Desaulniers Patrice, Lavoie Pierre-André, Gardiner Phillip F
Département de Kinésiologie, Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montréal, Québec H3C-3J7, Canada.
Muscle Nerve. 2002 Dec;26(6):810-6. doi: 10.1002/mus.10275.
Studies dealing with neuromuscular transmission efficacy typically employ continuous patterns of activation to demonstrate decrements in endplate potential (epp) amplitude. Recent evidence from rat diaphragm muscle has shown that including periods of quiescence to the stimulation protocol allows epp amplitude to recover between series of contractions. Whether similar recovery occurs in rat hindlimb muscle is unknown. In this study, we have measured declines in epp amplitude in rat soleus muscle during trains of stimulation evoked either continuously (10 s) or intermittently (400 ms repeated every second), using an in situ approach. As in diaphragm, we found that rest periods within the intermittent trains significantly improved neuromuscular transmission efficacy. However, unlike the diaphragm, epp amplitude recovery was incomplete even by the second train in the intermittent protocols, recovery being frequency-dependent and ranging from 40 to 50%. The results suggest that the kinetics of epp amplitude rundown and recovery may be muscle-specific, and should be considered when evaluating situations in which neuromuscular transmission efficacy may be altered.
研究神经肌肉传递效能的实验通常采用连续激活模式来证明终板电位（epp）幅度的衰减。最近来自大鼠膈肌的证据表明，在刺激方案中加入静息期可使epp幅度在一系列收缩之间恢复。尚不清楚大鼠后肢肌肉是否会出现类似的恢复情况。在本研究中，我们采用原位方法，测量了大鼠比目鱼肌在连续（10秒）或间歇（每秒重复400毫秒）刺激串期间epp幅度的下降情况。与膈肌一样，我们发现间歇刺激串中的休息期显著提高了神经肌肉传递效能。然而，与膈肌不同的是，即使在间歇方案中的第二串刺激时，epp幅度的恢复也不完全，恢复程度与频率相关，范围在40%至50%之间。结果表明，epp幅度衰减和恢复的动力学可能具有肌肉特异性，在评估神经肌肉传递效能可能改变的情况时应予以考虑。
