挥发性麻醉药通过抑制偶极诱发的突触前和突触后机制来降低兴奋性突触传递，其中包括抑制突触前细胞内钙离子浓度的去极化诱导的增加和阻断突触后的兴奋性谷氨酸受体。导致减少电刺激诱发的突触前细胞内钙离子浓度和钙依赖的胞吐是未知的。内质网中Ca2+通过ryanodine受体1 (RyR1)释放和被SERCA摄取对调控细胞内Ca2+是至关重要的，并且是麻醉作用的潜在靶点。肌浆网释放通道中的突变介导的可挥发性麻醉诱导的恶性高热(MH)，是一种可能致命的药物遗传学疾病，其特点是钙离子的非调节释放和肌肉高代谢。然而，MH突变对神经功能的影响尚不清楚。我们使用了新生后海马神经元的原代培养，通过在大鼠和小鼠野生型神经元以及携带RYR1 T4826I MH易感突变的小鼠突变神经元中使用基因光标的内质网靶向荧光Ca2+传感器，分析了挥发性麻醉引起的ER Ca2+动态变化。异氟醚独立于其对突触前细胞质Ca2+浓度的抑制作用，降低了神经元中ER Ca2+浓度的基线和电刺激诱发的增加。异氟醚和地氟醚，但不是丙泊酚，显著降低了小鼠RYR1 T4826I突变神经元中去极化诱导的ER Ca2+浓度的增加。同时RYR1 T4826I突变神经元还表现出明显增加的异氟醚诱导的突触前细胞质Ca2+浓度降低和突触小泡胞吐。这些发现将RyR1定位为异氟醚对突触前Ca2+处理效果的分子靶点。 意义陈述尽管它们在临床中起着重要的作用，但全身麻醉药的分子和细胞机制尚不完全了解。恶性高热是一种可能致命的药物遗传性疾病，其在对挥发性麻醉诱发过程中引起细胞内Ca2+处理的失调。尽管对恶性高热的研究主要集中在骨骼肌效应上，但对其神经元效应的了解则较少。我们确定了神经元内质网Ca2+调节作为挥发性麻醉作用的新靶点，以及作为恶性高热潜在靶点的重要性。尽管在动物模型中观察到麻醉通过抑制中枢神经系统电活动，但是我们的研究揭示了挥发性麻醉的基本突触前机制，对发展更选择性麻醉药物以及预防和治疗恶性高热具有重要意义。 版权所有 © 2023 Osman等

Volatile anesthetics reduce excitatory synaptic transmission by both presynaptic and postsynaptic mechanisms which include inhibition of depolarization-evoked increases in presynaptic Ca2+ concentration and blockade of postsynaptic excitatory glutamate receptors. The presynaptic sites of action leading to reduced electrically evoked increases in presynaptic Ca2+ concentration and Ca2+-dependent exocytosis are unknown. Endoplasmic reticulum (ER) of Ca2+ release via ryanodine receptor 1 (RyR1) and uptake by SERCA are essential for regulation intracellular Ca2+ and are potential targets for anesthetic action. Mutations in sarcoplasmic reticulum release channels mediate volatile anesthetic-induced malignant hyperthermia (MH), a potentially fatal pharmacogenetic condition characterized by unregulated Ca2+ release and muscle hypermetabolism. However, the impact of MH mutations on neuronal function are unknown. We used primary cultures of postnatal hippocampal neurons to analyze volatile anesthetic-induced changes in ER Ca2+ dynamics using a genetically encoded ER-targeted fluorescent Ca2+ sensor in both rat and mouse wild-type neurons and in mouse mutant neurons harboring the RYR1 T4826I MH-susceptibility mutation. The volatile anesthetic isoflurane reduced both baseline and electrical stimulation-evoked increases in ER Ca2+ concentration in neurons independent of its depression of presynaptic cytoplasmic Ca2+ concentrations. Isoflurane and sevoflurane, but not propofol, depressed depolarization-evoked increases in ER Ca2+ concentration significantly more in mouse RYR1 T4826I mutant neurons than in wild-type neurons. The RYR1 T4826I mutant neurons also showed markedly greater isoflurane-induced reductions in presynaptic cytosolic Ca2+ concentration and synaptic vesicle exocytosis. These findings implicate RyR1 as a molecular target for the effects of isoflurane on presynaptic Ca2+ handling.Significance StatementDespite their essential clinical roles, the molecular and cellular mechanisms of action of general anesthetics are not fully understood. Malignant hyperthermia is a potentially fatal pharmacogenetic disorder that leads to dysregulation of intracellular Ca2+ handling in response to triggering by volatile anesthetics. While research on malignant hyperthermia has focused on skeletal muscle effects, much less is known about its neuronal effects. We identify neuronal endoplasmic reticulum Ca2+ regulation as a novel target for volatile anesthetic action and as a potential target in malignant hyperthermia. While depression of CNS electrical activity in vivo by anesthesia has been observed in another model of malignant hyperthermia, our study reveals fundamental presynaptic mechanisms of volatile anesthetics with implications for the development of more selective anesthetics and for prevention and treatment of malignant hyperthermia.Copyright © 2023 Osman et al.