Department of Kinesiology & Health Sciences, College of William & Mary, Williamsburg, VA 23187, USA.
Program in Neuroscience, College of William & Mary, Williamsburg, VA 23187, USA.
Cells. 2023 Jan 18;12(3):361. doi: 10.3390/cells12030361.
The neuromuscular system accounts for a large portion (~40%) of whole body mass while enabling body movement, including physical work and exercise. At the core of this system is the neuromuscular junction (NMJ) which is the vital synapse transducing electrical impulses from the motor neurons to their post-synaptic myofibers. Recent findings suggest that subcellular features (active zones) of the NMJ are distinctly sensitive to changes in activity relative to cellular features (nerve terminal branches, vesicles, receptors) of the NMJ. In the present investigation, muscles with different recruitment patterns, functions, and myofiber type profiles (soleus, plantaris, extensor digitorum longus [EDL]) were studied to quantify both cellular and subcellular NMJ characteristics along with myofiber type profiles. Results indicated that, in general, dimensions of subcellular components of NMJs mirrored cellular NMJ features when examining inter-muscle NMJ architecture. Typically, it was noted that the NMJs of the soleus, with its most pronounced recruitment pattern, were larger ( < 0.05) than NMJs of less recruited muscles. Moreover, it was revealed that myofiber size did not dictate NMJ size as soleus muscles displayed the smallest fibers ( < 0.05) while the plantaris muscles exhibited the largest fibers. In total, these data show that activity determines the size of NMJs and that generally, size dimensions of cellular and subcellular components of the NMJ are matched, and that the size of NMJs and their underlying myofibers are uncoupled.
神经系统占人体总质量的很大一部分（约 40%），同时使身体能够运动，包括体力劳动和锻炼。该系统的核心是神经肌肉接点（NMJ），它是将电脉冲从运动神经元传递到其突触后肌纤维的重要突触。最近的研究结果表明，与 NMJ 的细胞特征（神经末梢分支、囊泡、受体）相比，NMJ 的亚细胞特征（活性区）对活动变化更为敏感。在本研究中，研究了具有不同募集模式、功能和肌纤维类型特征的肌肉（比目鱼肌、跖肌、趾长伸肌[EDL]），以定量研究 NMJ 的细胞和亚细胞特征以及肌纤维类型特征。结果表明，一般来说，当检查肌肉间 NMJ 结构时，NMJ 的亚细胞成分的尺寸反映了细胞 NMJ 特征。通常，比目鱼肌具有最明显的募集模式，其 NMJ 比募集较少的肌肉的 NMJ 更大（<0.05）。此外，研究结果表明肌纤维大小并不能决定 NMJ 的大小，因为比目鱼肌具有最小的纤维（<0.05），而跖肌具有最大的纤维。总的来说，这些数据表明，活动决定了 NMJ 的大小，并且通常情况下，NMJ 的细胞和亚细胞成分的尺寸是匹配的，并且 NMJ 的大小及其潜在的肌纤维是不相关的。
