EXPRESSION OF C-FOS AND C-JUN IN RAT RETINA FOLLOWING PROTRACTED ILLUMINATION

Illumination produces degeneration of outer photoreceptor segments, a phenomenon that may be reversed after a period of darkness. Neuronal e xpression of the immediate early genes (IEGs) c-fos and c-jun, both re cognized as proto-oncogenes, has been reported after stimulation of di fferent regions in the central nervous system (CNS). We performed a se quential study on Fos and Jun immunoreactivity to investigate the role of IEGs following 8 days of continuous illumination in 30-35-day-old Wistar rats. Retinas were fixed by perfusion in 4% paraformaldehyde, a fter a period of illumination followed by 0, 2, 7, 10 and 20 days in t otal darkness. Cryostat sections were immunocytochemically stained usi ng antibodies to Fos and Jun. Fos and Jun immunoreactivities were dete cted in all photoreceptors evaluated, peaking in nuclei of rats kept i n total darkness for 2 days, and becoming negative as from 7 days. Inc reases in c-fos and c-jun products during the darkness period may play a role in triggering molecular events participating in plastic change s in photoreceptors and/or in the protection from oxidative damage cau sed by free radicals induced by light irradiation.