What is the important action of nitrates in angina?: (A) Coronary vasodilation, (B) Decreases preload, (C) Decreases afterload, (D) Decreases heart rate
Answer is B. Ans. B. Decreases preloadNitrates cause release of nitric oxide which causes activation of guanylyl cyclase and through series of steps (via activation of protein kinase and phosphatases) activate myosin light chain through dephosphorylation which causes smooth muscle relaxation and hence vasodilatation. This decreases systemic vascular resistance and there will be increased pooling of blood. All of these events can lead to decrease in preload.