Brimonidine and inhibition of nitrite production in isolated porcine ciliary processes.
OBJECTIVE
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.
Liu
R
R
Laboratory of Ocular Pharmacology and Physiology, University Eye Clinic Basel, Mittlere Strasse 91, PO Box, CH-4012 Basel.
Flammer
J
J
Haefliger
I O
IO
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism; D000068438:Brimonidine Tartrate; D002924:Ciliary Body / Q000187:drug effects* / Q000502:physiology; D005576:Colforsin / Q000494:pharmacology; D007429:Intraocular Pressure / Q000187:drug effects / Q000502:physiology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors* / Q000502:physiology; D009573:Nitrites / Q000378:metabolism; D011810:Quinoxalines / Q000494:pharmacology*; D013552:Swine
D000316:Adrenergic alpha-Agonists; D009573:Nitrites; D011810:Quinoxalines; D005576:Colforsin; D009569:Nitric Oxide; D000068438:Brimonidine Tartrate