Dopamine D1 and D3 Genes
In addition studying genes associated with DRD2 receptors, genes associated with dopamine D1 and D3 receptors have also been tied to addiction.
A study released in January 2007 described the subtle, yet substantial impact prenatal cocaine exposure had in rabbits. “Teenage” rabbits who were exposed to cocaine while in utero had altered dopamine D1 receptors. Although the number of D1 receptors was the same as a control group, the location of the D1 receptors was abnormal. Rather than being located on neuron’s cell surfaces, these D1 receptors were “sequestered” inside the cells, which altered normal function. Behaviorally, this resulted in attention problems and insensitivity to stimulants, like amphetamines.1
In another study, a drug which acts as a D3 antagonist, binding to D3 receptors so dopamine can’t, was administered in rats bred to seek alcohol. The rats reduced their drinking significantly. The drug, “also reduces cocaine-seeking behavior, as well as behavior involving other drugs of abuse, such as nicotine and heroin.”2
Other dopamine-related genes have also been linked to addiction. For example, genetic differences in a protein called alpha synuclein (SNCA), which plays an important role in regulating dopamine, have also been explored. An alteration in the SNCA-encoding gene was found to contribute to the intensity of cravings. This was originally shown in rats and was subsequently found in humans as well.3
1. Prenatal Cocaine’s Lasting Cellular Effects; medicalnewstoday.com, Jan. 16, 2007.
2. Two Studies Offer Clues About How Alcoholic Behavior Is “Switched” On, Brookhaven National Laboratory Press Release, May 9, 2005.
3. Sequence Variation In ‘The Alpha Synuclein Gene Contributes To Alcohol Craving, medicalnewstoday.com, March 30, 2007.