Renin as a biological marker of the NREM-REM sleep cycle: effect of REM sleep suppression.

We have previously described that, in normal man, the nocturnal oscillations of plasma renin activity (PRA) exactly reflect the rapid eye movement (REM)-non(N)REM sleep cycles, with increasing PRA levels during NREM sleep and decreasing levels during REM sleep. This study was carried out to determine whether REM sleep suppression affects nocturnal renin profiles and to define which sleep stage is essential for renin release. In a first experimental series, REM sleep was suppressed by using clomipramine, a tricyclic antidepressant. Seven healthy young men were studied once during a night when a placebo was given and once during a night following a single dose of 50 mg clomipramine. Blood was collected every 10 min from 23.00 hours to 07.00 hours. PRA was measured by radio-immunoassay and the nocturnal profiles were analysed using the pulse detection program ULTRA. Clomipramine suppressed REM sleep in all subjects but one, but did not affect the number of SWS episodes nor their duration. Similar PRA profiles were observed in both experimental conditions. Neither the mean levels, nor the number and the amplitude of the oscillations were modified and the normal relationship between slow wave sleep and increasing PRA levels was preserved. In a second experimental series, REM sleep was prevented by rapidly awakening the subjects as soon as they fell into REM sleep. The four subjects studied attempted several times to go into REM sleep, but only when PRA levels were decreasing. The interruption of REM sleep by short waking periods did not disturb PRA for which the oscillations remained unaffected. Again, the relationship between SWS and increasing PRA levels was preserved. These results provide evidence that mechanisms increasing slow-wave activity are principally involved in increasing PRA levels and that replacing REM sleep by waking periods and light sleep does not modify nocturnal PRA oscillations.