The fact that men are twice as likely as women to develop alcoholism is common knowledge. Until now, the underlying biology contributing to this difference in vulnerability has remained unclear.
The scientists studied male and female college-aged social drinkers in a laboratory test of alcohol consumption.
After consuming an alcoholic or non-alcoholic drink, each participant underwent a specialized positron emission tomography (PET) scan, an imaging technique that can measure the amount of alcohol-induced dopamine release.
Dopamine has multiple functions in the brain, but is important in this context because of its pleasurable effects when it is released by rewarding experiences, such as sex or drugs.
Despite similar consumptions of alcohol, the men had greater dopamine release than women.
This increase was found in the ventral striatum, an area in the brain strongly associated with pleasure, reinforcement and addiction formation.
“In men, increased dopamine release also had a stronger association with subjective positive effects of alcohol intoxication,” explained Dr. Nina Urban, corresponding author for this study.
“This may contribute to the initial reinforcing properties of alcohol and the risk for habit formation.”
Dr. Anissa Abi-Dargham, senior author on this project, notes that “another important observation from this study is the decline in alcohol-induced dopamine release with repeated heavy drinking episodes. This may be one of the hallmarks of developing tolerance or transitioning into habit.”
These findings indicate that the ability of alcohol to stimulate dopamine release may play an important and complex role in its rewarding effects and abuse liability in humans.
This identification of an in vivo neurochemical mechanism that could help explain the sex difference in alcoholism is an exciting step forward in alcoholism research.