Drinking alcohol leads to the release of endorphins（内啡肽） in areas of the brain that produce feelings of pleasure and reward, according to a study led by researchers at the Ernest Gallo Clinic and Research Center at the University of California, San Francisco (UCSF). The finding marks the first time that endorphin release in the nucleus accumbens and orbitofrontal cortex（眼眶前额皮质） 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," said lead author Jennifer Mitchell, PhD, clinical project director at the Gallo Center and an adjunct（附属的） assistant professor of neurology at UCSF. "It provides the first direct evidence of how alcohol makes people feel good."

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, said senior author Howard L. Fields, MD, PhD, a professor of neurology and Endowed Chair in Pharmacology of Addiction in Neurology at UCSF and director of human clinical research at the Gallo Center.

The study appears on January 11, 2012, in Science Translational Medicine.

The researchers used positron emission tomography（正电子成像术） , or PET imaging, to observe the immediate effects of alcohol in the brains of 13 heavy drinkers and 12 matched "control" subjects who were not heavy drinkers.

In all of the subjects, alcohol intake led to a release of endorphins. And, in all of the subjects, the more endorphins released in the nucleus accumbens, the greater the feelings of pleasure reported by each drinker.

In addition, the more endorphins released in the orbitofrontal cortex, the greater the feelings of intoxication in the heavy drinkers, but not in the control subjects.

"This indicates that the brains of heavy or problem drinkers are changed in a way that makes them more likely to find alcohol pleasant, and may be a clue to how problem drinking develops in the first place," said Mitchell. "That greater feeling of reward might cause them to drink too much."