Evidence of a cerebrovascular postarteriole windkessel with delayed compliance.
A pronounced temporal mismatch was observed between the responses of relative cerebral blood volume (rCBV) measured by magnetic resonance imaging and relative cerebral blood flow measured by laser-Doppler flowmetry in rat somatosensory cortex after electrical forepaw stimulation. The increase of relative cerebral blood flow after stimulus onset and decrease after stimulus cessation were accurately described with a single exponential time constant of 2.4 +/- 0.8 seconds. In contrast, rCBV exhibited two distinct and nearly sequential processes after both onset and cessation of stimulation. A rapid change of rCBV (1.5 +/- 0.8 seconds) occurring immediately after onset and cessation was not statistically different from the time constant for relative cerebral blood flow. However, a slow phase of increase (onset) and decrease (cessation) with an exponential time constant of 14 +/- 13 seconds began approximately 8 seconds after the rapid phase of CBV change. A modified windkessel model was developed to describe the temporal evolution of rCBV as a rapid elastic response of capillaries and veins followed by slow venous relaxation of stress. Venous delayed compliance was suggested as the mechanism for the poststimulus undershoot in blood oxygen-sensitive magnetic resonance imaging signal that has been observed in this animal model and in human data.
Mandeville
J B
JB
MGH-NMR Center and Department of Radiology, Massachusetts General Hospital, Boston, 02129, USA.
Marota
J J
JJ
Ayata
C
C
Zaharchuk
G
G
Moskowitz
M A
MA
Rosen
B R
BR
Weisskoff
R M
RM
D000465:Algorithms; D000818:Animals; D001160:Arterioles / Q000502:physiology; D001810:Blood Volume / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003187:Compliance; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008279:Magnetic Resonance Imaging; D008297:Male; D008959:Models, Neurological; D051381:Rats; D017207:Rats, Sprague-Dawley; D013312:Stress, Physiological / Q000503:physiopathology