NMDA RECEPTORS IN LEAD-INDUCED COGNITIVE DEFICIT

铅引起的认知缺陷中的 NMDA 受体

• 批准号: 3254027
• 负责人: Edson X. Albuquerque
• 金额: $ 13.79万
• 依托单位: UNIVERSITY OF MARYLAND BALTIMORE
• 依托单位国家: 美国
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-06-01 至 1996-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3254027
• 关键词: NMDA receptors; cell age; cognition disorders; developmental neurobiology; electrophysiology; environmental toxicology; hippocampus; laboratory rat; lead; neurons; neurotoxins; nicotinic receptors; toxicant interaction; voltage /patch clamp

The ability of lead (Pb2+) to impair mental activity and neurodevelopment underscores its role as a pervasive environmental threat. Recently, we have observed that this cation is able to inhibit whole cell and single channel currents activated by N-methyl-D-aspartate (NMDA) in rat cultured hippocampal neurons in a concentration-dependent but voltage-independent manner, without significantly altering currents induced by either quisqualate or kainate. In view of the involvement of NMDA receptors in important physiological processes such as memory and learning, a detailed evaluation of the effect of Pb2+ on these receptors is vital. Furthermore, it is known that the impairment of neurodevelopment and cognitive processes induced by this element is much more severe in children than in adults. Indeed, our preliminary work showed that the effects of Pb2+ on NMDA receptors seem to be much more dramatic at early stages of neuronal development. Thus, several fundamental questions are raised: 1) How does Pb2+ affect the different conductance states of NMDA receptor channels at various stages of neuronal development in culture? 2) What is the site of action of Pb2+ on NMDA receptors? 3) At what age of culture of hippocampal neurons are the NMDA receptors most sensitive to the Pb2+? 4) Do glycine, Zn2+, Ca2+ and Mg2+ affect the actions of Pb2+ on NMDA receptors? 5) How does cell maturation influence the effects of Pb2+ on NMDA receptors? 6) What are the chronic effects of Pb2+ on cell development and NMDA receptor function in hippocampal neurons? To provide the answers to these questions, this project is aimed at studying the electrophysiological responses of cultured rat hippocampal neurons to NMDA in the absence of Pb2+ (control condition), and after acute as well as chronic exposure of the cell culture preparation to different concentrations of the cation. Recordings of whole cell and single channel currents activated by different agonists will be performed on the cultured neurons using standard patch clamp techniques. In addition, a new fast drug perfusion and withdrawal system developed in our laboratory will enable us to make a quantitative kinetic analysis of these currents. The elucidation of the actions of Pb2+ on NMDA receptors should constitute the first and most important step in an attempt to design a rational treatment of its neurotoxic effects in the central nervous system (CNS). As a secondary aim of the proposal, we would like to evaluate the interactions of Pb2+ with neuronal nicotinic acetylcholine receptors (AChR), since there is compelling evidence that in addition to NMDA receptors, AChRs may also play a significant role in cognitive processes. We have already demonstrated that low concentrations of Pb2+ similar to those that block NMDA receptors, markedly depress whole cell currents activated by anatoxin-a and ACh, well known agonists of the AChR. The studies described in this proposal will allow us to determine some of the molecular mechanisms that underlie the complex effects of Pb2+ in the CNS.

铅（Pb 2+）损害智力活动和神经发育的能力 强调了其作为普遍环境威胁的作用。 最近我们 已经观察到这种阳离子能够抑制整个细胞和单个细胞， N-甲基-D-天冬氨酸（NMDA）激活的大鼠离体培养心肌细胞通道电流 海马神经元呈浓度依赖性但电压非依赖性 方式，而不显著改变由任一种方式引起的电流 使君子酸或红藻氨酸。 鉴于NMDA受体参与了 重要的生理过程，如记忆和学习，详细的 评价Pb 2+对这些受体的作用是至关重要的。 此外，委员会认为， 众所周知，神经发育和认知过程的损害 由这种元素引起的儿童比成人严重得多。 事实上，我们的初步工作表明，铅对NMDA的影响， 受体似乎在神经元的早期阶段更显着， 发展 因此，提出了几个基本问题：1）如何 Pb ~（2+）对NMDA受体通道不同电导状态的影响 培养中神经元发育的不同阶段2)什么是网站的 Pb 2+对NMDA受体的作用3)海马神经元培养的年龄 神经元的NMDA受体最敏感的Pb 2+？4)做甘氨酸， Zn ~（2+）、Ca ~（2+）、Mg ~（2+）影响Pb ~（2+）对NMDA受体的作用。5)如何 细胞成熟是否影响Pb ~（2+）对NMDA受体的作用？六、 Pb 2+对细胞发育和NMDA受体的慢性影响是什么 海马神经元的功能为了回答这些问题， 该项目旨在研究 培养的大鼠海马神经元在无Pb ~（2+）的情况下（对照 条件），以及在细胞培养物的急性和慢性暴露之后， 制备不同浓度的阳离子。 整体记录 由不同激动剂激活的细胞和单通道电流将 使用标准膜片钳技术在培养的神经元上进行。 此外，还开发了一种新的快速药物灌注和撤回系统， 我们的实验室将使我们能够进行定量动力学分析 这些电流。 Pb ~（2+）对NMDA受体作用的研究 应该是试图设计一个 合理治疗其中枢神经毒性作用 系统（CNS）。 作为该提案的第二个目的，我们希望 评价Pb 2+与神经元烟碱乙酰胆碱的相互作用 受体（AChR），因为有令人信服的证据表明，除了 NMDA受体、AChRs也可能在认知功能障碍中发挥重要作用。 流程. 我们已经证明，低浓度的Pb 2 + 与阻断NMDA受体的药物类似， 由类毒素-a和ACh（AChR的众所周知的激动剂）激活的电流。 本提案中描述的研究将使我们能够确定一些 探讨了Pb 2+在细胞内复杂作用的分子机制， CNS。