Cone-associated c-fos gene expression in the light-damaged rat retina

Purpose, To examine whether light-controlled c-fos gene expression is mediated by a cone-specific pathway in the rat retina. Methods, To produce a cone-rich retina, rats were placed under continuous lighting for 21 days. The illuminance in the cages ranged from 1200 to 2000 lux. The presence of cones was determined by peanut agglutinin and rods by the monoclonal antibody 1-E7. The presence of c-fos transcripts in the retinas was analyzed by in situ hybridization using single-stranded RNA probes. Results, After long-term exposure to continuous light, the 1-E7 immunoreactivity was not detected in the outer nuclear layer. The cone photoreceptors and cells in the ganglion cell (GCL) and inner nuclear layers (INL) survived. In normal retinas, there was strong hybridization for c-fos expression in the GCL and the INL 30 minutes after the onset of the light cycle. Light-damaged retinas also showed hybridization in the GCL but not in the INL under the same light regime. Conclusions, These results suggest that c-fos gene expression can be controlled through a cone-specific pathway in the retina.