Naloxone and the ventilatory response to exercise in man.
Endogenous opiate peptides are known to exert a depressant action on ventilation (VE), and their plasma levels have been shown to be elevated during a variety of exercise protocols. We investigated whether they might modulate the control of the hyperpnea of short-term constant-load (CLE) and incremental (IE) cycle-ergometer exercise. Four healthy subjects performed CLE tests at ca. 80% of the anaerobic threshold (theta an) for 5 min following a period of unloaded pedaling, and IE tests (10 or 20 W min-1) to the limit of tolerance. Normal saline (3 ml) or the opiate antagonist naloxone (1.2 mg in 3 ml) were administered intravenously prior to each test. Naloxone elicited no discernible effect on VE, alveolar gas tensions, or heart rate throughout the entire range of work rates; neither were theta an nor the maximum work rate affected. It is concluded that, for short-term exercise ranging in intensity from moderate to severe, the role played by endogenous opiate peptides in the control of the exercise hyperpnea appears to be negligible in man.
D000328:Adult; D004723:Endorphins / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D009270:Naloxone / Q000494:pharmacology; D005082:Physical Exertion; D011659:Pulmonary Gas Exchange / Q000187:drug effects; D012119:Respiration / Q000187:drug effects
D004723:Endorphins; D009270:Naloxone