A new study has shown that drinking alcohol causes a pleasant feeling because it releases endorphins, the brain’s natural opioids. It adds that problem drinkers differ from social drinkers in the way alcohol affects one part of the brain. The report appeared Wednesday in Science Translational Medicine.
Researchers performed PET imaging on 13 heavy drinkers and 12 social drinkers after each had had a standardized amount of alcohol. The scientists traced the release of endorphins in two regions of the brain — the nucleus accumbens and the orbitofrontal cortex — and recorded the volunteers’ subjective feelings of intoxication.
They noted that all subjects reported feelings of intoxication as the researchers observed changes in opioid release in the nucleus accumbens. There was no difference between heavy drinkers and the control group when it came to changes in blood alcohol levels over time. But with the heavy drinkers, unlike with the healthy controls, there was a positive correlation between the release of endorphins in the orbitofrontal cortex and the subjects’ subjective feeling of drunkenness. This phenomenon, the authors write, may contribute to an increased perception of pleasure and to excessive alcohol consumption in these drinkers.
The lead author, Jennifer M. Mitchell, a neuroscientist at the University of California, San Francisco, said that her aim is to find better ways to treat alcoholism. “There’s an interesting relationship between endorphin release and problem drinking,” she said. “By understanding where the endorphin release occurs, and which receptors it binds to, we can make a better drug.”
“Greater endorphin release was associated with more hazardous drinking,” Mitchell says. “We believe this is an important step in understanding where and how alcohol acts in the brain.” Mitchell adds that the findings could lead to better versions of the existing alcohol abuse drug naltrexone, which blocks the opioid response and blunts alcohol cravings in some, but not all people. Mitchell says a better understanding of the specific endorphin receptors involved in the alcohol “high” could lead to treatments that better target these reward centers. Currently, naltrexone acts by affecting multiple receptors. This research could lead to more focused medications.
Raymond F. Anton, who directs the Center for Drug and Alcohol Programs at the Medical University of South Carolina, says it is likely that there are other, as-yet-unidentified regions of the brain associated with addiction. “It is also likely that alcohol dependence is not one disease, but many, with many systems involved,” he says. “People drink for different reasons, so a treatment that works for one person may not work for another.” Anton is conducting genetic research in hopes of discovering why naltrexone blunts alcohol cravings in some people but not others. “We may be able to say in a few years if genetic predisposition can predict who will and will not respond to this drug,” Anton says.
“If you’re getting some reinforcement or reward from something, like alcohol or other kinds of abusable drugs, at that level your brain is telling you this is something important to you,” said Michael Owens, a neuropharmacologist at Emory University who was not involved in the study. That means if you're an alcoholic, and consciously want to stop drinking, it's hard to stop because part of your brain has learned that drinking is important and compels you to continue. “It’s something you have to fight to not partake in again,” he said. Owens said the results of this study were not surprising, but it was good that the hypothesis about how alcohol works in the brain was confirmed by science.
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