Circadian Rhythms of Epinephrine and Norepinephrine in Man*

TLDR

The study investigated the diurnal rhythms of plasma epinephrine and norepinephrine in normal young men. Sleep, posture, illumination, and food intake were monitored. Plasma epinephrine and norepinephrine both exhibited significant diurnal rhythms (amplitudes 14 pg/ml and 111 pg/ml, troughs at 03:20 h and 02:20 h, respectively) with a moderate correlation (r = 0.49); epinephrine levels were independent of sleep or posture, whereas norepinephrine rose with upright posture and wakefulness, suggesting the norepinephrine rhythm reflects behavioral state while the epinephrine rhythm is governed by a circadian oscillator.

Abstract

The diurnal rhythms of plasma epinephrine and norepinephrine were investigated in a group of normal young men. Sleep, posture, illumination, and food intake were monitored. Plasma epinephrine demonstrated a statistically significant diurnal rhythm, with a mean amplitude of 14 ± 1.6 (±SE) pg/ml superimposed on a mean level of 43 ± 5.3 pg/ml. The trough occurred at 03.20 h ± 35 min. Plasma norepinephrine had a significant diurnal rhythm, with a mean amplitude of 111 ± 19 pg/ml superimposed on a mean level of 413 ± 25 pg/ml, with the trough occurring at 02.20 h ± 30 min. There was a significant correlation between the two rhythms at zero phase shift, with a pooled value for the group of r = 0.49. Epinephrine levels had no direct relationship to sleep or posture, whereas norepinephrine levels were significantly higher with upright posture and higher when the men were awake than when asleep. Our results indicate that circadian variations in the sympatheticadrenal medullary system are not explained by a single controlling influence and that the norepinephrine rhythm can be accounted for as a direct response to changes in posture and sleep, whereas the epinephrine rhythm is probably controlled by a circadian oscillator.