号传导的影响及神经毒性效应,本论文根据发育期儿童为HBCD暴露的高风险人群的特点,实验选取新生3天的SD大鼠(PND3)；依据环境真实暴露水平设计HBCD的暴露剂量,设置对照组和10、50、100、300μg/kg的HBCD染毒组等5个组别；根据大鼠脑发育的特点,将暴露时间划分为21天、42天、90天等3个不同的脑发育期时间节点；通过对动物神经行为、甲状腺激素水平、甲状腺激素核受体(TR)信号传导过程的相关基因表达、神经递质及相关酶活性等几个方面指标的测试,尝试从动物个体、生化指标及基因水平揭示HBCD甲状腺激素干扰的机制与神经毒性效应的内在关联,实验结果显示：1、利用Morris水迷宫和旷场实验分别对21d和90d两个暴露时间节点下大鼠的神经行为进行了检测。Morris实验结果显示,21d的短期暴露后,对于逃避潜伏期、穿越平台次数两个指标,10μg/kg的低剂量染毒组和300μg/kg的高剂量染毒组能够促进大鼠学习记忆能力,并且影响显著(P<0.05)。而平台所在象限活动以及调换平台后的逃避潜伏期两个指标显示300μg/kg的高剂量染毒组能够促进大鼠记忆和再学习能力,并且呈现显著性(P<0.05)。经过90d的暴露后,实验结果与21d较为一致,不同的是50μg/kg染毒组却表现出损害大鼠记忆和再学习的能力并且呈现显著性(P<0.05)。旷场实验结果显示,21d的短期暴露后,活动总路程的指标显示出50～300μg/kg染毒组大鼠运动活性显著增强(P<0.05)；中央活动路程指标显示出10μg/kg染毒组大鼠有显著性的心理焦虑(P<0.05),但是,这种影响随着大鼠的生长发育逐渐减弱,暴露90d后,已经无统计学意义(P>0.05)。2、利用125I-甲状腺激素与抗血清放射免疫分析法测定血清中甲状腺激素相关指标的变化,包括：TT3、TT4、FT3、FT3、TSH等。实验结果显示,经过21d短期暴露,各染毒组大鼠血清中TT3、TT4、FT3、FT4的浓度均显著升高(P<0.05), TSH浓度降低但无统计学意义(P>0.05)。经过42d暴露,10μg/kg的染毒组大鼠血清中TT3、TT4、FT3、FT4的浓度均升高,并且FT3、FT4的浓度显著升高(P<0.05)；染毒组血清中TSH的浓度下降,10、50、300μg/kg染毒组呈现显著降低(P<0.05)。经过90d暴露,染毒组大鼠出现了血清中TT3、TT4、FT3、FT4的浓度均上升的趋势,其中各染毒组的TT4浓度显著升高(P<0.05),50μg/kg染毒组的FT4浓度显著升高(P<0.05),50和100μg/kg染毒组的TT3、FT3浓度显著升高(P<0.05); 10μg/kg染毒组的TSH浓度显著降低(P<0.05),其他各染毒组中的TSH浓度均显著升高(P<0.05)。3、利用real-time PCR法定量测定大鼠海马TR传导过程相关基因表达水平的变化,包括3种不同构型的TR基因TRα1、TRα2、TRβ1;参与甲状腺激素与TR结合的复合物与甲状腺激素应答元件(TRE)的转录基因BTEB; TR信号调控的下游神经功能基因RC3、NGF;以及神经递质代谢酶相关的功能基因MAO-A、MAO-B、ChAT等。TR基因检测结果显示,各暴露时间染毒组大鼠海马TRα1 mRNA的表达水平都有上升趋势,其中暴露42d,50μg/kg染毒组和暴露90d,300μg/kg染毒组TRα1表达水平显著升高(P<0.05)；暴露21d和90d,各染毒组大鼠海马TRα2 mRNA的表达水平上升,暴露42d,各染毒组表达水平下降,10、50和300ug/kg染毒组呈现显著降低(P<0.05)；暴露21d, 10ug/kg染毒组大鼠海马TRβ1 mRNA表达水平显著升高(P<0.05),暴露42d和90d,各染毒组大鼠海马TRβ1 mRNA表达水平呈现上升趋势,其中暴露42d,100～300ug/kg染毒组和暴露90d,50～300ug/kg染毒组呈现显著升高(P<0.05)。BTEB基因的检测结果显示,暴露21d,各染毒组大鼠海马BTEB mRNA的表达水平均显著降低(P<0.05)；暴露42d染毒组BTEB mRNA的表达有降低趋势,暴露90d染毒组BTEB mRNA的表达有升高的趋势,两个时间暴露均未有统计学意义(P>0.05)。NGF、RC3基因检测结果显示,暴露42d染毒组大鼠海马NGF mRNA表达显著升高(P<0.05),暴露21d和90d的影响没有统计学意义；暴露21d和90d染毒组大鼠海马RC3 mRNA表达有下降趋势,暴露42d有升高趋势,其中21d、10ug/kg染毒组表达显著降低(P<0.05)。MAO-A、MAO-B、ChAT等基因的检测结果显示,暴露21d染毒组MAO-A mRNA表达有下降趋势,暴露90d,染毒组MAO-A mRNA表达有升高趋势,但均无统计学意义(P>0.05)；染毒组MAO-B mRNA表达在暴露21d和90d有升高趋势,暴露42d有降低趋势,并有100ug/kg染毒组表达显著降低(P<0.05)。暴露21d, 100ug/kg染毒组ChAT mRNA表达显著降低(P<0.05)；暴露42d,染毒组ChAT mRNA表达升高,并且50～100μg/kg染毒组的表达显著升高(P<0.05)；暴露90d,10染毒组表达显著升高(P<0.05)。4、利用分光光度法、荧光定量法和ELISA试剂盒法测定大鼠脑中单胺、胆碱类神经递质含量及其相关代谢酶活性,单胺类包括DA、NE、5-HT (?)神经递质及MAO酶；胆碱类包括Ach神经递质及AchE、ChAT等代谢酶。实验结果显示,在单胺能系统中,暴露21d,100～300ug/kg染毒组DA含量显著降低(P<0.05),50～100ug/kg染毒组NE含量显著降低(P<0.05),300ug/kg染毒组5-HT含量显著降低(P<0.05),50～300ug/kg染毒组MAO活性升高；暴露42d,染毒组DA含量升高,其中10和100ug/kg染毒组DA含量显著升高(P<0.05),染毒组NE含量显变化不明显,50～100 ug/k染毒组5-HT含量显著升高(P<0.05), MAO活性变化无统计学意义(P>0.05)；暴露90d,300ug/kg染毒组DA含量显著降低(P<0.05), 100ug/kg染毒组NE含量显著降低(P<0.05),300ug/kg染毒组5-HT含量显著升高(P<0.05), MAO含量变化无统计学意义(P>0.05)。在胆碱能系统中,经HBCD不同暴露时间,染毒组Ach含量水平均有下降趋势,其中21d、100～300μg/kg染毒组Ach的含量显著降低(P<0.05)；暴露21d和42d,染毒组AchE活性有升高趋势,并且300μg/kg染毒组AchE活性显著升高(P<0.05),暴露90d, AchE活性变化无统计学意义(P>0.05)；暴露21d,染毒组ChAT活性变化无统计学意义(P>0.05),暴露42d, 10ug/kg染毒组ChAT活性显著升高(P<0.05),暴露90d,100～300μg/kg染毒组ChAT活性显著降低(P<0.05)。根据以上实验结果可以得出结论：1、动物神经行为实验表明21d和90d的HBCD暴露可以引起大鼠的神经兴奋,对大鼠的学习记忆以及再学习能力有一定促进作用,极低剂量(10μg/kg)和高剂量(300μg/kg)更能促进这种作用的发挥。21 d HBCD的短期暴露还可以引起大鼠的活动性能增加,极低剂量(10μg/kg)的暴露还可能引起大鼠的焦虑和紧张心理,但是这些作用随着大鼠的生长发育逐渐减弱。21d的HBCD暴露对大鼠神经行为影响显著。2、甲状腺激素水平的变化表明HBCD暴露可以促进大鼠血清中甲状腺激素水平。虽然甲状腺激素在不同暴露时间、不同暴露剂量有差异,但是总的趋势较为一致,TT3、TT4、FT3、FT4的含量升高,TSH的含量降低。