GABAergic excitation in human hypothalamic hamartoma

人下丘脑错构瘤中的 GABA 能兴奋

• 批准号: 7135841
• 负责人: JIE WU
• 金额: $ 20.17万
• 依托单位: ST. JOSEPH'S HOSPITAL AND MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-06-01 至 2008-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7135841
• 关键词: clinical research; human; intracellular; neurons; phenotype; receptor; tissues

DESCRIPTION (provided by applicant): The long-term goal of this project is to understand the etiopathogenesis of human gelastic epilepsy. Human hypothalamic hamartoma (HH) is a rare developmental malformation often characterized by gelastic seizures, which are refractory to medical therapy. Based on ictal EEG recordings from HH, the gelastic seizures are postulated to arise from the HH lesion itself. This idea is well supported by evidence of dramatic improvements in seizure control using a novel neurosurgical approach allowing for safe resection of HH. However, the mechanisms of epileptogenesis operative in this subcortical lesion are unknown. We have recently characterized, for the first time, the electrophysiological properties of single HH neurons acutely dissociated from surgical specimens. The objective of the proposed study is to explore a novel mechanism of epileptogenesis of human gelastic seizures using surgically resected HH tissues. The central hypothesis is that GABAA receptors expressed in HH neurons exhibit an excitatory phenotype, which may serve as a source of human gelastic seizures. The rationale for the project is that HH neurons may exhibit immature features due to or combined with their ectopic location and abnormal cytoarchitecture, as well as their persistent epileptic activity. This immaturity may underlie GABAergic excitation. The central hypothesis will be tested by pursuing two specific aims. Aim 1 is to characterize GABAA receptor-mediated excitation. The working hypothesis is that GABA exerts an excitatory role mediated through functional GABAA receptors. This idea will be tested by defining a dominant expression of functional GABAA receptors with a limited expression of functional ionotropic glutamate receptors, as well as showing a positive shift of the reversal potential of the GABAA receptor-mediated currents and a GABA-induced depolarization and excitation using gramicidin-perforated patch recordings in acutely dissociated HH neurons. Aim 2 is to determine levels of expression of the Na+-K+-Cl- cotransporter (NKCC1) and the K+-Cl- cotransporter (KCC2) in HH tissues. The working hypothesis is that HH tissues express an abnormally high ratio of NKCC1 to KCC2 genes, contributing to elevated intracellular CI- levels and excitatory, rather than inhibitory, GABA responses. Quantitative RT-PCR techniques will be used to measure NKCC1 and KCC2 mRNA levels. The planned studies will establish and test a novel hypothesis that enhances understanding of mechanisms involved in human gelastic seizures. Knowledge about excitatory GABAA receptor function of HH neurons will also aid selection of superior strategies for pharmaceutical development to prevent and control human gelastic seizures.

描述（由申请人提供）：该项目的长期目标是了解人类凝胶性癫痫的发病机制。人类下丘脑错构瘤（HH）是一种罕见的发育畸形，通常以痉挛性癫痫发作为特征，药物治疗难以治愈。根据 HH 的发作期脑电图记录，推测痉挛性癫痫发作是由 HH 病变本身引起的。这一想法得到了证据的充分支持，证据表明，使用新型神经外科方法可以安全切除 HH，癫痫发作控制得到显着改善。然而，在这种皮质下病变中癫痫发生的机制尚不清楚。我们最近首次表征了与手术标本急剧分离的单个 HH 神经元的电生理特性。本研究的目的是利用手术切除的 HH 组织探索人类癫痫发作的新机制。中心假设是 HH 神经元中表达的 GABAA 受体表现出兴奋性表型，这可能是人类癫痫发作的根源。该项目的基本原理是，HH 神经元可能由于其异位位置和异常细胞结构以及其持续的癫痫活动而表现出不成熟的特征。这种不成熟可能是 GABA 能兴奋的基础。中心假设将通过追求两个具体目标来检验。目标 1 是表征 GABAA 受体介导的兴奋。有效的假设是 GABA 通过功能性 GABAA 受体发挥兴奋作用。通过定义功能性 GABAA 受体的显性表达和功能性离子型谷氨酸受体的有限表达，以及显示 GABAA 受体介导的电流的反转电位和 GABA 诱导的去极化和激发的正向转变，来测试这一想法。在急性分离的 HH 神经元中使用短杆菌肽穿孔贴片记录。目标 2 是确定 HH 组织中 Na+-K+-Cl- 协同转运蛋白 (NKCC1) 和 K+-Cl- 协同转运蛋白 (KCC2) 的表达水平。目前的假设是，HH 组织表达异常高比例的 NKCC1 与 KCC2 基因，导致细胞内 CI 水平升高和兴奋性而非抑制性 GABA 反应。定量 RT-PCR 技术将用于测量 NKCC1 和 KCC2 mRNA 水平。计划中的研究将建立并测试一个新的假设，以增强对人类癫痫发作机制的理解。关于 HH 神经元兴奋性 GABAA 受体功能的了解也将有助于选择更好的药物开发策略来预防和控制人类癫痫发作。