title: Dopamine receptor blockade improves pulmonary gas exchange but decreases exercise performance in healthy humans.
abstract: Pulmonary gas exchange, as evaluated by the alveolar-arterial oxygen difference (A-aDO2), is impaired during intense exercise, and has been correlated with recruitment of intrapulmonary arteriovenous anastomoses (IPAVA) as measured by agitated saline contrast echocardiography. Previous work has shown that dopamine (DA) recruits IPAVA and increases venous admixture (Q̇s/Q̇t) at rest. As circulating DA increases during exercise, we hypothesized that A-aDO2 and IPAVA recruitment would be decreased with DA receptor blockade. Twelve healthy males (age: 25 ± 6 years, V̇O2 max : 58.6 ± 6.5 ml kg(-1) min(-1) ) performed two incremental staged cycling exercise sessions after ingestion of either placebo or a DA receptor blocker (metoclopramide 20 mg). Arterial blood gas, cardiorespiratory and IPAVA recruitment (evaluated by agitated saline contrast echocardiography) data were obtained at rest and during exercise up to 85% of V̇O2 max . On different days, participants also completed incremental exercise tests and exercise tolerance (time-to-exhaustion (TTE) at 85% of V̇O2 max ) with or without dopamine blockade. Compared to placebo, DA blockade did not change O2 consumption, CO2 production, or respiratory exchange ratio at any intensity. At 85% V̇O2 max , DA blockade decreased A-aDO2, increased arterial O2 saturation and minute ventilation, but did not reduce IPAVA recruitment, suggesting that positive saline contrast is unrelated to A-aDO2. Compared to placebo, DA blockade decreased maximal cardiac output, V̇O2 max and TTE. Despite improving pulmonary gas exchange, blocking dopamine receptors appears to be detrimental to exercise performance. These findings suggest that endogenous dopamine is important to the normal cardiopulmonary response to exercise and is necessary for optimal high-intensity exercise performance.
authors.affiliation: Pulmonary Division, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.|Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Vincent
authors.initials: V
authors.lastname: Tedjasaputra
authors.affiliation: Pulmonary Division, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Tracey L
authors.initials: TL
authors.lastname: Bryan
authors.affiliation: Division of Critical Care, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.|Division of Cardiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Sean
authors.initials: S
authors.lastname: van Diepen
authors.affiliation: Pulmonary Division, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.|Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Linn E
authors.initials: LE
authors.lastname: Moore
authors.affiliation: Pulmonary Division, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.|Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Melissa M
authors.initials: MM
authors.lastname: Bouwsema
authors.affiliation: Division of Cardiology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Welsh
authors.affiliation: Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Stewart R
authors.initials: SR
authors.lastname: Petersen
authors.affiliation: Pulmonary Division, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada.|G. F. MacDonald Centre for Lung Health, Covenant Health, Edmonton, Alberta, Canada.
authors.forename: Michael K
authors.initials: MK
authors.lastname: Stickland
mesh_terms: D000328:Adult; D001163:Arteriovenous Anastomosis / Q000187:drug effects / Q000502:physiology; D002302:Cardiac Output / Q000187:drug effects; D065127:Dopamine D2 Receptor Antagonists / Q000494:pharmacology*; D017079:Exercise Tolerance / Q000187:drug effects*; D006801:Humans; D008297:Male; D008787:Metoclopramide / Q000494:pharmacology*; D011659:Pulmonary Gas Exchange / Q000187:drug effects*
chemical_list: D065127:Dopamine D2 Receptor Antagonists; D008787:Metoclopramide