其中,FT3、FT4的变化更为敏感,表明HBCD更容易通过影响FT3、FT4的水平对机体生理过程的产生影响。实验结果同样显示出暴露21d的甲状腺激素变化较42d、90d更为显著。甲状腺激素水平的上升表明HBCD暴露引起了甲状腺功能亢进,可以解释神经行为结果中HBCD暴露后大鼠神经兴奋、活动性能增加等现象。3、TR信号传导过程相关基因表达水平的变化表明甲状腺激素干扰效应及TR信号传导过程可能是HBCD的神经毒性效应的内在作用机制之一。3种不同构型的TR基因表达主要是受甲状腺激素T3控制的,HBCD暴露能够引起TRα1和mRNA的表达上升,42d的TRα2表达水平下降,说明HBCD可以通过改变TR基因表达干扰甲状腺激素。21d的HBCD暴露可引起BTEB基因表达显著下降,BTEB是参与甲状腺激素与TR结合的复合物与TRE的转录基因,受甲状腺激素的调控,BTEB mRNA表达的变化也是甲状腺激素受到HBCD干扰的结果。TR信号调控的下游神经功能基因NGF在42d表达上升,作为神经修复的重要因子,NGF表达上升可以提示神经已经受到损害。RC3在变更Ca2+/钙调蛋白信号途径、突触可塑性的区域特异性损害和认知功能衰减中起作用,42d RC3 mRNA表达降低,表明HBCD对脑具有神经毒性效应。神经递质代谢酶相关的功能基因MAO-A受HBCD影响变化较小,而MAO-B的变化较为显著,表明HBCD更能够影响MAO-B的表达。而ChAT mRNA的表达在21d暴露中表达下降而42d表达有升高趋势。MAO和ChAT基因都与大脑认知、学习记忆和神经功能有关。HBCD对于甲状腺激素及TR信号传导过程的干扰效应,可以产生神经毒性效应,可能具有脑损害甚至可能导致中枢神经系统发育严重受损,产生学习记忆能力损伤、认知障碍,引发一些与神经相关的疾病等。21和42d的HBCD暴露对于基因表达的影响更加突出。4、神经递质含量与酶活性等生化指标的变化表明HBCD暴露不仅在分子水平改变了神经递质相关酶的表达,并在生化水平上也表现出神经毒性效应。单胺能系统中,暴露21d, HBCD主要通过促进MAO活性抑制DA、NE、5-HT的含量对单胺能体系产生影响；而42d和90d, HBCD对MAO活性的影响较小,直接作用于神经递质。单胺类神经递质是中枢神经内重要的信息传递物质,参与镇痛、躯体运动、精神情绪活动、睡眠、觉醒、应激等多种生理过程,特别是对中枢神经系统的兴奋或抑制起着协调作用。DA、NE、5-HT的含量变化可以解释大鼠神经行为中学习记忆能力提高、活动性能增加、焦虑心理产生等现象。胆碱能系统中,HBCD主要通过降低ChAT活性并且促进AchE活性控制Ach的含量,造成乙酰胆碱系统功能不足。Ach含量降低会引起学习记忆的障碍,同时也是阿尔茨海默病(AD)的重要成因。ChAT催化合成Ach控制胆碱能神经元突触间的信息传递,调节大脑功能,影响机体学习和记忆能力,ChAT活性降低能够直接影响Ach的合成和胆碱能系统的功能。AchE在脑发育的关键时期作为神经营养因子,也是脑内与学习记忆相关的重要酶之一,AchE活性增加会导致脑内学习记忆活动障碍。更多还原

【Abstract】 Hexabromocyclododecane as one kind of add flame retardant agent is the world’s third largest brominated flame retardants in addition to bromine biphenyl ether (PBDE), tetrabromobis phenol A (TBBPA). It is widely used in polystyrene foam, interior decoration, textiles and electronics. As the use of PBDE in Europe and North America and other countries was banned, HBCD as substitute of PBDE is more extensively used. Currently, HBCD has become the ubiquity of pollutants in environment and have been detected in the environment and/or human body fluids, including those of children. It has been suggested that HBCD could have endocrine disruptive and neurotoxic effects. Impaired oligodendroglial development in the brain, impairment in learning and memory, and aberrant spontaneous behavior have also been reported. There are very few studies focused specifically on the effects of HBCD, as many of their effects are similar to PBDEs, which has a stronger presence effect in the environment and on human health (Ibhazehiebo et al.,2011).In order to study effects on thyroid receptor signal transduction and neurotoxicity after developmental exposure to HBCD, according to the characteristics of the high risk population of the development children exposure to HBCD, the new born 3 days SD rats (PND3) were selected. On the real content of HBCD in environment, exposure doses were divided into the control group and 10,50,100,300μg/kg groups. According to the characteristics of the rats development, exposed time was as for 21 days,42 days and 90 days three different brain development time node. By testing the indexes of animal behavior, thyroid hormone levels nerve, thyroid hormones nuclear receptor (TR) signal transmission process related gene expression, neurotransmitters and related enzyme activity and so on, try to reveal relation of the internal mechanism between thyroid hormone disturbance and neurotoxic effects