Overview of the mechanisms of action of NO donors and related drugs. Abbreviations are as follows: cGMP, cyclic guanosine 3′,5′-monophosphate; eNOS, endothelial nitric oxide synthase; GSNO, S-nitrosogluthione; GSNOR, S-nitrosoglutathione reductase; GTP, guanosine triphosphate; NO, nitric oxide; PDE5, phosphodiesterase 5; sGC, soluble guanylyl cyclase; SNOs, S-nitosothiols