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胶质癫痫的疗法发生。人类下丘脑瘤瘤（HH）是一种罕见的发育畸形，通常以胶质性癫痫发作为特征，对药物治疗难治性。基于HH的发作性脑电图记录，假定胶质性癫痫发作是由HH病变本身引起的。这种想法得到了通过新型神经外科方法允许安全切除HH的癫痫发作控制的巨大改善的证据。然而，在该皮层病变中癫痫生成作用的机制尚不清楚。最近，我们首次表征了单个HH神经元与手术标本急性分离的电生理特性。拟议的研究的目的是探索使用手术切除的HH组织对人胶质癫痫发作的新型机制。中心假设是，在HH神经元中表达的GABAA受体表现出兴奋性表型，可以作为人胶质性癫痫发作的来源。该项目的理由是，HH神经元可能由于其异位位置和异常的细胞结构及其持续性癫痫活性而表现出不成熟的特征。这种不成熟可能是GABA能激发的基础。中心假设将通过追求两个具体目标来检验。目的1是表征GABAA受体介导的激发。工作假设是GABA发挥了通过功能性GABAA受体介导的兴奋性作用。 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是确定HH组织中Na+-K+-Cl-Cotransporter（NKCC1）和K+-cl- cotransporter（KCC2）的表达水平。工作假设是HH组织表达了NKCC1与KCC2基因异常高的比例，导致细胞内CI-CI-水平和兴奋性升高，而不是抑制性GABA反应。定量RT-PCR技术将用于测量NKCC1和KCC2 mRNA水平。计划的研究将建立并检验一个新的假设，以增强对涉及人类胶质癫痫发作的机制的理解。关于HH神经元的兴奋性GABAA受体功能的知识还将有助于选择用于预防和控制人胶质癫痫发育的卓越策略。