Yamashita T, Ishii S, Oota I
Department of Orthopaedic Surgery, Sapporo Medical College, Japan.
Med Sci Sports Exerc. 1992 Jan;24(1):80-4.
The purpose of this study was to investigate how muscle stretching affects the activity of neuromuscular transmission. The magnitude of the post-tetanic potentiation (PTP) of miniature end-plate potential (m.e.p.p.) frequency was measured in the rat soleus muscle at resting length and stretched length. The parameters of the magnitude of PTP can be indicators of the kinetics of Ca2+ metabolism in the nerve terminal. One of the parameters, normalized initial post-tetanic frequency (f), was significantly increased by stretching muscle 10% (P less than 0.05) and 20% (P less than 0.01) of its resting length. Another parameter, the time constant of augmentation (tau a), was not significantly changed by muscle stretching. The time constant of potentiation (tau p) was significantly increased by 20% muscle stretching (P less than 0.05). These results indicate that the Ca2+ conductance, especially the voltage-dependent Ca2+ influx, of the nerve terminal could be increased by muscle stretching. Greater Ca2+ conductance of the nerve terminal would increase intracellular free Ca2+. Consequently, the probability of transmitter release would be increased, because Ca2+ is closely related to the activity of the transmitter release mechanism.
本研究的目的是探讨肌肉拉伸如何影响神经肌肉传递的活性。在大鼠比目鱼肌的静息长度和拉伸长度下，测量微小终板电位（m.e.p.p.）频率的强直后增强（PTP）幅度。PTP幅度的参数可作为神经末梢Ca2+代谢动力学的指标。其中一个参数，归一化初始强直后频率（f），在肌肉拉伸至静息长度的10%（P<0.05）和20%（P<0.01）时显著增加。另一个参数，增强时间常数（tau a），在肌肉拉伸时无显著变化。强直增强时间常数（tau p）在肌肉拉伸20%时显著增加（P<0.05）。这些结果表明，神经末梢的Ca2+电导，尤其是电压依赖性Ca2+内流，可因肌肉拉伸而增加。神经末梢更大的Ca2+电导会增加细胞内游离Ca2+。因此，递质释放的概率会增加，因为Ca2+与递质释放机制的活性密切相关。
