Sohal G S, Boydston W R
J Cell Biol. 1982 Sep;94(3):540-8. doi: 10.1083/jcb.94.3.540.
The postulated role of the acetylcholine receptor in the formation of neuromuscular synapses during the course of embryonic development was investigated in the superior oblique muscle of white Peking duck embryos. The possibility that the number of receptors could be experimentally lowered by chronic injections of the anticholinesterase agent, neostigmine methylsulfate, was determined using 125I-alpha-bungarotoxin. The total number of acetylcholine receptors on incubation day 12, 2 d subsequent to the onset of treatment, was reducted 45% as compared to saline-treated controls. A similar reduction in total receptor content (49%) was also observed on day 19. Radioautographic preparations showed that clusters of acetylcholine receptors were rare and that the grain density of extrajunctional receptors was also reduced. Hence, chronic treatment with neostigimine during development was observed to exert an effect on both the number and distribution of receptors in the developing superior oblique muscle. These changes occurred in the absence of any apparent effect on muscle differentiation in general. Myoblasts and myotubes were present on day 14 and further differentiated into myofibers by day 18 in both neostigmine and saline-treated muscles. The cytology of the develop;ing muscle cells also appeared normal. This is in contradistinction to the striking morphological changes that take place in adult mammalian and avian muscle after anticholinesterase treatment. More significantly, the decreased total receptor content and sparsity of clusters had no apparent effect on the formation of developing neuromuscular junctions at the electron microscopic level. The frequency of neuromuscular junctions in neostigmine-treated muscles was similar to that of the controls. It is concluded that acetylcholine receptor clusters are not required for the events leading to the morphological formation of neuromuscular junctions during in vivo development.
在白北京鸭胚胎的上斜肌中，研究了乙酰胆碱受体在胚胎发育过程中神经肌肉突触形成中的假定作用。使用125I-α-银环蛇毒素确定了通过长期注射抗胆碱酯酶药物甲基硫酸新斯的明来实验性降低受体数量的可能性。在治疗开始后2天的孵化第12天，与盐水处理的对照组相比，乙酰胆碱受体的总数减少了45%。在第19天也观察到总受体含量有类似的降低（49%）。放射自显影片显示乙酰胆碱受体簇很少见，且接头外受体的颗粒密度也降低了。因此，观察到发育期间用新斯的明进行长期治疗对发育中的上斜肌中受体的数量和分布均有影响。这些变化在总体上对肌肉分化没有任何明显影响的情况下发生。在新斯的明和盐水处理的肌肉中，成肌细胞和肌管在第14天存在，并在第18天进一步分化为肌纤维。发育中的肌肉细胞的细胞学也看起来正常。这与成年哺乳动物和鸟类肌肉在抗胆碱酯酶治疗后发生的显著形态学变化形成对比。更重要的是，总受体含量的降低和簇的稀疏在电子显微镜水平上对发育中的神经肌肉接头的形成没有明显影响。新斯的明处理的肌肉中神经肌肉接头的频率与对照组相似。得出的结论是，在体内发育过程中，导致神经肌肉接头形态形成的事件不需要乙酰胆碱受体簇。
