Brimonidine and inhibition of nitrite production in isolated porcine ciliary processes

Purpose: To investigate whether the alpha (2)-adrenoreceptor agonist brimon idine (a drug that decreases intraocular pressure in part by reducing aqueo us humor production) can inhibit the production of nitrite induced by forsk olin in isolated porcine ciliary processes. Methods: Nitrite (a metabolite of nitric oxide) was measured (Griess reacti on) before and two hours after exposure to the adenylcyclase activator fors kolin (0.1 muM) in the presence or in the absence of the brimonidine (10 mu M) and/or the alpha (2)-adrenoreceptor antagonist yohimbine (10 muM). Results: The increase of nitrite production evoked by forskolin (139 +/-9%) was significantly (P<0.01) inhibited by brimonidine (108<plus/minus>6%). T he inhibitory effect of brimonidine on the increase of nitrite production i nduced by forskolin was significantly (P < 0.01) reversed by yohimbine (136 <plus/minus>7%). Conclusions: The results of this pilot study suggest that brimonidine inhib its the production of nitrite evoked by forskolin through a mechanism that could involve alpha (2)-adrenoreceptor activation in isolated porcine cilia ry processes.