[Renin and its relations to the internal structure of sleep]

Simultaneous monitoring of plasma renin activity (PRA) levels and changes in sleep stages provides evidence of a close relation between PRA levels and the rapid eye movement (REM) and non (N)REM sleep cycles. NREM sleep is invariably linked to increasing PRA levels, and declining levels are observed when sleep become slighter. Spontaneous and provoked awakenings blunt the rise in PRA normally associated with NREM sleep. Thus, PRA curves exactly reflect the pattern of sleep stage distribution. When the sleep cycles are regular, PRA levels oscillate at a regular period. For incomplete sleep cycles, PRA curves reflect all irregularities in sleep structure. It appears that this association cannot be broken. In normal man, modifying the renal renin content only modulates the amplitude of the nocturnal oscillations without disturbing their relation to sleep stages. This relation persists in some pathological cases, such as narcolepsy and moderate hypertension. These results bear witness to the strength of the sleep-related processes generating the oscillations which are amplified or depressed by other factors known to control renin release.