NOS1 and muscular dystrophy: Amplification of NO-cGMP signaling by administration of the PDE5A inhibitor sildenafil reduces functional deficits in cardiac performance and skeletal muscle pathology and function in aged mdx mice.72–73 The nNOS signaling pathway is a potential therapeutic target not only for DMD, but for multiple other muscular dystrophies in which nNOSμ is also mislocalized.