A QUANTITATIVE-EVALUATION OF THE RELATIONSHIPS BETWEEN GROWTH-HORMONESECRETION AND DELTA-WAVE ELECTROENCEPHALOGRAPHIC ACTIVITY DURING NORMAL SLEEP AND AFTER ENRICHMENT IN DELTA-WAVES

The existence of a relationship between growth hormone (GH) release an d slow-wave sleep (SWS), often studied in the past using conventional scoring of sleep stages, remains controversial. In the present study, this relationship was reevaluated by spectral analysis of the sleep el ectroencephalogram (EEG) and deconvolution analysis of the plasma GH c oncentrations during normal nocturnal sleep and after enrichment in SW S by means of ritanserin, a selective 5-HT2 receptor antagonist. Eight healthy male subjects each participated in two randomized night studi es after having received either a placebo or a 5-mg dose of ritanserin . They were subjected to 8 hours of polysomnography, including spectra l analysis of the sleep EEG. Plasma GH levels were measured at 10-minu te intervals. The mean delta absolute power and the mean GH secretory rates were significantly higher under ritanserin than under placebo fo r the first 3 hours after sleep onset (+24% and +29%, respectively). T heir nocturnal profiles were significantly and positively correlated i n all subjects (average r = 0.710 under placebo, 0.567 under ritanseri n; p < 0.0001 in both cases). GH secretory pulses were found to be coi ncident with delta activity peaks in both directions. The amount of GH secreted during significant GH pulses was correlated with the amount of concomitant delta wave activity (r = 0.803 under placebo, r = 0.764 under ritanserin, p < 0.0001). Similarly, the amount of delta wave ac tivity found during delta wave peaks was correlated with the amount of GH secreted concomitantly (r = 0.715 under placebo, r = 0.723 under r itanserin; p < 0.0001). These results demonstrate a close temporal and quantitative relationship between GH secretion and delta wave activit y, which may be evidence of common stimulatory mechanisms.