Endogenous Opioids May Modulate Catecholamine Secretion During High-Intensity Exercise
Human Performance and Recreation
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.
European Journal of Applied Physiology and Occupational Physiology
Angelopoulos, T. J.,
Denys, B. G.,
Dasilva, S. G.,
Michael, T. J.,
Robertson, R. J.
(1995). Endogenous Opioids May Modulate Catecholamine Secretion During High-Intensity Exercise. European Journal of Applied Physiology and Occupational Physiology, 70(3), 195-199.
Available at: http://aquila.usm.edu/fac_pubs/5842