Gene Therapy for Drug Abuse

Brookhaven National Laboratory News is reporting about the use of gene therapy to reduce cocaine addiction in rats. Cocaine works by increasing the level of the neurotransmitter dopamine in the synapse. This large increase activates the dopamine type 2 receptor (D2 for short) and can cause intense feelings of pleasure and euphoria. The problem with using addictive drugs is that over time they downregulate the D2 receptor. Researchers have found that there are fewer D2 receptors in a drug addict's brain and this may cause a breakdown in the brain's pleasure system.

Drug addicts often experience anhedonia (the inability to experience pleasure) and dysphoria due to reduced activation of D2 receptors. In this new study, researchers introduced the gene for the D2 receptor into the nucleus accumbens (the pleasure center) of rats. Cocaine can reduce the number of D2 receptors by as much as 75 percent, so this gene therapy was able to restore the number of receptors in that area of the brain. After adding the gene, the rats showed a 75 percent decrease in self-administration of cocaine. Researchers have used D2 gene therapy in the past to improve alcohol addiction in rats, but this is the first time they have shown that cocaine addiction could also be ameliorated by this therapy.

Gene therapy in the brain has already been successfully used on human parkinson's patients. So in the future people who are addicted to drugs may be able to get gene therapy to improve their symptoms. More speculatively, adding D2 receptors to a normal person's pleasure center could concievably improve their hedonic capacity for reward if done properly. This type of gene therapy may be somewhat difficult to do considering that extremely high levels of D2 receptors may be associated with psychosis and mania. So for human trials, researchers might have difficulty in increasing the D2 receptor the right amount and not too much. However, I think that clinical trials for this therapy could actually happen in the next 10 to 20 years.