New animal research finds that light to moderate drinking releases pleasure-causing endorphins in the brain, but the same is not true of heavy drinking, Science Daily reported March 20.

Researchers at McGill University in Montreal found that low to moderate alcohol consumption affected the release of beta-endorphins in the midbrain/ventral tegmental area (VTA) of lab rats’ brains.

“We found that low to moderate but not high doses of alcohol increase the release of beta-endorphin in the VTA, one of the brain regions shown to be important for mediating the rewarding effect of alcohol,” said researcher Christina Gianoulakis. “This supports a role of beta-endorphin in mediating some of the rewarding effects of alcohol. However, the same doses of alcohol that increase beta-endorphin release in the VTA have no significant effect on the release of enkephalins and dynorphins, the other two families of endogenous opioid peptides we examined.”

Heavy drinking, on the other hand “is known to induce sedative and hypnotic effects, and often increase rather than decrease anxiety,” Gianoulakis noted.

“Like morphine, endogenous opioid peptides can induce analgesia and a mild euphoric effect, reduce anxiety, and may lead to a general feeling of well being,” she added. “Therefore, increased release of endogenous opioid peptides in response to drinking could be partially responsible for the mild euphoric and anxiolytic effects associated with low to moderate amounts of alcoholic beverages.”

The study could have implications for addiction treatment, the researchers said. “VTA beta-endorphin appears to play a significant role in alcohol reinforcement, and may partially explain the effectiveness of naltrexone — an opioid receptor antagonist currently used as treatment of alcoholism — in reducing alcohol consumption by some individuals,” said Gianoulakis.

“While current alcoholism treatment blocks opioids in a nonspecific fashion, this research suggests that a more targeted approach would be more beneficial,” added Li Bai, study co-author. “Researchers now have to specifically target endorphins in the VTA to see if it really does affect alcohol abuse and craving.”

The study appears in the March 2009 issue of the journal Alcoholism: Clinical and Experimental Research.