Study tracks booze’s buzz in the brain

Morphinelike chemicals released in both heavy and moderate drinkers

A shot of high-octane booze causes the brain to pump out its own version of morphine, a new study finds. If confirmed, the results may help explain why drinking the hard stuff feels good.

Many animal studies have found that alcohol can cause release of feel-good endorphins in the brain, but the new brain scan study, which appears in the Jan. 11 Science Translational Medicine, is the first to show the effect in humans and to home in on where the effect occurs.

Knowing exactly where alcohol causes its effects brings scientists closer to developing drugs that could block the “high” that alcohol brings without unpleasant side effects, says study coauthor Jennifer Mitchell of the Ernest Gallo Clinic and Research Center in Emeryville, Calif., and the University of California, San Francisco.  “I really think we’re close,” she says. “There’s a lot of hope.”

Mitchell and her colleagues studied 13 heavy drinkers (10 to 16 drinks per week for women, and 14 to 20 for men) and 12 light and nondrinkers (fewer than five drinks a week for women, and fewer than seven for men). To get a sense of how many endorphin-detecting proteins were in the participants’ brains, the team injected a radiolabeled chemical that latched onto the detectors — a signal picked up with a PET scan.

 After an initial scan, the team brought out the cocktails.

Each participant downed a shot of extra-potent, lab-grade alcohol mixed with juice. The drink was strong enough to raise blood alcohol levels to about 0.05 percent with a single dose. (Because the participants had to lie still in the scanner for several hours with no possibility of a bathroom break, the researchers wanted to minimize the volume of liquid.)

The participants then underwent a second scan. The same radioactive chemical was injected, but this time, some of the sites in the brain where it had originally bound were already occupied by the brain’s endorphins, which had been released after the drink. The brains of the heavy drinkers and the light and nondrinkers showed similar boosts in endorphin levels.

“Our results were a bit unexpected,” Mitchell says. “We didn’t see a big difference.” In both groups, endorphin release was prominent in a region called the nucleus accumbens, a pleasure center in the brain. The authors also found evidence implicating another region in the front of the brain called the orbitofrontal cortex, which is thought to help process rewards.

The results need to be confirmed in larger studies with more carefully selected participants, says psychiatrist Raymond Anton of the Medical University of South Carolina in Charleston. “People with alcohol use disorders are drinking probably twice as much as these heavy drinkers,” he says. Also, Anton believes the data are insufficient regarding the orbitofrontal cortex’s involvement.

The amount of endorphins released after a drink seemed to correlate with how good the drinker reported feeling on a questionnaire. This finding complements a recent study by University of Chicago researchers, who found that in heavy drinkers, the pleasure derived from alcohol predicted levels of alcohol abuse, says psychiatrist and addiction researcher Henry Kranzler of the University of Pennsylvania in Philadelphia.

Ultimately, the results need to be replicated in real-world situations, Kranzler says. “We don’t care about what happens in a PET scanner. We care about what happens in bars.”

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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