甲醛暴露对小鼠行为的影响及相关神经内分泌机制的研究

发布时间：2018-05-26 09:20

本文选题：甲醛 + 认知　；参考：《陕西师范大学》2016年博士论文

【摘要】：甲醛(Formaldehyde)是醛族分子结构最简单而且易挥发的有机化合物之一,在自然界中广泛存在,由于甲醛是一种活性较强的有机物而且比较廉价,所以广泛应用于各个领域并且在工业上有很重要的作用,主要应用于建筑材料、人造板、涂料等建筑材料中。目前,甲醛已经成为一种常见的室内空气污染物,在住宅和建筑中都能获得相对较高的浓度。这种甲醛污染主要是由于人造涂料和油漆的应用所引起的,而且甲醛很容易通过血-脑屏障,最终在人体内蓄积,并有可能影响大脑中的神经胶质细胞和神经细胞。研究表明,甲醛是有毒的,它的毒性主要表现在可引起过敏和致癌,而对于过敏人群来说,主要是建议远离有甲醛的地方,而且长期接触甲醛可引起胃肠道问题,头痛和记忆力减退等症状。动物研究表明,吸入甲醛暴露可引起活动性的降低和学习记忆能力的损伤,表明有明显的神经系统毒性。而这些研究主要是集中在环境管理和流行病学的研究,但是甲醛引起的潜在的神经毒性机制研究的较少。研究表明,吸入甲醛暴露或海马内注射甲醛导致动物在水迷宫中的空间学习和记忆的损伤,这种损伤是和脑内降低的超氧化物歧化酶(SOD)的活性,丙二醛(MDA)含量的减少及脑中DNA转录的稳态失调以及降低的脑内NR1,NR2B mRNA的表达有关。海马是参与空间学习记忆最主要的脑区,但是损伤海马的机制还不清楚。文献报道,急性甲醛暴露在5ppm会降低大鼠的运动能力,而且为期一周的甲醛吸入会增加雄性小鼠的抑郁样行为,然而研究表明,甲醛对小鼠的活动性的影响具有两性差异,那么长期的甲醛暴露是否会产生焦虑和抑郁样行为以及这些行为的影响是否存在两性差异,还不清楚,也未见相关报道。甲醛暴露会影响动物在水迷宫中的空间学习记忆和新物体识别能力,水迷宫实验主要是检验动物在水迷宫你中找到隐性平台的能力,新物体识别主要是检测动物对物体位置的记忆和区别不同形状物体的能力,而社会识别不同于水迷宫实验和心物体识别实验,它是检测动物识别和记忆同种其它个体的能力,但是甲醛暴露是否会损伤社会识别能力,还不清楚。神经递质多巴胺和谷氨酸N-甲基-D-天冬氨酸(NMDA)受体亚型在脑功能方面起着非常重要的作用。海马和杏仁核内含有大量的NMDA受体和多巴胺受体,这些核团(海马和杏仁核)在情绪和认知方面发挥着非常重要的作用。研究表明,甲醛暴露可以降低大鼠的活动性,增加前额叶皮质的多巴胺水平。表明甲醛暴露与多巴胺的变化有关。而且研究也表明,甲醛暴露降低了小鼠脑内NRlmRNA的表达水平。但是甲醛暴露对情绪和认知的影响是否与DA系统和NMDA相关,还没有这方面的研究。在本研究中我们探讨了吸入甲醛暴露对Morris水迷宫实验的影响以及相关的神经生物学机制。并且研究了甲醛暴露对焦虑、抑郁样行为和社会识别的影响以及与这些影响有关的多巴胺D1型受体和D2型受体以及NR1的基因表达的变化。母亲-婴儿的相互作用是导致行为长期变化的关键。产后应激或某些化学暴露能改变泌乳期雌性对幼仔的照顾行为,而且也会影响幼仔的发育。有研究报道,甲醛暴露可以引起雌性小鼠体内雌激素水平的变化,另有文献表明,甲醛也是一种化学应激物,是否吸入甲醛暴露能改变母本行为,也未见相关报道。甲醛吸入暴露是否能改变母本行为,并且对动物以后的脑发育和行为产生影响也未见相关报道。因此,我们还研究了吸入甲醛暴露对产后母本行为的影响及产后暴露甲醛对成年小鼠脑发育和行为的影响。(1)甲醛暴露对小鼠空间学习记忆的影响及对海马内糖皮质激素和血清中皮质酮的影响的研究表明,2ppm甲醛吸入组的小鼠在水迷宫中游到平台的潜伏期和花费在水迷宫中的贴壁时间显著延长。在记忆保留期,2ppm甲醛组的小鼠找到隐性平台的潜伏期和错误次数显著增加,这些行为实验研究结果都说明吸入甲醛损伤了小鼠在水迷宫中的空间学习记忆能力,并且没有显著的两性差异。免疫组织化学实验结果表明,2ppm甲醛组的小鼠海马中糖皮质激素受体的阳性神经元的表达在海马CA1区和CA3区都有很显著性的降低;Western blot实验结果显示,吸入2ppmn浓度甲醛的小鼠降低了海马内糖皮质激素受体的表达量;而且酶联免疫实验结果也表明,小鼠吸入2ppm浓度的甲醛显著性的提高了血清中的糖皮质激素的水平。这些实验结果都表明,高浓度(2ppm)的甲醛暴露损伤了小鼠对空间学习记忆,而且这种损伤可能是由于甲醛暴露引起皮质酮的改变而引起海马内糖皮质激素受体水平的改变,从而损伤了小鼠的空间学习记忆能力。(2)甲醛暴露对小鼠焦虑、抑郁行为和社会识别的影响及相关内分泌机制的研究中发现,吸入甲醛暴露在2ppm组的雌雄小鼠都降低了活动性,降低了两性在旷场中心场所呆的时间百分比,并且表现出显著的两性差异。在高架试验检测中,甲醛处理很明显降低了活动性,穿越开臂的次数和穿越开臂的时间,并且这种影响表现出明显的两性差异。在强迫游泳实验中发现,甲醛暴露很明显增加了两性在水中的不动时间,而且甲醛处理表现出很明显的两性差异。这些行为实验结果表明,甲醛暴露产生了很严重的焦虑和抑郁样行为。在社会识别实验中,甲醛暴露降低了两性(雌雄)小鼠对刺激鼠的探究时间;吸入2ppm甲醛组的小鼠在习惯化和去习惯化实验中,并不能识别熟悉鼠和陌生鼠,并且与对照组相比,2ppm甲醛组的小鼠很明显降低了对刺激鼠的探究时间,表明损伤了社会识别能力。用实时定量PCR分析显示,与对照组相比,2ppm甲醛暴露上调了海马D1RmRNA和D2RmRNA的表达,而在杏仁核,上调了 D1RmRNA,降低了 D2RmRNA的水平;2ppm甲醛处理组的小鼠下调了海马和杏仁核中谷氨酸N-甲基-D-天冬氨酸I型受体(NR1)mRNA的表达。然而,在0.4ppm甲醛暴露组没有出现这些影响。这些结果说明甲醛对行为和神经内分泌参数的的影响具有剂量依赖性。(3)我们研究了幼仔在出生后1-6天的母本行为的研究结果表明,产后吸入甲醛对泌乳期的雌性的母本行为没有显著的影响。只是甲醛暴露在0.4ppm组的小鼠在第五天时活动性显著增加。产后吸入甲醛对泌乳期的雌性的母本行为没有显著的影响。但是出生后甲醛暴露在0.4ppm组减少了在旷场中心场和高架开臂所呆的时间,表明出生后甲醛暴露增加了成年后的焦虑样行为,0.4ppm组雌雄小鼠和0.08ppm组雄性小鼠增加了在水迷宫中的不动时间,表明增加了抑郁样行为。实时定量分析表明,出生后甲醛暴露增加了海马D1RmRNA的表达,降低了 NRlmRNA在海马的表达。这些结果表明出生后甲醛暴露没有改变母本行为,但是增加了幼仔在成年后的焦虑和抑郁水平,改变海马内D1R和NRlmRNA的表达,说明甲醛暴露可能直接作用于幼仔而影响了幼仔的脑和行为的发育。通过这些研究结果,我们可以得出结论,吸入甲醛暴露对情绪和认知都产生显著影响,这些行为的改变和认知的损伤是和海马内的糖皮质激素水平、多巴胺系统和NMDA的改变有关。这些研究也表明,甲醛可以引起多方面的的神经毒性。产后暴露甲醛没有改变母本行为,却改变了后代成年后脑和行为的发育,表明甲醛可能是直接作用于小鼠幼仔从而影响成年行为和神经内分泌系统的发育。这些结论说明,不同时期甲醛暴露都可能会影响动物的行为和大脑的神经可塑性,同时也为甲醛的生态风险、健康评估以及甲醛的污染监测和控制标准的制订提供参考。
