A COUPLED NETWORK FOR PARASOL BUT NOT MIDGET GANGLION-CELLS IN THE PRIMATE RETINA
A COUPLED NETWORK FOR PARASOL BUT NOT MIDGET GANGLION-CELLS IN THE PRIMATE RETINA
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DOI：
10.1017/s0952523800010695
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发表时间：
1992-09-01
影响因子：
1.9
通讯作者：
BRACE, S
中科院分区：
文献类型：
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作者：
DACEY, DM;BRACE, S
细胞内注射神经生物素被用来确定猕猴视网膜的主要神经节细胞类别、投射大细胞的遮阳伞和投射微小细胞的侏儒细胞是否显示出与最近描述的猫视网膜神经节细胞类似的细胞耦合的证据。在体外分离的视网膜制剂中，神经节细胞被荧光染料丫啶橙标记，并在直接显微镜下选择性地靶向细胞内注射。猕猴的侏儒细胞，就像猫视网膜的β细胞一样，在注射神经生物素时没有显示出示踪剂偶联的证据。相反，与猫α细胞一样，充满神经生物素的遮阳伞细胞显示出明显的示踪剂相互偶联(同型偶联)和无长突细胞偶联(异型偶联)的模式。在同型偶联的情况下，注射的遮阳伞细胞被规则的3-6个相邻遮阳伞细胞阵列包围。这些示踪剂偶联细胞的胞体和近端树突被轻度标记，似乎与注射的细胞共层。最近邻距离分析表明，随着树突野直径从100-400亩-m增加，树突场重叠保持不变。至少有两种类型的无长突细胞与伞细胞表现出示踪剂偶联。一种无长突型有一个小的胞体和内网状层延伸1-2 mm的稀疏分枝的树突。第二种无长突细胞胞体较大，主树突粗，内网状层突起明显，轴突至少延伸2-3 mm。大的无长突细胞的主要树突与副细胞的树突紧密相对，可能是神经生物素在两种细胞之间转移的部位。我们认为，相邻遮阳伞细胞之间的示踪剂偶联是通过大的无长突细胞的树突间接发生的，这为增加遮阳伞细胞的感受野大小和亮度对比度敏感性提供了一种机制，而侏儒细胞中没有这种机制。
Intracellular injections of Neurobiotin were used to determine whether the major ganglion cell classes of the macaque monkey retina, the magnocellular-projecting parasol, and the parvocellular-projecting midget cells showed evidence of cellular coupling similar to that recently described for cat retinal ganglion cells. Ganglion cells were labeled with the fluorescent dye acridine orange in an in vitro, isolated retina preparation and were selectively targeted for intracellular injection under direct microscopic control. The macaque midget cells, like the beta cells of the cat's retina, showed no evidence of tracer coupling when injected with Neurobiotin. By contrast, Neurobiotin-filled parasol cells, like cat alpha cells, showed a distinct pattern of tracer coupling to each other (homotypic coupling) and to amacrine cells (heterotypic coupling).In instances of homotypic coupling, the injected parasol cell was surrounded by a regular array of 3-6 neighboring parasol cells. The somata and proximal dendrites of these tracer-coupled cells were lightly labeled and appeared to costratify with the injected cell. Analysis of the nearest-neighbor distances for the parasol cell clusters showed that dendritic-field overlap remained constant as dendritic-field size increased from 100-400-mu-m in diameter.At least two amacrine cell types showed tracer coupling to parasol cells. One amacrine type had a small soma and thin, sparsely branching dendrites that extended for 1-2 mm in the inner plexiform layer. A second amacrine type had a relatively large soma, thick main dendrites, and distinct, axon-like processes that extended for at least 2-3 mm in the inner plexiform layer. The main dendrites of the large amacrine cells were closely apposed to the dendrites of parasol cells and may be the site of Neurobiotin transfer between the two cell types. We suggest that the tracer coupling between neighboring parasol cells takes place indirectly via the dendrites of the large amacrine cells and provides a mechanism, absent in midget cells, for increasing parasol cell receptive-field size and luminance contrast sensitivity.