NEURONAL BASIS UNDERLYING VOLATILE ANESTHETIC INDUCED HYPNOSIS

描述（由申请人提供）：尽管在解释麻醉药对单个离子通道的影响方面已经取得了很大进展，但确定麻醉药作用于其产生行为效应的神经基质仍然是一个挑战。在表征麻醉状态的关键组成部分中，我们重点关注挥发性麻醉诱导催眠，定义为对非有害刺激缺乏意识。了解麻醉药如何产生催眠已经不仅仅是神经科学的一个核心问题，因为过去十年的多个报告表明，现有的全身麻醉药每年可能会伤害4000万需要麻醉的美国患者中的一部分。一种假设的替代麻醉引起的无意识的方法是产生一种可逆的生理无意识状态，比如睡眠，在这种状态下，病人被锁在清醒状态之外。为了确定现有的挥发性麻醉药是否通过与内源性睡眠促进神经基质的相互作用而产生理想的催眠效果，本研究主要关注两个新兴的下丘脑靶点，它们已被证明能够影响唤醒状态：正中视前核MnPO和腹外侧视前核VLPO。这两个区域的去极化分别被认为是自然睡眠开始和维持的基础。我们的总体假设是挥发性麻醉药通过影响VLPO和MnPO功能导致催眠。在Aim 1中，我们将通过c-Fos免疫组织化学和切片电生理显示暴露于催眠剂量的挥发性麻醉剂激活VLPO和MnPO。我们将证实，暴露于非固定化剂不能激活小鼠和离体暴露的下丘脑切片中的VLPO和MnPO。在目的2中，我们将确定在自然睡眠期间激活的神经元子集是否与麻醉暴露激活的神经元子集相同。在Aim 3中，我们将通过翻正反射实验和处理后的脑电图熵来确定VLPO和MnPO的局部破坏、微量注射损害VLPO和MnPO放电的药物或VLPO光致超极化是否会导致麻醉催眠抵抗。最后，我们将确定光诱导的VLPO去极化是否会导致对麻醉催眠的超敏反应。累积起来，这些目标将决定挥发性麻醉诱导催眠是否是由VLPO和/或MnPO的招募引起的。

DESCRIPTION (provided by applicant): Although much progress has been made deciphering the effects of anesthetics upon individual ion channels, identification of the neural substrates upon which anesthetics act to produce their behavioral effects remains as a challenge. Of the key components that characterize the anesthetized state, we focus on volatile anesthetic-induced hypnosis, defined as a lack of awareness to non-noxious stimuli. Understanding how anesthetics produce hypnosis has become more than a central question for neuroscience, as multiple reports over the past decade suggest that existing general anesthetics may annually harm a subset of the 40 million US patients who require anesthesia. One hypothetical alternative to anesthetic-induced unconsciousness is to generate a state of reversible physiological unconsciousness, such as sleep, in which the patient is locked out of access to the state of wakefulness. To determine whether existing volatile anesthetics cause their desirable hypnotic effects through interactions with endogenous sleep-promoting neural substrates, this proposal focuses on two emerging hypothalamic targets with proven ability to affect arousal state: the median preoptic nucleus, MnPO, and ventrolateral preoptic nucleus, VLPO. Depolarization of these two regions is respectively thought to underlie onset and maintenance of natural sleep. Our global hypothesis is that volatile anesthetics cause hypnosis by affecting VLPO and MnPO function. In Aim 1, we will show that exposure to hypnotic doses of volatile anesthetics activates VLPO and MnPO using c-Fos immunohistochemistry and slice electrophysiology. We will establish that exposure to a non-immobilizer fails to activate VLPO and MnPO in mice and in hypothalamic slices exposed ex vivo. In Aim 2, we will determine if the subset of neurons activated during natural sleep is the same subset activated by anesthetic exposure. In Aim 3, we will determine whether local destruction of VLPO and MnPO, microinjection of drugs that impair firing of VLPO and MnPO, or light-induced hyperpolarization of VLPO cause resistance to anesthetic hypnosis as determined by righting reflex assays and processed EEG entropy. Finally, we will determine if light-induced depolarization of VLPO causes hypersensitivity to anesthetic hypnosis. Cumulatively, these aims will determine whether or not volatile anesthetic-induced hypnosis is caused by recruitment of VLPO and/or MnPO. PUBLIC HEALTH RELEVANCE: Inhaled volatile anesthetics are safely used in the vast majority of the nation's 40 million patients who annually require general anesthesia; however, these drugs may harm a subset of vulnerable patients. Surprisingly, mechanisms of anesthetic-induced unconsciousness remain poorly understood. This research will evaluate the effects of volatile anesthetics upon hypothalamic sleep-promoting neurons to test the hypothesis that volatile anesthetic-induced unconsciousness is caused by recruitment of endogenous sleep- promoting substrates.