Metabolism and Excitability in Rodent Hippocampus

描述（由申请人提供）：兴奋性和抑制性突触传递都依赖于谷氨酸的供应。谷氨酸由葡萄糖重新合成，也通过神经元和星形胶质细胞之间的谷氨酸-谷氨酰胺循环再循环。用于突触传递的GABA也依赖于神经元-神经胶质细胞循环，因为GABA由谷氨酸合成，谷氨酸可以通过摄取或通过谷氨酰胺进入中间神经元。本提案的主要目的是检验细胞兴奋性与谷氨酸-谷氨酰胺-GABA循环状态密切相关的广泛假设，特别是在持续神经元活动期间，由于GABA合成所需的额外能量依赖步骤，GABA能传递比兴奋性传递对循环中断更敏感。在具体目标1中，我们将在几个不同的水平上中断循环，包括阻断谷氨酰胺、谷氨酸和GABA的合成酶以及阻断谷氨酰胺摄取。这些代谢抑制剂对突触抑制的影响将在生理学上进行检查。 在具体目标2中，我们将使用质谱法测量组织和浸浴介质中神经递质循环改变诱导的谷氨酸、谷氨酰胺和GABA水平的变化，以解决递质水平的时间依赖性变化。 在特定目标3中，将使用13 C异构体光谱法评估那些穿过血脑屏障的化合物（GS抑制剂甲硫氨酸亚砜亚胺和谷氨酰胺转运蛋白MeAIB）对对照动物中谷氨酸-谷氨酰胺-GABA循环的影响。 这些实验应该提供关于正常突触传递的调节的重要数据，以及对许多神经系统疾病的病理学的理解，其中已经看到神经能量学的变化，包括癫痫、ALS和亨廷顿病。

DESCRIPTION (provided by applicant): Both excitatory and inhibitory synaptic transmission rely on the supply of glutamate. Glutamate is synthesized de novo from glucose and also recycled through the glutamate-glutamine cycle between neurons and astrocytes. GABA used for synaptic transmission is also dependent on neuronal-glial cycling as GABA is synthesized from glutamate which can enter interneurons either via uptake or through glutamine. The main goal of this proposal is to test the broad hypothesis that cellular excitability is intimately tied to the status of glutamate-glutamine-GABA cycling and specifically that GABAergic transmission is more sensitive than excitatory transmission to disruption in cycling during periods of sustained neuronal activity because of the added energy-dependent steps needed for the synthesis of GABA. In Specific Aim 1 we will interrupt cycling a several different levels including blockade of the synthetic enzymes of glutamine, glutamate and GABA as well as by blocking glutamine uptake. The effect of these metabolic inhibitors on synaptic inhibition will be examined physiologically. In Specific Aim 2, we will use mass spectometry to measure the changes in the levels of glutamate, glutamine and GABA induced by alterations in neurotransmitter cycling in both the tissue and in the bathing medium to address the time-dependent changes in transmitter levels. In Specific Aim 3 will use 13C isomer spectroscopy to assess the effect of those compounds that cross the blood brain barrier (the GS inhibitor methionine sulfoximine and the glutamine transporter MeAIB) on glutamate-glutamine-GABA cycling in control animals. These experiments should provide important data on the regulation of normal synaptic transmission as well as an understanding of the pathology of a number of neurological disorders where changes in neural energetics have been seen including epilepsy, ALS and Huntington's disease.