Axonal Sprouting and Epilepsy after Traumatic CNS Injury

中枢神经系统外伤后的轴突出芽和癫痫

• 批准号: 6875711
• 负责人: SCOTT M. THOMPSON
• 金额: $ 28.22万
• 依托单位: UNIVERSITY OF MARYLAND BALTIMORE
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-04-01 至 2007-12-14
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6875711
• 关键词: action potentials; axon; brain injury; denervation; electrophysiology; epilepsy; genetically modified animals; glutamate receptor; glutamates; laboratory mouse; laboratory rat; neuronal guidance; neurophysiology; neurotransmitter metabolism; neurotrophic factors; pyramidal cells; synapses; trauma; voltage /patch clamp

The Problem: Epilepsy is a common consequence of traumatic head injury. Its cause is unknown. The Hypotheses: 1) The release of neurotrophins after traumatic CNS injury triggers axonal sprouting by pyramidal cells. 2) The glutamate sensitivity and excitability of postsynaptic target cells increase as a consequence of partial denervation. 3) Injury-induced presynaptic axonal sprouting and increased postsynaptic excitability combine synergistically to cause posttraumatic epilepsy. The Model: After Schaffer collateral transection, CA3 cells in hippocampal slice cultures sprout new axon collaterals and CA1 cells become supersensitive to glutamate. These phenomena may account for the lesion-induced hyperexcitability. This model provides an experimentally tractable and informative approach for studying pre- and postsynaptic mechanisms of posttraumatic epilepsy. The genesis of hyperexcitability after axonal injury in this model will therefore be investigated using neuroanatomical, cell biological, and electrophysiological techniques. AIM 1: Determine the presynaptic mechanisms underlying injury- induced hyperexcitability. TrkB immunoadhesins, biolistic transfection with full length and dominant negative neurotrophin receptor constructs, and cultures derived from trk receptor knockout mice will be used to test the hypothesis that activation of trk receptors is required for injury-induced axonal sprouting. The hypothesis predicts that lesion-induced sprouting will not occur in the presence of trkB immunoadhesin, in cells transfected with dominant negative irk receptors or in cultures made from trk receptor knock-out mice. Lack of axonal sprouting is predicted to eliminate injury-induced hyperexcitability. AIM 2: Determine the postsynaptic mechanisms underlying injury- induced hyperexcitability. Using whole-cell voltage-clamp and laser microphotolysis of caged neurotransmitters targeted to individual distal dendrites, we will test the hypotheses that glutamate supersensitivity and intrinsic hyperexcitability occur in CA1 cells after denervation. The hypothesis predicts that changes in the levels of expression of neurotransmitter receptors and/or changes in intrinsic voltage-dependent ionic conductances underlie the potentiation of dendritic glutamate responses observed previously after Schaffer collateral transection. The Goal: to better understand the causes of posttraumatic epilepsy and, ultimately, to offer new and improved prophylactic therapeutic strategies to cure this disease.

问题：癫痫是头部损伤的常见结果。 它的原因是未知的。假设：1）创伤性中枢神经系统损伤后神经营养蛋白的释放触发了金字塔细胞的轴突发芽。 2）突触后靶细胞的谷氨酸敏感性和兴奋性由于部分神经支配而增加。 3）损伤引起的突触前轴突发芽和突触后兴奋性的增加结合起来引起创伤后癫痫。该模型：在沙夫侧外横向后，海马切片中的CA3细胞培养了新的轴突侧支和CA1细胞对谷氨酸的超级敏感。 这些现象可能解释了病变引起的过度兴奋性。 该模型为研究创伤后癫痫的突触前和突触后机制提供了一种可实验且信息丰富的方法。 因此，将使用神经解剖学，细胞生物学和电生理技术研究轴突损伤后过度刺激性的发生。目标1：确定损伤引起的过度兴奋性的突触前机制。 TRKB免疫粘附素，具有全长和显性阴性神经营养蛋白受体构建体的生物学转染，并且将使用TRK受体敲除小鼠衍生的培养物来检验以下假设：损伤诱导的轴突芽剂需要激活TRK受体。该假设预测，在具有主要的阴性IRK受体转染的细胞或TRK受体敲除小鼠中转染的细胞中，病变诱导的发芽不会发生。 预计缺乏轴突发芽可以消除损伤引起的过度兴奋性。 AIM 2：确定损伤引起的过度兴奋性的突触后机制。 使用针对单个远端树突远端的蛋白神经递质的全细胞电压钳和激光麦粒溶解，我们将测试在树脂后CA1细胞中发生谷氨酸超敏和内在过度抗性的假设。 该假设预测，神经递质受体的表达水平的变化和/或固有电压依赖性离子电导的变化是在沙弗侧支转移后先前观察到的树突状谷氨酸反应的增强。目的：更好地了解创伤后癫痫的原因，并最终提供新的和改进的预防性治疗策略来治愈这种疾病。