title: Endogenous opioids may modulate catecholamine secretion during high intensity exercise.
abstract: To determine the effect of endogenous opioids on catecholamine response during intense exercise [80% maximal oxygen uptake (VO2max)], nine fit men [mean (SE) VO2max, 63.9 (1.7) ml.kg-1.min-1; age 27.6 (1.6) years] were studied during two treadmill exercise trials. A double-blind experimental design was used with subjects undertaking the two exercise trials in counterbalanced order. Exercise trials were 20 min in duration and were conducted 7 days apart. One exercise trial was undertaken following administration of naloxone (N; 1.2 mmol.l-1; 3 ml) and the other after receiving a placebo (P; 0.9% saline; 3 ml). Prior to each experimental trial a flexible catheter was placed into an antecubital vein and baseline blood samples were collected. Immediately afterwards, each subject received bolus injection of either N or P. Blood samples were also collected after 20 min of continuous exercise while running. Epinephrine and norepinephrine were higher (P < 0.05) in the N than P exercise trial with mean (SE) values of 1679 (196) versus 1196 (155) pmol.l-1 and 24 (2.2) versus 20 (1.7) nmol.l-1, respectively. Glucose and lactate were higher (P < 0.05) in the N than P exercise trial with values of 7 (0.37) versus 5.9 (0.31) mmol.l-1 and 6.9 (1.1) versus 5.3 (0.9) mmol.l-1 respectively. These data suggest an opioid inhibition in the release of catecholamines during intense exercise.
authors.affiliation: Human Energy Research Laboratory, University of Pittsburgh, PA 15261, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Angelopoulos
authors.forename: B G
authors.initials: BG
authors.lastname: Denys
authors.forename: C
authors.initials: C
authors.lastname: Weikart
authors.forename: S G
authors.initials: SG
authors.lastname: Dasilva
authors.forename: T J
authors.initials: TJ
authors.lastname: Michael
authors.forename: R J
authors.initials: RJ
authors.lastname: Robertson
mesh_terms: D000328:Adult; D001786:Blood Glucose; D004837:Epinephrine / Q000097:blood*; D015444:Exercise / Q000502:physiology*; D006339:Heart Rate; D006801:Humans; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009638:Norepinephrine / Q000097:blood*; D018847:Opioid Peptides / Q000502:physiology*; D010101:Oxygen Consumption
chemical_list: D001786:Blood Glucose; D018847:Opioid Peptides; D009270:Naloxone; D009638:Norepinephrine; D004837:Epinephrine