HUMAN PLASMA DSIP DECREASES AT THE INITIATION OF SLEEP AT DIFFERENT CIRCADIAN TIMES

Nocturnal plasma delta sleep-inducing peptide-like immunoreactivity (D SIP-LI) was determined serially in seven healthy male subjects. Time c ourses during nocturnal sleep (2300-0800 h), nocturnal sleep deprivati on (2300-0500 h), and morning recovery sleep (0500-0800 h) after sleep deprivation were compared. A significant decrease in plasma DSIP-LI w as found at the transition from wakefulness to sleep in both evening s leep (2300 h) and morning recovery sleep (0500 h). Time courses were a ccompanied by physiological changes in sleep electroencephalographic s low-wave activity, and in plasma concentrations of cortisol and human growth hormone. No sleep stage specificity was found. It is concluded that DSIP is influenced by the initiation of sleep.