Etomidate (ET) is a widely used intravenous imidazole general anesthetic, which depresses the cerebellar neuronal activity by modulating various receptors activity and synaptic transmission. In this study, we investigated the effects of ET on the cerebellar climbing fiber-Purkinje cells (CF-PC) plasticity in vitro in mice using whole-cell recording technique and pharmacological methods. Our results demonstrated that CF tetanic stimulation produced a mGluR1-dependent long-term depression (LTD) of CF-PC excitatory postsynaptic currents (EPSCs), which was enhanced by bath application of ET (10 µM). Blockade of mGluR1 receptor with JNJ16259685, ET triggered the tetanic stimulation to induce a CF-PC LTD accompanied with an increase in paired-pulse ratio (PPR). The ET-triggered CF-PC LTD was abolished by extracellular administration of an N-methyl-(D)-aspartate (NMDA) receptor antagonist, D-APV, as well as by intracellular blockade of NMDA receptors activity with MK801. Furthermore, blocking cannabinoids 1 (CB1) receptor with AM251 or chelating intracellular Ca with BAPTA, ET failed to trigger the CF-PC LTD. Moreover, the ET-triggered CF-PC LTD was abolished by inhibition of protein kinase A (PKA), but not by inhibition of protein kinase C inhibiter. The present results suggest that ET acts on postsynaptic NMDA receptor resulting in an enhancement of the cerebellar CF-PC LTD through CB1 receptor/PKA cascade in vitro in mice. These results provide new evidence and possible mechanism for ET anesthesia to affect motor learning and motor coordination by regulating cerebellar CF-PC LTD.

中文翻译：

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依托咪酯在体外通过 CB1 受体/PKA 级联增强小鼠小脑 CF-PC 突触可塑性

依托咪酯（ET）是一种广泛使用的静脉咪唑全身麻醉剂，通过调节各种受体活性和突触传递来抑制小脑神经元活动。在本研究中，我们采用全细胞记录技术和药理学方法，研究了ET对体外小鼠小脑攀缘纤维浦肯野细胞（CF-PC）可塑性的影响。我们的结果表明，CF 强直性刺激产生了 CF-PC 兴奋性突触后电流 (EPSC) 的 mGluR1 依赖性长期抑制 (LTD)，通过 ET (10 µM) 浴应用增强了这种抑制。用 JNJ16259685、ET 阻断 mGluR1 受体触发强直刺激，诱导 CF-PC LTD，并伴随配对脉冲比 (PPR) 的增加。通过细胞外给予 N-甲基-(D)-天冬氨酸 (NMDA) 受体拮抗剂 D-APV 以及细胞内用 MK801 阻断 NMDA 受体活性，可以消除 ET 触发的 CF-PC LTD。此外，用 AM251 阻断大麻素 1 (CB1) 受体或用 BAPTA、ET 螯合细胞内 Ca，未能触发 CF-PC LTD。此外，ET 触发的 CF-PC LTD 可以通过抑制蛋白激酶 A (PKA) 来消除，但不能通过抑制蛋白激酶 C 抑制剂来消除。目前的结果表明，ET 作用于突触后 NMDA 受体，导致小鼠体外通过 CB1 受体/PKA 级联增强小脑 CF-PC LTD。这些结果为ET麻醉通过调节小脑CF-PC LTD影响运动学习和运动协调提供了新的证据和可能的机制。