PHYSIOLOGICAL STUDIES OF NEUROSTEROID ANALOGS

神经活性类固醇及其苯并[e]吲烯(BI)三环类似物 是γ-氨基丁酸A的强效调节剂 受体-氯离子通道复合体(GABA A R)。处于低谷 浓度，这些药物显著增强GABA的作用 增加对亚EC 50 GABA浓度的响应，同时具有 对饱和GABA浓度的峰值响应几乎没有影响。在… 微摩尔浓度，类固醇类似物直接激活氯 在没有GABA的情况下的通道。这些影响可能会 有助于神经类固醇作为麻醉剂的临床作用， 抗惊厥药和抗焦虑药。其他类固醇，特别是那些 在3α位上被硫酸盐化，是一种负调节剂 GABAAR和改变变力性谷氨酸受体的功能 (Glur)。尽管类固醇是高度亲脂的，但这些制剂 据信作用于受体蛋白上的特定位置。在过去的时间里 在资助期间，一系列类固醇和BI类似物被研究以 研究结构-活性关系以增强GABAAR 功能。这些研究中包括了类固醇- BI介导的增强和GABAAR的直接门控发生 对映体选择性。这些研究为 类固醇作用于GABAAR上的特定位点而不是VIA的假设 对膜脂的影响。在本提案中，对 类固醇和BIS将通过解决三个具体目标而得到推广：1. 以获得有关类固醇和类固醇的结构要求的新信息 BI对培养大鼠海马区GABAAR和GLUR的影响 神经元。这些研究将与D·柯维合作进行。 并将进一步检测类固醇作用的对映体敏感性。2.至 了解神经类固醇介导的调节机制 海马GABA能和谷氨酸能突触传递。 这些研究将探讨类固醇和Bis对突触的影响 主要通过突触后动作和类固醇如何调节 使抑制性突触电流显著延长。3.至 检查导致类固醇作用异质性的因素。 GABAAR在培养的海马神经元中的作用 兴奋性和抑制性GABAAR亚基表达的差异 海马神经元。这些研究有可能提供 关于中枢神经系统中神经类固醇作用的新信息和更好的 了解类固醇诱导麻醉的相关机制。

Neuroactive steroids and their benz[e]indene (BI) tricyclic analogues are potent and effective modulators of the gamma-aminobutyric acid A receptor-chloride channel complex (GABA A R). At low concentration, these agents augment the actions of GABA, markedly increasing responses to sub-EC 50 GABA concentrations, while having little effect on peak responses to saturating GABA concentrations. At micromolar concentrations, steroid analogues directly activate chloride channels in the absence of GABA. These effects are likely to contribute to the clinical actions of neurosteroids as anesthetics, anticonvulsants and anxiolytics. Other steroids, particularly those that are sulfated at the 3alpha-position, are negative modulators of GABAAR and alter the function of inotropic glutamate receptors (GluR). Although steroids are highly lipophilic, these agents are believed to act at specific sites on receptor proteins. Over the past funding period, a series of steroid and BI analogues were studied to examine structure-activity relationships for enhancement of GABAAR function. Included in these studies was the demonstration that steroid- and BI-mediated potentiation and direct gating of GABAAR occur enantioselectively. These studies provide strong support for the hypothesis that steroids act at specific loci on GABAAR and not via effects on membrane lipids. In the present proposal, initial studies of steroids and Bis will be extended by addressing three specific aims: 1. To gain new information about structural requirements for steroid and BI effects on GABAAR and GluR in cultured rat hippocampal neurons. These studies will conducted in collaboration with D. Covey and will examine further the enantioselctivity of steroid actions. 2. To understand mechanisms involved in neurosteroid-mediated modulation of hippocampal GABAergic and glutamatergic synaptic transmission. These studies will address whether synaptic effects of steroids and Bis are mediated primarily via postsynaptic actions and how steroids produce marked prolongation of inhibitory synaptic currents. 3. To examine factors contributing to the heterogeneity of steroid effects on GABAAR in cultured hippocampal neurons with specific emphasis on differences in GABAAR subunits expressed in excitatory and inhibitory hippocampal neurons. These studies have the potential to provide new information about neurosteroid effects in the CNS and a better understanding of mechanisms involved in steroid-induced anesthesia.