[Abstract]:Formaldehyde (Formaldehyde) is one of the simplest and volatile organic compounds of the aldehyde group. It exists widely in nature. As formaldehyde is a kind of strong organic substance and cheap, it is widely used in various fields and has very important role in industry. It is mainly used in building materials, wood-based panels, and coatings. At present, formaldehyde has become a common indoor air pollutant, which can obtain relatively high concentration in both houses and buildings. This formaldehyde pollution is mainly caused by the application of artificial coatings and paints, and formaldehyde is easily accumulated through blood - brain barrier and eventually accumulates in the human body, and may affect big Neuroglia and nerve cells in the brain. Studies have shown that formaldehyde is toxic and its toxicity is mainly caused by allergies and carcinogens, and for allergic populations, it is mainly recommended to stay away from formaldehyde, and long-term exposure to formaldehyde can cause gastrointestinal problems, headache and memory impairment. Animal studies have shown that Exposure to inhaled formaldehyde can cause a decrease in activity and impairment of learning and memory ability, indicating a significant neurotoxicity. These studies are mainly focused on environmental management and epidemiological studies, but the underlying neurotoxicity mechanism caused by formaldehyde is less. Aldehydes cause damage to space learning and memory in the water maze of animals, such as the activity of superoxide dismutase (SOD), the decrease of the content of malondialdehyde (MDA) and the homeostasis of DNA transcription in the brain, and the reduced expression of NR1 in the brain, and the expression of NR2B mRNA. The hippocampus is the most important brain area involved in spatial learning and memory. But the mechanism for damaging the hippocampus is not clear. It is reported that exposure to acute formaldehyde in 5ppm can reduce the exercise ability of rats, and a week of formaldehyde inhalation will increase the depressive behavior of male mice. However, the study shows that formaldehyde has a two sex difference in the effect of the activity of mice, then whether long-term formaldehyde exposure will be produced. It is not clear that there is a gender difference between the behavior of anxiety and depression and the effects of these behaviors. It is not clear, and no related reports. Formaldehyde exposure affects the spatial learning and memory of animals and the ability to recognize new objects in the water maze. The water maze experiment is mainly to test the ability of the animals to find the hidden platform in the water maze. It is different from the water maze test and the heart object recognition experiment to detect the memory of the animal's location and the ability to distinguish the different shapes of objects. It is the ability to detect and memory the other individuals of the same species, but it is not clear whether the formaldehyde exposure can damage the social recognition ability. It is not clear that neurotransmitter dopamine and glutamine can be found. The acid N- methyl -D- aspartic acid (NMDA) receptor subtype plays a very important role in brain function. The hippocampus and amygdala contain a large number of NMDA receptors and dopamine receptors. These nuclei (hippocampus and amygdala) play a very important role in emotional and cognitive aspects. The level of dopamine in the prefrontal cortex was increased. It showed that exposure to formaldehyde was associated with changes in dopamine. Moreover, the study also showed that exposure to formaldehyde decreased the