Endogenous neurosteroids constrain network activity and limit seizure susceptibility

项目摘要 神经活性类固醇的抗惊厥作用有广泛的临床前证据， 通过其作为GABAA受体的正变构调节剂（PAM）的作用介导 （GABAARs）.这些研究依赖于外源性神经活性类固醇的施用，尽管， 神经类固醇也可以在大脑中合成。然而，我们对它的功能知之甚少。 内源性神经类固醇，因为缺乏必要的工具来研究它们的功能。的限速 参与神经类固醇合成的酶，5α-还原酶1或2，在海马中表达， 他们的行动作为PAM在GABAAR，他们非常适合限制网络兴奋性在这一地区。到 研究内源性神经类固醇的功能，我们产生了新的小鼠模型（floxed Srd 5a 1- IRES-GFP和floxed Srd 5a 2-IRES-tdTomato），使得能够可视化和定量细胞中的变化。 这些相关酶的表达以及在细胞类型中敲除这些酶的能力-和 大脑区域特异性的方式。在这里，我们建议利用这些新的工具来测试假设， 内源性神经甾体抑制神经元兴奋性和5α-还原酶1和2表达缺陷 与癫痫易感性有关我们将确定5α-还原酶1和/或2 在慢性癫痫小鼠中表达发生改变（特异性目的1），如果5α-还原酶1和/或2 海马中的表达增加了网络兴奋性和急性癫痫发作易感性（具体目标2） 或增加慢性癫痫小鼠的癫痫发作频率（具体目标3）。

Project Summary There is extensive preclinical evidence for anticonvulsant effects of neuroactive steroids, which are thought to be mediated through their actions as positive allosteric modulators (PAMs) on GABAA receptors (GABAARs). These studies have relied on the administration of exogenous neuroactive steroids, although, neurosteroids can also be synthesized in the brain. However, we know very little about the function of endogenous neurosteroids due to the lack of tools necessary to investigate their function. The rate-limiting enzymes involved in neurosteroid synthesis, 5α-reductase 1 or 2, are expressed in the hippocampus and given their actions as PAMs at GABAARs, they are well-suited to constrain network excitability in this region. To investigate the function of endogenous neurosteroids, we generated novel mouse models (floxed Srd5a1- IRES-GFP and floxed Srd5a2-IRES-tdTomato) enabling visualization and quantification of changes in the expression of these enzymes associated as well as the ability to knockout these enzymes in a cell type- and brain region-specific manner. Here we propose to utilize these novel tools to test the hypothesis that endogenous neurosteroids constrain neuronal excitability and that deficits in 5α-reductase 1 and 2 expression in the hippocampus contributes to seizure susceptibility. We will determine whether 5α-reductase 1 and/or 2 expression is altered in chronically epileptic mice (Specific Aim 1) and if loss of 5α-reductase 1 and/or 2 expression in the hippocampus increases network excitability and acute seizure susceptibility (Specific Aim 2) or increases seizure frequency in chronically epileptic mice (Specific Aim 3).