Dan Y, Poo M M
Department of Biological Sciences, Columbia University, New York, New York 10027.
Nature. 1992 Oct 22;359(6397):733-6. doi: 10.1038/359733a0.
It is well known that transmitter secretion requires specialized secretory organelles, the synaptic vesicles, for the packaging, storage and exocytotic release of the transmitter. Here we report that when acetylcholine (ACh) is loaded into an isolated Xenopus myocyte, there is spontaneous quantal release of ACh from the myocyte which results in activation of its own surface ACh channels and the appearance of membrane currents resembling miniature endplate currents. This myocyte secretion probably reflects Ca(2+)-regulated exocytosis of ACh-filled cytoplasmic compartments. Furthermore, step depolarization of the myocyte membrane triggers evoked ACh release from the myocyte with a weak excitation-secretion coupling. These findings suggest that quantal transmitter secretion does not require secretory pathways unique to neurons and that the essence of presynaptic differentiation may reside in the provision of transmitter supply and modification of the preexisting secretion pathway.
众所周知，递质分泌需要专门的分泌细胞器——突触小泡，用于递质的包装、储存和胞吐释放。在此我们报告，当将乙酰胆碱（ACh）加载到分离的非洲爪蟾肌细胞中时，肌细胞会自发地以量子化方式释放ACh，这导致其自身表面的ACh通道被激活，并出现类似于微小终板电流的膜电流。这种肌细胞分泌可能反映了Ca(2+)调节的充满ACh的细胞质区室的胞吐作用。此外，肌细胞膜的阶跃去极化以较弱的兴奋-分泌偶联触发肌细胞诱发的ACh释放。这些发现表明，量子化递质分泌并不需要神经元特有的分泌途径，并且突触前分化的本质可能在于递质供应的提供以及对已有分泌途径的修饰。
