NITRIC-OXIDE INDUCES LIGHT-ADAPTIVE MORPHOLOGICAL-CHANGES IN RETINAL NEURONS

THIS Study tested the possible involvement of nitric oxide (NO) in light-adaptive morphological changes in the outer retina of a cyprinid fish, the roach. Isolated retinae were treated in the dark by either of two NO-donor compounds (S-nitroso-n-acetylpenicillamine and sodium nitroprusside) and then studied by light and electron microscopy; similar results were obtained in both cases. Application of NO induced contraction of cone photoreceptor myoids (i.e. retinomotor movements) and formation of horizontal cell spinules. Accordingly the cone index and the spinule/ribbon ratio showed 15-20% and 49-95% change, respectively, compared with controls. These results are consistent with involvement of NO in the light adaptation process in the outer retina of teleost fish.