Binge-Drinking Mice Able to Control Themselves After Scientists Tweaked Their Brains

Scientists who used a chemical to get mice to cut down on binge-drinking hope their research could one day help humans who struggle with alcohol problems.

The researchers used a substance to block what are known as kappa opioid receptors in a network of structures in the brain called the extended amygdala.

The kappa opioid receptor system is thought to play a role in making drug and alcohol use appealing in times of stress, even though this can be destructive.

These receptors are present in the brain, spinal cord, and the surrounding tissues—including the extended amygdala. J.R. Haun, co-author of the study published in Elsevier's Journal of Neuropharmacology and a graduate student at the Department of Neuroscience, Medical University of South Carolina, explained in a statement that the extended amygdala plays a role in motivational behavior, responds to stress, and is associated with compulsive drinking.

To explore the link between alcoholism and these parts of the brain, the team gave mice alcohol in their cages so they could drink to excess and get their alcohol blood levels up to levels comparable to a binge-drinking human's.

Referring to the National Institute on Alcohol Abuse and Alcoholism guide for drinking levels, Haun said a drink is defined as around a 12-ounce can of beer, a five-ounce glass of wine or a standard 1.5 ounce shot of distilled spirits. But he stressed this can depend on the percentage of pure alcohol in the drink.

Binge-drinking is defined as consuming four of these drinks for a woman, or five for a man, over a period of two hours, Haun said.

In their lab, the scientists watched how much the mice drank before and after being dosed with a substance called norbinaltorphimine, which blocked their kappa opioid receptors.

Haun said the team found this "didn't completely abolish drinking. It brought it down to a more moderate level, the equivalent being a glass of wine at dinner opposed to a bottle."

The researchers also found that female mice drank more than males on average, and were also more likely to suppress drinking when given norbinaltorphimine.

Haun said it is unclear why turning off these receptors had such an effect on the mice.

"But what we do know is that kappa opioid receptors play an important role in the negative emotional state that drives drinking when it becomes compulsive in alcohol use disorders."

Howard C. Becker, professor in the Department of Psychiatry and Behavioral Sciences who lead the study, said in a statement: "Binge drinking is one of the most common patterns in which alcohol is consumed.

"It's a risky behavior, and one consequence of repeated binge drinking is increasing risk for developing an alcohol use disorder."

According to the U.S. Centers for Disease Control and Prevention, "binge drinking is the most common, costly, and deadly pattern of excessive alcohol use in the United States." One in six adults in the country binge drink around four times a month, consuming around seven beverages per session.

Addressing whether a drug could be developed to stop this behaviour in humans, Haun said: "I think the ultimate goal is to better understand new potential treatment targets and how new therapeutics may have some value in helping to quell the desire and motivation to drink excessively in those who have developed an alcohol use disorder or are on the threshold of doing so."

Ian Hamilton, an expert in drug use and mental health at the Department of Health Sciences at the U.K.'s University of York, who did not work on the study, told Newsweek the article has confirmed some early previous research on which parts of the brain are active and responsive to excessive alcohol use, particularly binge drinking.

Hamilton praised the team for exploring the differences between the responses of the male and female mice "as this basic factor is often ignored or under-reported in most research.

"This information has the potential to cut short the dangerous trajectory of some females' risky relationship with alcohol," he said.

Pointing out the study's flaws, Hamilton said research such as this which investigates neurotransmitters and brain activity relies on mice. Although the brains of mice are similar to ours, "they are not identical so we should be cautious about directly applying these findings to humans."

Despite its drawbacks, Hamilton said the research could help with developing drugs to intervene early when a person starts drinking to prevent them from consuming alcohol to excess.

Hamilton said the study brings us closer to understanding why some people who drink do so excessively and others don't.

"Recent surveys are showing some people are drinking excessively as a way of coping with the stress of COVID-19, this study provides some useful insights about how the brain reacts to binge drinking and how potentially we could help those individuals regain control over their consumption of alcohol. This is potentially life saving as binge drinking can kill or elevate the risk of health problems such as liver damage or cancer."