RECURRENT AXON SPROUTING IN EPILEPSY

癫痫中的复发性轴突萌发

• 批准号: 6273666
• 负责人: J V NADLER
• 金额: $ 22.03万
• 依托单位: DUKE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-05-01 至 1999-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6273666
• 关键词: epilepsy; excitatory aminoacid; glutamates; granule cell; hippocampus; kainate; laboratory rat; mossy fiber; neural inhibition; neuronal guidance; neuropharmacology; pilocarpine; synaptogenesis

The ultimate goal of this project is to understand the role of axon sprouting, in particular recurrent mossy fiber sprouting, in the propagation and pathophysiology of hippocampal seizures. Recurrent mossy fiber sprouting occurs in the hippocampus of persons with complex partial epilepsy and in several animal models of epilepsy. At least one effect of this seizure-induced growth is to create a recurrent excitatory circuit in the dentate gyrus that is either not present normally or is normally very sparse. It has been proposed that such a circuit would contribute to epileptogenesis by diminishing the resistance of the dentate gyrus toward seizure propagation. In contrast, some evidence suggests that recurrent mossy fibers also project to inhibitory neurons and serve to restore synaptic inhibition that was lost as a result of seizure-induced damage. There is also disagreement about the stimulus that triggers mossy fiber growth. Some studies indicate that the seizure-induced degeneration of hilar neurons, especially of mossy cells, opens up synaptic territory that is then occupied by mossy fibers. Other studies, however, suggest that recurrent mossy fiber sprouting might be triggered by seizures per se. These issues will be investigate with use of two animal models. The pilocarpine-treated rat is the only available model that is characterized by both consistently robust recurrent mossy fiber sprouting and spontaneous seizures. Mice genetically engineered to carry a null mutation for the alpha subunit of CaM kinase II also develop spontaneous seizures, accompanied by a lesser number of recurrent mossy fibers that develop in the rat pilocarpine model. Recurrent excitation, polysynaptic inhibition and monosynaptic inhibition will be tested in dentate granule cells by simultaneous recording of field potentials and whole cell currents. Recordings will be made at different times after pilocarpine-induced status epilepticus, after different durations of status epilepticus and at different times in the seizure history of the mutant mice. The hypothesis underlying this work predicts that the magnitude of excitatory and inhibitory synaptic currents, as well as the granule cell firing pattern, will correlate with the extent of recurrent mossy fiber sprouting. The recurrent mossy fiber EPSC will be characterized unambiguously by activating single granule cells with glutamate uncaged by highly focused laser UV light. An in vitro model of "maximal dentate activation" will be used to determine the extent to which recurrent mossy fiber sprouting accounts for enhanced propagation of seizure discharge through the dentate gyrus. Excitatory hilar neurons will be labeled by their immunoreactivity for glutamate and their abundance will be compared tot he extent of recurrent mossy fiber sprouting. This study will determine whether or not the occurrence of sprouting depends on loss of these neurons. Finally, we will investigate the possibility that axons of CA3 hippocampal pyramidal cells also sprout in these epilepsy models and form a second type of recurrent excitatory circuit in the dentate gyrus.

这个项目的最终目标是了解轴突的作用 发芽，特别是复发苔藓纤维发芽，在 海马癫痫发作的传播和病理生理学。 返生苔 纤维发芽发生在复杂部分脑梗死患者的海马体中， 癫痫和几种癫痫动物模型。 的至少一种作用 这一刺激性生长是为了在大脑中建立一个反复出现的兴奋回路， 齿状回要么不正常出现，要么通常非常 稀疏。 有人提出，这样的电路将有助于 通过减少齿状回对癫痫的抵抗， 癫痫发作传播。 相反，一些证据表明， 苔藓纤维还投射到抑制神经元并用于恢复 突触抑制，由于神经元损伤而丧失。 关于触发苔藓纤维的刺激也存在分歧 增长 一些研究表明， 门神经元，特别是苔藓细胞，打开突触领域， 被苔藓纤维占据 然而，其他研究表明， 复发性苔藓纤维发芽可能由癫痫发作本身触发。 这些问题将使用两种动物模型进行研究。 的 毛果芸香碱处理的大鼠是唯一可用的模型， 通过持续强劲的反复苔藓纤维发芽和自发 癫痫发作。 小鼠基因工程携带无效突变， CaM激酶II的α亚单位也会发生自发性癫痫发作， 伴随着较少数量的复发苔藓纤维， 大鼠毛果芸香碱模型。 反复兴奋，多突触抑制 和单突触抑制将在齿状颗粒细胞中进行测试， 同时记录场电位和全细胞电流。 在匹罗卡品诱导状态后的不同时间进行记录 癫痫持续状态，在不同的持续时间后， 突变小鼠癫痫发作的不同时间 的假设 这项工作的基础预测，兴奋性和 抑制性突触电流，以及颗粒细胞放电模式， 将与复发性苔藓纤维发芽的程度相关。 的 复发苔藓纤维EPSC的特征将明确， 用高聚焦的谷氨酸释放激活单个颗粒细胞 激光紫外线 “最大齿状激活”的体外模型将是 用于确定复发苔藓纤维发芽的程度 解释了癫痫放电通过齿状突的增强传播 脑回 兴奋性肺门神经元将被标记的免疫反应 他们的丰功伟绩，将被视为他们的丰功伟绩。 经常性苔藓纤维发芽。 这项研究将确定 发芽的发生取决于这些神经元的损失。 最后我们 将研究CA3海马锥体的轴突 细胞也在这些癫痫模型中发芽，形成第二种类型的 齿状回的兴奋性回路