PROLACTIN SECRETION AND SLEEP

To clarify the relationship between prolactin (PRL) secretion and slee p, three experimental procedures were employed and secretory rates wer e estimated from plasma levels using a deconvolution procedure. Eight healthy young men participated in two 24-hour studies, one using norma l night sleep and one using delayed sleep, to determine the influence of sleep as a whole on the PRL rhythm. Another group of 24 subjects un derwent a 1-night study to investigate the relationship between PRL se cretion and the internal sleep structure. The influence of sleep quali ty was studied in two more groups of eight subjects. Secretory rates w ere calculated by deconvolution from plasma PRL measured at 10-minute intervals. Sleep was recorded polygraphically in all experiments. PRL secretory pulses occurred throughout the 24-hour cycle without signifi cant variation in frequency, but with enhanced pulse amplitude for bot h night and day sleep periods. Sleep onset was rapidly followed by an increase in secretion, and awakenings coincided with an immediate offs et of active secretion. Analyzing the association between secretory pu lses and sleep stages demonstrated that PRL secretory rate is low at t he time of rapid eye movement sleep onset. Sleep quality appeared not to affect the PRL secretory profile. These results confirmed that PRL secretion is enhanced during the whole sleep period, as inferred from plasma levels. Considering secretory pulses provides a precise determi nation of the temporal relations between PRL and sleep structure and d emonstrates that occasionally poor sleep does not influence PRL secret ion in normal humans.