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

说明(申请人提供)：补充申请1RO1 NS048589：“癫痫中谷氨酸控制的13C和15N MRS研究”。提交此补充申请是为了完成将我们的4.7特斯拉磁共振光谱仪升级到Bruker Avance控制台。在我们获奖的奖助金的具体目标#1，即研究谷氨酰胺(Gln)从神经胶质细胞转运到细胞外液(ECF)的动力学和神经元摄取GLNECF的机制方面取得了实质性进展，而GLNECF是谷氨酰胺/谷氨酸循环中缺失的一环。为了进一步发展，迫切需要对我们已有20年历史的动物扫描仪进行升级。我们的具体目标#2建议研究谷氨酸(GLU)兴奋毒性如何导致癫痫发作。这将使用慢性红藻氨酸诱导(KA)癫痫大鼠模型进行研究，该模型最接近于人类颞叶癫痫(TIE)。神经递质谷氨酸(GLU)向ECF的过度释放和/或GLUECF对星形胶质细胞的摄取受损可导致GLU受体的过度刺激和神经元变性(GLU兴奋毒性)。体内GLU释放和摄取的通量速率将在受损的和对侧的海马区被测量，并与(A)电生理和行为惊厥，以及(B)直到最近在死后大脑中检测到的组织学变化的形态变化相关。MRI/MRS的最新进展提出了一种令人兴奋的可能性，即可以从1-2微升的啮齿动物脑中非侵入性地检测到组织病理或代谢变化，如苔藓纤维发芽(在人TLE和KA大鼠中都观察到)、神经元变性、神经元标志物N-乙酰天冬氨酸的减少以及星形胶质细胞肿胀所致的水肿。升级到Bruker Avance控制台将提供最先进的成像和光谱功能，可以对KA大鼠的这些变化进行非侵入性纵向监测。这将允许确定(A)癫痫的发生和传播如何与海马亚区的形态和代谢变化相关，以及(B)癫痫发作是由GLU异常释放、胶质转运体清除GLU受损还是这些过程的组合造成的。总之，这些研究将有助于更好地理解KA模型中Gln/GLU循环的调节事件，并导致更有效地预防人类癫痫的兴奋性毒性。

DESCRIPTION (provided by applicant): Supplemental Application 1RO1 NS048589: "13C and 15N MRS study of glutamate control in epilepsy". This supplemental application is submitted to complete the upgrade of our 4.7 Tesla MR spectrometer to Bruker Avance console. Substantial progress has been made in Specific Aim #1 of our awarded Grant, viz study of the kinetics of glutamine (GLN) transport from the glia to the extracellular fluid (ECF) and the mechanism of neuronal uptake of GLNECF, which had been a missing link in the glutamine/glutamate cycle. For further progress, upgrade of our 20-year-old animal scanner is urgently needed. Our Specific Aim #2 proposes to examine how glutamate (GLU) excitotoxicity may cause epileptic seizures. This will be studied using the chronic kainate-induced (KA) epileptic rat model, which most closely resembles human temporal lobe epilepsy (TIE). Excessive release of the neurotransmitter glutamate (GLU) into ECF and/or impaired uptake of GLUECF into astrocytes can lead to excessive stimulation of the GLU receptors and to neuronal degeneration (GLU excitotoxicity). In vivo flux rates of GLU release and uptake will be measured in the lesioned and contralateral hippocampus, and correlated with (a) electrophysiological and behavioral seizures, and (b) morphological changes which had, until recently, been detected histologically in post- mortem brain. Recent advances in MRI/MRS raise an exciting possibility that histopathological or metabolic changes such as mossy fiber sprouting (observed in both human TLE and KA rats), neuronal degeneration, reduction in the neuronal marker N-acetylaspartate, and edema due to astrocyte swelling, may be detected non-invasively from 1-2 microliter of rodent brain. Upgrade to Bruker Avance console will provide state-of- the-art imaging and spectroscopy capability which can permit non-invasive longitudinal monitoring of these changes in KA rats. This will allow determination of (a) how the onset and propagation of seizures are correlated with the morphological and metabolic changes in hippocampal sub-regions, and (b) whether the seizures are the result of abnormal GLU release, impaired GLU clearance by glial transporters, or a combination of these processes. Together these studies will contribute to a better understanding of the regulatory events of the GLN/GLU cycle in the KA model and lead to more effective preventions of excitotoxicity in human epilepsy.