Neuroendocrine processes underlying ultradian sleep regulation in man.
Sleep is not a uniform state but is characterized by the cyclic alternation between rapid eye movement (REM) and non-REM sleep with a periodicity of 90-110 min. This cycle length corresponds to one of the oscillations in electroencephalographic (EEG) activity in the delta frequency band (0.5-3.5 Hz), which reflect the depth of sleep. To demonstrate the intimate link between EEG and neuroendocrine rhythmic activities in man, we adopted a procedure permitting simultaneous analysis of sleep EEG activity in the delta band and of two activating systems: the adrenocorticotropic system and the autonomic nervous system. Adrenocorticotropic activity was evaluated by calculating the cortisol secretory rate in blood samples taken at 10-min intervals. Autonomic activity was estimated by two measures of heart rate variability: 1) by the ratio of low-frequency (LF) to high-frequency (HF) power from spectral analysis of R-R intervals; and 2) by the interbeat autocorrelation coefficient of R-R intervals (rRR intervals between two successive cardiac beats). The results revealed that oscillations in delta wave activity, adrenocorticotropic activity, and autonomic activity are linked in a well-defined manner. Delta wave activity developed when cortisol secretory rates had returned to low levels and sympathetic tone was low or decreasing, as reflected by a low LF/HF ratio and by low levels in rRR. Conversely, the decrease in delta wave activity occurred together with an increase in the LF/HF ratio and in rRR. REM sleep was associated with a decrease in cortisol secretory rates preceding REM sleep onset, whereas the LF/HF ratio and rRR remained high. These results demonstrate a close coupling of adrenocorticotropic, autonomic, and EEG ultradian rhythms during sleep in man. They suggest that low neuroendocrine activity is a prerequisite for the increase in slow wave activity.
Gronfier
C
C
Laboratoire des Régulations Physiologiques et des Rythmes Biologiques, Strasbourg, France.
Simon
C
C
Piquard
F
F
Ehrhart
J
J
Brandenberger
G
G
D000328:Adult; D002940:Circadian Rhythm; D004562:Electrocardiography; D004569:Electroencephalography; D006339:Heart Rate; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D008297:Male; D012890:Sleep / Q000502:physiology*
D006854:Hydrocortisone