RETROGRADE FLUORESCENT DOUBLE-LABELING STUDY OF BILATERALLY PROJECTING RETINAL GANGLION-CELLS IN ALBINO-RATS AT DIFFERENT STAGES OF DEVELOPMENT

Injection of the fluorescent tracers 10% Evans blue (EB) and 4% fluoro -gold (FG) into the right and the left dorsal lateral geniculate nucle us, respectively, of albino rats at different stages of development de monstrated the presence of double-labeled retinal ganglion cells that projected bilaterally into both the dorsal lateral geniculate nuclei ( dLGN). Findings confirmed that the distribution of these double-labele d cells was gradually reduced after birth, being confined to the perip heral temporoventral quarter (temporal-ventral crescent) of the retina after postnatal day 15. We estimated the proportion of double-labeled cells to total labeled cells in the same area at different stages of development (0-90 days); values ranged from 35.3% in the neonate to 5. 27% in the adult rat which suggests that the majority of double-labele d cells and/or their axons were lost early in development. That a smal l number of ganglion cells were observed to project bilaterally in the adult rats suggested that these cells conduct the same visual informa tion to both hemispheres throughout the animal's life.