Role of nitric oxide in photoreceptor survival in embryonic chick retinal cell culture

The presence of nitric oxide synthase (NOS) in chick retina during development has allowed us to study the role of nitric oxide (NO) during retinal differentiation in dissociated chick retinal cell culture from embryonic day 6. We have demonstrated the presence of nicotinamide adenine dinucleotide phosphate diaphorase staining in these cultures after 3 days in vitro (Div), with a maximal intensity after 8 Div, corresponding to embryonic day 14. Immunohistochemistry studies confirmed the presence of the two isoforms of NOS, NOS-I and -III, in dissociated retinal cell cultures at 8 Div. Addition of NG-monomethyl-L-arginine, a NOS inhibitor, to retinal cell cultures prevented NO production but did not modify the appearance and the survival of ganglion and amacrine cells. However, immunohistochemical analysis with distinct markers for photoreceptor cells (rods and cones) showed that inhibition of endogenous NOS in retinal cell cultures prevented the developmental decrease of rod number between 5 and 8 Div, thus supporting the hypothesis that NO may be involved in the cell death of rods during the development of the retina.