Carotid chemoreceptor modulation of blood flow during exercise in healthy humans.
Carotid chemoreceptor (CC) inhibition reduces sympathetic nervous outflow in exercising dogs and humans. We sought to determine if CC suppression increases muscle blood flow in humans during exercise and hypoxia. Healthy subjects (N = 13) were evaluated at rest and during constant-work leg extension exercise while exposed to either normoxia or hypoxia (inspired O(2) tension, F(IO(2)), ≈ 0.12, target arterial O(2) saturation = 85%). Subjects breathed hyperoxic gas (F(IO(2)) ≈ 1.0) and/or received intravenous dopamine to inhibit the CC while femoral arterial blood flow data were obtained continuously with pulsed Doppler ultrasound. Exercise increased heart rate, mean arterial pressure, femoral blood flow and conductance compared to rest. Transient hyperoxia had no significant effect on blood flow at rest, but increased femoral blood flow and conductance transiently during exercise without changing blood pressure. Similarly, dopamine had no effect on steady-state blood flow at rest, but increased femoral blood flow and conductance during exercise. The transient vasodilatory response observed by CC inhibition with hyperoxia during exercise could be blocked with simultaneous CC inhibition with dopamine. Despite evidence of dopamine reducing ventilation during hypoxia, no effect on femoral blood flow, conductance or mean arterial pressure was observed either at rest or during exercise with CC inhibition with dopamine while breathing hypoxia. These findings indicate that the carotid chemoreceptor contributes to skeletal muscle blood flow regulation during normoxic exercise in healthy humans, but that the influence of the CC on blood flow regulation in hypoxia is limited.
Division of Pulmonary Medicine, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada. michael.stickland@ualberta.ca
Michael K
MK
Stickland
Desi P
DP
Fuhr
Mark J
MJ
Haykowsky
Kelvin E
KE
Jones
D Ian
DI
Paterson
Justin A
JA
Ezekowitz
M Sean
MS
McMurtry
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D002344:Carotid Body / Q000502:physiology*; D004298:Dopamine / Q000494:pharmacology; D015444:Exercise / Q000502:physiology*; D005260:Female; D005263:Femoral Artery / Q000187:drug effects / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D007866:Leg; D008297:Male; D018482:Muscle, Skeletal / Q000098:blood supply / Q000502:physiology*; D012039:Regional Blood Flow / Q000502:physiology*; D014664:Vasodilation / Q000187:drug effects
D004298:Dopamine