Nitric Oxide Synthase (NOS) catalyses the formation of nitric oxide (NO) and citruline from L-arginine, oxygen and cofactors. Three family members have been characterized: neuronal NOS (nNOS), which is found primarily in neuronal tissue; inducible NOS (iNOS), which is induced by interferon gamma and lipopolysaccharides in the kidney and cardiovascular system; and endothelial NOS (eNOS), which is expressed in blood vessels (1). NO is a messenger molecule with diverse functions throughout the body including the maintenance of vascular integrity, homeostasis, synaptic plasticity, long-term potentiation, learning, and memory (2,3). nNOS binds selectively to the second PDZ domain of PSD-95, and the enzymatic activity of nNOS is either downregulated by phosphorylation at Ser847 by CaM-KII or stimulated by calcium influxes governed by the NMDA receptor channels (4-5).