Nitric oxide synthase (NOS) inhibitors ameliorate retinal damage induced by ischemia in rats.

The dose effects of two nitric oxide synthase (NOS) inhibitors: NG-nitro-L-arginine (L-NNA) and N omega-monomethyl-L-arginine (L-NMMA), were evaluated in an established rat model of retinal ischemia using morphometry of the inner retina: inner retinal thickness (IRT) measurements and retinal ganglion cell counts (RGCCs) of the posterior and peripheral retina. By IRT and RGCCs of the posterior retina, there were dose dependent beneficial effects of both inhibitors. However, by RGCCs of the peripheral retina, there was no significant beneficial effect by either inhibitor. In addition, L-NMMA at 0.3 mg/kg aggravated the loss of RGC in both the posterior and peripheral retina. An important role and a possible differential site of action of NOS in the pathophysiology of retinal ischemia are implicated.