title: Cholinergic and opioid involvement in release of growth hormone during exercise and recovery.
abstract: Cholinergic and opioid pathways have been implicated as mediators of the increased growth hormone (GH) release observed during exercise. This study compared the GH responses induced by a moderate-intensity exercise bout during treatment with placebo (Plac), the opioid receptor antagonist naltrexone (Nalt), the indirect cholinergic agonist pyridostigmine (PD), or a combination of the two drugs (P + N). Ten active males served as subjects (age, 25.1 +/- 0.6 yr; wt, 79.7 +/- 2.5 kg; % body fat, 14.9 +/- 1.4; peak oxygen consumption, 46.2 +/- 2.7 ml.kg-1 x min-1). Blood samples were drawn at 5-min intervals during the 4.5-h testing period to determine the GH concentration. The testing period was divided as follows: 0600-700 h = baseline, 0700-0800 h = preexercise, 0800-0830 h = exercise, and 0830-1030 h = recovery. Drugs were administered 1 h before exercise (at 0700 h). Exercise consisted of 30 min of cycling at an individualized work load previously found to elicit a blood lactate concentration of 2.5 mM. Heart rate, oxygen consumption, blood lactate, and blood glucose were measured throughout the exercise period. Results indicated that neither the resting GH concentration nor the metabolic parameters during exercise were altered by the treatments. Peak serum GH concentration was not significantly altered by the treatments (range 7.3 +/- 2.0 to 12.6 +/- 4.4 micrograms/l).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Human Services, Curry School of Education, University of Virginia, Charlottesville 22903.
authors.forename: D L
authors.initials: DL
authors.lastname: Thompson
authors.forename: J Y
authors.initials: JY
authors.lastname: Weltman
authors.forename: A D
authors.initials: AD
authors.lastname: Rogol
authors.forename: D L
authors.initials: DL
authors.lastname: Metzger
authors.forename: J D
authors.initials: JD
authors.lastname: Veldhuis
authors.forename: A
authors.initials: A
authors.lastname: Weltman
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D004723:Endorphins / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D013006:Growth Hormone / Q000378:metabolism*; D006801:Humans; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D008297:Male; D009271:Naltrexone / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology; D010275:Parasympathetic Nervous System / Q000502:physiology*; D017729:Presynaptic Terminals / Q000378:metabolism; D011659:Pulmonary Gas Exchange / Q000502:physiology; D011729:Pyridostigmine Bromide / Q000494:pharmacology
chemical_list: D001786:Blood Glucose; D004723:Endorphins; D007773:Lactates; D019344:Lactic Acid; D009271:Naltrexone; D013006:Growth Hormone; D011729:Pyridostigmine Bromide