The effect of changes in cardiac output on middle cerebral artery mean blood velocity at rest and during exercise.
We examined the relationship between changes in cardiac output and middle cerebral artery mean blood velocity (MCA V(mean)) in seven healthy volunteer men at rest and during 50% maximal oxygen uptake steady-state submaximal cycling exercise. Reductions in were accomplished using lower body negative pressure (LBNP), while increases in were accomplished using infusions of 25% human serum albumin. Heart rate (HR), arterial blood pressure and MCA V(mean) were continuously recorded. At each stage of LBNP and albumin infusion was measured using an acetylene rebreathing technique. Arterial blood samples were analysed for partial pressure of carbon dioxide tension (P(a,CO2). During exercise HR and were increased above rest (P < 0.001), while neither MCA V(mean) nor P(a,CO2) was altered (P > 0.05). The MCA V(mean) and were linearly related at rest (P < 0.001) and during exercise (P = 0.035). The slope of the regression relationship between MCA V(mean) and at rest was greater (P = 0.035) than during exercise. In addition, the phase and gain between MCA V(mean) and mean arterial pressure in the low frequency range were not altered from rest to exercise indicating that the cerebral autoregulation was maintained. These data suggest that the associated with the changes in central blood volume influence the MCA V(mean) at rest and during exercise and its regulation is independent of cerebral autoregulation. It appears that the exercise induced sympathoexcitation and the change in the distribution of between the cerebral and the systemic circulation modifies the relationship between MCA V(mean) and .
Ogoh
Shigehiko
S
Department of Integrative Physiology, University of North Texas Health Science Center at Fort Worth, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA. sogoh@hsc.unt.edu
Brothers
R Matthew
RM
Barnes
Quinton
Q
Eubank
Wendy L
WL
Hawkins
Megan N
MN
Purkayastha
Sushmita
S
O-Yurvati
Albert
A
Raven
Peter B
PB
D000328:Adult; D017704:Baroreflex / Q000502:physiology; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D001810:Blood Volume / Q000502:physiology; D002302:Cardiac Output / Q000502:physiology*; D003627:Data Interpretation, Statistical; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D020768:Middle Cerebral Artery / Q000502:physiology*; D012044:Regression Analysis; D012146:Rest / Q000502:physiology*; D012709:Serum Albumin / Q000008:administration & dosage
D012709:Serum Albumin