[Effect of a nitric oxide donor on intraocular pressure]

We examined the effect of nitric oxide (NO) on intraocular pressure (IOP) and aqueous humor dynamics by using a NO donor, S-nitroso-N-acetyl-DL-penicillamine (SNAP) in rabbits. Intravitreal injection of 20 microliters of SNAP solution (10(-4) to 10(-2)M) reduced IOP from 60 to 120 min after injection. The magnitude of IOP reduction was dose-dependent within 10(-4) and 10(-3)M. The IOP reduction was inhibited by pretreatment with a NO trapping agent, carboxy-PTIO, indicating that IOP reduction was induced by NO released from SNAP. The aqueous flare as assessed with a laser cell flare meter was not accompanied with the IOP reduction indicating that no inflammatory response occurred. Neither tonographic outflow facility nor aqueous flow rate was affected by the treatment with SNAP. We conclude that NO reduces IOP through a mechanism which is not directly involved with the change of conventional outflow or aqueous formation in rabbits.