Famiglietti E V
Department of Anatomy, University of Calgary, Faculty of Medicine, AB, Canada.
J Comp Neurol. 1991 Jul 1;309(1):40-70. doi: 10.1002/cne.903090105.
The synaptic organization of starburst amacrine cells was studied by electron microscopy of individual or overlapping pairs of Golgi-impregnated cells. Both type a and type b cells were analyzed, the former with normally placed somata and dendritic branching in sublamina a, and the latter with somata displaced to the ganglion cell layer and branching in sublamina b. Starburst amacrine cells were thin-sectioned horizontally, tangential to the retinal surface, and electron micrographs of each section in a series were taken en montage. Cell bodies and dendritic trees were reconstructed graphically from sets of photographic montages representing the serial sections. Synaptic inputs from cone bipolar cells and amacrine cells are distributed sparsely and irregularly all along the dendritic tree. Sites of termination include the synaptic boutons of starburst amacrine cells, which lie at the perimeter of the dendritic tree in the "distal dendritic zone." In central retina, bipolar cell input is associated with very small dendritic spines near the cell body in the "proximal dendritic zone." The proximal dendrites of type a and type b cells generally lie in planes or "strata" of the inner plexiform layer (IPL), near the margins of the IPL. The boutons and varicosities of starburst amacrine cells, distributed int he distal dendritic zone, lie in the "starburst substrata," which occupy a narrow middle region in each of the two sublaminae, a and b, in rabbit retina. As a consequence of differences in stratification, proximal and distal dendritic zones are potentially subject to different types of input. Type b starburst amacrines do not receive inputs from rod bipolar terminals, which lie mainly in the inner marginal zone of the IPL (stratum 5), but type a cells receive some input from the lobular presynaptic appendages of rod amacrine cells in sublamina a, at the border of strata 1 and 2. There is good correspondence between boutons or varicosities and synaptic outputs of starburst amacrine cells, but not all boutons gave ultrastructural evidence of presynaptic junctions. The boutons and varicosities may be both pre- and postsynaptic. They are postsynaptic to cone bipolar cell and amacrine cell terminals, and presynaptic primarily to ganglion cell dendrites. In two pairs of type b starburst amacrine cells with overlapping dendritic fields, close apposition of synaptic boutons was observed, raising the possibility of synaptic contact between them. The density of the Golgi-impregnation and other technical factors prevented definite resolution of this question. No unimpregnated profiles, obviously amacrine in origin, were found postsynaptic to the impregnated starburst boutons.(ABSTRACT TRUNCATED AT 400 WORDS)
通过对单个或重叠的高尔基染色细胞对进行电子显微镜观察，研究了星爆无长突细胞的突触组织。对a型和b型细胞均进行了分析，前者的胞体位置正常，树突分支位于a亚层，后者的胞体移位至神经节细胞层，树突分支位于b亚层。星爆无长突细胞水平薄切片，与视网膜表面相切，并对一系列切片中的每一片进行连续电子显微镜图像采集。从代表连续切片的摄影拼接图集中以图形方式重建细胞体和树突树。来自视锥双极细胞和无长突细胞的突触输入沿树突树稀疏且不规则地分布。终末部位包括星爆无长突细胞的突触小体，其位于树突树周边的“远端树突区”。在视网膜中央，双极细胞输入与“近端树突区”靠近细胞体处的非常小的树突棘相关。a型和b型细胞的近端树突通常位于内网状层（IPL）的平面或“层”中，靠近IPL的边缘。分布在远端树突区的星爆无长突细胞的突触小体和曲张体位于“星爆层”，在兔视网膜的a和b两个亚层的每一层中占据狭窄的中间区域。由于分层差异，近端和远端树突区可能受到不同类型的输入。b型星爆无长突细胞不接受主要位于IPL内边缘区（第5层）的视杆双极终末的输入，但a型细胞在第1层和第2层边界的a亚层中接受来自视杆无长突细胞小叶状突触前附属物的一些输入。星爆无长突细胞的突触小体或曲张体与突触输出之间有良好的对应关系，但并非所有突触小体都有突触前连接的超微结构证据。突触小体和曲张体可能既是突触前的也是突触后的。它们是视锥双极细胞和无长突细胞终末的突触后结构，主要是神经节细胞树突的突触前结构。在两对树突野重叠的b型星爆无长突细胞中，观察到突触小体紧密并列，增加了它们之间突触接触的可能性。高尔基染色密度和其他技术因素妨碍了对这个问题的明确解决。在染色的星爆突触小体的突触后未发现明显起源于无长突细胞的未染色轮廓。（摘要截断于400字）
