DIFFERENTIAL ULTRASTRUCTURE OF SYNAPTIC TERMINALS ON VENTRAL LONGITUDINAL ABDOMINAL MUSCLES IN DROSOPHILA LARVAE
DIFFERENTIAL ULTRASTRUCTURE OF SYNAPTIC TERMINALS ON VENTRAL LONGITUDINAL ABDOMINAL MUSCLES IN DROSOPHILA LARVAE
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DOI：
10.1002/neu.480240803
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发表时间：
1993-08-01
期刊：
影响因子：
--
通讯作者：
WU, CF
中科院分区：
文献类型：
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作者：
ATWOOD, HL;GOVIND, CK;WU, CF
用Nomarski显微镜、共聚焦显微镜和电子显微镜研究了果蝇三龄幼虫腹纵腹肌（肌肉6、7、12和13）的神经支配，以确定突触末梢的超微结构特征。如先前的工作者所示，肌肉6和7在大多数腹部节中接收“I型”末端，其分布受限并且具有相对突出的周期性末端扩大（“终扣”）;而肌肉12和13另外具有“II型”末端，其分布更广泛并且具有较小的“终扣”。对第6和第7肌的I型神经支配的连续切片显示，两个具有独特末端的轴突对其起作用。一个轴突（称为轴突1）具有稍大的终扣，包含许多突触和突触前致密体（推定的释放递质的活性区）。这个轴突也有更多的终末内线粒体，以及在突触终扣周围或下方丰富的突触下网状结构。第二个轴突（Axon 2）提供了较小的终扣，每个终扣的突触和致密体较少，终末内线粒体较少，突触下网状结构不发达。两个轴突都含有清晰的突触囊泡，偶尔有大而致密的囊泡。轴突1向肌肉6和7提供大约800个突触，轴突2提供大约250个突触。在肌肉12和13中，发现了以透明突触囊泡为主的末梢，通常与肌肉6和7的I型末梢相似，沿着另一种类型的末梢，主要含有致密核心囊泡，具有小簇的透明突触囊泡。第二种类型的末梢最常见于第12号肌肉，可能对应于光学显微镜下看到的“II型”末梢的一个子集。I型末梢被认为产生在电生理记录中看到的“快”和“慢”连接电位，而II型末梢的生理作用目前尚不清楚。 (C)John Wiley & Sons，Inc.
The innervation of ventral longitudinal abdominal muscles (muscles 6, 7, 12, and 13) of third-instar Drosophila larvae was investigated with Nomarski, confocal, and electron microscopy to define the ultrastructural features of synapse-bearing terminals. As shown by previous workers, muscles 6 and 7 receive in most abdominal segments ''Type I'' endings, which are restricted in distribution and possess relatively prominent periodic terminal enlargements (''boutons''); whereas muscles 12 and 13 have in addition ''Type II'' terminals, which are more widely distributed and have smaller ''boutons.'' Serial sectioning of the Type I innervation of muscles 6 and 7 showed that two axons with distinctive endings contribute to it. One axon (termed Axon 1) has somewhat larger boutons, containing numerous synapses and presynaptic dense bodies (putative active zones for transmitter release). This axon also has more numerous intraterminal mitochondria, and a profuse subsynaptic reticulum around or under the synaptic boutons. The second axon (Axon 2) provides somewhat smaller boutons, with fewer synapses and dense bodies per bouton, fewer intraterminal mitochondria, and less-developed subsynaptic reticulum. Both axons contain clear synaptic vesicles, with occasional large dense vesicles. Approximately 800 synapses are provided by Axon 1 to muscles 6 and 7, and approximately 250 synapses are provided by Axon 2. In muscles 12 and 13, endings with predominantly clear synaptic vesicles, generally similar to the Type I endings of muscles 6 and 7, were found, along with another type of ending containing predominantly dense-cored vesicles, with small clusters of clear synaptic vesicles. This second type of ending was found most frequently in muscle 12, and probably corresponds to a subset of the ''Type II'' endings seen in the light microscope. Type I endings are thought to generate the 'fast' and 'slow' junctional potentials seen in electrophysiological recordings, whereas the physiological actions of Type II endings are presently not known. (C) 1993 John Wiley & Sons, Inc.