大脑结构适应环境变化

海马体能适应环境压力在恶劣条件下储存神经干细胞，在有利条件下产生更多神经元对神经干细胞如何产生神经元的了解可能有助于治疗神经退行性疾病如阿尔茨海默病和帕金森病

科学家们多年前就已经知道，哺乳动物大脑的海马体在整个成年期都会发生神经发生。现在哥伦比亚大学的研究人员发现，在压力条件下，成年海马体中的神经干细胞不仅能产生神经元，还能产生新的干细胞。大脑储存了神经干细胞，当条件有利时，这些干细胞可能会产生神经元。这种对环境条件的反应代表了大脑可塑性的一种新形式。这项研究结果于2011年6月9日发表在《神经元》杂志的网站上。海马体与记忆、学习和情感有关。哥伦比亚大学医学中心临床精神病学助理教授、纽约州立精神病学研究所/哥伦比亚精神病学综合神经科学部门的研究科学家Alex Dranovsky博士领导的研究小组比较了隔离小鼠和丰富环境小鼠的神经干细胞和神经元的生成。然后，他们使用谱系研究(一种追踪干细胞从形成到最终分化成特定细胞类型的技术)来观察产生神经元的神经干细胞的比例。贫穷和富裕的环境产生了相反的影响。社会隔离小鼠的大脑积累了神经干细胞，但没有神经元。 The brains of mice housed in enriched environments produced far more neurons, but not more stem cells. The average mouse dentate gyrus, the area of the hippocampus where neurogenesis takes place, has about 500,000 neurons; the enriched environment caused an increase of about 70,000 neurons. ”We already knew that enriching environments are neurogenic, but ours is the first report that neural stem cells, currently thought of as ‘quiescent,’ can accumulate in the live animal,” said Dr. Dranovsky. “Since this was revealed simply by changing the animal’s living conditions, we think that it is an adaptation to stressful environments. When conditions turn more favorable, the stockpiled stem cells have the opportunity to produce more neurons—a form of ‘neurons on demand.’” The researchers also looked at neuronal survival. They found that social isolation did not cause it to decrease. Scientists already knew that environmental enrichment increased neuronal survival―further increasing the neuron population. To a lesser extent, location within the hippocampus affected whether stem cells became neurons. While the ratio of stem cells to neurons remained constant in the lower blade of the dentrate gyrus, it varied in the upper blade. Age also affected the results. After three months, the brains of the isolated mice stopped accumulating neural stem cells. But the mice in enriched environments continued to produce more neurons. Dranovsky and his team now want to see whether this hippocampal response is specific to social isolation or is a more general response to stress. Another question is whether all neural stem cells have the same potential to produce neurons. “The long-term goal.” Said Dr. Dranovsky, “is to figure out how to instruct neural stem cells to produce neurons or more stem cells. This could lead to the eventual use of stem cells in neuronal replacement therapy for neurodegenerative diseases and other central nervous system conditions.” Authors of the Neuron study are Alex Dranovsky, Alyssa M. Picchini, Tiffany Moadel, Alexander C. Sisti, Atsushi Yamada, Shioko Kimura, E. David Leonardo, and Rene Hen. This study was supported by the NIH, NARSAD, NYSTEM, and NCI CCR. R.H. receives compensation as a consultant for Braincells, in relation to the generation of novel antidepressants. E.D.L. receives compensation as a consultant from PGxHealth. The other authors have no conflicts to disclose.

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哥伦比亚大学医学中心在基础、临床前和临床研究、医学和健康科学教育以及病人护理方面具有国际领先地位。该医疗中心培养未来的领导者，包括内科和外科医生学院、梅尔曼公共卫生学院、牙科医学院、护理学院、艺术和科学研究生院生物医学系以及联合研究中心和机构的许多医生、科学家、公共卫生专业人员、牙医和护士的奉献工作。成立于1767年，哥伦比亚的内科医生和外科医生学院是第一个机构在该国授予医学博士学位，是最挑剔的医学院在该国。哥伦比亚大学医学中心是纽约市和纽约州最大的医学研究企业，也是美国最大的医学研究企业之一。