Evaluation Of Novel Epilepsy Treatment Approaches

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探索药物治疗癫痫的策略。研究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），通过直接作用于膜离子通道，包括GABA-A和NMDA受体，迅速改变神经元的兴奋性。在之前的报道中，我们证实了生殖激素黄体酮具有强大的抗惊厥活性，我们证明了这是由于它转化为神经活性类固醇异孕酮。我们提出，在月经期（孕酮水平下降时），许多女性癫痫患者发作频率的增加可能与异孕酮的停药有关。目前，没有专门的治疗癫痫的方法。然而，我们对兔兔癫痫动物模型的研究表明，神经类固醇替代可能是有用的。我们已经启动了临床研究来验证双侧癫痫的神经类固醇停药假说，我们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诱导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，其合成在应激时增强。我们的研究结果表明，DOC是急性应激生理效应的中介，可能通过其转化为神经类固醇，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，从而促进应激诱导的癫痫易感性变化。我们的研究结果进一步表明，神经活性类固醇作为一种治疗压力相关癫痫发作的方法。在本报告期间，我们开发了一个体外模型来评估神经类固醇对癫痫易感性的影响，在没有诸如吸收、代谢和大脑可及性差异等混杂因素的情况下。

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.