MODULATION OF SYNAPTIC EFFICACY & MECHANISMS OF EPILEPSY

描述：(申请人摘要)这项拨款建议审查 兴奋性和抑制性的短期频率依赖性可塑性 突触功能，其目标是有助于理解 癫痫患者在癫痫发作过程中发生的事件 焦点和癫痫发作从局部异常区域蔓延到 整个大脑皮层。中心假设是，微分规则 抑制性和兴奋性突触的数量是发育的主要原因 癫痫发作活动在大脑皮层的扩散。众所周知，在 大多数情况下，重复激活会导致抑制作用减弱 以及对势的激发。为了分析这些过程，在 在细胞水平上，一种简化的制剂被开发出来，以允许 细胞膜片钳记录突触对中的两个神经元 定量分析在帮助确定机理方面的应用 潜在的突触可塑性。在海马区培养中，突触 抑制会随着重复刺激而大大减少，这就是 由于突触前因素。兴奋性突触后电流也 重复动作中的递减，也是通过突触前机制， 然而，自发释放的递质却矛盾地被促进了。 即使在基线、非刺激条件下，也存在差异 在抑制神经递质释放的机制中 和兴奋性神经元，而这些可能在不同的 可塑性。所有观察到的突触可塑性形式都是 依赖于突触终末钙离子的变化，它是 假设一定涉及几个钙依赖的过程。这个 钙依赖的细节将被表征，其机制将通过 肾小管内钙的哪些变化会影响钙的释放 兴奋性和抑制性终末的神经递质 下定决心。短期塑性也将在更成熟的情况下进行研究 海马片培养中的组织。在这个准备过程中，作为切片 成熟后，兴奋性突触通过重复激活而增强。 使用与细胞培养系统中采用的技术类似的技术， 增强和发展的机制 将对增强机理进行分析。最后，使用一个新的 允许从单个核糖核酸中进行定量扩增的技术 识别兴奋性和抑制性的细胞、mRNA表达谱 神经元，无论是在细胞培养还是切片培养中都会 检查过了。在配位分子表达上的差异 这两种表型将被分析，重点是突触蛋白， 钙通道，是神经分泌的一部分，依赖钙的酶 机制和其他钙结合蛋白。分子的碱基 不同形式的短期可塑性，兴奋和 抑制性神经元的表现将被确定。据推测， 癫痫发作发生在异常兴奋的区域，原因是 兴奋性神经元和抑制性神经元的差异调节 癫痫发作通过类似的机制在整个大脑中传播。希望是这样的 对这些生物可塑性的本质有了更多的理解 两种不同的细胞类型将导致制定战略 抑制癫痫的发展和扩散。

DESCRIPTION: (Applicant's Abstract) This grant proposes to examine short term, frequency-dependent plasticity of excitatory and inhibitory synaptic function with the goal of contributing to an understanding of events which occur during the development of seizures in an epileptic focus and the spread of seizures from a focal area of abnormality to the entire cortex. The central hypothesis is that differential regualtion of inhibitory and excitatory synapses is responsible for the development and spread of seizure activity in the cortex. It is known that under most circumstances, repetitive activation causes inhibition to diminish and excitation to potential. In order to analyze such processes at the cellular level, a simplified preparation was developed to allow whole cell patch clamp recording of both neurons in a synaptic pair and the application of quantal analysis to help determine the mechanisms underlying synaptic plasticity. In the hippocampal cultures, synaptic inhibition profoundly decrements with repeated stimulation and this is due to presynaptic factors. Excitatory postsynaptic currents also decrement during repetitive action, also via a presynaptic mechanisms, whereas spontaneous transmitter released is paradoxically facilitated. Even under baseline, non-stimulated conditions, there are differences in the mechanisms underlying neurotransmitter release between inhibitory and excitatory neurons, and these may play a role in the differences in plasticity. All of the observed forms of synaptic plasticity are dependent on changes in Ca in the synaptic terminals and it is hypothesized that several Ca-dependent processes must be involved. The details of the Ca dependence will be characterized and the mechanisms by which changes in intraterminal Ca differential affect the release of neurotransmitter at excitatory and inhibitory terminals will be determined. Short term plasticity will also be studied in more mature tissue in hippocampal slice cultures. In this preparation, as the slice matures, excitatory synapse potentiate with repetitive activation. Using similar techniques to those employed in the cell culture system, the mechanisms underlying the potentiation and the development of the potentiating mechanisms will be analyzed. Finally, using a new technique which allows quantitative amplification of mRNAs from single cells, mRNA expression profiles of identified excitatory and inhibitory neurons, both in the cell culture ant the slice culture will be examined. The differences in the coordinated molecular expression in these two phenotypes will be analyzed, focusing on synaptic proteins, Ca channels, Ca-dependent enzymes which are part of the neurosecretory mechanisms and other Ca binding proteins. The molecular bases of the different forms of short term plasticity which the excitatory and inhibitory neurons exhibit will be determined. It is hypothesized that seizure develop in areas of abnormal excitability because of a differential regulation of excitatory and inhibitory neurons and that seizures spread throughout the brain by similar mechanisms. It is hoped that an increased understand of the nature of this plasticity in these two distinct cell types will lead to the development of strategies to suppress seizure development and spread.