Lead author Jennifer Mitchell, clinical project director at the Gallo Center and an adjunct assistant professor of neurology at University of California, San Francisco, said the finding is the first time that endorphin release in response to alcohol consumption has been directly observed in humans.
Endorphins are small proteins with opiate-like effects that are produced naturally in the brain.
"This is something that we've speculated about for 30 years, based on animal studies, but haven't observed in humans until now," Mitchell said in a statement. "It provides the first direct evidence of how alcohol makes people feel good."
Senior author Howard L. Fields said the discovery of the precise locations in the brain where endorphins are released provides a possible target for the development of more effective drugs for the treatment of alcohol abuse.
The researchers used positron emission tomography imaging to observe the immediate effects of alcohol in the brains of 13 heavy drinkers and 12 matched controls, who were not heavy drinkers.
The study, published in the Science Translational Medicine, found alcohol intake in all subjects led to a release of endorphins -- and the more endorphins released in the nucleus accumbens part of the brain, the greater the feelings of pleasure reported by each drinker.