Evaluation Of Novel Epilepsy Treatment Approaches

新型癫痫治疗方法的评价

• 批准号: 6842958
• 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
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6842958
• 关键词: anticonvulsants; brain disorder chemotherapy; disease /disorder proneness /risk; drug screening /evaluation; epilepsy; female; hormone therapy; human subject; human therapy evaluation; menstrual cycle; neurohormones; neuropharmacology; patient oriented research; physiologic stressor; steroid hormone; stress

The overall goal of this project is to investigate strategies for the drug treatment of epilepsy through pharmacological studies in animal models and clinical investigation in human subjects. Research was continued evaluating the role of neuroactive steroids in epilepsy and their possible uses in epilepsy therapy. Neuroactive steroids are endogenous steroid hormones (and their synthetic analogs) that rapidly alter the excitability of neurons by direct actions on membrane ion channels, including GABA-A and NMDA receptors. In prior reporting periods, we confirmed that the reproductive hormone progesterone has powerful anticonvulsant activity and we demonstrated that this results from its conversion to the neuroactive steroid allopregnanolone. We proposed that perimenstrual catamenial epilepsy, the increase in seizure frequency that many women with epilepsy experience near the time of menstruation (when progesterone levels fall) may, in part, be related to withdrawal of allopregnanolone. At present, there is no specific treatment for catamenial epilepsy. However, our studies with an animal model of catamenial epilepsy suggested that neurosteroid replacement could be useful. We have initiated clinical studies to validate the neurosteroid withdrawal hypothesis of catamenial epilepsy and we plan a clinical trial to evaluate the utility of neurosteroid replacement. In addition, we have investigated the role of neurosteroids in stress-induced alterations in seizure susceptibility, focusing specifically on tetrahydrodeoxycorticosterone (DOC), an adrenal steroid whose synthesis is enhanced during stress. Our results demonstrated that DOC is a mediator of the physiological effects of acute stress that could contribute to stress-induced changes in seizure susceptibility through its conversion to neurosteroids with modulatory actions on GABA-A receptors including THDOC and possibly also dihydrodeoxycorticosterone (DHDOC). Our results further suggest a role for neuroactive steroids as a treatment approach for stress-related seizures. In the present reporting period we developed an in vitro model to assess neurosteroid effects on seizure susceptibility in the absence of confounding factors such as differences in absorption, metabolism, and brain accessibility. The neurosteroids allopregnanolone and its 5beta-epimer pregnanolone, and pregnenolone sulfate (PS) were examined for effects on spontaneous epileptiform discharges induced by picrotoxin (PTX) and 4-aminopyridine (4-AP) in the CA3 region of the rat hippocampal slice. At a low concentration, allopregnanolone partially reduced PTX-induced bursting and at higher concentrations completely suppressed bursting. In contrast, pregnanolone failed to alter the discharge frequency. Allopregnanolone depressed 4-AP-induced bursting with similar potency as in the PTX model; pregnanolone was also partially effective. In the 4-AP model, allopregnanolone inhibited both the more frequent predominantly positive-going potentials as well as the less frequent negative-going potentials that may be generated by synchronous GABAergic interneuron firing. PS enhanced the PTX bursting frequency and, in the 4-AP model, increased the frequency of negative potentials but did not alter the frequency of positive potentials. By itself, PS did not induce bursting. The effects of the steroids in the in vitro seizure models largely correspond with their activities on GABA-A receptors; suppression of discharges may occur as a result of direct activation of these receptors rather than modulation of GABA-mediated synaptic responses. We conclude that PTX and 4-AP-induced bursting in the hippocampal slice are useful models for directly assessing neurosteroid effects on seizure susceptibility under conditions that eliminate the factor of brain bioavailability.

该项目的总体目标是通过动物模型的药理学研究和人类受试者的临床研究来研究癫痫药物治疗策略。研究仍在继续评估神经活性类固醇在癫痫中的作用及其在癫痫治疗中的可能用途。神经活性类固醇是内源性类固醇激素（及其合成类似物），可通过直接作用于膜离子通道（包括 GABA-A 和 NMDA 受体）来快速改变神经元的兴奋性。在之前的报告期中，我们证实生殖激素黄体酮具有强大的抗惊厥活性，并且我们证明这是由于其转化为神经活性类固醇四氢孕酮的结果。我们提出，月经期周围性经期癫痫，即许多癫痫女性在月经临近时（黄体酮水平下降时）癫痫发作频率增加，可能部分与四氢孕酮停药有关。目前，经期癫痫尚无特效治疗方法。然而，我们对经期癫痫动物模型的研究表明，神经类固醇替代可能有用。我们已经启动了临床研究来验证经期性癫痫的神经类固醇戒断假说，并计划进行一项临床试验来评估神经类固醇替代的效用。此外，我们还研究了神经类固醇在应激引起的癫痫易感性改变中的作用，特别关注四氢脱氧皮质酮（DOC），这是一种肾上腺类固醇，其合成在应激期间增强。我们的结果表明，DOC 是急性应激生理效应的介质，通过转化为对 GABA-A 受体（包括 THDOC 和可能的二氢脱氧皮质酮 (DHDOC)）具有调节作用的神经类固醇，可能导致应激引起的癫痫易感性变化。我们的结果进一步表明神经活性类固醇作为治疗压力相关癫痫发作的方法的作用。在本报告期内，我们开发了一种体外模型，在没有吸收、代谢和大脑可及性差异等混杂因素的情况下评估神经类固醇对癫痫易感性的影响。 检查神经类固醇四氢孕烯醇酮及其 5β-差向异构体孕烯醇酮和硫酸孕烯醇酮 (PS) 对印防己毒素 (PTX) 和 4-氨基吡啶 (4-AP) 在大鼠海马切片 CA3 区诱导的自发性癫痫样放电的影响。在低浓度下，四氢孕酮部分减少了 PTX 诱导的爆发，在较高浓度下则完全抑制了爆发。相反，孕烯醇酮未能改变放电频率。 Allopregnanolone 抑制 4-AP 诱导的爆发，其效力与 PTX 模型相似；孕烯醇酮也有部分效果。在 4-AP 模型中，四氢孕酮抑制了更频繁的主要正向电位以及不太频繁的负向电位，这些电位可能由同步 GABA 能中间神经元放电产生。 PS 增强了 PTX 爆发频率，并且在 4-AP 模型中，增加了负电位的频率，但没有改变正电位的频率。 PS 本身不会引起爆裂。类固醇在体外癫痫模型中的作用很大程度上与其对 GABA-A 受体的活性相对应；放电抑制可能是这些受体直接激活的结果，而不是 GABA 介导的突触反应调节的结果。我们得出的结论是，PTX 和 4-AP 诱导的海马切片爆发是在消除大脑生物利用度因素的条件下直接评估神经类固醇对癫痫易感性的影响的有用模型。