Frederick J M
Cullen Eye Institute, Baylor College of Medicine, Houston, TX 77030.
Exp Eye Res. 1987 Dec;45(6):933-45. doi: 10.1016/s0014-4835(87)80107-0.
The emergence of GABA-accumulating neurons was studied from stages 29 to 40 during retinal histogenesis in the chick, covering embryonic (E) days E6-E14, using autoradiographic analysis following incubation of isolated retinas with [3H]GABA (2 microM). Analysis was restricted to central retina which is more advanced in its differentiation than the periphery. On E6 numerous mitotic figures were present along the scleral border of the unstratified neuroepithelium. Specific localization of [3H]GABA was associated initially with somata situated in middle regions of the retinal expanse. Occasionally contiguous pairs of labeled cells were seen. The inner plexiform layer makes its appearance during E7; at that time silver grains were present over cell bodies located in the ganglion cell layer and the proximal portion of the inner nuclear layer, those of probable amacrine cells. As retinal stratification continued, more cells were observed to have elaborated membrane systems for GABA uptake with varying degrees of affinity. By E8, although dividing, non-labeled cells were in close proximity, GABA-labeled cells were observed in positions of horizontal cells. By E14, the pattern of label distribution appeared essentially similar to that reported for adult retina, i.e. [3H]GABA labeling was observed over horizontal cells and their processes, subpopulations of amacrine cells which appear to ramify extensively across the inner plexiform layer, selected perikarya of the ganglion cell layer, and the nerve fiber layer. In addition, a subpopulation of labeled photoreceptors, some identified as cones by virtue of oil droplets, was observed. Thus, preferential accumulation of GABA appears during E6, prior to formation of either inner or outer plexiform layers. The localization of [3H]GABA demonstrates that ganglion and amacrine cell bodies are labeled initially, followed by horizontal cells. Specific accumulation of [3H]muscimol, a potent agonist of GABA receptors, appears about E12 over cells located in proximal regions of the inner nuclear layer; these somata later ramify in sublaminae 2 and 4 of the inner plexiform layer.
在鸡视网膜组织发生过程中的第29至40阶段（涵盖胚胎期（E）的E6 - E14天），利用分离的视网膜与[3H]GABA（2微摩尔）孵育后的放射自显影分析，研究了GABA积累神经元的出现情况。分析仅限于中央视网膜，其分化程度比周边视网膜更高级。在E6时，未分层的神经上皮的巩膜边界沿线存在大量有丝分裂图像。[3H]GABA的特异性定位最初与位于视网膜区域中部的胞体相关。偶尔可见相邻的成对标记细胞。内网状层在E7时出现；此时，银颗粒出现在位于神经节细胞层和内核层近端部分的细胞体上，这些可能是无长突细胞的细胞体。随着视网膜分层的继续，观察到更多细胞已经形成了具有不同亲和力的GABA摄取膜系统。到E8时，尽管有正在分裂的未标记细胞紧邻，但在水平细胞的位置观察到了GABA标记细胞。到E14时，标记分布模式与成年视网膜报道的基本相似，即[3H]GABA标记出现在水平细胞及其突起、似乎在内网状层广泛分支的无长突细胞亚群、神经节细胞层的选定核周体以及神经纤维层上。此外，还观察到一群标记的光感受器，其中一些因油滴而被鉴定为视锥细胞。因此，GABA的优先积累出现在E6，在内、外网状层形成之前。[3H]GABA的定位表明，神经节细胞和无长突细胞体最初被标记，随后是水平细胞。GABA受体的强效激动剂[3H]蝇蕈醇的特异性积累大约在E12时出现在内核层近端区域的细胞上；这些细胞体后来在内网状层的2层和4层亚层中分支。