from animal individual, biochemical and genetic levels.The results showed that: 1^ By the methods of Morris’s Water maze and open field experiment, Neurobehavioral in rats are tested separately in 21 days and 90 days. The Results suggest, when the exposure time are 21 days, the 10μg/kg low-dose exposure group and the 30μg/kg high-dose exposure group used in rats can promote the capacity of study and memory, these capacity are shown in the index of escaping an incubation period and crossing a platform, and the influences are remarkable (P<0.05). And the two indexes that rats live in quadrant platform and escape the incubation period after changing another platform also show an apparent reaction. In contrast, when the exposure time become 90 days, results are consistent with the former test, the exposure group can impaired the capacity of learning and memory with 50μg/kg. According to the open field test in 21 days exposure time, the results are shown below. In the range of 50～300μg/kg exposure groups, the motor activity increased significantly (P<0.05) by total distance; and in the central distance area, exposure groups of rats appear the most significant psychological anxiety (P<0.05) with 10μg/kg. However, these effects are less clear with the growth of rats. So after the exposure time pass 90 days, it is useless in statistics.2、Using radioimmunoassay with 1251-anti-serum thyroid hormones to test related parameters on Serum thyroid hormone, indexes include:TT3、TT4、FT3、FT3、TSH and so on. the experiment results indicate the concentrations of TT3、TT4、FT3 and FT4 on a rise trend, and the exposed group of rats live in 21 days. Though the concentration of TSH declines, it is not important. In the condition of 42 exposed days, when the dosage is 10μg/kg, all the parameters’concentrations rise in the body of rats-group and the index of FT3 and FT4 increase apparently. Besides, in other exposed groups, the concentrations decline, thus, the results are not statistically significant (P> 0.05).in the condition of 90 exposed days, the concentrations of TT3、TT4、FT3 and FT4 rise in the body of all rats-group, and the index of TT4 increase apparently. What’s more, when the dosage is 50μg/kg, the FT4’s index is much higher, and the indexes of TT3 and FT3 both are improving in the condition of 50μg/kg and 100μg/kg exposed group. In addition, the 10μg/kg dose exposed group’s TSH concentration drops. And in other groups this parameter Show the opposite trend.3、Using the measure of real-time PCR, the transfer process of rats’ hippocampus TR are in a quantitative determination, the level of gene expressions are determined the expermeriments. There are three genes in configuration, the TR genes inclued TRα1、TRα2 and TRβ1; The complexes of Thyroid hormone in combination with TR and Xist genes of BTEB in Thyroid hormone response element (TRE); Neurological genes downstream controlled by TR single named RC3 and NGF; and the genes related to neurotransmitter-metabolizing enzymes function called MAOA、MAOB、ChAT and etc. The TR genes test results are shown as follown. In each exposure time,the expression levels of hippocampal TRα1 and mRNA are on a increasing trend (P<0.05). In these groups, the exposure group of 42 days with 50μg/kg and the exposure group of 90 days