Epilepsy: Ion Channels As Antiepileptic Targets

癫痫：离子通道作为抗癫痫靶点

基本信息

批准号：
6990039
负责人：
MICHAEL A. ROGAWSKI
金额：
--
依托单位：
NATIONAL INSTITUTE OF NEUROLOGICAL DISORDERS AND STROKE
依托单位国家：
美国
项目类别：
财政年份：
资助国家：
美国
起止时间：
至
项目状态：
未结题

项目摘要

The objective of this project is to explore new strategies for the rational development of antiepileptic drugs based upon their interaction with neuronal ion channel systems. Cellular electrophysiological recording techniques are used to study drug modulation of neurotransmitter-gated and voltage-activated ion channels in brain slices, cultured neurons and heterologous cells transfected with cloned ion channel subunit genes. Correlative studies are carried out in animal models. Recent studies have focused on kainate-type glutamate receptors. We have demonstrated that a component of the excitatory synaptic response evoked in basolateral amygdala neurons by external capsule stimulation is mediated by kainate receptors containing the GluR5 subunit and we have shown that these receptors elicit a novel form of synaptic plasticity that could mediate some types of epileptogenesis in the amygdala. In brain slice recordings from basolateral amygdala principal neurons, we demonstrated that topiramate, a widely used antiepileptic agent, selectively and potently inhibits GluR5 kainate receptor mediated synaptic responses. The ability of topiramate to antagonize kainate receptors is intriguing inasmuch as no other clinically used antiseizure medication targets these receptors at therapeutic concentrations. To determine if the inhibitory action of topiramate on GluR5 kainate receptors as shown in brain slice recordings is relevant to the anticonvulsant effects of the drug in vivo, we determined the protective activity of topiramate against seizures induced by intravenous infusion of various ionotropic glutamate receptor agonists in mice. Topiramate (25-100 mg/kg, i.p.) produced a dose-dependent elevation in the threshold for clonic seizures induced by infusion of ATPA, a selective agonist of GluR5 kainate receptors. Topiramate was less effective in protecting against clonic seizures induced by kainate, a mixed agonist of AMPA and kainate receptors. Topiramate did not affect clonic seizures induced by AMPA or NMDA. In contrast, the thresholds for tonic seizures induced by higher doses of these various glutamate receptor agonists were all elevated by topiramate. Unlike topiramate, carbamazepine elevated the threshold for AMPA- but not ATPA-induced clonic seizures. Our results are consistent with the possibility that the effects of topiramate on clonic seizure activity are due to functional blockade of GluR5 kainate receptors. Protection from tonic seizures may be mediated by other actions of the drug. Together with our in vitro cellular electrophysiological results, the present observations strongly support a unique mechanism of action of topiramate, which involves GluR5 kainate receptors. Overall, our studies indicate that GluR5 kainate receptors represent a promising novel target for antiepileptic drug development.

该项目的目的是基于抗癫痫药物与神经离子通道系统的相互作用，探索合理开发抗癫痫药物的新策略。细胞电生理记录技术用于研究脑切片、培养神经元和用克隆离子通道亚基基因转染的异源细胞中神经递质门控和电压激活离子通道的药物调节。在动物模型中进行了相关研究。最近的研究集中在红藻氨酸型谷氨酸受体上。我们已经证明，由外部囊刺激在基底外侧杏仁核神经元中引起的兴奋性突触反应的一个组成部分是由含有 GluR5 亚基的红藻氨酸受体介导的，并且我们已经证明这些受体引发了一种新形式的突触可塑性，可以介导某些类型的癫痫发生在杏仁核中。在基底外侧杏仁核主要神经元的脑切片记录中，我们证明托吡酯（一种广泛使用的抗癫痫药）可选择性且有效地抑制 GluR5 红藻氨酸受体介导的突触反应。托吡酯拮抗红藻氨酸受体的能力很有趣，因为没有其他临床使用的抗癫痫药物以治疗浓度靶向这些受体。为了确定脑切片记录中显示的托吡酯对 GluR5 红藻氨酸受体的抑制作用是否与药物体内抗惊厥作用相关，我们确定了托吡酯对静脉输注各种离子型谷氨酸受体激动剂引起的癫痫发作的保护活性。老鼠。托吡酯（25-100 mg/kg，腹膜内注射）可导致输注 ATPA（一种 GluR5 红藻氨酸受体的选择性激动剂）引起的阵挛性癫痫发作阈值呈剂量依赖性升高。托吡酯在预防红藻氨酸（AMPA 和红藻氨酸受体的混合激动剂）引起的阵挛性癫痫发作方面效果较差。托吡酯不影响 AMPA 或 NMDA 诱发的阵挛性癫痫发作。相比之下，托吡酯均提高了高剂量的这些不同谷氨酸受体激动剂诱发的强直性癫痫发作的阈值。与托吡酯不同，卡马西平提高了 AMPA 诱发的阵挛性癫痫发作的阈值，但不会提高 ATPA 诱发的阵挛性癫痫发作的阈值。我们的结果与托吡酯对阵挛性癫痫发作活动的影响是由于 GluR5 红藻氨酸受体的功能性阻断所致的可能性是一致的。药物的其他作用可能会介导对强直性癫痫发作的保护。结合我们的体外细胞电生理学结果，目前的观察结果强烈支持托吡酯的独特作用机制，其中涉及 GluR5 红藻氨酸受体。总的来说，我们的研究表明 GluR5 红藻氨酸受体代表了抗癫痫药物开发的一个有前途的新靶标。