Effect of apomorphine on melatonin secretion in normal subjects

There is some evidence in animals that dopamine (DA) affects melatonin secretion. The effect of apomorphine (Apo), a selective DA receptor agonist, and placebo on day-time melatonin secretion was studied in six normal men. Apo HCl in a dose (0.5 mg sc) which increased growth hormone secretion in all subjects had no effect on day-time melatonin concentrations in plasma. In keeping with other clinical studies these data suggest that melatonin secretion is not regulated by a DA mechanism in man.