Department of Anesthesiology, General Hospital of Ning Xia Medical University, Yin Chuan, China.
Institute of Brain Sciences, YICHUANG Institute of Bio-Industry, Beijing, China.
J Neurochem. 2020 Jul;154(2):144-157. doi: 10.1111/jnc.14924. Epub 2020 Jan 7.
Local anesthetics can cause severe toxicity when absorbed systemically. Rapid intravenous administration of lipid emulsion (LE) is the standard of care for severe local anesthetic systemic toxicity which can cause cardiovascular and central nervous system (CNS) injury. The biological mechanism by which LE alleviates CNS toxicity remains unknown and understudied. Previous research has suggested that local anesthetics cause an imbalance of excitatory and inhibitory transmission in the brain. Therefore, this study aimed to observe the effect of LE on glutamate- and GABA-induced currents in CA1 pyramidal neurons after bupivacaine-induced CNS toxicity. We further characterized post-synaptic modifications in these cells to try to elucidate the mechanism by which LE mediates bupivacaine-induced CNS toxicity. Sprague-Dawley rats received intravenous bupivacaine (1 mg kg min ) in either normal saline or LE (or LE without bupivacaine) for 5 min. An acute brain slice preparation and a combination of whole-cell patch clamp techniques and whole-cell recordings were used to characterize action potential properties, miniature excitatory, and inhibitory post-synaptic currents, and post-synaptic modifications of excitatory and inhibitory transmission in CA1 hippocampal pyramidal neurons. The expression level of GABAA receptors were assessed with western blotting, whereas H&E and TUNEL staining were used to assess cytoarchitecture and apoptosis levels respectively. Bupivacaine treatment significantly increased the number of observed action potentials, whereas significantly decreasing rheobase, the first interspike interval (ISI), and hyperpolarization-activated cation currents (Ih) in CA1 pyramidal neurons. LE treatment significantly reduced the frequency of miniature inhibitory post-synaptic currents and enhanced GABA-induced paired pulse ratio with 50 ms interval stimulation in bupivacaine-treated rats. Regulation of GABAA levels is a promising mechanism by which LE may ameliorate CNS toxicity after systemic absorption of bupivacaine.
局部麻醉剂在被全身吸收时会引起严重的毒性。快速静脉注射脂肪乳剂（LE）是治疗严重局部麻醉剂全身毒性的标准方法，这种毒性会导致心血管和中枢神经系统（CNS）损伤。LE 缓解 CNS 毒性的生物学机制尚不清楚，也没有得到充分研究。先前的研究表明，局部麻醉剂会导致大脑中兴奋和抑制性传递失衡。因此，本研究旨在观察 LE 对布比卡因引起的 CNS 毒性后 CA1 锥体神经元中谷氨酸和 GABA 诱导电流的影响。我们进一步对这些细胞中的突触后修饰进行了特征描述，试图阐明 LE 介导布比卡因引起的 CNS 毒性的机制。Sprague-Dawley 大鼠静脉注射布比卡因（1mgkg min ），生理盐水或 LE（或无布比卡因的 LE）5min。急性脑切片制备和全细胞膜片钳技术与全细胞记录的结合，用于描述 CA1 海马锥体神经元的动作电位特性、微小兴奋性和抑制性突触后电流，以及兴奋性和抑制性传递的突触后修饰。用 Western blot 评估 GABAA 受体的表达水平，而 H&E 和 TUNEL 染色分别用于评估细胞结构和细胞凋亡水平。布比卡因处理显著增加了观察到的动作电位数量，而显著降低了 CA1 锥体神经元的阈强度、第一个峰间间隔（ISI）和超极化激活阳离子电流（Ih）。LE 处理显著降低了布比卡因处理大鼠的微小抑制性突触后电流频率，并增强了 GABA 诱导的 50ms 间隔刺激的成对脉冲比。调节 GABAA 水平是 LE 减轻全身吸收布比卡因后 CNS 毒性的一种有前途的机制。
