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Beta-endorphin immunoreactivity during high-intensity exercise with and without opiate blockade.
1Exercise Physiology Laboratory, University of Central Florida, College of Education, Orlando 32816-1250, USA. tangelop@maimi.ucf.edu
European Journal of Applied Physiology
|February 1, 2002
Summary
Intense exercise significantly increases beta-endorphin levels in highly fit men. Naloxone administration further elevated these beta-endorphin responses during exercise, suggesting an interaction effect.
Area of Science:
- Exercise Physiology
- Neuroendocrinology
Background:
- Intense exercise is known to stimulate the endogenous opioid system.
- Understanding the role of beta-endorphin during sustained high-intensity exercise is crucial.
Purpose of the Study:
- To investigate plasma beta-endorphin immunoreactivity during intense exercise (80% VO2max) in highly fit men.
- To examine the effect of naloxone, an opioid antagonist, on beta-endorphin levels during exercise.
Main Methods:
- Nine highly fit men participated in two double-blind, counterbalanced treadmill exercise trials (30 min at 80% VO2max).
- Subjects received either naloxone or a placebo injection prior to each trial.
- Blood samples were collected at baseline and at 10, 20, and 30 minutes of exercise to measure beta-endorphin immunoreactivity.
Main Results:
- Plasma beta-endorphin levels were significantly higher during exercise compared to pre-exercise in both trials.
- Beta-endorphin levels remained elevated throughout the 30-minute exercise period.
- Significantly greater beta-endorphin immunoreactivity was observed in the naloxone trial compared to the placebo trial at all exercise time points.
Conclusions:
- Intense, steady-rate exercise induces sustained increases in plasma beta-endorphin in highly fit individuals.
- Naloxone administration interacts with exercise to modulate beta-endorphin release, indicating a role for opioid receptors in this response.