Effects of nitric oxide synthase inhibitor on intraocular pressure and ocular inflammation following laser irradiation in rabbits.

PURPOSE

To examine the effects of nitric oxide synthase (NOS) inhibitors on intraocular pressure (IOP) and ocular inflammation following laser irradiation of the rabbit iris, and to investigate the involvement of nitric oxide (NO).

METHODS

Thirty min after the intravenous administration of a nonselective inhibitor of NOS, N omega-nitro-L-arginine methyl ester (L-NAME, 1-100 mg/kg), or a selective inhibitor of iNOS, aminoguanidine (AG, 100 mg/kg), Q-switched Nd:YAG laser irradiation was applied to the iris of albino rabbits at an energy level of 48 mJ. IOP was measured prior to and for 24 h after irradiation. In separate groups of rabbits, aqueous humor was withdrawn 30 min after irradiation to determine protein and prostaglandin (PG) E2 concentrations.

RESULTS

Intravenously administered L-NAME dose-dependently inhibited the acute increase in IOP, the peak of which was observed at 30 min, following laser irradiation. The IOP increase was completely abolished by 100 mg/kg of L-NAME. This dose of L-NAME significantly reduced the elevation of protein concentration in aqueous humor following irradiation; however, this dose failed to affect the increase in PGE2 concentration On the other hand, the inhibitory effects of AG (100 mg/kg) on the increase in IOP and aqueous protein following laser irradiation were not significant.

CONCLUSIONS

Intravenous administration of L-NAME significantly inhibits the IOP rise and the increase in protein concentration in aqueous humor following laser irradiation, but AG does not, suggest the involvement of cNOS in these ocular responses to laser irradiation.