MECHANISMS OF EXCITATORY AMINO ACID ACTIONS AND TOXICITY

兴奋性氨基酸作用和毒性机制

• 批准号: 3407714
• 负责人: DAVID Orlo CARPENTER
• 金额: $ 11.94万
• 依托单位: WADSWORTH CENTER
• 依托单位国家: 美国
• 财政年份: 1986
• 资助国家: 美国
• 起止时间: 1986-07-01 至 1996-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3407714
• 关键词: NMDA receptors; aspartate; calcium; calcium channel; calcium channel blockers; cell death; cerebral cortex; chloride channels; excitatory aminoacid; free radical oxygen; glutamate receptor; glutamates; kainate; laboratory mouse; laboratory rat; membrane channels; membrane permeability; neural transmission; neurochemistry; neurons; neurotransmitters; receptor sensitivity; stimulant /agonist; temporal lobe /cortex; tissue /cell culture; trypsin; voltage /patch clamp; voltage gated channel

The excitatory amino acids are probably the most important class of excitatory transmitters in the brain, but in excess they cause the death of neurons. There are at least three types of excitatory amino acid receptors, defined by the "specific" agonists N-methyl-Daspartate (NMDA), quisqualate and kainate, and each can cause excitotoxicity, although kainate is the most toxic. In spite of recent advance the mechanisms of excitotoxicity are unclear and may not be the same at the three types of receptors. The present proposal is for continued support for studies on excitotoxicity. We will test four possible mechanisms of toxicity, including a) accumulation of intracellular calcium beyond the ability of the cell to buffer it, with the calcium entering through either agonist-activated channels or voltage-dependent calcium channels; b) osmotic and concentration gradient disruption secondary to excessive entry of sodium and chloride; c) free radical formation, possibly secondary to calcium accumulation leading to activation of proteases; and d) lack of receptor desensitization, especially of the kainate receptor, leads to damage secondary to one or more of the above factors. We propose to perform whole cell patch recordings from acute dissociated piriform and hippocampal neurons, and study electrophysiologic indicators of toxicity in piriform cortex slices, using intracellular and population response recordings with bath application of agonists. We will study the three specific agonists and BMAA and BOAA, two unique amino acids associated with human disease. In the patch studies we will compare trypsin and mechanically dissociated neurons for differences in desensitization and current-voltage relations, then use mechanically dissociated neurons to study the role of divalent cations in carrying or blocking agonist-activated currents, analyze the properties of desensitization if it occurs and characterize receptors for the two unique amino acids. In the slice studies we will evaluate the effect of calcium, sodium and chloride concentrations and inhibitors of free radical production or scavengers on loss of excitability for each of the give agonists. The proposed studies have the potential to both contribute to the fundamental knowledge of the actions of the excitatory amino acids, and to lead to increased understanding of the variety of mechanisms responsible for excitotoxicity.

兴奋性氨基酸可能是最重要的一类 大脑中的兴奋性递质，但过量会导致死亡 神经元。 兴奋性氨基酸至少有3种 受体，由“特异性”激动剂 N-甲基-Daspartate 定义 (NMDA)、使君子酸盐和红藻氨酸盐，每种都可引起兴奋性毒性， 虽然红藻氨酸的毒性最强。 尽管最近取得了进展 兴奋性毒性的机制尚不清楚，并且可能在不同的情况下有所不同 三种类型的受体。 目前的提案是为了继续支持 用于兴奋性毒性研究。 我们将测试四种可能的机制 毒性，包括 a) 细胞内钙的积累超过 细胞缓冲它的能力，钙通过 激动剂激活通道或电压依赖性钙通道； b) 过量继发的渗透压和浓度梯度破坏 钠和氯的进入； c) 自由基形成，可能 继发于钙积累，导致蛋白酶激活； d) 缺乏受体脱敏作用，尤其是红藻氨酸 受体，导致继发于上述一种或多种因素的损害。 我们建议对急性解离的细胞进行全细胞贴片记录 梨状神经元和海马神经元，并研究电生理学 梨状皮层切片的毒性指标，使用细胞内 以及激动剂沐浴应用的人群反应记录。 我们将研究三种特定的激动剂以及 BMAA 和 BOAA，这两种独特的激动剂 与人类疾病相关的氨基酸。 在补丁研究中我们将 比较胰蛋白酶和机械分离神经元的差异 脱敏和电流电压关系，然后机械地使用 分离的神经元来研究二价阳离子在携带或 阻断激动剂激活电流，分析其特性 脱敏（如果发生）并表征两者的受体 独特的氨基酸。 在切片研究中，我们将评估以下效果： 钙、钠和氯的浓度以及游离抑制剂 自由基产生或清除剂对每个兴奋性的丧失 给予激动剂。 拟议的研究有潜力 有助于兴奋性行为的基本知识 氨基酸，并增加对各种氨基酸的了解 负责兴奋性毒性的机制。