Tassinari G, Bentivoglio M, Chen S, Campara D
Dipartimento di Scienze Neurologiche e della Visione, Sezione di Fisiologia Umana, Verona, Italy.
Brain Res Bull. 1997;43(2):127-39. doi: 10.1016/s0361-9230(96)00215-8.
To analyze the relative proportion and distribution of retinal ganglion cells projecting ipsilaterally and contralaterally in the cat, large injections of the fluorescent tracers Fluoro Gold, Fast Blue, and Diamidino Yellow were made in the main layers of the lateral geniculate nucleus (LGN) and superior colliculus (SC). One tracer was injected in both the LGN and SC on one side, and the other two tracers were injected contralaterally, in the LGN and SC, respectively; labelled ganglion cells were charted on retinal whole mounts. Ganglion cells labelled from the LGN and SC were highly intermingled in both the ipsilateral and contralateral retinae. The adopted combinations of tracers allowed the detection of cells double labelled from the SC and LGN, supporting the occurrence of branched retino-thalamic axons to the SC. About one-fourth of the ganglion cells labelled from the LGN and SC was located in the eye ipsilateral to the injection. Retrograde labelling from the ipsilateral side was almost entirely confined to the temporal hemiretina. In the contralateral eye, labelled cells were mainly concentrated in the nasal hemiretina, but more than 10% were also detected in the temporal half of the retina. In the latter area, cells displaying the entire range of sizes of the retinal ganglion cells, labelled from the contralateral LGN and SC, were found throughout the entire hemiretina. However, more than 50% of such "wrong" projecting cells were grouped in a strip of 2 mm closest to the nasotemporal division. Control experiments, in which the tracers injections were restricted to the rostral and dorsal portions of the LGN to avoid optic tract contamination, consistently confirmed the occurrence and distribution of the "wrong" projecting cells in the temporal hemiretina. Thus, these latter cells are not grouped in a central strip, where ganglion cells would have the same chance of projecting to the same or to the opposite side, and sparsely distributed in the temporal periphery, as previously believed. Instead, the present findings indicate that the retinal ganglion cells of origin of contralateral projections are distributed more in a continuum, with a naso-temporal gradient of density, across the temporal hemiretina.
为了分析猫视网膜神经节细胞同侧和对侧投射的相对比例及分布情况，将大量荧光示踪剂氟金、快蓝和双脒基黄注入外侧膝状体（LGN）和上丘（SC）的主要层。在一侧的LGN和SC中都注入一种示踪剂，另外两种示踪剂分别注入对侧的LGN和SC；在视网膜整装片上绘制标记的神经节细胞。从LGN和SC标记的神经节细胞在同侧和对侧视网膜中高度混合。所采用的示踪剂组合能够检测到从SC和LGN双重标记的细胞，支持存在分支的视网膜 - 丘脑轴突投射至上丘。从LGN和SC标记的神经节细胞中约四分之一位于注射同侧的眼睛中。同侧逆行标记几乎完全局限于颞侧半视网膜。在对侧眼中，标记细胞主要集中在鼻侧半视网膜，但在视网膜颞侧半部也检测到超过10%的标记细胞。在后者区域，从对侧LGN和SC标记的、显示出视网膜神经节细胞全尺寸范围的细胞在整个半视网膜中均有发现。然而，超过50%的此类“错误”投射细胞聚集在最靠近鼻颞分界线的2毫米宽的条带中。对照实验中，将示踪剂注射限制在LGN的 Rostral 和背侧部分以避免视束污染，始终证实了颞侧半视网膜中“错误”投射细胞的出现和分布。因此，这些细胞并非如先前认为的那样聚集在中央条带中，在中央条带中神经节细胞向同侧或对侧投射的机会相同，而是稀疏分布在颞侧周边；相反，目前的研究结果表明，对侧投射的起源视网膜神经节细胞在颞侧半视网膜上以密度的鼻颞梯度更连续地分布。
