Circadian and Aminergic Regulation of Orexin Neurons

描述(申请人提供)：神经肽增食欲素(也称为 )在睡眠/清醒行为的调节中起着核心作用 嗜睡症的病理学。发作性睡病患者难以维持 觉醒时常有侵入的REM睡眠样现象 保持清醒。这些个体的食欲素神经元数量通常减少。 和脑脊液中无法检测到的增食欲素浓度，以及小鼠和 携带食欲素或其受体基因突变的狗有一种表型 类似发作性睡病的。因为增食欲素似乎是正常维护所必需的 觉醒和快速眼动睡眠的抑制，关键是我们要确定 影响食欲素神经元活性的因素。 我们提出了一个食欲素神经元促进觉醒和抑制快速眼动的模型 通过激活胺能觉醒区域，进而激活食欲素神经元来睡眠 是由这些胺能区激活的。因此，增食欲素神经元应该是活跃的。 在清醒时，这种食欲素神经元的活动应该会进一步增加 胺能觉觉区的活动，从而促进和稳定 保持清醒。通过增加胺能活动，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， 应该减少觉醒，清醒的次数应该更短， 应该增加快速眼动睡眠的时间。觉醒和快速眼动睡眠紧密相关 受昼夜节律因素的调节，我们还提出食欲素神经元是 受昼夜节律因素的影响，从而有助于昼夜节律 睡眠/清醒行为。在老鼠身上，这种昼夜节律信号将有助于 在夜间阶段激活食欲素神经元，从而促进 清醒和抑制快速眼动。在没有食欲素的情况下，昼夜节律 对觉醒和快速眼动的影响应该消失。我们提议的实验将 测试这些胺能和昼夜节律影响的作用。 我们将首先确定清醒时增食欲素神经元是否活跃 以及这种激活是否依赖于昼夜节律。我们将使用 增食欲素神经元Fos蛋白和c-fos mRNA的表达 脑脊液中食欲素浓度作为食欲素神经元活性的指标 会将这些测量与睡眠/醒来行为相关联。然后我们将确定 食欲素是否通过以下途径调节昼夜节律对睡眠/觉醒结构的影响 在明/暗周期或持续黑暗中研究啮齿动物；这些 实验将使用两种食欲素缺乏的模型：食欲素基因敲除小鼠和食欲素缺失小鼠 与人类相似的获得性食欲素神经元丢失的转基因大鼠 嗜睡症。接下来，我们将确定增食欲素神经元是否受到 胺能觉醒区域和表达兴奋性胺受体。要测试 这些胺能传入的重要性，我们将研究对 食欲素基因敲除小鼠和缺乏食欲素神经元的转基因大鼠的苯丙胺。 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关键见解 应该为正常行为状态控制和 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.