Nocturnal Elevation of Plasma Melatonin and Urinary 5-Hydroxyindoleacetic Acid in Young Men: Attempts at Modification by Brief Changes in Environmental Lighting and Sleep and by Autonomic Drugs.

摘要

In order to determine if the human pattern of circulating melatonin resembles that described in lower animals, men 19 to 32 years old were exposed to a light-dark cycle with 14 hours of light per day (L:D 14:10). In whites and blacks, nocturnal (dark phase, sleeping) melatonin levels were almost always elevated to 0.5 to 1.0 ng/10 ml of plasma compared to lower or undetectable levels during the day, measured by the tadpole bioassay. Thin-layer migration of bioactive material was identical to that for melatonin standard. Nocturnal (sleep phase) rise in blood melatonin continued during 2-1/2 day-night cycle lengths after onset of constant light. A sleep period at the end of a light phase in the standard light cycle failed to prematurely elevate melatonin. A rhythm with nocturnal elevation of urinary 5-hydroxyindoleacetic acid (5-HIAA) was observed. This was abolished after two days of constant light, but no clear effect was seen after reversing the sleep cycle. Though marked cardiovascular and other effects were produced by intravenous isoproterenol or scopolamine, no definite effect on melatonin levels was observed after either drug during the light phase in waking subjects.