NUMBER OF ACETYLCHOLINE MOLECULES IN A QUANTUM AND INTERACTION BETWEEN QUANTA AT SUBSYNAPTIC MEMBRANE OF SKELETAL NEUROMUSCULAR SYNAPSE
NUMBER OF ACETYLCHOLINE MOLECULES IN A QUANTUM AND INTERACTION BETWEEN QUANTA AT SUBSYNAPTIC MEMBRANE OF SKELETAL NEUROMUSCULAR SYNAPSE
复制标题
DOI：
10.1101/sqb.1976.040.01.019
复制
发表时间：
1975-01-01
期刊：
影响因子：
--
通讯作者：
YOSHIKAMI, D
中科院分区：
文献类型：
--
作者：
HARTZELL, HC;KUFFLER, SW;YOSHIKAMI, D
对我们的研究有很大帮助的准备是丝带蛇和束带蛇（Thamnophis sp.）的骨骼神经肌肉突触。蛇的体壁含有薄的肌肉，其中突触排列的细节在孤立的活体标本中很容易看到。每一条肌颤纤维在终板上单独受神经支配，终板的形态特征类似于哺乳动物的终板（图1）。图1A示出了用碘化锌和锇固定和染色的肌肉。神经终止于肌肉纤维表面的一簇密集的被染成黑色的终扣。终板中通常有50-70个终扣，终板的平均直径约为40-60 μ m。图1B示出了用Nomarski光学器件观察的活体准备中的相应端板。终扣清晰可见，其大小、形状和分布与染色标本中所见相同。钮扣位于肌肉纤维表面凹陷的凹坑中。通过其中一个终扣的电子显微镜横截面（图1C）显示了化学突触的超微结构特征。图1C的插图是相同放大倍数的电子显微照片，显示了用于离子电渗施用ACh的移液管。移液管尖端的外径约为100 nm，其内孔估计约为50 nm，顺便说一句，这与突触囊泡的尺寸相当。这种吸管可以放在突触终扣的边缘，这样ACh就可以直接释放到突触下膜上。蛇神经肌肉突触的另一个优点是它的突触下膜可以相对容易地暴露于乙酰胆碱吸管的直接探测。将胶原酶添加到浴液中或仅添加到几个选定的终板中，使终末周围的结缔组织松弛（图2A）。运动神经及其终末终扣可以从肌肉中取出。这就留下了空的突触坑，里面衬着突触下膜（图2B）。肌肉纤维本身保持完整，并保持其对ACh的敏感性。
The preparation which has greatly helped our study is the skeletal neuromuscular synapse of the ribbon and garter snakes (Thamnophis sp.). The body wall of the snake contains thin muscles in which details of the synaptic arrangement are easily seen in the isolated, living preparation. Each twitch fiber is singly innervated at an end plate whose morphological features resemble those of mammals (Fig. 1). Figure 1A illustrates a muscle fixed and stained with zinc iodide and osmium. The nerve terminates on the muscle-fiber surface in a dense cluster of boutons that are stained black. There are usually about 50-70 such boutons in the end plate, which has an average diameter of about 40-60~ m. Figure 1B shows a corresponding end plate in a living preparation viewed with Nomarski optics. The boutons are clearly visible, and their sizes, shapes and distribution are the same as those seen in the stained preparation. Boutons rest in craters sunk in the surface of the muscle fiber. An electron microscopic cross section through one of the boutons (Fig. 1C) shows the ultrastructural features characteristic of chemical synapses. The inset of Figure 1C is an electron micrograph at the same magnification showing a pipette used to apply ACh iontophoretically. The outer diameter of the pipette tip is about 100 nm, and its inner bore is estimated to be about 50 nm, which, incidentally, is comparable to the dimensions of a synaptic vesicle. Such a pipette can be placed at the edge of a synaptic bouton so that ACh can be released from it directly onto the subsynaptic membrane. An additional advantage of the snake neuromuscular synapse is the relative ease with which its subsynaptic membrane can be exposed to direct probing by the ACh pipette. Addition of the enzyme collagenase, either to the bathing fluid or to just a few selected end plates, loosens the connective tissue around the terminal (Fig. 2A). The motor nerve, together with its terminal boutons, can then be removed from the muscle. This leaves behind the empty synaptic craters, lined with the subsynaptic membrane (Fig. 2B). The muscle fiber itself remains intact and retains its sensitivity to ACh.