with 300μg/kg go up in the expression levels of TRα1 gene. And when the exposure time are 21 days and 90 days, the hippocampal TRα2 and mRNA levels emergence in all experiment groups. However, when the exposure time change to 42 days, the results are opposite, and this tendency Shows significantly in the groups of 10ug/kg,50ug/kg and 300ug/kg dosage (P<0.05); the expression level of hippocampal TRβ1 and mRNA rises in the exposure group of 21 days with lOug/kg (P<0.05) in according with 42 days and 90 days, in which the rising tendency are higher in 42 days at the range of 1100～300ug/kg groups and in 90 days the range is50～300ug/kg groups (P<0.05)The following are the BTEB gene’s level test results. the expression levels of hippocampal BTEB mRNA in 90 exposure days are on a increasing trend (P<0.05),while the reduction in 21 days exposure group show much more significant than in 42 days exposure group,which is pointless; The NGF and RC3 genes test results indicate the expression levels of hippocampal NGF mRNA improved excepting that the 21 days and 90 days experiments are useless. And when the exposure time are 21 days and 90 days, the hippocampal T RC3 mRNA levels are in a dropping trend in all experiment groups, but in 42 days exposure group it is in a improving way, In these groups, the exposure group of 21 days with 10μg/kg reducesd obviously.The MAO-A, MAO-B, ChAT genes test results are shown that 21 days exposure group of the MAO-A mRNA genes express a downward trend, when exposed to 90 days, though the exposure group tended to increase, it is adjective. And when the exposure time are 21 days and 90 days, the hippocampal MAO-B mRNA levels are in a rising trend in all experiment groups, but in 42 days exposure group it is in a reducing trend, and in which the exposure group with 100μg/kg reducesd more quickly (P<0.05).in these groups, when the exposure time is 21 days, the ChAT mRNA genes express a upward trend in 100ug/kg (P<0.05); when the exposure time is 42 days, the ChAT mRNA genes express a rising trend, in addition, the groups with a range of 50-100ug/kg increase higher (P<0.05);while the exposure time turns to 90 days, thes genes express a upward trend in 10ug/kg (P<0.05)4、Spectrophotometric method, Fluorescent quantitative method and Kit method had been used to gauge the values of monoamines and cholinergic neurotransmitters in rats’brain and the related metabolic activity. The kinds of monoamines are DA, NE,5-HT neurotransmitter and MAO enzymes; while Ach and AchE, ChAT and other metabolic enzymes belong to cholinergic neurotransmitters. The analysis are discussed as below, In the monoaminergic system, the DA level decreased sharply in the exposure groups at the range of 100～300μg/kg, the range between 50μg/kg and 300μg/kg where the NE level decreased sharply in the body of the rats groups, and the 5-HT level shows the same tendency in the range of 300μg/kg, but the content of MAO’s activity is enhanced in 50～300ug/kg. In contrast, when the time prolong to 42 days, the groups with 10μg/kg and 100μg/kg keep the similar law in the level of DA (P<0.05),but the level of NE change little in such rats. And in the range of 50～100μ/kg, the 5-HT level shows a different trend. Besides, MAO activity is on the rise, but this change is