level of NRlmRNA expression in the brain of mice. However, the effects of formaldehyde exposure on emotion and cognition were related to the DA system and NMDA, and there was no study in this field. The effects of exposure to formaldehyde exposure on the Morris water maze experiment and related neurobiological mechanisms. And the effects of formaldehyde exposure on anxiety, depressive behavior and social recognition, and the changes in the D1 receptor and D2 receptor as well as the gene expression of NR1 related to these effects. The key to long-term changes in behavior. Postpartum stress or some chemical exposure can change the behavior of the female in lactation, and also affect the development of the young. Exposure can change maternal behavior and no related reports. Whether formaldehyde inhalation exposure can change maternal behavior and effect on brain development and behavior in animals has not been reported. Therefore, we also studied the effects of inhaled formaldehyde exposure on maternal behavior and postpartum exposure to brain development and behavior in adult mice. (1) the effects of formaldehyde exposure on the spatial learning and memory of mice and the effects on corticosteroids and serum corticosterone in the hippocampus showed that the incubation period of the 2ppm formaldehyde inhalation group in the water maze and the time spent in the water maze were significantly longer. In the memory retention period, the mice in the 2ppm formaldehyde group were in the mice. The incubation period and the number of errors found in the recessive platform increased significantly. The results of these behavioral experiments showed that inhaled formaldehyde had damaged the spatial learning and memory ability of mice in the water maze, and there was no significant gender difference. The results of immunohistochemistry showed that the glucocorticoid receptor in the hippocampus of the 2ppm formaldehyde group was positive. The expression of neurons in the hippocampal CA1 region and CA3 region decreased significantly; the Western blot test showed that the mice inhaled 2ppmn with formaldehyde decreased the expression of glucocorticoid receptor in the hippocampus, and the enzyme linked immunosorbent assay also showed that the concentration of formaldehyde in the mice inhaled 2ppm increased the sugar cortex in the serum. The level of hormone. These results show that high concentration (2ppm) exposure to formaldehyde can damage the learning and memory of mice, and this damage may be caused by changes in corticosterone induced by formaldehyde exposure, causing changes in the level of glucocorticoid receptor in the hippocampus, thereby damaging the learning and memory ability of mice. (2) exposure to formaldehyde. In the study of the influence of mouse anxiety, depression behavior and social recognition and related endocrine mechanisms, it was found that the female and male mice exposed to formaldehyde in the 2ppm group reduced the activity, reduced the percentage of the sex in the center of the open field, and showed a significant difference in two. In the elevated test, the formaldehyde treatment was very clear. The activity, the number of times of crossing the arm and the time of crossing the arm, and the effect showed obvious gender differences. In the forced swimming test, it was found that formaldehyde exposure