BACKGROUND We performed an experiment to assess whether in ciliary processes adrenergic-receptor agents can modulate the production of nitrite, an oxidized metabolite of nitric oxide (NO). METHODS The porcine ciliary processes and the iris were dissected and stored at -20 degrees C. Later, tissues were thawed, and nitrite measured by Griess reaction, before and 2 h after exposure to various drugs. RESULTS In the ciliary processes, but not in the iris, the alpha-, beta-adrenergic receptor agonist, norepinephrine (0.01-10 microM), increased nitrite production (95 +/- 12%, P < 0.01). The norepinephrine-induced (0.1 microM) nitrite production was inhibited by the inhibitor of NO synthase, N omega-nitro-L-arginine methyl ester (0.5 mM; P < 0.05) and by the non-selective beta-adrenergic receptor antagonist, propranolol (10 microM; P < 0.01), but not by the non-selective alpha-adrenergic receptor antagonist, phentolamine (10 microM). CONCLUSIONS In isolated porcine ciliary processes, beta-adrenergic receptor stimulation increases NO production.