Efficacy of GluR5 Antogonists Against Soman-Induced Seizures and Neuropathology

描述（由申请人提供）：神经毒剂是具有高毒性的有机磷酸盐，其主要作用是不可逆地抑制乙酰胆碱酯酶。神经毒剂暴露后的临床表现包括惊厥发作，可造成严重脑损伤，导致死亡或长期认知缺陷。目前，还没有预防性的治疗方法可以有效地预防神经毒剂引起的癫痫发作，而不会产生明显的副作用。目前可用的暴露后治疗可以预防死亡，但它们在预防癫痫发作和相关脑损伤方面的效果并不令人满意。暴露于神经毒剂后，癫痫发作主要是由于毒蕈碱受体的过度刺激引起的。胆碱能过度刺激引发谷氨酸能过度活动，从而加剧并维持癫痫发作，最终导致神经元损伤。因此，抗谷氨酸能药物对胆碱能过度刺激引起的癫痫发作有效。事实上，最近对GluR5盐酸盐受体（GluR5KRs，谷氨酸受体的盐酸盐亚型，含有GluR5亚基）功能的发现表明，阻断这些受体可阻断毒蕈碱激动剂匹罗卡平诱导的癫痫发作。由于匹罗卡品诱发的癫痫发作和神经毒剂诱发的癫痫发作之间存在共同的机制，我们假设GluR5KRs拮抗剂对神经毒剂诱发的癫痫发作也有效。我们提出用于验证我们假设的动物模型是体内暴露于索曼的大鼠，以及体外暴露于索曼的大鼠杏仁核和海马切片。GluR5KR选择性拮抗剂LY293558和UBP302将在暴露于人体前作为预防性治疗，或在暴露后的不同时间点作为治疗。这些拮抗剂在体内暴露于索曼后的体外研究中，其抗癫痫的功效将与其在预防脑病理以及杏仁核和海马的病理生理改变方面的功效相关。体外实验将在杏仁核和海马体中进行，因为这些大脑区域在大脑癫痫发作的产生中起着关键作用，包括由神经毒剂引起的癫痫发作。此外，GluR5KRs在海马和杏仁核的神经元兴奋性调节中发挥重要作用，我们发现，在杏仁核中，GluR5KRs的强激活抑制诱发的GABA释放，并诱导癫痫样活动。由于GluR5KRs拮抗剂不影响正常的突触传递，并且GluR5KRs在大脑中的分布相对有限，因此使用GluR5KR拮抗剂治疗可能产生很小的副作用或没有副作用。因此，拟议的研究可能会导致开发一种新的、安全有效的预防和/或治疗神经毒剂引起的脑损伤的方法，这将提高我们在紧急情况下的治疗反应能力。

DESCRIPTION (provided by applicant): Nerve agents are organophosphates with high toxicity, whose primary action is the irreversible inhibition of acetylcholinesterase. Clinical manifestations following nerve-agent exposure include the development of convulsive seizures, which can cause profound brain damage, resulting in death, or long-term cognitive deficits. At present, there are no prophylactic treatments that can effectively protect against nerve agent induced seizures, without causing significant side effects. Currently available post-exposure treatments can prevent death, but their efficacy in preventing seizures and associated brain damage has not been satisfactory. After exposure to a nerve agent, seizures are initiated primarily due to hyper-stimulation of muscarinic receptors. Cholinergic hyper-stimulation triggers glutamatergic hyperactivity, which intensifies and sustains seizures, and is ultimately responsible for neuronal damage. Therefore, anti-glutamatergic agents can be effective against seizures induced by cholinergic hyper-stimulation. Indeed, recent discoveries in the function of GluR5 kainate receptors (GluR5KRs, a kainate subtype of glutamate receptors containing the GluR5 subunit) have revealed that blockade of these receptors blocks epileptic seizures induced by the muscarinic agonist pilocarpine. As there are common mechanisms between pilocarpine-induced seizures and seizures induced by nerve agents, we hypothesize that antagonists of GluR5KRs will also be effective against nerve agent-induced seizures. The animal model we propose to use to test our hypothesis is in vivo exposure of rats to soman, as well as in vitro exposure of rat amygdala and hippocampal slices to soman. The selective GluR5KR antagonists LY293558 and UBP302 will be administered as a prophylactic treatment before exposure to soman, or as a therapy at different time points post-exposure. The efficacy of these antagonists against seizures will be correlated with their efficacy in preventing brain pathology, as well as pathophysiological alterations in the amygdala and hippocampus, studied in vitro after in vivo exposure to soman. The in vitro experiments will be performed in the amygdala and hippocampus because these brain regions play a pivotal role in the generation of brain seizures, including seizures induced by nerve agents. Furthermore, GluR5KRs play an important role in the regulation of neuronal excitability in the hippocampus, as well as in the amygdala, where we have found that strong activation of GluR5KRs inhibits evoked GABA release, and induces epileptiform activity. Because antagonists of GluR5KRs do not affect normal synaptic transmission, and the distribution of GluR5KRs in the brain is relatively limited, treatment with GluR5KR antagonists is likely to produce minimal or no side effects. Thus, the proposed investigations may result in the development of a novel, safe and effective prophylactic and/or therapeutic treatment against nerve agent-induced brain damage that will enhance our treatment response capabilities during an emergency.