Mechanism and Treatment of nerve agent-induced seizures

神经毒剂诱发癫痫发作的机制和治疗

• 批准号: 7224508
• 负责人: Jaideep Kapur
• 金额: $ 54.71万
• 依托单位: UNIVERSITY OF VIRGINIA
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-27 至 2011-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7224508
• 关键词: analog; dyes; galanin; generalized seizures; glutamates; hippocampus; neural transmission; neuropeptide Y; voltage /patch clamp

DESCRIPTION (provided by applicant): This proposal proposes to develop novel, mechanism-based therapies for the treatment of organophosphate (OP) nerve agent-induced seizures. OP nerve agents, such as sarin, soman and VX act by central and peripheral cholinesterase inhibition and enhance cholinergic transmission. In experimental animals, all known nerve agents, produce convulsive seizures and status epilepticus within minutes of exposure. Seizures were also observed in humans exposed to nerve agent poisoning during the Iran-Iraq war, and in the Tokyo subway attacks where sarin and VX were used. The mechanism of OP-induced seizures remains uncertain. Preliminary studies in our laboratory have used the OP, paraoxon, as a surrogate agent to study OP-induced seizures. We demonstrate that low doses of paraoxon infused into the hippocampus cause prolonged seizures. Furthermore, we demonstrate that the concentrations of paraoxon that cause seizures in hippocampal slices can enhance excitatory neurotransmission by stimulating glutamate release from presynaptic terminals. These findings lead to the formulation of the central hypothesis guiding this proposal: convulsant concentrations of OP nerve agents enhance glutamatergic neurotransmission. This proposal seeks to confirm preliminary findings regarding the effect of OP agent on excitatory transmission and to test candidate compounds that diminish glutamate release from presynaptic terminals as potential therapy against seizures induced by cholinergic agents. Experiments are proposed within three aims, each group has specific milestones toward therapeutic interventions. We present quantitative outcomes criteria that represent "go-no go" decision points. Experiments outlined in Aim 1 seek to confirm and extend the observation that OP cholinesterase inhibitors enhance glutamate release from presynaptic terminals in the hippocampus, using patch clamp electrophysiology and FM dye technique. Experiments proposed in Aim 2 seek to test two classes of compounds, somatostatin and its analogs, and adenosine and its analogs, for their ability to diminish glutamate release during control resting conditions and following OP stimulation, using patch clamp technique and FM dye technique. Two classes of compounds, galanin and neuropeptide Y, are held in reserve and will be tested in case either one of the two proposed agents fail to reduce glutamate release by 30%. Aim 3: To test anticonvulsant action of two classes of compounds in controlling lithium/pilocarpine and OP paraoxon-induced status epilepticus. Two classes of compounds, neuropeptide Y and galanin are held in reserve and will be tested in case either one of the two proposed agents fail to control diazepam refractory seizures in 50% of experimental animals. By studying the mechanisms of OP-induced seizures, we are proposing to identify novel therapeutic targets for the treatment of OP-induced seizures. Second, we propose to develop therapies based on novel therapeutic targets. Furthermore, we develop a model of OP-induced seizures that can be used in civilian

描述（由申请人提供）：该提案提议开发新颖的、基于机制的疗法来治疗有机磷（OP）神经毒剂引起的癫痫发作。 OP神经毒剂，如沙林、梭曼和VX，通过抑制中枢和外周胆碱酯酶起作用并增强胆碱能传递。在实验动物中，所有已知的神经毒剂在接触后几分钟内都会产生惊厥性癫痫发作和癫痫持续状态。在两伊战争期间，以及在使用沙林和 VX 的东京地铁袭击事件中，暴露于神经毒剂中毒的人类中也观察到癫痫发作。 OP 诱发癫痫发作的机制仍不确定。我们实验室的初步研究使用 OP（对氧磷）作为替代药物来研究 OP 诱发的癫痫发作。我们证明，低剂量的对氧磷注入海马会导致长时间的癫痫发作。此外，我们证明，引起海马切片癫痫发作的对氧磷浓度可以通过刺激突触前末梢释放谷氨酸来增强兴奋性神经传递。这些发现导致指导该提议的中心假设的形成：OP神经毒剂的惊厥浓度增强谷氨酸能神经传递。该提案旨在确认 OP 剂对兴奋性传递影响的初步发现，并测试减少突触前末梢谷氨酸释放的候选化合物，作为对抗胆碱能药物引起的癫痫发作的潜在疗法。实验提出了三个目标，每个组都有治疗干预的具体里程碑。我们提出了代表“继续或不继续”决策点的定量结果标准。目标 1 中概述的实验旨在利用膜片钳电生理学和 FM 染料技术来证实和扩展 OP 胆碱酯酶抑制剂增强海马突触前末梢谷氨酸释放的观察结果。目标 2 中提出的实验旨在使用膜片钳技术和 FM 染料技术测试两类化合物：生长抑素及其类似物、腺苷及其类似物，在控制静息条件下和 OP 刺激后减少谷氨酸释放的能力。两类化合物（甘丙肽和神经肽 Y）被保留，并将进行测试，以防两种拟议药物中的任何一种未能将谷氨酸释放减少 30%。目标 3：测试两类化合物在控制锂/毛果芸香碱和 OP 对氧磷诱发的癫痫持续状态方面的抗惊厥作用。两类化合物，神经肽 Y 和甘丙肽被保留，并将进行测试，以防两种拟议药物中的任何一种无法控制 50% 实验动物的地西泮难治性癫痫发作。通过研究 OP 诱发的癫痫发作机制，我们建议确定治疗 OP 诱发的癫痫发作的新治疗靶点。其次，我们建议开发基于新治疗靶点的疗法。此外，我们开发了一种 OP 引起的癫痫发作模型，可用于民用