A study of double-labeled retinal ganglion cells from the superior colliculus in the developing albino rat

We studied the distribution pattern and percentage of bilaterally projecting, double-labeled retinal ganglion cells in the albino rat by the retrograde fluorescent double labeling. Forty-five albino (Wistar, Japan Clea) rats of either sex and of different stage of development ranging in age from the day of birth (Day 0) to Day 30, were used. With the rats under deep anesthesia, we pressure injected 0.02 microliter of 15% Evans blue (EB) and 0.02 microliter of 4% Fluoro-gold (FG) into the right and left superior colliculi, respectively; for rats older than 5 days, the volume of each tracer was 0.04 microliter. The animals were perfused with formol-saline 48 to 72 h later and the brain and eyeballs were excised and sectioned. Double-labeled cells were found over almost the entire retina, with the concentration in the lower temporal crescent in rats up to day 1; concentration gradually shifted to the ventral half between days 5 and 10. After day 15, double-labeled cells were found only in the ventral-temporal crescent of the retina, which is the pattern in the adult rats. The percentages of retinal ganglion cells that were double-labeled at days 0, 1, 5, 7, 10, 15, 20, 25 and 30 were 60.2, 51.6, 60.5, 57.6, 62.2, 60.7, 55.7, 45.2, and 39.1, respectively. After day 10, the percentage of such cells decreased steadily.