An organic nitrate with vasodilator activity. Nitroglycerin is converted into nitric oxide (NO) in smooth muscle and activates guanylyl cyclase, thereby increasing cGMP concentration, and resulting in smooth muscle relaxation. Dilatation of the veins results in decreased venous return to the heart, thereby decreasing left ventricular volume (reduced preload) and decreasing myocardial oxygen requirements. Arteriolar relaxation reduces arteriolar resistance (reduced afterload), thereby decreasing myocardial oxygen demands. In addition, nitroglycerin causes coronary artery dilatation, thereby improving myocardial blood distribution.