Effect of isoproterenol upon serotonin N-acetyltransferase (SNAT) activity and melatonin production in the chick pineal gland

The administration of isoproterenol to chicks (5 days after hatching) resulted in a modest increase in pineal serotonin N-acetyltransferase (SNAT) activity and a decrease in pineal melatonin levels. The changes observed following isoproterenol administration did not occur consistently in a dose-related or time-course related manner, nor were these changes of the magnitude seen in endogenous nocturnal melatonin levels. Therefore, interpretation of the physiological significance of the isoproterenol-induced changes in melatonin and SNAT must be carefully evaluated.