NEURONAL BASIS UNDERLYING VOLATILE ANESTHETIC INDUCED HYPNOSIS

描述（由申请人提供）：尽管在解释麻醉剂对单个离子通道的影响方面取得了很大进展，但麻醉剂作用于其上以产生其行为效应的神经底物的鉴定仍然是一个挑战。在麻醉状态的主要特征中，我们关注挥发性麻醉剂诱导的催眠，定义为对非伤害性刺激缺乏意识。了解麻醉剂如何产生催眠已经成为神经科学的一个中心问题，因为过去十年的多份报告表明，现有的全身麻醉剂每年可能会伤害4000万需要麻醉的美国患者中的一部分。麻醉诱导的无意识的一种假设的替代方案是产生可逆的生理无意识状态，例如睡眠，其中患者被锁定无法进入清醒状态。为了确定现有的挥发性麻醉剂是否通过与内源性促进睡眠的神经底物的相互作用而引起其理想的催眠作用，本建议集中在两个新兴的下丘脑靶点上，这些靶点已被证明具有影响唤醒状态的能力：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的开始和维持的基础。我们的总体假设是，挥发性麻醉剂通过影响VLPO和MnPO功能引起催眠。在目标1中，我们将使用c-Fos免疫组织化学和切片电生理学显示，暴露于催眠剂量的挥发性麻醉药激活VLPO和MnPO。我们将确定暴露于非固定剂不能激活小鼠和离体暴露的下丘脑切片中的VLPO和MnPO。在目标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剂暴露激活的神经元子集相同。在目标3中，我们将确定是否局部破坏VLPO和MnPO，微量注射的药物，损害放电的VLPO和MnPO，或光诱导超极化VLPO引起麻醉催眠的阻力，通过翻正反射测定和处理EEG熵。最后，我们将确定光诱导的VLPO去极化是否会引起麻醉催眠的超敏反应。累积起来，这些目标将确定挥发性麻醉剂诱导的催眠是否由VLPO和/或MnPO的募集引起。 公共卫生相关性：吸入性挥发性麻醉剂安全地用于每年需要全身麻醉的全国4000万患者中的绝大多数;然而，这些药物可能会伤害一部分脆弱的患者。令人惊讶的是，麻醉诱导的无意识的机制仍然知之甚少。本研究将评估挥发性麻醉药对下丘脑促睡眠神经元的影响，以验证挥发性麻醉药诱导的无意识是由内源性促睡眠底物的募集引起的假设。

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.