Impact of melatonin on central blood pressure regulation

The dysbalance between the sympathetic and parasympathetic vegetative system and increased free radical burden in the central nervous system (CNS) are the important pathophysiological disorders and therapeutic targets in hypertension. Besides the effects on cardiovascular system, the pineal hormone, melatonin (N-acetyl-5-methoxytryptamine) may exert part of its antihypertensive action just through its interaction with the CNS. Melatonin may be protective in CNS on several different levels: it reduces production of reactive oxygen species, improves endothelial dysfunction, reduces inflammation and shifts the balance between the sympathetic and parasympathetic system in favor of the parasympathetic system. Increased level of serum melatonin observed in some types of hypertension may represent a counterregulatory adaptive mechanism against the sympathetic overstimulation. All these effects of melatonin may include increased production of nitric oxide in their mechanisms of protection. In different experimental models of hypertension upregulation of nitric oxide synthase (NOS) activity and NOS isoform expression in different parts of brain after melatonin treatment have been documented. Thus, it is supposed that the correction of absolute or relative melatonin deficiency by exogenous melatonin administration in conditions of increased blood pressure, may help to attenuate the excessive catecholamine outflow providing a rational background for therapeutic application of melatonin in hypertension treatment.