NITRIC-OXIDE SYNTHASE INHIBITORS PROTECT RAT RETINA AGAINST ISCHEMIC-INJURY

Elevation of the ocular pressure in the anterior chamber of the rat ey e caused major ischemic damage, manifested as changes in retinal morph ology. The two most affected structures were the inner plexiform layer , which decreased in thickness by 90%, and the number of ganglion cell s, which decreased by 80%. Pretreatment of the animals with N-omega-ni tro-L-arginine, a nitric oxide (NOS) inhibitor, almost completely abol ished the ischemic damage. Administration of aminoguanidine, a NOS inh ibitor se selective for the inducible enzyme, partially abolished the ischemic damage. Moreover, administration of the NOS inhibitors 1 h af ter ischemia, also protected the retina from damage, suggesting that s imilarly acting drugs could be used clinically to limit ischemic injur y in humans, We conclude that NOS, and therefore NO, may be involved i n the mechanism of ischemic injury to the retina.