nNOS (Neuronal Nitric Oxide Synthase)

Nitric Oxide Synthases are a family of enzymes responsible for the synthesis of nitric oxide from L-arginine and molecular oxygen. There are at least three nitric oxide synthases; NOS I, also known as neuronal NOS or nNOS, NOS II, which is referred to as inducible NOS or iNOS and NOS III, also known as endothelial NOS or eNOS. nNOS plays a role in  the upregulation of microglial phospho-p38 MAPK. Such p38 MAPK activation in microglia is consistent with a potential role in the development of morphine antinociceptive tolerance.