Neurosteroid regulation of cholinergic neurotransmission

神经类固醇对胆碱能神经传递的调节

• 批准号: RGPIN-2019-04989
• 负责人: Bailey, Craig
• 金额: $ 2.33万
• 依托单位: University of Guelph
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=737994
• 关键词: Neurosteroid; regulation; cholinergic; neurotransmission

Progesterone-based neurosteroids, including progesterone and its metabolites 5a-dihydroprogesterone and 3a,5a-tetrahydroprogesterone (allopregnanolone; ALLO), are produced within the brain and induce rapid non-genomic effects at specific targets within the brain. The influence of these progesterone neurosteroids on higher-order cognitive functions appears to follow an inverted U-shaped curve, for example, as relative low levels of ALLO are beneficial whereas relative high levels of ALLO are detrimental. The mechanisms by which ALLO may impair cognitive functions are not known. We have determined that ALLO rapidly inhibits the nicotinic acetylcholine receptor (nAChR) within the prefrontal cortex, which is important because cholinergic neurotransmission at this receptor in this brain region is critical for normal cognitive functioning. Mechanistic experiments suggest that this inhibition is mediated by a combination of (i) indirect action of ALLO stimulating the membrane progesterone receptor (mPR) complex, which initiates an intracellular signalling pathway that inhibits the nAChR, and (ii) direct allosteric action of ALLO at the nAChR. The specific mechanisms of these indirect and direct actions of ALLO to regulate nAChR function, and the effects of ALLO on nAChR-dependent cognitive functions, will be investigated in the proposed research. We will test the overarching hypothesis that progesterone neurosteroids regulate cholinergic neurotransmission via a combination of indirect and direct interactions with the nAChR. We will complete three primary objectives: (1) To determine the intracellular signalling pathway linking ALLO activation of the mPR complex with ALLO inhibition of the nAChR. We will use whole-cell electrophysiology and proteomic techniques to test the postulate that the mPR G protein-coupled signalling pathway modifies the phosphorylation of the nAChR to regulate its function. (2) To determine whether ALLO is a direct allosteric modulator of the nAChR. We will use radioligand binding assays in brain synaptosomes to test the postulate that ALLO is a positive allosteric modulator of the nAChR. (3) To determine the influence of ALLO on nAChR-dependent cognitive functions. We will test the postulate that ALLO inhibits the role of nAChRs to facilitate prefrontal cortex-dependent attention and cognitive flexibility. The proposed research will contribute to the fundamental understanding of neurosteroid action within the brain. This work is important because the brain is exposed to progesterone neurosteroids throughout an organism's life, but the neurobiological consequences of this exposure are not fully known. Discoveries made within this research program will address this outstanding question and provide a foundation from which to study the neurobiology of cognitive functions during states of varying progesterone neurosteroid levels, such as development, the menstrual/estrous cycle, pregnancy, and exposure to stressful environments.

基于孕酮的神经类固醇，包括孕酮及其代谢物5 α-二氢孕酮和3 α，5 α-四氢孕酮（别孕烯醇酮; ALLO），在脑内产生，并在脑内的特定靶点诱导快速的非基因组效应。这些孕酮神经类固醇对高阶认知功能的影响似乎遵循倒U形曲线，例如，相对低水平的ALLO是有益的，而相对高水平的ALLO是有害的。ALLO可能损害认知功能的机制尚不清楚。我们已经确定，ALLO迅速抑制前额叶皮层内的烟碱乙酰胆碱受体（nAChR），这是很重要的，因为在这个大脑区域的受体的胆碱能神经传递是正常的认知功能的关键。机制实验表明，这种抑制作用是由（i）ALLO刺激膜孕酮受体（mPR）复合物的间接作用介导的，这启动了抑制nAChR的细胞内信号传导途径，（ii）ALLO对nAChR的直接变构作用。这些间接和直接作用的ALLO调节nAChR功能的具体机制，以及ALLO对nAChR依赖的认知功能的影响，将在拟议的研究中进行调查。我们将测试的总体假设，孕激素神经甾体调节胆碱能神经传递通过与nAChR的间接和直接相互作用的组合。我们将完成三个主要目标：（1）确定连接mPR复合物的ALLO激活与nAChR的ALLO抑制的细胞内信号通路。我们将使用全细胞电生理学和蛋白质组学技术来测试的假设，mPR G蛋白偶联信号通路修改磷酸化的nAChR调节其功能。(2)确定ALLO是否是nAChR的直接变构调节剂。我们将在脑突触体中使用放射性配体结合测定来测试ALLO是nAChR的正变构调节剂的假设。(3)确定ALLO对nAChR依赖性认知功能的影响。我们将测试的假设，ALLO抑制nAChRs的作用，以促进前额叶皮层依赖的注意力和认知灵活性。拟议的研究将有助于对脑内神经类固醇作用的基本理解。这项工作很重要，因为大脑在生物体的整个生命中都暴露于孕酮神经类固醇，但这种暴露的神经生物学后果尚不完全清楚。本研究计划中的发现将解决这一悬而未决的问题，并提供一个基础，从中研究不同孕酮神经类固醇水平状态下认知功能的神经生物学，如发育，月经/发情周期，怀孕和暴露于压力环境。