Djamgoz M B, Greenstreet E H
Department of Biology, Imperial College of Science, Technology and Medicine, London, U.K.
Vision Res. 1996 Dec;36(24):4007-14. doi: 10.1016/s0042-6989(96)00144-7.
Although horizontal cells encode chromatic information by means of a variety of spectrally opponent light-evoked response patterns, their synaptic connections with the different spectral classes of cone are not completely understood. In the cyprinid fish retina, where a hierarchical set of interactions between horizontal cells and cone types has been proposed, a particular type of horizontal cell generates light-evoked triphasic (red-hyperpolarizing/green depolarizing/blue-hyperpolarizing) responses. In the present study, we have studied the cone connectivity of these cells by intracellular recording and staining in the roach retina. The horizontal cells were first identified electrophysiologically using spectral stimuli, and then stained intracellularly with horseradish peroxidase. Light microscopy revealed that the cells had consistent H3-like morphologies. At an ultrastructural level, these horizontal cells were deduced to contact selectively blue-sensitive cones. Within the cone pedicles, the majority (approximately 80%) of the contacts were "central" to synaptic ribbons. Some 50% of the "lateral" processes were large and engulfed cone cytoplasm. Spinules were present within the contacted pedicles but not upon the dendrites of the stained horizontal cells, although previous work had suggested that horseradish peroxidase would not interfere with spinule dynamics. The results are discussed in terms of existing modes of horizontal cell-cone connectivity in cyprinid fish retinae.
尽管水平细胞通过多种光谱拮抗的光诱发反应模式对颜色信息进行编码，但其与不同光谱类型视锥细胞的突触连接尚未完全明确。在鲤科鱼类视网膜中，有人提出水平细胞与视锥细胞类型之间存在层级式相互作用，其中一种特殊类型的水平细胞会产生光诱发的三相反应（红色超极化/绿色去极化/蓝色超极化）。在本研究中，我们通过在拟鲤视网膜中进行细胞内记录和染色，研究了这些细胞与视锥细胞的连接情况。首先使用光谱刺激对视水平细胞进行电生理鉴定，然后用辣根过氧化物酶进行细胞内染色。光学显微镜显示这些细胞具有一致的H3样形态。在超微结构水平上，推断这些水平细胞选择性地与蓝色敏感视锥细胞接触。在视锥细胞终足内，大部分（约80%）接触位于突触带的“中央”。约50%的“外侧”突起较大并吞噬视锥细胞的细胞质。在被接触的终足内存在棘状突起，但在染色的水平细胞的树突上没有，尽管先前的研究表明辣根过氧化物酶不会干扰棘状突起的动态变化。根据鲤科鱼类视网膜中水平细胞 - 视锥细胞连接的现有模式对结果进行了讨论。
