NEURONAL BASIS UNDERLYING VOLATILE ANESTHETIC INDUCED HYPNOSIS

描述(由申请人提供)：尽管在破译麻醉剂对个体离子通道的影响方面已经取得了很大进展，但识别麻醉剂作用于其行为影响的神经基质仍然是一个挑战。在表征麻醉状态的关键成分中，我们重点关注挥发性麻醉剂诱导的催眠，定义为对非有害刺激缺乏意识。了解麻醉剂如何产生催眠作用已经不仅仅是神经科学的中心问题，因为过去十年的多份报告表明，现有的全麻药每年可能会伤害需要麻醉的美国4000万患者中的一部分。麻醉剂诱导的无意识的一个假设替代方案是产生一种可逆的生理无意识状态，例如睡眠，在这种状态下，患者被锁在进入清醒状态的门外。为了确定现有的挥发性麻醉药是否通过与内源性促进睡眠的神经底物相互作用而产生理想的催眠效果，本研究将重点放在两个已被证实有能力影响觉醒状态的新出现的下丘脑靶点：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，挥发性麻醉剂通过影响VLPO和MnPO功能而导致催眠。在目标1中，我们将利用c-Fos免疫组织化学和切片电生理学证明，暴露于催眠剂量的挥发性麻醉剂可以激活VLPO和MnPO。我们将确定暴露在非固定剂下不能激活小鼠和体外暴露的下丘脑片中的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暴露时激活的子集相同。在目标3中，我们将确定VLPO和MnPO的局部破坏，微量注射影响VLPO和MnPO放电的药物，或光诱导的VLPO超极化是否会导致麻醉催眠抵抗，这是通过翻正反射分析和脑电熵处理来确定的。最后，我们将确定光诱导的VLPO去极化是否会导致麻醉催眠的超敏反应。总而言之，这些目标将决定挥发性麻醉剂诱导的催眠是否由VLPO和/或MnPO的招募引起。

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.