New York, April 18 (IANS) Binge drinkers, here comes good news. A team of US researchers has found that deactivating a stress-signaling system in a brain area known for motivation and emotion-related behaviours can decrease binge drinking.

The US National Institutes of Health-funded study from the Medical University of South Carolina in mice pinpointed a particular system in a specific brain region that can be manipulated to reduce harmful binge drinking.

"Binge drinking is a risky behaviour, and one consequence of repeated binge drinking is increasing risk for developing an alcohol use disorder," said Howard C Becker, director of the Charleston Alcohol Research Center and professor in the Department of Psychiatry and Behavioral Sciences.

A binge, as defined by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) means drinking to the legal limit of intoxication within two hours.

"This is four standard drinks for a woman or five drinks for a male - consumed over about a two-hour period," Becker explained.

In the study, published online and to appear in the May issue of Neuropharmacology journal, Becker and JR Haun, a graduate student in the Becker laboratory, tested a potential strategy for reducing risky binge drinking.

The system that the team investigated - the opioid receptor system - is well-recognized in the addiction field.

Notorious narcotic drugs of abuse, such as morphine, heroin and oxycontin/oxycodone act on the opioid-receptor system, producing the pleasurable effects that make these drugs so addictive.

However, there is an odd opioid receptor out, that is not involved in signaling pleasure.

"The kappa opioid-receptor system is the antithesis to other opioid receptors," explained Haun. "It's often referred to as an anti-reward system".

Instead of feelings of pleasure, the kappa opioid receptor produces stress and discontent.

Becker's team found that turning off the kappa opioid receptors in the brain decreased binge drinking.

The finding suggests that the kappa opioid receptor system is important not only in the negative state of withdrawal but also in driving binge drinking itself.

To begin testing their hypothesis, Becker and Haun first identified the exact region in the brain that is involved in binge drinking driven by kappa opioid receptors.

Becker's team homed in on a network of structures called the extended amygdala.

To determine how kappa opioid receptors in the extended amygdala affect binge drinking, Becker's team specifically inactivated kappa opioid receptors in this region in mice.

"Haun actually introduced a drug that blocks kappa opioid receptors right into the extended amygdala," explained Becker.
This study used a binge-drinking mouse model, which allowed the mice to drink freely for four hours each night.

After blocking the kappa opioid receptors in these mice, the team tested how much alcohol the animals voluntarily consumed.

"Blocking these kappa receptors in the extended amygdala didn't completely abolish drinking," explained Haun. "It brought it down to a more moderate level, the equivalent being a glass of wine at dinner opposed to a bottle."

This finding supports Becker and Haun's hypothesis that the kappa opioid receptor system in the extended amygdala promotes binge drinking.

Blocking kappa opioid receptors in the extended amygdala, therefore, could act as a therapy to taper binge drinking.

"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," explained Becker.

--IANS na/