Sympatho‐Adrenal Activity in Different Hypertensive Disorders in Pregnancy: A short review

The sympathetic nervous system is involved in blood pressure regulation in normal and hypertensive man via postganglionic nerve transmission mediated by norepinephrine, acting mainly on the α‐receptor to cause vaso‐constriction, and also via adrenomedullary secretion by epinephrine, acting mainly on the β‐receptors which will give rise to increased cardiac output and vasodilation in the muscular beds. Conflicting results regarding the role of the sympathoadrenal system in hypertension of pregnancy have been reported. This may be attributed partly to the varying methods that have been used to study this system. Specific measurement of the the activity of the sympathetic nerves is difficult, although direct recording of their activity has been performed (15). At present, plasma norepinephrine is considered to be an index of sympathoneural activity, reflecting the rate of release at the postganglionic nerve endings (5, 11) and plasma epinephrine is considered to be a marker of adrenal activity, since it is derived almost exclusively from the adrenal glands (5).