Kolb H, Dekorver L
Physiology Department, University of Utah School of Medicine, Salt Lake City 84108.
J Comp Neurol. 1991 Jan 22;303(4):617-36. doi: 10.1002/cne.903030408.
In this study we used serial section electron microscopy and three-dimensional reconstructions to examine four midget ganglion cells of the human retina. The four cells were located in the parafoveal retina 2.5 mm or 8 degrees from the foveal center. Both type a (with dendritic trees in distal inner plexiform layer) and type b (with dendritic trees in proximal inner plexiform layer) midget ganglion cells have been studied. These cells have dendritic trees of 7-9 microns diameter, and their complete dendritic trees in the neuropil of the inner plexiform layer can be analyzed, as well as the bipolar cell axon terminals having synaptic input, by a study of 100-150 serial ultrathin sections. Type a midget ganglion cells appear to be in a one-to-one relationship with flat midget bipolar cell axon terminals ending in distal inner plexiform layer. Type b midget ganglion cells are in a one-to-one synaptic relationship with invaginating midget bipolar cell axon terminals in proximal inner plexiform layer. The midget bipolar cells primarily involved with the midget ganglion cells do not contact other ganglion cell dendrites. In other words, midget bipolar cells appear to be in exclusive contact with single midget ganglion cells in the human retina. The midget ganglion cells receive most of their input from their associated midget bipolar cells in the form of ribbon synapses at dyads or monads (55-81 ribbons total), although ribbonless synapses are seen occasionally. In all four midget ganglion cells reconstructed, one or two other bipolar cell axon terminals, presumed to be from wide-field bipolar types, provide 1-3 ribbon synapses each. The number of amacrine synapses upon a midget ganglion cell's dendritic tree is approximately equal to the number of bipolar ribbon inputs (43%-56% bipolar ribbons: 44%-57% amacrine synapses). We assume from our knowledge of response characteristics of ganglion cells in other mammalian retinas (Nelson et al., '78: J. Neurophysiol. 41:427-483), that the type a midget ganglion cell and its exclusive connectivity with a flat midget bipolar cell forms a single cone connected OFF-center pathway, whereas the type b midget ganglion cell with its exclusive connectivity to an invaginating midget bipolar cell forms a single cone connected ON-center pathway, through the retina to the brain.
在本研究中,我们使用连续切片电子显微镜和三维重建技术来检查人类视网膜的四个侏儒神经节细胞。这四个细胞位于距中央凹中心2.5毫米或8度的中央凹旁视网膜。我们研究了a型(树突树位于远端内网状层)和b型(树突树位于近端内网状层)侏儒神经节细胞。这些细胞的树突树直径为7 - 9微米,通过研究100 - 150个连续超薄切片,可以分析它们在内网状层神经毡中的完整树突树,以及具有突触输入的双极细胞轴突终末。a型侏儒神经节细胞似乎与终止于远端内网状层的扁平侏儒双极细胞轴突终末呈一对一关系。b型侏儒神经节细胞与近端内网状层中凹陷的侏儒双极细胞轴突终末呈一对一突触关系。主要与侏儒神经节细胞相关的侏儒双极细胞不与其他神经节细胞树突接触。换句话说,在人类视网膜中,侏儒双极细胞似乎仅与单个侏儒神经节细胞接触。侏儒神经节细胞的大部分输入来自与其相关的侏儒双极细胞,以二联体或单联体处的带状突触形式(总共55 - 81个带状突触),尽管偶尔也会看到无带状突触。在所有重建的四个侏儒神经节细胞中,一两个其他双极细胞轴突终末(推测来自宽视野双极细胞类型)每个提供1 - 3个带状突触。侏儒神经节细胞树突树上无长突细胞突触的数量大约等于双极带状输入的数量(43% - 56%双极带状突触:44% - 57%无长突细胞突触)。根据我们对其他哺乳动物视网膜神经节细胞反应特性的了解(Nelson等人,'78:《神经生理学杂志》41:427 - 483),我们假设a型侏儒神经节细胞及其与扁平侏儒双极细胞的排他性连接形成了一条单一的视锥细胞连接的离中心通路,而b型侏儒神经节细胞与其与凹陷的侏儒双极细胞的排他性连接形成了一条单一的视锥细胞连接的on - 中心通路,通过视网膜通向大脑。