CHANGES IN NADPH DIAPHORASE REACTIVITY AND NEURONAL NITRIC-OXIDE SYNTHASE IN THE RAT RETINA FOLLOWING CONSTANT ILLUMINATION

The distribution of nicotinamide adenine dinucleotide phosphate diapho rase (NADPHd) reactivity and neuronal nitric oxide synthase immunoreac tivity (nNOS-IR) was investigated in the rat retina during photorecept or regeneration. Photoreceptor damage and the disappearance of a NADPH d reactive/nNOS-IR band corresponding to inner photoreceptor segments were observed after continuous exposure to light irradiation. Both eve nts were reversible after 20 days of total darkness. Also a progressiv e decrease in the number and in the staining intensity of NADPHd react ivity in amacrine cells were found along the first 3-6 days of darknes s stabilizing thereafter in both illuminated and control groups. Howev er, staining intensity in the former group remained more elevated than in the latter one. NOS activity in the retina varies depending on fun ctional and pathological states. (C) 1997 Elsevier Science Ireland Ltd .