Beta-adrenoceptor agonists do not stimulate daytime melatonin secretion in healthy subjects. A double blind placebo...

Noradrenergic stimulation of pineal beta-adrenoceptors results in melatonin secretion. To investigate beta-adrenoceptor mediated plasma melatonin responses in humans, ritodrine, salbutamol (beta 2-adrenoceptor agonists) and dobutamine (beta 1-adrenoceptor agonist) were infused from 0900 to 1200 h to 8 healthy subjects (four men and four women) in a double blind, crossover, placebo controlled study. Ritodrine and salbutamol significantly increased plasma cyclic AMP and decreased serum potassium concentrations indicating the presence of beta 2-adrenoceptor stimulation. Dobutamine substantially increased systolic blood pressure corresponding to its beta 1-adrenoceptor agonist propriety. However, neither beta 2- nor beta 1-adrenoceptor stimulation modified plasma melatonin concentration. These results show that beta-adrenoceptor agonists do not increase daytime plasma melatonin concentration.