GREATER EFFICACY OF EPISODIC THAN CONTINUOUS GROWTH HORMONE-RELEASINGHORMONE (GHRH) ADMINISTRATION IN PROMOTING SLOW-WAVE SLEEP (SWS)

It has been suggested that growth hormone (GH)-releasing hormone (GHRH ) stimulates the surge in GH and enhances slow-wave sleep (SWS), two p henomena that characterize the beginning of nocturnal sleep. However, in human studies the effects of systemic GHRH administration on sleep were not consistent. This may reflect the differential influence of ad ministration procedures being episodic in one of the above studies, bu t either a continuous infusion or a single bolus in the others. The pr esent study in healthy volunteers compared changes in nocturnal sleep following 200 mu g GHRH administered iv either episodically (4 boluses of 50 mu g each at 2200, 2300, 2400, and 0100 h) or as a continuous i nfusion (57 mu g/h between 2130 and 0100 h). Time spent in stage 4 of SWS on nights of episodic GHRH administration significantly exceeded t hat on nights of continuous GHRH administration (P < 0.01). Compared w ith a placebo condition, episodic administration of GHRH enhanced SWS (P < 0.01) and rapid eye movement (REM) sleep (P < 0.05) and diminishe d time spent in wakefulness and sleep stage 1 (P < 0.05). Effects of c ontinuous GHRH infusion on sleep generally remained insignificant comp ared with placebo. Plasma GH concentrations were enhanced during both conditions of GHRH administration (P < 0.01), with the increase follow ing episodic administration slightly exceeding that during continuous infusuion (P < 0.05). The results support a greater physiological effi cacy of episodic GHRH stimulation in promoting sleep.