Circadian and Aminergic Regulation of Orexin Neurons

描述（由申请人提供）：神经肽食欲素（也称为 下丘脑分泌素）在睡眠/觉醒行为的调节中起中心作用， 嗜睡症的病理学嗜睡症患者很难维持 经常有快速眼动睡眠样现象侵入 清醒这些人的食欲素神经元数量通常减少 以及脑脊液中无法检测到的食欲素浓度， 食欲素或其受体基因发生突变的狗， 类似于嗜睡症。因为食欲素对于维持正常的 清醒和抑制快速眼动睡眠，这是至关重要的，我们确定 影响食欲素神经元活性的因素。 我们提出了一个模型，其中食欲素神经元促进觉醒和抑制快速眼动 睡眠通过激活胺能唤醒区域，反过来，食欲素神经元 被这些胺能区域激活。因此，食欲素神经元应该是活跃的， 这种食欲素神经元的活动应该会进一步增加 胺能唤醒区域的活动，从而促进和稳定 清醒通过增加胺能活性，食欲素神经元也应该 抑制快速眼动睡眠在没有这种积极反馈的情况下， 清醒应该减少，清醒的发作应该更短， 应该增加REM睡眠。清醒和快速眼动睡眠 调节昼夜因素，我们还提出，食欲素神经元是 受昼夜因素的影响，从而有助于昼夜调节 睡眠/觉醒行为。在大鼠中，这种昼夜节律信号将促进 在夜间激活食欲素神经元，从而促进 失眠和抑制快速眼动在缺乏食欲素的情况下， 对清醒和快速眼动的影响应该消失。我们提出的实验将 测试这些胺能和昼夜节律影响的作用。 我们将首先确定食欲素神经元在清醒时是否活跃 以及这种激活是否依赖于昼夜节律相位。我们将使用 Fos蛋白和c-fos mRNA在增食欲素神经元的表达以及 CSF中食欲素的浓度作为食欲素神经元活性的指标，我们 将这些测量与睡眠/觉醒行为相关联。然后我们将决定 食欲素是否介导昼夜节律对睡眠/觉醒结构的影响， 研究啮齿动物在光/暗周期或在恒定的黑暗;这些 实验将使用两种食欲素缺乏模型：食欲素敲除小鼠和 获得性食欲素神经元缺失的转基因大鼠 嗜睡症接下来，我们将确定食欲素神经元是否受 胺能唤醒区域并表达兴奋性胺受体。测试 这些胺能传入的重要性，我们将研究的反应， 苯丙胺的食欲素敲除小鼠和缺乏食欲素神经元的转基因大鼠。 通过研究这些昼夜节律和胺能对食欲素神经元的影响，我们 将获得对食欲素神经元正常功能的重要见解， 应该为正常行为状态控制提供新的视角， 嗜睡症的神经生物学

DESCRIPTION (provided by applicant): The neuropeptide orexin (also known as hypocretin) plays a central role in the regulation of sleep/wake behavior and the pathology of narcolepsy. People with narcolepsy have difficulty maintaining wakefulness and often have intrusions of REM sleep-like phenomena into wakefulness. These individuals often have decreased numbers of orexin neurons and undetectable concentrations of orexin in cerebrospinal fluid, and mice and dogs with mutations in the genes for orexin or its receptors have a phenotype resembling narcolepsy. As orexin appears necessary for the normal maintenance of wakefulness and suppression of REM sleep, it is critical that we identify the factors that influence the activity of orexin neurons. We propose a model in which orexin neurons promote wakefulness and inhibit REM sleep by activating aminergic arousal regions, and, in turn, the orexin neurons are activated by these aminergic regions. Thus, orexin neurons should be active during wakefulness, and this orexin neuron activity should further increase the activity of aminergic arousal regions, thereby promoting and stabilizing wakefulness. By increasing aminergic activity, orexin neurons also should inhibit REM sleep. In the absence of this positive feedback, the amount of wakefulness should be reduced, bouts of wakefulness should be shorter, and the amount of REM sleep should be increased. Wakefulness and REM sleep are tightly regulated by circadian factors, and we also propose that orexin neurons are influenced by circadian factors, thus contributing to the circadian regulation of sleep/wake behavior. In rats, this circadian signal would facilitate the activation of orexin neurons during the night phase, thereby promoting wakefulness and suppressing REM. In the absence of orexin, the circadian influence on wakefulness and REM should be lost. Our proposed experiments will test the roles of these aminergic and circadian influences. We will first determine whether orexin neurons are active during wakefulness and whether this activation is dependent upon circadian phase. We will use the expression of Fos protein and c-fos mRNA in orexin neurons as well as the concentration of orexin in CSF as indicators of orexin neuron activity, and we will correlate these measures with sleep/wake behavior. We then will determine whether orexin mediates circadian influences on sleep/wake architecture by studying rodents in a light/dark cycle or in constant darkness; these experiments will use two models of orexin deficiency: orexin knockout mice and transgenic rats with an acquired loss of orexin neurons similar to human narcolepsy. Next, we will determine whether orexin neurons are innervated by aminergic arousal regions and express excitatory amine receptors. To test the importance of these aminergic afferents, we will study the response to amphetamine of orexin knockout mice and transgenic rats lacking orexin neurons. By investigating these circadian and aminergic influences on orexin neurons, we will gain critical insights into the normal function of orexin neurons that should provide new perspectives on normal behavioral state control and the neurobiology of narcolepsy.