(Ivanhoe Newswire) — The first experimental evidence to directly support the idea that genetic differences make some people more susceptible to the addictive effects of alcohol and other drugs was provided in this study.
The study compared the brain’s response to long-term alcohol drinking in two genetic variants of mice. One strain lacked the gene for dopamine D2, a specific brain receptor that responds to dopamine. Dopamine is the brain’s “feel good” chemical. It produces feelings of pleasure and reward. The other strain was genetically normal. In the dopamine-receptor-deficient mice, long-term alcohol drinking resulted in significant biochemical changes in areas of the brain known to be involved in alcoholism and addiction.
“This study shows that the effects of chronic alcohol consumption on brain chemistry are critically influenced by an individual’s pre-existing genetic makeup,” lead author Panayotis (Peter) Thanos, a neuroscientist with Brookhaven Lab and the National Institute on Alcohol Abuse and Alcoholism (NIAAA) Laboratory of Neuroimaging was quoted as saying. “Our findings may help explain how someone’s genetic profile can interact with the environment “” in this case, chronic alcohol drinking “” to produce these changes only in some individuals, but not in others with a less vulnerable genetic profile. The work supports the idea that genetic screening could provide individuals with valuable information relevant to understanding risks when deciding whether or not to consume alcohol.”
The scientists were particularly interested in the dopamine system because many studies suggest that deficiency in dopamine D2 receptors may make people less able to experience ordinary pleasures and more vulnerable to alcoholism, drug abuse, and even obesity. The ability to genetically engineer mice lacking the D2 gene, along with carefully controlling and monitoring their alcohol intake, made it possible to test the effect of this genetic influence on the brain’s response to chronic alcohol drinking. This was the first study of its kind.
In the study, scientists studied male mice lacking the dopamine D2 gene and genetically normal male mice. They gave half of each group only water to drink, and the other half a solution of 20 percent ethanol to stimulate heavy drinking. After six months, the scientists compared the levels of a different kind of brain receptor known as cannabinoid type 1 (CB1) in various parts of the brain in all four groups. CB1 receptors are located near dopamine receptors and are also known to play a role in alcohol consumption and addiction. Many findings indicate that the two types of receptors may influence one another.
SOURCE: Alcoholism Clinical Experimental Research, published online October 19, 2010