Effects of visual or light deprivation on the morphology, and the elimination of the transient features during development, of type I retinal ganglion cells in hamsters.

Intracellular injection of Lucifer Yellow (LY) was used to study the detailed morphology of the normal visually deprived, and light-deprived superior colliculus projecting Type I retinal ganglion cells (RGCs) in hamsters. The soma size of the normal Type I cells ranged from 337 to 583 microns 2 with a mean of 436 microns 2. Two to six primary dendrites were observed in these cells. The mean dendritic field diameter was 495 microns and ranged from 309 to 702 microns. The dendritic field diameter of this population of cells exhibited an eccentricity dependence. Quantitative comparisons between the normal and visually deprived or light-deprived Type I RGCs indicated that the morphology of these three groups of cells were similar to each other in terms of the soma size, dendritic field diameter, branching pattern, and total length of the dendrites. During the normal development of cats and hamsters, several transient features, such as exuberant dendritic spines and intraretinal axonal branches, have been observed in the developing RGCs. The complete elimination of these transient features occurs at about 3 and 2 weeks after the opening of the eyes in cats and hamsters, respectively. In the present study, the hypothesis whether visual experience or light stimulation is required for the elimination of these transient features during development was examined. After studying a total of 115 mature Type I RGCs, which included cells from the normal, visually deprived and light deprived animals, no transient feature was observed. We conclude that visual or light deprivation has no effect on the morphological development of superior colliculus projecting Type I RGCs in hamsters, and the elimination of the transient features on the Type I RGCs during development does not depend on visual experience or light stimulation.