Department of Anesthesiology, Eye Ear Nose and Throat Hospital, Fudan University, Shanghai 200031, China.
Chin Med J (Engl). 2012 May;125(10):1747-52.
Muscles present different responses to muscle relaxants, a mechanism of importance in surgeries requiring facial nerve evoked electromyography under general anaesthesia. The non-depolarizing muscle relaxants have multiple reaction formats in the neuromuscular junction, in which pre-synaptic quantal release of acetylcholine was one of the important mechanisms. This study was to compare the pre-synaptic quantal release of acetylcholine from the neuromuscular junctions innervated by normal/damaged facial nerves and somatic nerve under the effect of rocuronium in rats in vitro.
Acute right-sided facial nerve injury was induced by nerve crush axotomies. Both sided facial nerve connected orbicularis oris strips and tibial nerve connected gastrocnemius strips were isolated to measure endplate potentials (EPP) and miniature endplate potentials (MEPP) using an intracellular microelectrode gauge under different rocuronium concentrations. Then, the pre-synaptic quantal releases of acetylcholine were calculated by the ratios of the EPPs and the MEPPs, and compared among the damaged or normal facial nerve innervated orbicularis oris and tibial nerve innervated gastrocnemius.
The EPP/MEPP ratios of the three neuromuscular junctions decreased in a dose dependent manner with the increase of the rocuronium concentration. With the concentrations of rocuronium being 5 µg/ml, 7.5 µg/ml and 10 µg/ml, the decrease of the EPP/MEPP ratio in the damaged facial nerve group was greater than that in the normal facial nerve group. The decrease in the somatic nerve group was the biggest, with significant differences.
Rocuronium presented different levels of inhibition on the pre-synaptic quantal release of acetylcholine in the three groups of neuromuscular junctions. The levels of the inhibition showed the following sequence: somatic nerve > damaged facial nerve > normal facial nerve. The difference may be one of the reasons causing the different sensitivities to rocuronium among the muscles innervated by the normal/injured facial nerves and the somatic nerve. The results may provide some information for the proper usage of muscle relaxants in surgeries requiring electromyographic monitoring for the pre-surgically impaired facial nerves.
肌肉对肌肉松弛剂有不同的反应，这是在全身麻醉下进行面神经诱发肌电图检查的手术中非常重要的机制。非去极化肌松剂在神经肌肉接头处有多种反应形式，其中突触前量子释放乙酰胆碱是重要机制之一。本研究旨在比较罗库溴铵作用下正常/损伤面神经和躯体神经支配的神经肌肉接头突触前量子释放乙酰胆碱的情况。
采用神经挤压切断法制作右侧面神经急性损伤模型。分离双侧面神经支配的口轮匝肌条和胫神经支配的腓肠肌条，用细胞内微电极测量不同罗库溴铵浓度下的终板电位（EPP）和微终板电位（MEPP）。然后，通过 EPP 与 MEPP 的比值计算乙酰胆碱的突触前量子释放，并比较损伤或正常面神经支配的口轮匝肌与胫神经支配的腓肠肌之间的差异。
随着罗库溴铵浓度的增加，三个神经肌肉接头的 EPP/MEPP 比值呈剂量依赖性下降。在罗库溴铵浓度为 5μg/ml、7.5μg/ml 和 10μg/ml 时，损伤面神经组的 EPP/MEPP 比值下降幅度大于正常面神经组。而躯体神经组的下降幅度最大，差异有统计学意义。
罗库溴铵对三组神经肌肉接头的乙酰胆碱突触前量子释放有不同程度的抑制作用。抑制程度的顺序为：躯体神经>损伤面神经>正常面神经。这种差异可能是正常/损伤面神经和躯体神经支配的肌肉对罗库溴铵敏感性不同的原因之一。该结果可为术前受损面神经手术中肌电图监测时肌松剂的合理使用提供一定信息。
