Nitric oxide modulates signal transmission to on-center bipolar cells in the rabbit retina

Purpose. The novel and rather unusual messenger molecule, nitric oxide (NO) has been shown to be involved in a variety of neuronal functions. In this study we investigated the physiological role of NO in signal transmission in the outer retina of albino rabbits. Methods. Electroretinogram responses were recorded after intravitreal injection of a NO donor (sodium nitroprusside) and drugs that activate (L-arginine) or inhibit (N^G-nilro-L-arginine methyl ester, L-NAME) NO formation in vivo. 2-Amino-4-phosphonobutyric Acid (APB) was used as an antagonist of the ON pathway. Results. At short lime intervals (4hrs) after injection, L-arginine augmented and slowed down the ERG responses while L-NAME induced the opposite effects. Thereafter, the eye injected with L-arginine exhibited a slow deterioration while that injected by L-NAME recovered. Nitroprusside induced similar effects to L-arginine. Simultaneous injection of L-arginine or L-NAME with APB had negligible effects on the receptoral component of the ERG. Conclusions. These data are consistent with NO having a direct stimulatory effect on the guanylate cyclase in the ON-center bipolar cells which mediate the metabotrophic action of L-glutamate. Furthermore, excess NO, either exogenously applied or endogenously formed, is deleterious to the rabbit retina.