For decades, endorphins have hogged the credit for producing “runner’s high,” that fleeting sense of euphoria and calm that many people report experiencing after prolonged exercise. Who among us, after an especially satisfying workout, hasn’t thought, “ah, my endorphins are kicking in.” Endorphins are the world’s sole celebrity peptide.
Endorphins first gained notoriety in exercise back in the 1980s when researchers discovered increased blood levels of the substance after prolonged workouts. (Endorphins, for those who know the word but not the molecules’ actual function, are the body’s home-brewed opiates, with receptors and actions much like those of pain-relieving morphine.) Endorphins, however, are composed of relatively large molecules, “which are unable to pass the blood-brain barrier,” said Matthew Hill, a postdoctoral fellow at Rockefeller University in New York. Finding endorphins in the bloodstream after exercise could not, in other words, constitute proof that the substance was having an effect on the mind. So researchers started to look for other candidates to help explain runner’s high. Now an emerging field of neuroscience indicates that an altogether-different neurochemical system within the body and brain, the endocannabinoid system, may be more responsible for that feeling. Continue reading