DE ROBERTIS E, FRANCHI C M
J Biophys Biochem Cytol. 1956 May 25;2(3):307-18. doi: 10.1083/jcb.2.3.307.
The submicroscopic organization of the rod and cone synapses of the albino rabbit has been investigated with the use of the electron microscope. The most common rod synapse consists of an enlarged expansion of the rod fiber (the so called spherule) into which the dendritic postsynaptic fiber of the bipolar cell penetrates and digitates. The membrane surrounding the terminal consists of a double layer, the external of which is interpreted as belonging to the intervening glial cells. The synaptic membrane has a pre- and a postsynaptic layer with a total thickness of 180 to 300 A. The presynaptic layer is frequently denser and is intimately associated with the adjacent synaptic vesicles. The synaptic membrane shows processes constituted by foldings of the presynaptic layer. The entire spherule is filled with synaptic vesicles varying in diameter between 200 and 650 A with a mean of 386 A. In addition, the spherule contains a few large vacuoles near the rod fiber, interpreted as endoplasmic reticulum, and a matrix in which with high resolution a fine filamentous material can be observed. The postsynaptic fiber is homogeneous and usually does not show synaptic vesicles. In animals maintained in complete darkness for 24 hours vesicles appear to accumulate near the synaptic membrane and its processes. After 9 days there is a sharp decrease in size of the synaptic vesicles. A special rod synapse in which the dendritic postsynaptic expansion penetrates directly into the rod cell body has been identified. In line with Cajal's classification this type of synapse could be considered as a somatodendritic one. The cone synapse has a much larger terminal with a more complex relationship with the postsynaptic fiber. However, the same components recognized in the rod synapse can be observed. In animals maintained for 9 days in complete darkness there is also a considerable diminution in size of the synaptic vesicles.
利用电子显微镜对白化兔视杆和视锥突触的亚微观结构进行了研究。最常见的视杆突触由视杆纤维的膨大（即所谓的小球）组成，双极细胞的树突状突触后纤维穿入其中并分支。围绕终末的膜由双层组成，外层被解释为属于中间的神经胶质细胞。突触膜有一个突触前层和一个突触后层，总厚度为180至300埃。突触前层通常较致密，与相邻的突触小泡紧密相连。突触膜显示出由突触前层折叠构成的突起。整个小球充满了直径在200至650埃之间、平均为386埃的突触小泡。此外，小球在视杆纤维附近含有一些大液泡，被解释为内质网，以及一种基质，在高分辨率下可以观察到其中有精细的丝状物质。突触后纤维是均匀的，通常不显示突触小泡。在完全黑暗中饲养24小时的动物中，小泡似乎在突触膜及其突起附近聚集。9天后，突触小泡的大小急剧减小。已识别出一种特殊的视杆突触，其中突触后树突状膨大直接穿入视杆细胞体。根据 Cajal 的分类，这种类型的突触可被视为体树突突触。视锥突触有一个大得多的终末，与突触后纤维的关系更复杂。然而，可以观察到在视杆突触中识别出的相同成分。在完全黑暗中饲养9天的动物中，突触小泡的大小也有相当程度的减小。
