Nitric oxide inhibits depolarization-induced release of endogenous dopamine in the rabbit retina

The effect of nitric oxide donor compounds (sodium nitroprusside, hydroxylamine and S-nitroso-N-acetyl-D,L-penicillamine) on depolarization-induced release of endogenous dopamine in the light-adapted, isolated retina of the rabbit was studied by HPLC. All three compounds had the same effect, reducing the amount of dopamine released by up to 90%. The effect was concentration dependent, saturating at 300 microM; it was blocked by the nitric oxide scavenger, mannitol (50 mM), which by itself had no effect on the basal release of dopamine. GABAA receptors were not involved. Possible cellular mechanisms underlying the findings are discussed. It is suggested that the inhibitory interaction between dopamine and nitric oxide could represent a higher order function in the light adaptation process in the retina.