Sleep-related changes in the regulation of cerebral blood flow in newborn lambs.
OBJECTIVE
The interplay between cerebral perfusion pressure (CPP) and vascular resistance leads to fluctuations in cerebral blood flow (CBF). The relationship between fluctuations in CBF and those in CPP provides insight into the impact of the regulation of vascular resistance on CBF. The aim of this work was to study sleep-related changes in CBF regulation in newborn lambs, by quantifying the extent to which variability in CBF is related to that of CPP in the different wake-sleep states.


METHODS
Repeated-measurement within-subject.


METHODS
8 newborn lambs.


METHODS
Chronic instrumentation with electrodes (electrocorticogram, electrooculogram, nuchal electromyogram), an arterial catheter (arterial pressure), a subdural catheter (intracranial pressure), and an ultrasonic flow probe around the superior sagittal sinus (CBF).


RESULTS
The CPP (difference between arterial and intracranial pressure) and CBF data sequences during quiet wakefulness, rapid-eye-movement (REM) sleep and non-REM sleep were subject to spectral analysis. The fraction of CBF variability explained by CPP variability (CPP vs CBF squared coherence in the range 0.05-0.3 Hz) was highest in REM sleep (0.653) and lowest in non-REM sleep (0.413). The CBF variability (coefficient of variation due to fluctuations in the range 0.05-0.3 Hz) was higher than CPP variability in all states, albeit not significantly in REM sleep.


CONCLUSIONS
Results suggest that synchronized vasomotor fluctuations accounting for a quota of CBF variability not explained by CPP variability occur in all states in newborn lambs. Their relative contribution to CBF variability differs among wake-sleep states, being highest during non-REM sleep and lowest during REM sleep.
Dipartimento di Fisiologia Umana e Generale, Università di Bologna, Bologna, Italy.
Alessandro
A
Silvani
Tijana
T
Bojic
Carlo
C
Franzini
Pierluigi
P
Lenzi
Adrian M
AM
Walker
Daniel A
DA
Grant
Jennene
J
Wild
Giovanna
G
Zoccoli
D000818:Animals; D001921:Brain / Q000098:blood supply*; D004576:Electromyography; D004585:Electrooculography; D012756:Sheep; D012895:Sleep, REM / Q000502:physiology*; D015854:Up-Regulation; D014851:Wakefulness / Q000502:physiology