Brimonidine and inhibition of nitrite production in isolated porcine ciliary processes.

PURPOSE: To investigate whether the alpha 2-adrenoreceptor agonist brimonidine (a drug that decreases intraocular pressure in part by reducing aqueous humor production) can inhibit the production of nitrite induced by forskolin in isolated porcine ciliary processes.

METHODS

Nitrite (a metabolite of nitric oxide) was measured (Griess reaction) before and two hours after exposure to the adenylcyclase activator forskolin (0.1 microM) in the presence or in the absence of the brimonidine (10 microM) and/or the alpha 2-adrenoreceptor antagonist yohimbine (10 microM).

RESULTS

The increase of nitrite production evoked by forskolin (139 +/- 9%) was significantly (P < 0.01) inhibited by brimonidine (108 +/- 6%). The inhibitory effect of brimonidine on the increase of nitrite production induced by forskolin was significantly (P < 0.01) reversed by yohimbine (136 +/- 7%).

CONCLUSIONS

The results of this pilot study suggest that brimonidine inhibits the production of nitrite evoked by forskolin through a mechanism that could involve alpha 2-adrenoreceptor activation in isolated porcine ciliary processes.