The finding also provides evidence that an inborn high level of anxiety is part of this picture. The study appears in this week's issue of the Journal of Neuroscience.
Research has shown that alcohol addiction is a complex disease, with both genetics and a tendency toward anxiety playing "crucial roles," writes researcher Subhash C. Pandey, PhD, a psychiatrist with the University of Illinois at Chicago.
"Some 30% to 70% of alcoholics are reported to suffer from anxiety and depression," Pandey says in a news release. "Drinking is a way for these individuals to self-medicate."
Pandey's research focuses on the CREB gene, so-named because it produces a protein called CREB -- cyclic AMP responsive element binding protein. The CREB gene regulates brain function during development and learning. The gene is also involved in the process of alcohol tolerance, dependence, and withdrawal symptoms, writes Pandey.
A section of the brain -- called the central amygdala -- is another piece of this puzzle. Both the CREB gene and the central amygdala have been linked with withdrawal and anxiety. When there is less CREB in the central amygdala, rats show increased anxiety-like behaviors and preference for alcohol.
Pandey's newest study puts it all together: It is "the first direct evidence that a deficiency in the CREB gene is associated with anxiety and alcohol-drinking behavior," Pandey writes.
Mice Bred for Alcohol Addiction
In this study, Pandey and colleagues worked with rats specially bred to be deficient in the CREB "alcoholism" gene. In a series of experiments, he found that:
- Rats deficient in the CREB protein drank about 50% more alcohol than normal rats. They also showed more anxiety-like behavior in a maze test.
- These rats also showed a higher preference for alcohol over water compared with normal rats; yet they had similar preferences for sugar water -- indicating that the alcohol consumption was not related to taste preferences.
- These rats also displayed more anxiety than normal mice, which decreased when drinking alcohol. The anxiety-reducing effect of alcohol was not as great in the normal rats.
- Alcoholic rats had higher levels of the CREB protein in the central amygdala.
These results indicate that the CREB or alcoholism gene is "crucial" to the anxiety relief that triggers alcohol addiction, Pandey writes.