Sleep and stressor exposure in relation to circadian rhythms in catecholamine excretion

12 healthy male volunteers spent 64 h of continuous waking under strictly controlled environmental conditions (light, food, drink, activity) in isolation from the external world. Before and after the vigil the subjects slept in the laboratory. An additional group of five participated only during day time and spent the intervening night period asleep at home. Measurements were carried out in 3 h intervals except for sleep periods. Shortly before the circadian trough and peak of adrenaline excretion respectively, the subjects were exposed to a performance stressor. Results from the vigil showed a very pronounced circadian rhythm for adrenaline excretion but none for noradrenaline excretion. For adrenaline, night-time sleep reduced excretion levels, causing an even more pronounced circadian pattern. For noradrenaline, night-time sleep caused a drop in excretion giving the impression of a circadian rhythm. These and previous results led to the conclusion that the excretion of adrenaline exhibits a self-sustained rhythm while a rhythm in noradrenaline excretion is found only when caused by external synchronizers such as sleep-wake alternation. No difference in magnitude of stress response between peak and trough was observed for any of the catecholamines. Night-time (trough) exposure completely obliterated the circadian rhythm of adrenaline excretion for the duration of the exposure. It was concluded that the normal pronounced night-time trough of adrenaline cannot be due to unavailability of adrenaline in the medulla. With respect to sleep deprivation, no effect was found on excretion levels during waking, during sleep, or in response to the stressor as deprivation progressed. Finally, there was also found to be a close temporal covariation between adrenaline excretion and both rectal temperature and self-rated fatigue (neg.).