not statistically significant (P> 0.05). As the exposure time reaches to 90 days, the level of DA declined fast in the groups with 300μg/kg (P<0.05), the groups with 100μg/kg keep the similar law in the level of NE (P<0.05). On the contrary, the 5-HT levels increase quickly in 300μg/kg. MAO activity rise still but useless.In the cholinergic system, after a series of exposure times, the values of Ach in these experiments seem a downward trend, in which the exposure group of 21 days with 10～300μg/kg, the rats’Ach level reducesd apparently(P<0.05); And the group with 21 days and 42 days exposed are on a rise in the activity of AchE. What’s more, this level increases much in the groups with 300μg/kg, but it is not helpful when the time comes to 90 days in AchE activity testing and so it is in ChAT activity testing as it comes to 20 days. However, in these groups, when the exposure time is 42 days, the ChAT activity improves notablly with 10ug/kg, and it reduces significantly in the range of 100～300μg/kg (P<0.05)Based on the above results conclusions can be drawn as following:1、In the experiment on studying animals’neurobehavioral, the method of HBCD exposure in rats can cause nervous excitement in 21 days and 42 days. And it plays a positive role in promoting rat’s learning and memory ability. In addition, with a low dose of 10μg/kg and a high dose of 300μg/kg such influences appear more effective. Moreover, the HBCD exposure way can lead to improving the performance of activities in a short-term exposure of 21 days. Rats may also feel anxiety with the dose of 10μg/kg, but all these reactions would be weakened gradually with the growth of rats. Therefore,21 days of HBCD exposure on neurobehavioral effects in rats are significant.2、In the experiment of thyroid hormone levels, though the exposure time and doses are different, the changing trends are in consistence, that is the contents of TT3、TT4、FT3 and FT4 are on a rise and the TSH level is decline. A conclusion is that the effect of HBCD can promote the serum thyroid hormone levels. Among these factors the changes of FT3 and FT4 is adjective. So it is more easily for HBCD to affect FT3 and FT4 level of impacting the body’s physiological processes. The results also showed the reaction is much more significant in 21-days exposure groups than that in 42-days and 90-days groups. The increasing levels of thyroid hormone mean that the HBCD method can bring out hyperthyroidism. And this conclusion can be used to explain the neurobehavioral behaviors mentioned above.3、In the test of gauging the level of gene expressions, the thyroid hormone disrupting effects and TR signaling processes may be one of the mechanisms from the neurotoxic effects of HBCD. Three different configurations of the TR gene expression is mainly controlled by the thyroid hormone T3, the way in HBCD exposure groups cause levels of TRα1 and TRβ1 mRNA express a rise trend and cause level of TR a 2 express a oppsite trend. The results mentioned above show that using the method of HBCD to change the expression of TR gene can interfere with thyroid hormone.BTEB gene is complexes involved in thyroid hormone and TR binding as well as Xist with TRE, controlled by thyroid hormone. The change of BTEB mRNA expression is also affected by