Sleep-related changes in baroreflex sensitivity and cardiovascular autonomic modulation.
OBJECTIVE
We examined the effects of the various sleep stages on baroreflex sensitivity (BRS), and heart rate and blood pressure (BP) variability, and tested the hypothesis that there is a different behavior of the baroreflex control of the sinus node in response to hypertensive and hypotensive stimuli and in relation to different cycles of the overnight sleep.


METHODS
Polygraphic sleep recordings were performed in 10 healthy males. The BP and the RR interval were continuously recorded during sleep.


METHODS
BRS was calculated by the sequences method. Autoregressive power spectral analysis was used to investigate the RR-interval and BP variabilities.


RESULTS
During rapid eye movement (REM) sleep BRS significantly increased in response to hypertensive stimuli in comparison with non-rapid eye movement (NREM) sleep and the awake state, whereas it did not change in response to hypotensive stimuli. In the first sleep cycle, BRS significantly increased during NREM in comparison with wakefulness, whereas during REM BRS in response to hypertensive stimuli did not show significant changes as compared with the awake state and/or with NREM. During REM occurring in the sleep cycle before morning awakening, BRS showed a significant increase in response to hypertensive stimuli in comparison with both NREM and the awake state.


CONCLUSIONS
During sleep, arterial baroreflex modulation of the sinus node is different in response to hypotensive and hypertensive stimuli particularly during REM. Furthermore, baroreflex control of the sinus node shows a non-uniform behavior during REM occurring in different nocturnal sleep cycles. These findings suggest that the arterial baroreflex is more effective in buffering the increased sympathetic activation associated with REM at the end of sleep than in the early night.
Legramante
Jacopo M
JM
Dipartimento di Medicina Interna-Centro di Riabilitazione Cardiologica San Raffaele-Pisana, Université di Roma, Rome, Italy. legramante@med.uniroma2.it
Marciani
Maria G
MG
Placidi
Fabio
F
Aquilani
Stefano
S
Romigi
Andrea
A
Tombini
Massimo
M
Massaro
Michele
M
Galante
Alberto
A
Iellamo
Ferdinando
F
D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology*; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D001919:Bradycardia / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D012849:Sinoatrial Node / Q000294:innervation / Q000502:physiology; D012895:Sleep, REM / Q000502:physiology*