Abstract
Summary
Plasma 17-hydroxycorticosteroids (17-OHCS) exhibited a significant circadian rhythm in rhesus monkeys (M. mulatta) in the first week of life. In two experiments, plasma 17-OHCS levels averaged 35 μg/100 ml at 8-9:00 am, and declined to levels of 29 μg/100 ml at 9:00 pm (Expt. I) and 24 μg/100 ml at 12:00 midnight (Expt. II). These changes were about half the magnitude reported by others in the adult monkey. Correlated with this steroid rhythm, the infant monkey, although having a polyphasic 24-hr sleep pattern, also exhibited a tendency to sleep more at 1:00 and 3:00 am than at other times of the day. This suggested a relationship between sleep–activity cycles and steroid cycles in the infant monkey similar to that in the adult monkey.
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