NMDA RECEPTORS IN LEAD-INDUCED COGNITIVE DEFICIT

铅引起的认知缺陷中的 NMDA 受体

• 批准号: 3254028
• 负责人: Edson X. Albuquerque
• 金额: $ 13.9万
• 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/3254028
• 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(Pb2+)损害智力活动和神经发育的能力 强调其作为无处不在的环境威胁的作用。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-天冬氨酸激活的大鼠通道电流 浓度依赖但电压非依赖的海马神经元 方式，而不会显著改变由任一种方式引起的电流 合格的或凯恩式的。鉴于N-甲基-D-天冬氨酸受体参与了 记忆和学习等重要生理过程，详细介绍 评估Pb2+对这些受体的影响是至关重要的。此外， 众所周知，神经发育和认知过程的障碍 由这种因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，Pb2+对NMDA的影响 受体似乎在神经元发育的早期阶段更具戏剧性。 发展。因此，提出了几个基本问题：1)如何 Pb2+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) Pb2+对NMDA受体的作用？3)培养的海马神经元 神经元是对Pb2+最敏感的NMDA受体。 锌、钙和镁离子如何影响铅离子对NMDA受体的作用？ 细胞成熟是否影响Pb2+对NMDA受体的影响？ Pb2+对细胞发育和NMDA受体的慢性影响 海马神经元的功能？为了提供这些问题的答案， 本课题旨在研究大鼠的电生理反应。 培养的大鼠海马神经元在无Pb2+时对NMDA的影响(对照组 条件)，以及在细胞培养的急性和慢性暴露之后 制备不同浓度的阳离子。录制完整的 由不同激动剂激活的细胞和单通道电流 使用标准膜片钳技术对培养的神经元进行操作。 此外，在中国开发了一种新的快速药物灌流和撤药系统 我们的实验室将使我们能够对 这些洋流。Pb2+对NMDA受体作用的研究进展 应该构成尝试设计的第一步，也是最重要的一步 中枢神经毒性效应的合理治疗 系统(CNS)。作为该提案的次要目标，我们希望 Pb2+与神经元烟碱型乙酰胆碱相互作用的研究 受体(AChR)，因为有令人信服的证据表明 NMDA受体、AChRs也可能在认知过程中发挥重要作用 流程。我们已经证明了低浓度的Pb2+ 类似于那些阻断NMDA受体的药物，显著抑制整个细胞 由AChR激动剂Anatoxin-a和ACh激活的电流。 这项提案中描述的研究将使我们能够确定一些 Pb2+复合作用的分子机制 中枢神经系统。