Morphologic analysis and classification of ganglion cells of the chick retina by intracellular injection of Lucifer Yellow and retrograde labeling with DiI.

Retinal ganglion cells (RGCs) of chicks were labeled by using the techniques of intracellular filling with Lucifer Yellow and retrograde axonal labeling with carbocyanine dye (DiI). Labeled RGCs were morphologically analyzed and classified into four major groups: Group I cells (57.1%) with a small somal area (77.5 microm(2) on average) and narrow dendritic field (17,160 microm(2) on average), Group II cells (28%) with a middle-sized somal area (186 microm(2)) and middle-sized dendritic field (48,800 microm(2)), Group III cells (9.9%) with a middle-sized somal area (203 microm(2)) and wide dendritic field (114,000 microm(2)), and Group IV cells (5%) with a large somal area (399 microm(2)) and wide dendritic field (117,000 microm(2)). Of the four groups, Groups I and II were further subdivided into two types, simple and complex, on the basis of dendritic arborization: Groups Is, Ic, and Groups IIs, IIc. However, Group III and IV showed either a simple or complex type, Group IIIs and Group IVc, respectively. The density of branching points of dendrites was approximately 10 times higher in the complex types (18,350, 6,190, and 3,520 points/mm(2) in Group Ic, IIc, and IVc, respectively) than in the simple types (1,890, 640, and 480 points/mm(2) in Group Is, IIs, and IIIs). The branching density of Group I cells was extremely high in the central zone. The chick inner plexiform layer was divided into eight sublayers by dendritic strata of RGCs and 26 stratification patterns were discriminated. The central and peripheral retinal zones were characterized by branching density of dendrites and composition of RGC groups, respectively.