Histological and functional characterization of sleep-active cortical neurons in rats

人们普遍认为，睡眠不仅受到昼夜节律过程的调节，即我们发现晚上比白天更容易入睡，而且还受到体内平衡过程的调节，即我们经历了长时间的疲劳，需要睡眠来恢复。然而，稳态睡眠调节的神经机制还不清楚。最近，一群皮质中间神经元被发现在睡眠期间活跃，但在清醒期间不活跃。这些神经元的活动与慢波活动（睡眠需要的标志物）相关，这一事实表明它们参与了稳态睡眠调节。它们可以很容易地通过其对神经元型一氧化氮合酶（nNOS）的免疫反应性来识别。在建议的项目中，我将阐明这些神经元是如何调节的，以及它们对睡眠稳态和睡眠的一般功能。为此，我将采取三种并行的办法。1)我将研究它们带有哪些受体。结合现有文献，我将重点关注乙酰胆碱和P物质的受体。2）为了更多地了解它们是如何调节的，我将测试它们是否被通过不同药理学机制诱导睡眠或麻醉的选定药理学物质激活。3)我将测试这些神经元的靶向刺激和消融对睡眠稳态和睡眠期间皮质活动的影响。刺激性和毒性化合物的特异性将通过与P物质缀合来实现，靶向神经元具有P物质的受体。我们将从拟议的实验中获得的见解将增强我们对睡眠如何调节的理解，并可能对睡眠障碍（如失眠和与其他神经或精神疾病相关的睡眠障碍）产生影响。

It is widely accepted that sleep is regulated not only by a circadian process, i.e. we find it easier to sleep at night than during daytime, but also by a homeostatic process, i.e. we experience long waking times as tiring and need sleep to recover. However, the neural mechanisms underlying homeostatic sleep regulation are not well understood. Recently, a population of cortical interneurons were discovered that are active during sleep but not during wake. The fact that the activity of these neurons is correlated to slow-wave-activity, a marker for sleep need, suggests that they are involved in homeostatic sleep regulation. They can easily be identified by their immunoreactivity for the enzyme neuronal nitric oxide synthase (nNOS). In the proposed project, I will elucidate how these neurons are modulated and what functions they have for sleep-homeostasis and sleep in general. To this end, I will follow three parallel approaches. 1) I will investigate which receptors they bear. Linking to existing literature, I will focus on receptors for acetylcholine and substance P. 2) To find out more about how they are regulated, I will test whether they are activated by select pharmacological substances that induce sleep or anesthesia by distinct pharmacological mechanisms. 3) I will test the effects of targeted stimulation and ablation of these neurons on sleep homeostasis and cortical activity during sleep. Specificity of stimulating and toxic compounds will be achieved by conjugation with substance P, for which the targeted neurons bear a receptor. The insights we will gain from the proposed experiments will enhance our understanding of how sleep is regulated and may have implications for sleep disorders such as insomnia and sleep disturbances associated with other neurological or psychiatric disorders.