Anesthesia and Sleep: Mechanisms of Generating Two Similar Yet Distinct Unconscious States in the Medulla

虽然麻醉剂诱导无意识的确切机制仍然未知，但 有证据表明，一些麻醉剂激活调节睡眠的神经回路，抑制促进睡眠的神经系统。 醒来尽管全身麻醉和睡眠都激活了一个看似相似的子集，如果不是相同的， 神经元，这两种无意识状态之间存在明显差异，包括唤醒程度 阈值变化和状态转换的时间尺度。这些相关的神经机制，但 我们对不同的无意识状态知之甚少。 面旁区（parasfacial zone，PZ）最近被确定为促进非快速眼动（non-REM）睡眠的区域。 PZ中的GABA能神经元（PZ-GABA）在非REM睡眠期间活跃。我的初步 数据表明，在异氟烷暴露期间，PZ-GABA也是活跃的， 对异氟烷的耐受性。结果还表明，PZ内的非GABA能神经元也参与其中 异氟醚诱导的催眠首要的问题是，神经回路如何驱动不同的状态 非REM睡眠和异氟烷麻醉的收敛和分歧，首先检查PZ-GABA神经元， 然后扩展到PZ以外，以考虑髓质中的所有细胞类型。据推测，这些不同的 内源性和药物诱导的无意识状态是由部分重叠的共享回路产生的， 关键状态的差异来自不同的细胞激活模式。 我们将在本提案中解决的三个关键问题是：1）急性可逆激活/抑制是否 的PZ睡眠促进神经元改变麻醉敏感性？2)PZ的细胞组成是什么， 在每一种无意识状态下，哪些细胞被激活？3）什么是重叠和不同的元素 在异氟烷暴露期间参与的脑干神经回路与非REM期间参与的脑干神经回路之间 睡觉？这些问题将通过麻醉和睡眠表型分析，单细胞水平， 通过单核RNA测序，然后通过多重原位杂交进行转录组学分析，以及侧链- 通过在活跃人群中靶向扩增（TRAP）对活跃神经元的集合进行并排比较。 拟议的项目将揭示脑干神经回路的潜在机制，包括 PZ，调解这两种不同的无意识状态。了解大脑如何控制 无意识对于临床实践至关重要。它可以导致更有效和更安全的催眠药和新的潜力 镇静催眠麻醉剂，有一天可能用于睡眠障碍，如失眠和嗜睡症。

Although the exact mechanisms by which anesthetics induce unconsciousness remain unknown, there is evidence that some anesthetics activate neural circuits regulating sleep and inhibit neural systems promoting waking. Despite general anesthesia and sleep both activating a subset of seemingly similar, if not identical, neurons, there are clear differences between the two unconscious states, including the degree of arousal threshold changes and the timescale of state transition. The neural mechanisms underlying these related, yet distinct unconscious states are poorly understood. The parafacial zone (PZ) has recently been identified as a non-rapid-eye-movement (non-REM) sleep-promoting region; specifically, GABAergic neurons in the PZ (PZ-GABA) are active during non-REM sleep. My preliminary data demonstrate that PZ-GABA are also active during isoflurane exposure, and ablation of PZ-GABA increases resistance to isoflurane. The results also suggest that non-GABAergic neurons within the PZ are also involved in isoflurane-induced hypnosis. The overarching question asks how the neural circuitry driving distinct states of non-REM sleep and isoflurane anesthesia converge and diverge by first examining in PZ-GABA neurons, and then expanding beyond the PZ to consider all cell types in the medulla. It is hypothesized that these distinct endogenous and drug-induced unconscious states are generated by partially overlapping shared circuits but that key state differences arise from distinctive cellular activation patterns. The three key questions we will address during this proposal are: 1) Does acute reversible activation/inhibition of the PZ sleep-promoting neurons alter anesthetic sensitivity? 2) What is the cellular makeup of the PZ, and which cells are activated during each unconscious state? and 3) What are the overlapping and different elements between the brainstem neural circuits engaged during isoflurane exposure and those engaged during non-REM sleep? These questions will be addressed by anesthetic and sleep phenotyping assays, the single-cell level transcriptomic analysis by single nucleus RNA sequencing followed by multiplex in situ hybridization, and side- by-side comparison of ensembles of active neurons by Targeted Recombination in Active Population (TRAP). The proposed projects will uncover the underlying mechanism of how the brainstem neural circuits, including PZ, mediate these two different unconscious states. Understanding how the brain controls states of unconsciousness is vital for clinical practice. It can lead to more effective and safer somnogens and new potential sedative hypnotic anesthetics that may one day be used for sleep disorders such as insomnia and narcolepsy.