Diurnal rhythms of immunoreactive N-acetylserotonin and melatonin in the serum of male rats

Immunoreactive N-acetylserotonin and melatonin in rat serum were extracted by ethyl acetate at less than or equal to pH 3 and chloroform at greater than or equal to pH 10, respectively, following protein precipitation and were quantified by radioimmunoassays. There were diurnal rhythms of N-acetylserotonin and melatonin in the serum of rats (housed in 121/12d; lights on from 06.00-18.00 h for two weeks). Serum melatonin levels 20.00-04.00 h are …