Abstract

A specific and sensitive assay for N-acetylserotonin, the precursor of the pineal hormone melatonin, is described. The levels of N-acetylserotonin in the pineal gland rise in vivo after the administration of l-isoproterenol. l-Propranolol, a beta adrenergic blocking agent, reverses the rise in N-acetylserotonin caused by isoproterenol within 15 min. Phentolamine, an alpha adrenergic blocking agent, is without effect. Turning on the lights or administering l-propranolol at night causes a rapid decrease in the amount of N-acetylserotonin in the pineal. Thus the level of N-acetylserotonin varies as does the level of N-acetyltransferase, which in turn is controlled by stimulation of a beta adrenergic receptor.