Linberg K A, Fisher S K
IES Neuroscience Research Program, University of California, Santa Barbara 93106.
J Comp Neurol. 1988 Feb 8;268(2):281-97. doi: 10.1002/cne.902680211.
The organization of the rod spherule and of the horizontal cell axon terminals within the invagination of the rod spherule in the human retina was examined in serial sections by electron microscopy. Twenty-one rod spherules were reconstructed in this study. Axon terminal processes of type I horizontal cells consistently make one or two small punctate synapses onto each rod spherule within the invagination. In addition, these axon terminal processes make distinct synapses upon rod bipolar dendrites outside the spherule before both processes enter the invagination. This is the first positive description of a synapse from a horizontal cell axon terminal process onto a photoreceptor terminal and the first identification of a synapse from a horizontal cell to a rod bipolar cell in the mammalian outer plexiform layer. We speculate that the axon terminal-to-rod synapse is responsible for feedback while the synapse upon the rod bipolar cell is feed-forward and serves to expand the receptive field of the rod bipolar cell beyond its dendritic field. Alternatively, the latter may contribute to a center-surround organization of the rod bipolar's receptive field.
通过电子显微镜对人视网膜视杆小球内陷处的视杆小球和水平细胞轴突终末的组织结构进行了连续切片检查。本研究重建了21个视杆小球。I型水平细胞的轴突终末突起在视杆小球内陷处的每个视杆小球上始终形成一两个小的点状突触。此外，在这两个突起进入内陷之前，这些轴突终末突起在视杆小球外的视杆双极树突上形成明显的突触。这是对水平细胞轴突终末突起与光感受器终末之间突触的首次肯定性描述，也是在哺乳动物外网状层中首次鉴定出水平细胞与视杆双极细胞之间的突触。我们推测，轴突终末与视杆的突触负责反馈，而与视杆双极细胞的突触是前馈性的，有助于将视杆双极细胞的感受野扩展到其树突野之外。或者，后者可能有助于视杆双极细胞感受野的中心-外周组织形式。