the results of HBCD way interfering with thyroid hormones. In 21 days exposure time, the level of BTEB gene decreases while in 42says and 42 days the results are out of usage. As an important factor in nerve repair, the phenomenon of NGF expression can point the extent of damage of nerve. In 42 days exposure group this NGF gene display a sharp decline. RC3 plays a role on changing the Ca2+/calmodulin signaling, synaptic plasticity and cognitive function in region-specific attenuation of damage. In 42 days exposure group, the expression of 42d RC3 mRNA level decreased indicates that has neurotoxic effects on the brain.Related to the neurotransmitter-metabolizing enzymes, the functional genes of MAO-A affect less than MAO-B in the influence of HBCD, and it indicates that HBCD affects the expression of MAO-B more. However, the expression levels of ChAT mRNA decrease in 21 days but increase in 42 days. To conclude, the gene of MAO and ChAT are associated with brain cognition, learning and memory ability and neurological function. The interference of HBCD for thyroid hormone and TR signaling processes can produce neurotoxic effects, it is possible to damage brain, result in learning and memory impairments, cause cognitive impairment and nerve-related-nerve diseases. Besides, this may even lead to serious damages to the central nervous system development. The results found that the HBCD exposure in 21 days and 42 days for gene expression is more prominent.4、The content of neurotransmitters and the activity of enzyme are tested too. Biochemical markers show that the method of HBCD exposure can not only change the performance of neurotransmitter enzymes at the molecular level, but show the neurotoxic effects at the biochemical levels. In monoaminergic systems, when the exposure time is 21 days, HBCD play a role through inhibiting MAO gene’s activity and promoting the content of DA, NE and 5-HT. and when the exposure time is 42 days and 90 days, HBCD exposure has little effect on neurotransmitter through MAO activity. Monoamine neurotransmitter is a kind of information-passing material, which is important in the central nervous system. It involve in pain, physical exercise, emotional activity, sleep, arousal, stress and other physiological processes, it also play a coordinating role in exciting or inhibiting the central nervous system. DA,NE,5-HT levels in rats can reveal neurobehavioral such as learning and memory capacity, activity performance, anxiety psychology and so on. In cholinergic systems, HBCD, reducing ChAT activity and promoting the content of AchE activity in the control of Ach mainly, impact the acetylcholine system a lack of functionality. Expect for Alzheimer’s disease (AD), Ach cause disorders of learning and memory capacity as well. When the activity of ChAT decrease, it may affect the synthesis of Ach and the function of cholinergic system, so by synthesizing Ach, ChAT can control the transmission of information between synapses, regulate brain function and affect rat’s learning and memory ability. Moreover, as a neurotrophic factor and a kind of related enzyme, AchE plays a vital role in the critical period of brain development, and if the level increased, it will bring about the brain barrier in learning and remembering.更多还原