Schuetze S M, Vicini S
J Neurosci. 1984 Sep;4(9):2297-302. doi: 10.1523/JNEUROSCI.04-09-02297.1984.
The apparent mean channel open time (tau) of acetylcholine receptors (AChR) at skeletal muscle endplates decreases greater than 3-fold during development. In rat soleus muscles, the change occurs between postnatal days 8 and 18 as channels with long apparent open times (tau = 4.5 msec) disappear while channels with short apparent open times (tau = 1.5 msec) increase in number. We studied the role of innervation in this process by denervating neonatal soleus muscles prior to channel conversion. Tau at the denervated endplates was assayed at various times between days 8 and 18 by using fluctuation analysis. We found that early denervation blocked, or at least delayed, channel conversion. Unexpectedly, there was enhanced extrajunctional ACh sensitivity in the innervated muscles contralateral to the denervated ones. This observation allowed us to compare the apparent open times of junctional AChRs with those of extrajunctional AChRs 200 micron distant in the same innervated fibers. In developing muscles, tau at the extrajunctional sites decreased in parallel with tau at the endplates. Thus, neural regulation of AChR channel gating extends well beyond the endplate boundaries.
骨骼肌终板处乙酰胆碱受体（AChR）的表观平均通道开放时间（tau）在发育过程中减少超过3倍。在大鼠比目鱼肌中，这种变化发生在出生后第8天至第18天之间，表观开放时间长的通道（tau = 4.5毫秒）消失，而表观开放时间短的通道（tau = 1.5毫秒）数量增加。我们通过在通道转换前使新生比目鱼肌去神经支配，研究了神经支配在此过程中的作用。在第8天至第18天之间的不同时间，使用波动分析测定去神经支配终板处的tau。我们发现早期去神经支配阻断或至少延迟了通道转换。出乎意料的是，去神经支配侧对侧的受神经支配肌肉中的接头外乙酰胆碱敏感性增强。这一观察结果使我们能够比较同一受神经支配纤维中距接头200微米处的接头型AChR与接头外AChR的表观开放时间。在发育中的肌肉中，接头外位点的tau与终板处的tau平行下降。因此，AChR通道门控的神经调节远远超出终板边界。
