[Melatonin and regulation of the cardiovascular system]

Evidence from the last 10 years suggests that melatonin may influence the cardiovascular system. Vascular melatoninergic receptors/sites have been demonstrated and are functionally linked with vasoconstrictor or vasodilatory effects of low (10(-9)-10(-7) M) and high (10(-6)-10(-3) M) melatonin concentrations respectively. Furthermore several other properties of the neurohormone (e.g. sympathetic inhibition) could contribute to cardioprotection. In vivo melatonin beneficially affects the rat cerebrovascular circulation and protects the rat heart following myocardial ischaemia. In this regard, preliminary clinical data report some alteration of the melatoninergic system in human stroke and coronary heart disease. Finally, the suprachiasmatic nucleus and possibly the melatoninergic system may modulate cardiovascular rhythmicity. Clinical cardiovascular data on melatonin treatment are very scarce; the effects of a therapy modulating the melatoninergic system on cardiovascular haemodynamics and rhythmicity under several physiopathological conditions need to be further explored together with the possible impact on cardiovascular morbidity and mortality.