NADPH-DIAPHORASE DISTRIBUTION IN THE CHOROID AFTER CONTINUOUS ILLUMINATION

THE role of nitric oxide (NO) in the regulation of the tone of the blo od choroid vessels was investigated using the histochemical NADPH-diap horase technique. Rats were continuously illuminated with white light, 12000 lux, for 8 days and perfused after 1, 3, 10 and 20 days of tota l darkness. Cryostat sections were processed using the NADPH diaphoras e histochemical method. An increase in reactive fibres was observed du ring days 1, 3 and 10, but after 20 days in darkness, reactivity was s imilar to that observed in control sections. These results indicate th at NO plays a role in regulating the blood flow in the uveal vessels, and that there are changes in NO level dependent on the functional sta te of the retina.