RECURRENT AXON SPROUTING IN EPILEPSY

癫痫中的复发性轴突萌发

• 批准号: 6243510
• 负责人: J V NADLER
• 金额: $ 21.17万
• 依托单位: DUKE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-05-01 至 1998-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6243510
• 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，特别是复发性苔藓纤维发芽 海马区癫痫的传播和病理生理学。复发性苔藓 复杂部分性脑病患者的海马区可见纤维发芽 在癫痫和几种癫痫动物模型中。至少有一种效果 这种癫痫诱导的生长是在大脑中产生一个经常性的兴奋性环路 齿状回要么不正常出现，要么正常地 稀疏。有人提出，这样一条线路将有助于 减少齿状回对癫痫的抵抗力而致癫痫 癫痫的传播。相比之下，一些证据表明，反复出现的 苔藓纤维也投射到抑制性神经元，并用于修复 由于癫痫导致的损伤而失去的突触抑制。 对于触发苔藓纤维的刺激也存在分歧。 成长。一些研究表明，癫痫发作引起的退行性变 肺门神经元，尤其是苔藓细胞，打开了突触区域， 然后被苔藓纤维占据。然而，其他研究表明， 反复的苔藓纤维发芽可能是由癫痫发作本身引发的。 这些问题将通过使用两个动物模型进行研究。这个 匹罗卡品治疗的大鼠是唯一可用的模型，其特征是 通过持续健壮的复发性苔藓纤维萌发和自发 癫痫发作。基因改造的小鼠携带零突变 CaM激酶II的α亚基也会发生自发性癫痫发作， 伴随着较少数量的复发性苔藓纤维在 大鼠匹罗卡品模型。反复兴奋，多突触抑制 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电池电流。 在匹罗卡品诱导状态后的不同时间进行记录 不同持续时间的癫痫持续时间和持续时间 突变小鼠癫痫发作史上的不同时间。假说 这项工作背后的预测是，兴奋性和 抑制性突触电流，以及颗粒细胞的放电模式， 将与复发性苔藓纤维发芽的程度相关。这个 复发性苔藓纤维EPSC将明确地表现为 高聚焦谷氨酸激活单颗粒细胞 激光紫外线。一种“最大齿状细胞激活”的体外模型将是 用于确定复发性苔藓纤维发芽的程度 可解释通过齿状体内癫痫放电的增强传播 脑回。兴奋性肺门神经元将被标记为免疫反应性 因为谷氨酸和它们的丰度将被比作 反复发芽的苔藓纤维。这项研究将决定是否 发芽的发生取决于这些神经元的丧失。最后，我们 将研究CA3区海马锥体轴突的可能性 在这些癫痫模型中，细胞也会萌发，形成第二种类型的 海马齿状回内反复出现的兴奋回路。