Animation of the Nitric Oxide/Cyclic GMP Pathway

Fig. 1. The cyclic GMP pathway in vasodilation. When needed, certain drugs with vasoactive properties are released into the blood. These substances interact with specific receptors located at the endothelial layer of the vessel producing an elevation of calcium concentration inside the cells. Calcium activates an enzyme (endothelial nitric oxide synthase or eNOS) that makes nitric oxide (usually abbreviated as NO). Nitric oxide reach neighbour cells (other endothelial cells, blood cells and muscle cells of the vessel). In myocytes (muscle cells), nitric oxide stimulate other enzyme: soluble guanylyl cyclase. Guanylyl cyclase synthesizes cyclic GMP which is able to activate protein kinase G. This enzyme mediates vasodilation, that is the increase in the diameter of the blood vessel and in consequence the decrease in blood pressure.