The D2 receptor has been the subject of intense scrutiny. Some researchers have proposed that mutations in the D2 receptor gene in humans are one of the roots of alcoholism. The OHSU and VA research paints a more complex picture. "It says that the D2 receptor is in some way involved in the animal's choice to drink or not to drink," said David Grandy, Ph.D., associate professor of physiology and pharmacology at OHSU and a co-author of the paper. "But how the receptor relates to euphoria or abuse of the drug isn't yet clear. It will require extensive genetic screening of humans to determine which specific mutations in the D2 receptor gene may be connected with alcoholism. Our research doesn't point towards a single 'alcoholic' gene, but rather towards a complex interaction between several receptors and systems in the brain."
Further research will focus on measuring those interactions. Phillips and other OHSU and VA scientists have also found that mice without a receptor sensitive to serotonin, another substance connected with pleasure, drink more than mice that have the gene. Phillips, Grandy and others are now working on breeding mice that lack both the D2 and serotonin receptors.