What is the mechanism of action of nitroglycerin in treating angina pectoris?

Nitroglycerin is a nitric oxide (NO) donor. It is metabolized to release NO, which activates guanylyl cyclase in vascular smooth muscle cells. This leads to increased intracellular cyclic GMP (cGMP), which activates protein kinase G, dephosphorylates myosin light chains, and causes smooth muscle relaxation and vasodilation. The resulting venodilation reduces preload (cardiac filling) and reduces myocardial oxygen demand, relieving anginal pain. Nitroglycerin is the emergency treatment for acute angina in the dental office — patients should carry their nitroglycerin and take it sublingually.