PULSATILE CORTISOL SECRETION AND EEG DELTA-WAVES ARE CONTROLLED BY 2 INDEPENDENT BUT SYNCHRONIZED GENERATORS

We have previously described a temporal relationship between plasma co rtisol pulses and slow-wave sleep and, more recently, an inverse signi ficant crosscorrelation between cortisol secretory rates and delta wav e activity of the sleep electroencephalogram (EEG). The aim of this st udy was to observe ACTH, cortisol, and sleep delta wave activity varia tions throughout 24 h to get a better insight into their initiating me chanisms. Two groups of 10 subjects participated in a 24-h study one g roup with a night sleep (2300-0700) and the other with a day sleep (07 00-1500). Cortisol secretory rates were calculated by a deconvolution procedure from plasma levels measured at 10-min intervals. Delta wave activity was computed during sleep by spectral analysis of the sleep E EG. When delta waves and cortisol were present at the same time at the end of the night sleep as well as during the daytime sleep, they were negatively correlated, cortisol changes preceding variations in delta wave activity by similar to 10 min. Increases in delta wave activity occurred in the absence of cortisol pulses, as observed at the beginni ng of the night. Cortisol pulses occurred without any concomitant vari ations of sleep delta wave activity, as observed during wakefulness an d intrasleep awakenings. In no case did delta wave activity increase t ogether with an increase in cortisol secretory rates. In conclusion, c ortisol secretion and delta wave activity have independent generators. They can oscillate independently from each other, but when they are p resent at the same time, they are oscillating in phase opposition.