title: A cholinergic contribution to the circulatory responses evoked at the onset of handgrip exercise in humans.
abstract: A cholinergic (muscarinic) contribution to the initial circulatory response to exercise in humans remains controversial. Herein, we posit that this may be due to exercise mode with a cholinergic contribution being important during isometric handgrip exercise, where the hyperemic response of the muscle is relatively small compared with the onset of leg cycling, where a marked increase in muscle blood flow rapidly occurs as a consequence of multiple redundant mechanisms. We recorded blood pressure (BP; brachial artery), stroke volume (pulse contour analysis), cardiac output, and systemic vascular resistance (SVR) in young healthy males, while performing either 20 s of isometric handgrip contraction at 40% maximum voluntary contraction (protocol 1; n = 9) or 20 s of low-intensity leg cycling exercise (protocol 2; n = 8, 42 ± 8 W). Exercise trials were conducted under control (no drug) conditions and following cholinergic blockade (glycopyrrolate). Under control conditions, isometric handgrip elicited an initial increase in BP (+5 ± 2 mmHg at 3 s and +3 ± 1 mmHg at 10 s, P < 0.05), while SVR dropped after 3 s (-27 ± 6% at 20 s; P < 0.05). Cholinergic blockade abolished the isometric handgrip-induced fall in SVR and, thereby, augmented the pressor response (+13 ± 3 mmHg at 10 s; P < 0.05 vs. control). In contrast, cholinergic blockade had a nonsignificant effect on changes in BP and SVR at the onset of leg cycling exercise. These findings suggest that a cholinergic mechanism is important for the BP and SVR responses at the onset of isometric handgrip exercise in humans.
authors.affiliation: Faculty of Physical Education, University of Brasília, Brasília, Brazil;
authors.forename: Lauro C
authors.initials: LC
authors.lastname: Vianna
authors.affiliation: Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri;
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Fadel
authors.affiliation: Department of Anaesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Denmark; and.
authors.forename: Niels H
authors.initials: NH
authors.lastname: Secher
authors.affiliation: School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, United Kingdom j.p.fisher@bham.ac.uk.
authors.forename: James P
authors.initials: JP
authors.lastname: Fisher
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D001642:Bicycling; D001794:Blood Pressure; D001808:Blood Vessels / Q000294:innervation*; D002302:Cardiac Output; D002799:Cholinergic Fibers / Q000187:drug effects / Q000502:physiology*; D015444:Exercise; D006024:Glycopyrrolate / Q000494:pharmacology; D006225:Hand; D018737:Hand Strength; D064368:Healthy Volunteers; D006339:Heart Rate; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007537:Isometric Contraction; D035002:Lower Extremity; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D018482:Muscle, Skeletal / Q000098:blood supply*; D012039:Regional Blood Flow; D013997:Time Factors; D014655:Vascular Resistance; D055815:Young Adult
chemical_list: D018727:Muscarinic Antagonists; D006024:Glycopyrrolate
keywords: blood pressure; hemodynamic; systemic vascular resistance