Differential Regulation of the 24 Hour Pattern of Serum Melatonin and N-Acetylserotonin

While conducting a series of investigations with the objective of developing a highly specific radioimmunoassay for melatonin (MEL), we developed two assay systems one capable of measuring both MEL and N-acetylserotonin (NAS) activities, the other capable of measuring melatonin specifically. Results of investigations using these assays provided strong evidence that the 2 substances have different 24 hour patterns in serum. We have therefore undertaken the development of a highly specific radioimmunoassay for NAS and have used it to conduct a more detailed examination of this issue. Current findings indicate that dissociation of the 24 hour pattern of serum MEL and NAS occurs under conditions of short photoperiod. These findings suggest that different mechanisms may be involved in regulation of circulating NAS as compared to MEL.