Basal forebrain hypothalamic networks supporting wakefulness

 描述(申请人提供)：基底前脑(BF)在维持清醒和激活脑电(EEG)方面起着至关重要的作用。然而，BF调节行为和EEG觉醒的机制和底物仍然知之甚少。对文献的回顾表明，绝大多数关于BF回路的研究都集中在生理和病理生理环境中的胆碱能BF系统，尽管事实是：1)胆碱能BF系统的损伤对脑电或行为觉醒的影响有限；2)BF至少还包含另外两类神经元-GABA能和谷氨酸能神经元-大致与胆碱能神经元混合。虽然人们已经意识到，其他BF神经递质系统可能在控制睡眠和觉醒方面与胆碱能神经元相互作用或并行工作，但GABA能BF神经元，特别是它们的网络输出对这些过程的贡献仍未得到很大程度的探索。我们最近发现，选择性激活BF GABA能神经元，而不是胆碱能或谷氨酸能神经元，意外地产生持续的觉醒。在这项建议中，我们试图确定BF GABA能神经元支持觉醒的体外(细胞)和体内(系统)机制和底物。我们假设，BF GABA能群对行为觉醒的影响是通过激活下丘脑外侧核，特别是通过去抑制增食欲素/下丘脑神经元来实现的。我们的模型直接来自我们的初步数据，预测BF GABA能神经元通过两个输出来调节觉醒：电路的一个分支抑制视前下丘脑的睡眠调节神经元，而第二个分支通过局部GABA能神经元解除对增食欲素神经元的抑制。我们进一步提出，这些网络对动态平衡睡眠压力很敏感，腺苷可能以一种部位和受体依赖的方式作用于这些不同的节点。因此，目前的建议试图首先在体外，然后在体内，确定促进觉醒所必需的BF GABA能输入的突触后靶点。为了验证我们的假设，我们将首先在特定的目标1和2中使用体外电路映射范式，该范例结合了基于光遗传和AAV的通道视紫红质2(ChR2)辅助电路映射(CRACM)和逆行微球，以确定这些假定的皮质下电路如何支持觉醒。然后我们将确定腺苷是如何调节这些回路的。最后，在特定的目标3中，我们是否会将cre激活的病毒载体系统离散地注射到BF，并将cre激活的毒素注入这些BF神经元的三个传出(突触后)靶点之一？这样做将使我们能够激活行为小鼠的BF GABA能神经元，在这些小鼠中，这种BF输入的特定突触神经元目标已经被破坏。反过来，这将揭示哪些BF GABA能传出输出是支持行为动物清醒所必需的。我们期待这项合作工作的结果能为支持清醒的大脑回路提供重要而新颖的见解。

 DESCRIPTION (provided by applicant): The basal forebrain (BF) is critically involved in maintaining wakefulness and an activated electroencephalogram (EEG). The mechanisms and substrates by which the BF regulates behavioral and EEG wake remains however poorly understood. A review of the literature reveals that the vast majority of studies on BF circuitry have focused on the cholinergic BF system in physiological and pathophysiological contexts, despite the facts that 1) lesions of the cholinergic BF system produce limited changes in EEG or behavioral wake; and 2) the BF also contains at least other two neuronal populations - GABAergic and glutamatergic neurons - that roughly intermingle with the cholinergic neurons. While it has been appreciated for some time that other BF neurotransmitter systems may interact or work in parallel with cholinergic neurons in the control of sleep and wake, the contribution of GABAergic BF neurons, and in particular their network output, to these processes remains largely unexplored. We recently found that selective activation of BF GABAergic, but not cholinergic or glutamatergic, neurons unexpectedly produces sustained wakefulness. In this proposal we seek to determine the in vitro (cellular) and in vivo (system) mechanisms and substrates by which BF GABAergic neurons support wakefulness. We hypothesize that the influence of BF GABAergic population in behavioral arousal is mediated by activation of the lateral hypothalamus and specifically through disinhibition of orexin/hypocretin neurons. Our model, which derives directly from our preliminary data, predicts that BF GABAergic neurons regulate wakefulness through two outputs: one branch of the circuit inhibits sleep regulatory neurons in the preoptic hypothalamus whereas the second branch disinhibits orexin neurons through local GABAergic neurons. We further propose that these networks are sensitive to homeostatic sleep pressure and that adenosine might act on these different nodes, in a site- and receptor- dependent manner. The current proposal thus seeks to identify, first in vitro and then in vivo, the postsynaptic targets of BF GABAergic input that are necessary for promoting wakefulness. To test our hypotheses we will first employ in Specific Aims 1 and 2 an in vitro circuit mapping paradigm that combines optogenetic- and AAV- based channelrhodopsin2 (ChR2)-assisted circuit mapping (CRACM) and retrograde microspheres to determine how these putative subcortical circuits support wakefulness. We will then determine how adenosine modulates these circuits. Finally in Specific Aim 3 will we place discrete injections of a cre-enabled viral vector system into the BF and a cre-enabled toxin into one of three efferent (post-synaptic) targets of these BF neurons? Doing so will allow us to activate BF GABAergic neurons in behaving mice in which specific synaptic neuronal targets of this BF input have been disrupted. In turn this will reveal which BF GABAergic efferent outputs are necessary for supporting wakefulness in behaving animals. We expect the results from this collaborative work to provide important and novel insights into the brain circuitry supporting wakefulness.