[The synthesis and effects of nitric oxide at the retinal level]

Nitric oxide (NO) is synthetized from L-arginine by the aid of an enzyme--NO synthase (NOS). This enzyme has there isoforms, which are either constitutive; neural NOS (nNOS) and endothelial NOS (eNOS) or inducible (iNOS). These three isoforms are expressed also in the retina. NO produced in small amounts by nNOS and eNOS is involved in neurotransmission in the retina and in the regulation of retinal arteriolar tonicity. NO produced in large quantities by iNOS is a bactericidal agent but can also generate inflammation of the retina and even retinal degeneration.