Influences of melatonin administration on the circulation of women.

The cardiovascular effects induced by the daytime administration of melatonin (1 mg) were compared with those of placebo in 17 young, healthy, early follicular-phase women. Compared with placebo, the administration of melatonin modified, within 90 min, the pulsatility index (PI), evaluated by color Doppler ultrasound, of the internal carotid artery, abdominal aorta, and axillary artery. The effect was linearly related to baseline PI, higher baseline PI being associated with greater PI declines. Melatonin administration significantly decreased mean PI of internal carotid artery (P < 0.02), systolic and diastolic blood pressure (P < 0.01), and norepinephrine levels evaluated after 5 min of standing position (P < 0.02). Heart rate and supine catecholamine levels were not modified. These data indicate that in young, healthy women the administration of 1 mg of melatonin greatly influences artery blood flow, decreases blood pressure, and blunts noradrenergic activation. Clinical implications of present data are worthy to be fully explored.