Li Yong N, Matsui Jonathan I, Dowling John E
Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, BL2081, Cambridge, MA 02138, USA.
J Comp Neurol. 2009 Oct 10;516(5):442-53. doi: 10.1002/cne.22135.
Horizontal cells (HCs) are involved in establishing the center-surround receptive field organization of photoreceptor and bipolar cells. In many species, HCs respond differentially to colors and may play a role in color vision. An earlier study from our laboratory suggested that four types of HCs exist in the zebrafish retina: three cone HCs (H1, H2 and H3) and one rod HC. In this study, we describe their photoreceptor connections. Cones are arranged in a mosaic in which rows of alternating blue (B)- and ultraviolet (UV)-sensitive single cones alternate with rows of red (R)- and green (G)-sensitive double cones; the G cones are adjacent to UV cones and B cones adjacent to R cones. Two small-field (H1 and H2) and two large-field (H3 and rod HC) cells were observed. The cone HC dendritic terminals connected to cones with single boutons, doublets, or rosettes, whereas the rod HCs connected to rods with single boutons. The single boutons/doublets/rosettes of cone HCs were arranged in double rows separated by single rows for H1 cells, in pairs and singles for H2 cells, and in a rectilinear pattern for H3 cells. These connectivity patterns suggest that H1 cells contact R, G, and B cones, H2 cells G, B, and UV cones, and H3 cells B and UV cones. These predictions were confirmed by applying the DiI method to SWS1-GFP retinas whose UV cones express green fluorescent protein. Each rod HC was adjacent to the soma or axon of a DiI-labeled cone HC and connected to 50-200 rods.
水平细胞（HCs）参与建立光感受器和双极细胞的中心-外周感受野组织。在许多物种中，水平细胞对颜色有不同反应，可能在色觉中起作用。我们实验室早期的一项研究表明，斑马鱼视网膜中存在四种类型的水平细胞：三种视锥水平细胞（H1、H2和H3）和一种视杆水平细胞。在本研究中，我们描述了它们与光感受器的连接。视锥细胞呈镶嵌排列，其中交替排列的蓝色（B）和紫外（UV）敏感单视锥细胞行与红色（R）和绿色（G）敏感双视锥细胞行交替；G视锥细胞与UV视锥细胞相邻，B视锥细胞与R视锥细胞相邻。观察到两个小视野（H1和H2）和两个大视野（H3和视杆水平细胞）细胞。视锥水平细胞的树突末端通过单个终扣、双终扣或玫瑰花结与视锥细胞相连，而视杆水平细胞通过单个终扣与视杆细胞相连。视锥水平细胞的单个终扣/双终扣/玫瑰花结在H1细胞中以单行分隔的双行排列，在H2细胞中以成对和单个排列，在H3细胞中以直线模式排列。这些连接模式表明，H1细胞与R、G和B视锥细胞接触，H2细胞与G、B和UV视锥细胞接触，H3细胞与B和UV视锥细胞接触。通过将DiI方法应用于UV视锥细胞表达绿色荧光蛋白的SWS1-GFP视网膜，证实了这些预测。每个视杆水平细胞与一个DiI标记的视锥水平细胞的胞体或轴突相邻，并与50-200个视杆细胞相连。
