Imamura Toshihiro, Wasilczuk Andrzej Z, Reitz Sarah L, Lian Jie, Imamura Miyoko, Keenan Brendan T, Shimizu Naoki, Pack Allan I, Kelz Max B
Chronobiology and Sleep Institute, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA; Division of Pulmonary and Sleep Medicine, Children's Hospital of Philadelphia, Philadelphia, PA, USA; Division of Sleep Medicine, Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA; Neuroscience of Unconsciousness and Reanimation Research Alliance, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA.
Neuroscience of Unconsciousness and Reanimation Research Alliance, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA; Department of Anesthesiology and Critical Care, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA.
Br J Anaesth. 2025 Jun;134(6):1696-1708. doi: 10.1016/j.bja.2025.02.035. Epub 2025 Apr 15.
It is hypothesised that general anaesthetics co-opt the neural circuits regulating endogenous sleep and wakefulness to produce hypnosis. To further probe this association, we focused on the GABAergic neurones of the parafacial zone (PZ), a brainstem site capable of promoting non-rapid eye movement sleep.
To determine whether PZ neurones are activated by a hypnotic dose of anaesthetics, c-Fos immunohistochemistry was performed. The behavioural and physiological contributions of PZ neurones to anaesthetic sensitivity were assessed in mice transfected with an adeno-associated virus (AAV)-driving expression of an mCherry fluorescent control or a caspase that irreversibly eliminates PZ neurones. EEG-defined sleep was measured in PZ-ablated and mCherry control mice, as was the homeostatic drive to sleep after sleep deprivation.
Consistent with anaesthetic-induced depolarisation, hypnotic doses of isoflurane significantly increased c-Fos expression three-fold in PZ neurones compared with oxygen-exposed mice. PZ-ablated mice developed significant and durable behavioural resistance to both isoflurane- and sevoflurane-induced hypnosis, with roughly 50% higher likelihood of intact righting than controls. PZ-ablated mice emerged from isoflurane significantly faster than mCherry controls with purposeful movements. The degree of anaesthetic resistance was inversely correlated with the number of surviving PZ neurones. Despite confirming that PZ ablation reduced the potency of two distinct volatile anaesthetics behaviourally, ablation did not alter the amount of endogenous sleep or wakefulness, nor did it affect the homeostatic sleep drive after sleep deprivation, and it did not produce EEG signatures of anaesthetic resistance during isoflurane exposure.
There was an unexpected dissociation in which destruction of up to 70-80% of PZ neurones was sufficient to alter anaesthetic susceptibility behaviourally without causing insomnia or altering sleep pressure. These findings suggest that PZ neurones are more critical to drug-induced hypnosis than to the regulation of natural sleep and arousal.
据推测，全身麻醉药会利用调节内源性睡眠和觉醒的神经回路来产生催眠作用。为了进一步探究这种关联，我们聚焦于面神经旁区（PZ）的γ-氨基丁酸能神经元，这是一个能够促进非快速眼动睡眠的脑干部位。
为了确定PZ神经元是否会被催眠剂量的麻醉药激活，我们进行了c-Fos免疫组织化学实验。在转染了腺相关病毒（AAV）驱动的mCherry荧光对照或不可逆消除PZ神经元的半胱天冬酶的小鼠中，评估了PZ神经元对麻醉敏感性在行为和生理上的影响。在PZ切除小鼠和mCherry对照小鼠中测量了脑电图定义的睡眠，以及睡眠剥夺后的睡眠稳态驱动力。
与麻醉诱导的去极化一致，与暴露于氧气的小鼠相比，催眠剂量的异氟烷显著使PZ神经元中的c-Fos表达增加了三倍。PZ切除的小鼠对异氟烷和七氟烷诱导的催眠产生了显著且持久的行为抗性，其恢复翻正反射的可能性比对照组高约50%。PZ切除的小鼠从异氟烷麻醉中苏醒的速度明显快于有自主运动的mCherry对照小鼠。麻醉抗性程度与存活的PZ神经元数量呈负相关。尽管证实PZ切除在行为上降低了两种不同挥发性麻醉药的效力，但切除并未改变内源性睡眠或觉醒的量，也未影响睡眠剥夺后的睡眠稳态驱动力，并且在异氟烷暴露期间未产生麻醉抗性的脑电图特征。
出现了一种意外的分离现象，即高达70%-80%的PZ神经元被破坏足以在行为上改变麻醉易感性，而不会导致失眠或改变睡眠压力。这些发现表明，PZ神经元对药物诱导的催眠比对自然睡眠和觉醒的调节更为关键。
