title: Influence of muscle metaboreceptor stimulation on middle cerebral artery blood velocity in humans.
abstract: Regional anaesthesia to attenuate skeletal muscle afferent feedback abolishes the exercise-induced increase in middle cerebral artery mean blood velocity (MCA Vmean). However, such exercise-related increases in cerebral perfusion are not preserved during post exercise muscle ischaemia (PEMI) where the activation of metabolically sensitive muscle afferents is isolated. We tested the hypothesis that a hyperventilation-mediated decrease in the arterial partial pressure of CO2, hence cerebral vasoconstriction, masks the influence of muscle metaboreceptor stimulation on MCA Vmean during PEMI. Ten healthy men (20 ± 1 years old) performed two trials of fatiguing isometric hand-grip exercise followed by PEMI, in control conditions and with end-tidal CO2 (P ET ,CO2) clamped at ∼1 mmHg above the resting partial pressure. In the control trial, P ET ,CO2 decreased from rest during hand-grip exercise and PEMI, while MCA Vmean was unchanged from rest. By design, P ET ,CO2 remained unchanged from rest throughout the clamp trial, while MCA Vmean increased during hand-grip (+10.6 ±1.8 cm s(-1)) and PEMI (+9.2 ± 1.6 cm s(-1); P < 0.05 versus rest and control trial). Increases in minute ventilation and mean arterial pressure during hand-grip and PEMI were not different in the control and P ET ,CO2 clamp trials (P > 0.05). These findings indicate that metabolically sensitive skeletal muscle afferents play an important role in the regional increase in cerebral perfusion observed in exercise, but that influence can be masked by a decrease in P ET ,CO2 when they are activated in isolation during PEMI.
authors.affiliation: School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK.
authors.forename: Igor D
authors.initials: ID
authors.lastname: Braz
authors.affiliation: School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK.
authors.forename: Clare
authors.initials: C
authors.lastname: Scott
authors.affiliation: School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK.
authors.forename: Lydia L
authors.initials: LL
authors.lastname: Simpson
authors.affiliation: School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK.
authors.forename: Emma L
authors.initials: EL
authors.lastname: Springham
authors.affiliation: School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK.
authors.forename: Beverly W L
authors.initials: BW
authors.lastname: Tan
authors.affiliation: School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK.
authors.forename: George M
authors.initials: GM
authors.lastname: Balanos
authors.affiliation: School of Sport, Exercise & Rehabilitation Sciences, College of Life & Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UK j.p.fisher@bham.ac.uk.
authors.forename: James P
authors.initials: JP
authors.lastname: Fisher
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology*; D002245:Carbon Dioxide / Q000097:blood; D002560:Cerebrovascular Circulation / Q000502:physiology; D004562:Electrocardiography; D005260:Female; D006225:Hand / Q000502:physiology; D018737:Hand Strength / Q000502:physiology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D020768:Middle Cerebral Artery / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000378:metabolism* / Q000502:physiology*; D009475:Neurons, Afferent / Q000502:physiology*; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide