MECHANISMS OF INCREASED EXCITATORY AMINOACID IN ISCHEMIA

缺血时兴奋性氨基酸增加的机制

• 批准号: 6187299
• 负责人: Harold K Kimelberg
• 金额: $ 21.01万
• 依托单位: ALBANY MEDICAL COLLEGE
• 依托单位国家: 美国
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-05-01 至 2001-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6187299
• 关键词: aspartate; astrocytes; calcium; cerebral ischemia /hypoxia; excitatory aminoacid; glial fibrillary acidic protein; glutamate receptor; glutamate transporter; glutamates; high performance liquid chromatography; hippocampus; immunocytochemistry; kainate; laboratory rat; microdialysis; neurons; neuropharmacology; neurotoxins; potassium; rubidium; sodium; synaptosomes; temperature; tissue /cell culture

A major hypothesis of CNS injury is that the increased extracellular excitatory amino acid (EAA) levels which occur after such injuries cause increased intra-neuronal calcium levels due to excessive activation of glutamate receptors, leading to neuronal damage and death. This scheme is supported by several lines of evidence such as, that treatment with glutamate receptor blockers or inhibition of the increased EAA levels in vivo are protective. In sharp contrast to the considerable body of work on the effects of the increased EAA levels, the cellular sources and mechanisms of the increased EAR have been little-studied. Both increased release and decreased uptake would contribute to increased EAAs. Surprisingly, in recent microdialysis studies, much of the increased EAA levels seen in animal models of ischemia has been found to be Ca2+ insensitive, suggesting that exocytotic release from nerve terminals is not a major contributor to the increased EAA levels, and that other mechanisms and sources must be considered. Extracellular K+ increases markedly in ischemia, and two Ca2+-independent release mechanisms for EAAs have been identified in in vitro which are stimulated by raised K+. These are reversal of the glutamate transporter seen in synaptosomes and cultured neurons and astrocytes, and swelling- induced release of EAAs seen in astrocytes. We will study primary astrocyte cultures and synaptosomes derived from the hippocampus and cultured cerebellar granule cells for our in vitro studies, as there are no hippocampal neuronal cultures that provide sufficient quantities of cells for transport studies. By confirming the transporter forms seen in the different in vitro preparations we will see if they have different reversal characteristics. Another major contributor to the increased EAA levels would be inhibition of uptake and astrocytes have very active and astrocyte-specific EAA uptake systems. We will study inhibition of EAA uptake by increased medium K+ in astrocytes in vitro. Using the data obtained on the different systems in vitro, we will determine their contributions to the increased levels of EAAs in vivo by microdialysis experiments in the rat hippocampus with reversible global ischemia. In addition we will produce localized depletion of astrocytes with gliotoxins and neurons by kainic acid, and determine the influence of these procedures on the ischemia-induced release of EAAs. Understanding the different sources and mechanisms of EAA release or impaired uptake and their respective contributions to the elevated EAA levels in ischemia and other pathological states is vital to interpretation of current therapies for such states and devising new ones.

中枢神经系统损伤的一个主要假说是细胞外增加 在这种损伤后发生的兴奋性氨基酸(EAA)水平 神经细胞内钙离子水平升高是由于细胞过度激活 谷氨酸受体，导致神经元损伤和死亡。这项计划是 有几条证据支持，例如，用 谷氨酸受体阻滞剂或抑制大鼠体内升高的EAA水平 活体是有保护作用的。与大量的工作形成鲜明对比 EAA水平升高的影响，细胞来源和 耳朵增加的机制还很少被研究。两者都增加了 释放和减少摄取将有助于增加EaAs。 令人惊讶的是，在最近的微透析研究中，大部分增加的EAA 在动物缺血模型中发现的水平是钙离子 不敏感，表明神经末梢的胞吐释放 并不是导致地产代理监管局水平上升的主要原因，而另一个 必须考虑机制和来源。 细胞外K+在缺血时显著升高，且两种钙离子不依赖 EaAs的体外释放机制已被确定，它们是 由升高的K+刺激。这些都是谷氨酸转运体的逆转 在突触体、培养的神经元和星形胶质细胞中可见，肿胀- 诱导星形胶质细胞释放EaAs。我们将学习小学 星形胶质细胞培养和突触体来源于海马区和 培养的小脑颗粒细胞用于我们的体外研究，因为有 没有海马神经元培养能提供足够数量的 用于运输研究的细胞。通过确认中看到的运输商表格 不同的体外制剂我们会看看它们是否有不同的 反转特征。导致地产代理监管局增加的另一个主要因素 水平会抑制摄取，星形胶质细胞具有非常活跃的 星形胶质细胞特异性的EAA摄取系统。我们将研究抑制EAA 体外培养星形胶质细胞增加对K+的摄取。使用数据 在体外获得不同的系统，我们将确定它们的 微透析对体内EaAs水平升高的贡献 大鼠海马区可逆性全脑缺血实验。在……里面 此外，我们将用胶质毒素产生局部的星形胶质细胞耗竭。 和神经元，并确定这些因素的影响 脑缺血诱导的EaS释放的程序。了解 EAA释放或摄取受损的不同来源和机制 它们在脑缺血和脑缺血时EAA水平升高中的作用 其他病理状态对解释当前的治疗方法至关重要 并设计出新的州。