Vasomotor tone and the role of nitric oxide

Vasomotor tone is the end result of a complex set of interactions that control relaxation and contraction of blood vessels. The critical role of nitric oxide (NO) in modulating vasomotor tone has become increasingly apparent over the last 15 years. A phenomenal amount of resources have been invested in the study of this simple molecule, and the volume of scientific literature that has resulted is astounding. In this review, we discuss the pertinent physiology and biochemistry of NO as it relates to the control of vasomotor tone. Methods of measuring NO in basic science and clinical settings are outlined, and the derangements of endothelial NO production and release (endothelial dysfunction) in pathophysiologic and disease states are discussed. Finally, potential therapies aimed at preserving endothelial function and augmenting NO production also are reviewed.