Mechanisms of regulation of excitability in immature CNS

描述（由申请人提供）：长时间持续的癫痫发作活动（癫痫持续状态）与显著的死亡率和发病率相关，特别是在儿童中。在人类和动物癫痫模型中，未成熟的大脑极易发生癫痫发作。发育中的大脑中的神经递质系统倾向于兴奋，而发育中的大脑中存在的抑制兴奋的抑制系统尚未得到很好的表征。成人脑钾通道是神经元膜兴奋性的主要决定因素。一种特殊的钾离子通道Kv4.2定位于海马体神经元的树突，在那里它们形成瞬态a型钾离子电流。在这个神经元接受突触输入的区域，Kv4.2通道的电压依赖性激活为调节突触后兴奋性提供了一个关键机制。许多电压依赖性钾通道在发育早期的大脑中没有表达；然而，我们的初步研究表明，Kv4.2通道在未成熟的大脑中以成人水平表达。因此，我们假设钾通道Kv4.2在发育早期表达，可能对抑制未成熟大脑的兴奋性至关重要。我们提出以下目标：目的1：研究Kv4.2通道在未成熟大脑兴奋性调节中的作用。我们将评估未成熟小鼠和成年小鼠中Kv4.2通道亚基的表达水平和定位。为了评估Kv4.2通道在未成熟大脑癫痫易感性中的作用，我们将对Kv4.2基因敲除小鼠进行惊厥刺激，并与杂合子和野生型小鼠进行比较。目的2：探讨Kv4.2通道在早期癫痫发作后长期变化发展中的作用。与野生型和杂合子小鼠相比，我们将评估早期癫痫持续状态是否会导致Kv4.2基因敲除更深刻的长期改变。我们将监测的长期参数是自发性癫痫发作的发展、海马体的神经解剖变化和空间学习缺陷。本研究的总体目标是阐明未成熟大脑兴奋性和癫痫易感性调节的候选机制，以及早期癫痫持续状态的长期后果。相关性：癫痫持续状态（无法控制的持续发作）是许多大型儿童医院送往儿科重症监护病房的儿童最常见的诊断之一，并与严重的长期后果有关。我们的研究有望为大脑发育过程中癫痫易感性和癫痫持续状态的调节机制提供深入的见解，从而可能为儿童癫痫治疗找到新的候选靶点。

DESCRIPTION (provided by applicant): Prolonged, continuous seizure activity (status epilepticus) is associated with significant mortality and morbidity, particularly in children. In humans and animal models of epilepsy the immature brain is highly susceptible to seizures. The neurotransmitter systems in the developing brain are weighted toward excitation and the inhibitory systems present in developing brain to dampen excitation are not well characterized. In adult brain potassium channels are major determinants of membrane excitability in neurons. One particular potassium channel, Kv4.2 is localized to the dendrites of hippocampal neurons where they form the transient A-type K+ current. In this region where the neurons receive synaptic input, the voltage-dependent activation of Kv4.2 channels provides a critical mechanism for regulating postsynaptic excitability. A number of voltage-dependent potassium channels are not expressed early in developing brain; however our pilot studies show that Kv4.2 channels are expressed at adult levels in immature brain. Thus, we hypothesize that the potassium channel Kv4.2 is expressed early in development and may be critical for dampening excitability in the immature brain. We propose the following aims: Aim 1: Investigation of the role of Kv4.2 channels in the regulation of excitability in the immature brain. We will evaluate expression levels and localization of Kv4.2 channel subunits in immature compared with adult mice. To assess the role of Kv4.2 channels in seizure susceptibility in immature brain we will perform convulsant stimulation in Kv4.2 knockout compared with heterozygote and wildtype mice. Aim 2: Investigation of the role of Kv4.2 channels in the development of long-term changes after early-life seizures. We will evaluate whether early-life status epilepticus leads to more profound long-term alterations in Kv4.2 knockout compared to wildtype and heterozygous mice. Long-term parameters that we will monitor are development of spontaneous seizures, neuroanatomical changes in hippocampus, and spatial learning deficits. The overall goal of this proposal to elucidate candidate mechanisms involved in regulating excitability and seizure susceptibility in immature brain and the long-term consequences of early-life status epilepticus. Relevance: Status epilepticus (uncontrollable continuous seizures) is one of the most common diagnoses for children transported to the Pediatric Intensive Care Units at a number of major children's hospitals and is associated with serious long-term consequences. Our studies are anticipated to provide insights into the mechanisms involved in regulating seizure susceptibility and status epilepticus in the developing brain and thereby may identify novel candidate targets for therapeutics in childhood epilepsy.