Leave it to science to take the mystery out of the “I just love you so much, man,” beer buzz. But their findings may lead to better treatment for alcoholics, according to a study in the journal Science Translational Medicine.
Although researchers have known for decades that alcohol affects the brain, it remained unclear as to exactly how the hooch makes humans feel so darn happy. “We have three decades of animal data, but this study is the first direct evidence of how alcohol makes people feel good,” says lead author Jennifer Mitchell, PhD, clinical project director at the Ernest Gallo Clinic and Research Center at the University of California, San Francisco.
The research team found that found that drinking alcohol releases a flood of endorphins, the so-called “feel good” brain chemicals, in two very specific brain areas: the nucleus accumbens, which is linked to addictive behaviors, and the orbitofrontal cortex, which is involved in decision making.
Using positron emission tomography, or PET imaging, the team looked at the immediate effects of alcohol in the brains of 13 heavy drinkers, defined in the study as having two or three drinks every day, and 12 matched “control” subjects, who were not heavy drinkers.
Before imbibing a special cocktail of alcohol used for research purposes, along with a little orange juice, the subjects were given injections of a radioactive drug that binds to the brain’s opioid receptors, a place where endorphins also bind. The researchers then mapped the receptor sites that “lit up” on the PET image.
The subjects were then each given one minute to drink the special cocktail, a second injection of the radioactive drug, and another PET scan.
By comparing areas of radioactivity in the first and second PET images, the researchers were able to map the exact brain locations where endorphins were released in response to drinking.
In all of the subjects, alcohol led to endorphin release, but there were some differences between the control group and the heavy drinkers.
Although all participants reported feeling a greater sense of pleasure when more endorphins were released in the nucleus accumbens, heavy drinkers reported feeling more intoxicated than the control group when a greater number of endorphins were released in the orbitofrontal cortex.
“Heavy drinkers got more of a reward, more of a high,” says Mitchell. “Their brains are changed in a way that makes drinking extremely pleasurable.”
The study also found that endorphins released after drinking bind to the Mu receptor, the target of narcotics like morphine and heroin.
That finding could lead to “reverse engineering,” the drug naltrexone, which makes drinking and drugs like heroin less pleasurable by preventing binding at non-specific opioid receptor sites. Compliance, however, is low, because of side effects.
“People say they don’t like how the drug makes them feel, but now that we know that alcohol releases endorphins, we believe that we can make a better naltrexone, and it could be something that people who need help would want to take,” says Mitchell.