DEVELOPMENT OF MYOTOMAL NEUROMUSCULAR-JUNCTION IN XENOPUS-LAEVIS - ELECTROPHYSIOLOGICAL AND FINE-STRUCTURAL STUDY
DEVELOPMENT OF MYOTOMAL NEUROMUSCULAR-JUNCTION IN XENOPUS-LAEVIS - ELECTROPHYSIOLOGICAL AND FINE-STRUCTURAL STUDY
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DOI：
10.1016/0012-1606(77)90113-0
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发表时间：
1977-01-01
影响因子：
2.7
通讯作者：
COHEN, MW
中科院分区：
文献类型：
--
作者：
KULLBERG, RW;LENTZ, TL;COHEN, MW
通过电生理学和电镜研究了非洲爪蟾胚胎和蝌蚪肌节神经肌肉接头的正常发育。自发电位，即微型终板电位 (MEPP)，早在第 21 阶段就通过细胞内记录检测到，到第 24 阶段，在每个测试的胚胎中都观察到了自发电位。与后期的 MEPP 一样，它们被箭毒阻断，但不被河豚毒素阻断。终板电位 (EPP) 会受到河豚毒素的阻断，在 24 阶段的胚胎中通过电刺激脊髓而诱发，并早在 22 阶段就自发出现。MEPP 和 EPP 的持续时间最初相对较长。焦点外部记录显示，在发育过程中，持续时间缩短了 8 倍。早在第 21 阶段，神经突就从脊髓中出现，并与发育的肌肉细胞接触，但连接特化并不明显，即使在第 24 阶段胚胎中，囊泡也很少见。在接下来的 24 小时内，即第 25-36 阶段之间，囊泡数量增加，并定位于神经末梢的连接表面。基底层在裂隙和连接后脊中发育，并观察到密度。单个肌肉细胞也与多个神经过程接触。到了第 48-52 阶段，单个肌肉细胞上的接触较少，施万细胞突部分覆盖了神经末梢。在整个发育过程中，肌肉细胞之间都观察到间隙连接，但在后期阶段出现的频率较低。当它们到达肌肉细胞时，或此后不久，至少一些正在生长的神经过程可以释放递质，并且一些肌肉细胞对接触区域的乙酰胆碱足够敏感，以毫伏去极化做出反应。这些最早的功能性接触在形态上是未分化的。
The normal development of the myotomal neuromuscular junction in X. laevis embryos and tadpoles was investigated electrophysiologically and by EM. Spontaneous potentials, considered miniature end-plate potentials (MEPP), were detected by intracellular recording as early as stage 21 and by stage 24 they were observed in every embryo tested. Like MEPP at later stages they were blocked by curare but not by tetrodotoxin. End-plate potentials (EPP), subject to block by tetrodotoxin, were evoked by electrical stimulation of the spinal cord in embryos as young as stage 24 and occurred spontaneously as early as stage 22. The durations of MEPP and EPP were initially relatively long. Focal external recordings revealed an 8-fold decrease in duration during the course of development. Nerve processes emerged from the spinal cord and contacted developed muscle cells as early as stage 21, but junctional specializations were not apparent and vesicles were rare even in stage 24 embryos. During the next 24 h, between stages 25-36, vesicles increased in number and were localized toward the junctional surface of the nerve ending. Basement lamina developed in the cleft and postjunctional ridges and densities were observed. Individual muscle cells also were contacted by several nerve processes. By stages 48-52 there were fewer contacts on individual muscle cells and Schwann cell processes partially covered the nerve endings. Gap junctions were observed between the muscle cells throughout development but occurred less frequently at the later stages. By the time they reached the muscle cells, or very shortly thereafter, at least some of the growing nerve processes can release transmitter and some of the muscle cells were sufficiently sensitive to acetylcholine in the region of contact to respond with millivolt depolarizations. These earliest functional contacts were morphologically undifferentiated.