Fig. 1. Skeletal-muscle-derived NO enhances blood flow to contracting muscle. nNOSµ occurs at the skeletal muscle plasma membrane as a component of the dystrophin glycoprotein complex. The PDZ domain (pink) from nNOS binds to the PDZ domain of syntrophin (Syn), which independently binds to both dystrophin and dystrobrevin. Dystrophin itself adheres to the membrane by binding to glycoproteins such as dystroglycan (DG). Skeletal-muscle-derived NO diffuses to adjacent blood vessels to increase perfusion of contracting muscle.