NMDA RECEPTOR REGULATION IN LIMBIC EPILEPSY

这个实验室的长期目标是了解病理生理学。 边缘癫痫的分子特征。这项建议的两个目标 代表了实现这一目标的相关但不同的方法 点燃是研究最广泛的边缘癫痫动物模型。 使用NMDA亚型增强兴奋性突触的功能 谷氨酸受体可能参与了耐受细胞的表达 点燃时的过度兴奋。点燃大鼠CA3区锥体细胞 海马体表现出选择性和持久性的增强的敏感性 NMDA在NMDA引起的去极化中很明显。至少有一部分 这种敏感度增加的分子基础似乎是一个引人注目的 “新型”NMDARk受体(NMDARk)密度增加(大于10%1)， 在本供资期间确定的。我们认为NMDARK是 点燃后持久的超兴奋性的分子基础 大脑。我们的第一个目标是阐明NMDARK的分子基础。 编码N-甲基-D-天冬氨酸受体亚单位多个cDNA的分子克隆 提供了进行调查所需的试剂和见解。 因为配体对神经递质受体的亲和力可以是 由亚基组成或亚基组成的改变而差异调制的 磷酸化，我们假设NMDARk反映了一个带有受体的受体 或者这两种分子修饰。我们将测试这些替代方案 使用针对NMDA不同亚基的抗体的假说 受体在海马区表达。理解分子的本质 应该有助于阐明NMDARk是如何影响兴奋性的 CA3锥体细胞，其中(除CA3外)在点燃的大脑中 NMDARk的存在，nMDARk如何促进 点燃了动物，并最终引发了人类边缘癫痫。 我们出乎意料地发现，转基因小鼠携带了一个空 钙调素蛋白激酶II基因α亚基突变的研究 边缘癫痫。这个模型概括了人类的许多方面 边缘癫痫包括自发性癫痫发作，轴突发芽 海马齿状回颗粒上区的颗粒细胞轴突， 颗粒细胞层弥散分布。链接到一个单一的， 识别出的基因集中在寻找潜在的机制上。这个 这项提案的第二个目标是描述这一新模式的特征和 从而获得有助于进行机械分析的信息 Dingledine博士和Nadler博士。

The long term goal of this laboratory is to understand the pathophysiology of limbic epilepsy in molecular terms. The two objectives of this proposal represent related but distinct approaches to this goal Kindling is the most widely studied animal model of limbic epilepsy. Enhanced function of excitatory synapses using the NMDA subtype of glutamate receptor may contribute to the expression of the enduring hyperexcitability of kindling. CA3 pyramidal cells of the kindled hippocampus exhibit a selective and longlasting increased sensitivity to NMDA as evident in an NMDA-evoked depolarization. At least part of the molecular basis of this increased sensitivity appears to be a strikingly increased density (greater than 10% 1) of a "novel" NMDA receptor (NMDARk), identified during the present funding period. We think that NMDARk is part of the molecular basis of the lasting hyperexcitability of the kindled brain. Our first objective is to elucidate the molecular basis of NMDARk. The molecular cloning of multiple cDNAs encoding NMDA receptor subunits has provided both reagents and insights with which to pursue this inquiry. Since the affinity of ligands for neurotransmitter receptors can be differentially modulated by alterations of either subunit composition or phosphorylation, we hypothesize that NMDARk reflects a receptor bearing one or both of these molecular modifications. We will test these alternative hypotheses using antibodies specific to distinct subunits of the NMDA receptor expressed in the hippocampus. Understanding the molecular nature of NMDARk should facilitate elucidating how NMDARk affects the excitability of CA3 pyramidal cells, where (in addition to CA3) in a kindled brain NMDARk is present, how nMDARk contributes to the hyperexcitability of a kindled animal and, ultimately, of human limbic epilepsy. We have unexpectedly-discovered that transgenic mice carrying a null mutation of the alpha-subunit of calcium calmodulin kinase II gene exhibit limbic epilepsy. This model recapitulates a number of aspects of human limbic epilepsy including spontaneous seizures, axonal sprouting of hippocampal granule cell axons in the supragranular region of the dentate, and dispersion of the granule cell layer. The link to a single, identified gene focuses the search for the underlying mechanisms. The second objective of this proposal is to characterize this new model and thereby obtain information helpful for mechanistic analyses to be pursued by Drs. Dingledine and Nadler.