Moody-Corbett F, Cohen M W
J Neurosci. 1982 May;2(5):633-46. doi: 10.1523/JNEUROSCI.02-05-00633.1982.
Embryonic Xenopus muscle cells grown in culture develop discrete patches of high acetylcholine receptor (AChR) density. By following identified muscle cells after staining with fluorescent alpha-bungarotoxin, we have found that many of these AChR patches survive in a fixed position for several days. For AChR patches on the lower surface of the cell (the surface apposed to the culture dish), more than 60% of those which were followed beginning on day 2 survived for a further 4 days. The survival rate was greater when patches were followed from day 3 or later and was almost as high for AChR patches on the upper surface. New AChR patches also formed on all of the muscle cells. When muscle cells were cultured together with spinal cord cells, nerve-muscle contacts developed with a characteristic localization of AChRs along the path of contact. AChR patches did not form elsewhere on these contacted cells. Nerve-contacted muscle cells examined 2 to 3 days after adding spinal cord cells to established (2- to 5-day-old) muscle cultures also exhibited a marked reduction of AChR patches away from the site of contact. This reduction was not due to the nerve having contacted pre-existing AChR patches. Rather, the findings indicate that contact by an appropriate nerve inhibits the formation of AChR patches elsewhere on the contracted muscle cells and reduces the survival of pre-existing AChR patches. Nerve contact also inhibited the formation of cholinesterase (ChE) patches remote from the site of contact and appeared to cause some reduction in the survival of pre-existing ChE patches. Spontaneous twitching was not observed in these experiments, thereby indicating that the remote effects of nerve contact were not mediated by muscle action potentials or contraction. Such remote influences of the nerve may play a role in determining the pattern of innervation on individual muscle cells.
在培养中生长的非洲爪蟾胚胎肌肉细胞会形成乙酰胆碱受体（AChR）密度较高的离散斑块。在用荧光α-银环蛇毒素染色后追踪已鉴定的肌肉细胞，我们发现许多这些AChR斑块会在固定位置存活数天。对于细胞下表面（与培养皿相对的表面）的AChR斑块，从第2天开始追踪的斑块中，超过60%能再存活4天。从第3天或更晚开始追踪斑块时，存活率更高，而上表面的AChR斑块存活率也几乎一样高。所有肌肉细胞上也会形成新的AChR斑块。当肌肉细胞与脊髓细胞共同培养时，神经-肌肉接触会形成，且AChR沿着接触路径有特征性定位。在这些有接触的细胞上其他地方不会形成AChR斑块。在已建立的（2至5天大）肌肉培养物中加入脊髓细胞2至3天后检查有神经接触的肌肉细胞，远离接触部位的AChR斑块也显著减少。这种减少并非由于神经接触了预先存在的AChR斑块。相反，这些发现表明，适当的神经接触会抑制收缩的肌肉细胞上其他地方AChR斑块的形成，并降低预先存在的AChR斑块的存活率。神经接触还抑制了远离接触部位的胆碱酯酶（ChE）斑块的形成，并且似乎导致预先存在的ChE斑块的存活率有所降低。在这些实验中未观察到自发抽搐，从而表明神经接触的远程效应不是由肌肉动作电位或收缩介导的。神经的这种远程影响可能在决定单个肌肉细胞的神经支配模式中起作用。
