13C and 15N MRS Study of glutamate control in epilepsy

谷氨酸控制癫痫的 13C 和 15N MRS 研究

• 批准号: 7046374
• 负责人: BRIAN David ROSS
• 金额: $ 33.44万
• 依托单位: HUNTINGTON MEDICAL RESEARCH INSTITUTES
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-01-01 至 2009-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7046374
• 关键词: astrocytes; disease /disorder model; epilepsy; glutamate transporter; glutamates; glutamine; hippocampus; kainate; laboratory rat; magnetic resonance imaging; molecular pathology; neurons; neurotransmitter metabolism; neurotransmitter transport

DESCRIPTION (provided by applicant): Glutamate excitotoxicity has been implicated in epileptic seizures. Our objectives are 1) to clarify the mechanisms that control the metabolic flux and intercompartmental transport of glutamate and glutamine in the intact mammalian brain and 2) determine how glutamate excitotoxicity may cause epileptic seizures. Impaired glial uptake of GLU in the extracellular fluid (GLUECF) can lead to excessive stimulation of the GLU receptors and to neuronal degeneration (GLU excitotoxicity). The rate of uptake of neurotransmitter GLU from the extracellular fluid into astrocytes and subsequent metabolism to GLN has been measured through a) selective 13C enrichment of neurotransmitter GLU by isotope chase, b) collection of extracellular GLU by microdialysis and analysis of its 13C enrichment by gas-chromatography/mass spectrometry and c) observation of [5-13C, 5-15N] GLN formed in astrocytes using localized in vivo 13C and 15N MRS. Now, Specific Aim #1, a 'missing-link' in the GLN/GLU cycle, the kinetics and mechanism of transport of GLN from astrocytes to neurons will be determined using in vivo 15N, 1H-15N HMQC and 13C MRS. The results will clarify the roles of recently identified GLN transporters in the intact normal brain and determine whether the rate of glial GLN efflux (hypothesis #1) or of neuronal GLN uptake (hypothesis #2) limits the GLN/GLU cycle rate in vivo. Specific Aim #2 Kinetics of GLU release and uptake in temporal lobe epilepsy will be studied using the chronic kainate-induced epileptic (KA) rats model. In vivo flux rates will be measured in the lesioned and contralateral hippocampus and correlated with electrophysiological and behavioral seizures, to determine whether the onset and propogation of seizures is the result of (hypothesis #3) abnormal GLU release, (hypothesis #4) impaired GLU clearance by glial transporters, or (hypothesis #5) a combination of these processes. Together these studies will contribute to a better understanding of the regulatory events of the GLN/GLU cycle in KA and increase potential to replace surgical management of temporal lobe epilepsy.

描述（由申请人提供）：谷氨酸兴奋性毒性与癫痫发作有关。我们的目标是：(1)阐明控制完整哺乳动物大脑中谷氨酸和谷氨酰胺代谢通量和室间运输的机制；(2)确定谷氨酸兴奋性毒性如何导致癫痫发作。细胞外液（GLUECF）中GLU的胶质摄取受损可导致GLU受体的过度刺激和神经元变性（GLU兴奋性毒性）。从细胞外液中摄取神经递质GLU进入星形胶质细胞并随后代谢为GLN的速率已经通过a)同位素追踪法选择性地富集神经递质GLU， b)通过微透析收集细胞外GLU并通过气相色谱/质谱法分析其13C富集程度，以及c)使用体内定位的13C和15N ms观察星形胶质细胞中形成的[5-13C， 5-15N] GLN。作为GLN/GLU循环中的“缺失环节”，GLN从星形胶质细胞转运到神经元的动力学和机制将通过体内15N、1H-15N HMQC和13C mrs来确定。研究结果将阐明最近发现的GLN转运体在完整正常大脑中的作用，并确定胶质GLN外排（假设#1）或神经元GLN摄取（假设#2）的速率是否限制了体内GLN/GLU循环速率。本文将采用慢性盐酸盐诱导癫痫（KA）大鼠模型研究颞叶癫痫中GLU释放和摄取的动力学。体内通量率将在受损和对侧海马中测量，并与电生理和行为癫痫发作相关联，以确定癫痫发作的发生和持续是（假设#3）GLU释放异常的结果，（假设#4）胶质转运体对GLU清除受损的结果，还是（假设#5）这些过程的结合。总之，这些研究将有助于更好地了解KA中GLN/GLU周期的调节事件，并增加替代颞叶癫痫手术治疗的潜力。