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: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=746249
• 关键词: Neurosteroid; regulation; cholinergic; neurotransmission; 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.

孕酮基于孕酮及其代谢产物5a-二羟基丙酮和3A，5A四氢丙酮（Allopregnanolone; allo）在大脑内产生，并诱导大脑内特定靶标的非基因组效应的快速非基因组作用。这些孕酮神经固醇对高阶认知功能的影响似乎遵循倒下的U形曲线，因为相对低水平的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），这很重要，因为该大脑区域的该受体的胆碱能神经传递对于正常的认知功能至关重要。机械实验表明，这种抑制是通过刺激膜孕激素受体（MPR）复合物的（i）间接作用的组合来介导的，膜孕酮受体（MPR）复合物启动了抑制NACHR的细胞内信号传导途径，以及（II）Allo Allo在NACHR处的直接异质作用。在拟议的研究中将研究这些间接和直接作用在调节NACHR功能以及Allo对NACHR依赖性认知功能的影响的特定机制。我们将通过间接和与NACHR的直接相互作用的结合来检验孕酮神经固醇调节胆碱能神经传递的总体假设。我们将完成三个主要目标：（1）确定将MPR复合物的Allo激活与NACHR抑制相关的细胞内信号通路。我们将使用全细胞电生理学和蛋白质组学技术来测试MPR G蛋白偶联信号通路的假设修饰NACHR的磷酸化以调节其功能。 （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结合测定法来测试Allo是NACHR的阳性变构调节剂的假设。 （3）确定Allo对NACHR依赖性认知功能的影响。我们将测试以下假设，即Allo抑制NACHR的作用，以促进前额叶皮质依赖的注意力和认知灵活性。拟议的研究将有助于对大脑内神经类动作的基本理解。这项工作很重要，因为大脑在整个生物体的生命中都暴露于孕激素神经类固醇，但是这种暴露的神经生物学后果尚不清楚。该研究计划中的发现将解决这个杰出问题，并为在不同的孕酮神经固醇水平的状态（例如发育，月经/偏变周期，妊娠，妊娠和暴露于压力环境暴露的状态）中提供了一个基础来研究认知功能的神经生物学。