Muscle unloading imparts subtotal disuse on the neuromuscular system resulting in reduced performance capacity. This loss of function, at least in part, can be attributed to disruptions at the neuromuscular junction (NMJ). However, research has failed to document morphological remodeling of the NMJ with short term muscle unloading. Here, rather than quantifying cellular components of the NMJ, we examined subcellular active zone responses to 2 weeks of unloading in male Wistar rats. It was revealed that in the plantaris, but not the soleus muscles, unloading elicited significant (P ≤ 0.05) decrements in active zone staining as measured by Bassoon, and calcium channel expression. It was also discovered that unloading decreased the area of calcium channels staining relative to active zone areas of staining suggesting potential interference in the ability of calcium influx to trigger the release of vesicles docked at the active zone. Post-synaptic adaptations of the motor endplate were not evident. This presynaptic subcellular size reduction was not associated with atrophy of the underlying plantaris muscle fibers, although atrophy of the weight-bearing soleus fibers, where no subcellular remodeling was evident, was noted. These results suggest that the active zone is highly sensitive to alterations in neuromuscular activity, and that morphological adaptation of excitatory and contractile components of the NMJ can occur independently of each other.

中文翻译：

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神经肌肉接头的亚细胞成分对神经肌肉活动降低的敏感性

肌肉卸载会导致神经肌肉系统的次要废用，从而导致性能能力下降。这种功能丧失至少部分可归因于神经肌肉接头 (NMJ) 的中断。然而，研究未能记录短期肌肉卸载对 NMJ 的形态重塑。在这里，我们不是量化 NMJ 的细胞成分，而是检查了雄性 Wistar 大鼠对 2 周卸载的亚细胞活性区反应。结果表明，在跖肌中，但不是比目鱼肌，卸载引起了巴松管测量的活动区染色和钙通道表达的显着 (P ≤ 0.05) 减少。还发现，相对于染色的活性区面积，卸载减少了钙通道染色的面积，这表明钙内流触发停靠在活性区的囊泡释放的能力可能受到干扰。运动终板的突触后适应不明显。这种突触前亚细胞大小的减少与下方跖肌纤维的萎缩无关，尽管注意到负重比目鱼肌纤维的萎缩，其中没有明显的亚细胞重塑。这些结果表明，活动区对神经肌肉活动的变化高度敏感，并且 NMJ 的兴奋性和收缩性成分的形态适应可以相互独立地发生。