significantly increased the time of the amphoteric in the water, and the formaldehyde treatment showed a distinct gender difference. In the social identification experiment, the exposure to formaldehyde decreased the study time of the sexes (male and female) in the mice, and the mice inhaled in the 2ppm formaldehyde group did not recognize both the familiar and the unfamiliar mice in the customary and deformable experiments, and compared with the control group, the mice of the 2ppm formaldehyde group were very good. Compared with the control group, 2ppm formaldehyde exposure up-regulated the expression of D1RmRNA and D2RmRNA in the hippocampus compared with the control group, while in the amygdala, D1RmRNA was up and D2RmRNA was lowered in the amygdala, and the mice of the 2ppm formaldehyde treatment group lowered the hippocampus and amygdala in the 2ppm formaldehyde treatment group, compared with the control group. The expression of I type I receptor (NR1) mRNA of the glutamic acid N- methyl -D- aspartic acid in the nucleus, however, did not appear in the 0.4ppm formaldehyde exposure group. These results suggest that the effects of formaldehyde on behavioral and neuroendocrine parameters are dose-dependent. (3) we studied the results of maternal behavior at 1-6 days after birth. Formaldehyde inhalation did not significantly affect female parent behavior during the lactation period. Only the mice exposed to formaldehyde in the 0.4ppm group increased significantly at fifth days. The time of opening the arm showed that the exposure to formaldehyde increased the anxiety like behavior after birth. In group 0.4ppm, male and male mice and 0.08ppm male mice increased the time of immobility in the water maze, indicating an increase in depressive behavior. Real time quantitative analysis showed that after birth, formaldehyde exposure increased the expression of D1RmRNA in the hippocampus and reduced the NRlmRNA. Expression in the hippocampus. These results suggest that postnatal exposure to formaldehyde does not change maternal behavior, but increases the level of anxiety and depression in young adults, changes the expression of D1R and NRlmRNA in the hippocampus, indicating that exposure to formaldehyde may directly affect young children and affect the development of the brain and behavior of young children. It can be concluded that exposure to formaldehyde exposure has a significant effect on emotion and cognition. Changes in these behaviors and cognitive impairment are associated with levels of glucocorticoid in the hippocampus, the dopamine system and the changes in NMDA. These studies also suggest that formaldehyde can cause multiple neurotoxicity. Postpartum exposure to formaldehyde does not change maternal parents. Behavior, which changes the development of the brain and behavior of the offspring, indicates that formaldehyde may affect the adult behavior and the development of the neuroendocrine system. These conclusions suggest that exposure to formaldehyde in different periods may affect the behavior of the animals and the plasticity of the brain, and also the ecological risk of formaldehyde. It provides reference for health assessment and formaldehyde pollution monitoring and control standards.
【学位授予单位】：陕西师范大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：R114

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