Researchers gain insight into how brain learns cocaine addiction

A team of researchers led by a group at Johns Hopkins says it has solved the mystery of why a protein linked to learning is also integral to becoming addicted to cocaine. Cocaine addiction, experts say, is among the strongest of addictions.

Results of the study, published in the Aug. 1 issue of the journal Cell, describe how the learning-related protein works with other proteins to forge new pathways in the brain in response to a drug-induced rush of the "pleasure" molecule dopamine. By adding important detail to the process of addiction, the researchers say the work may lead to new treatments for addiction.

"The broad question was why and how cocaine strengthened certain circuits in the brain long term, effectively re-wiring the brain for addiction," says Paul Worley, a professor in the Department of Neuroscience at the Johns Hopkins University School of Medicine. "What we found in this study was how two very different types of systems in the brain work together to make that happen."

Worley didn't come to the problem as an addiction researcher, but as an expert on a group of genes known as immediate early genes, which rapidly ramp up production in neurons when the brain is exposed to new information. In 2001, he says, a European group reported that deleting a specific protein complex made mice unresponsive to cocaine.

The finding set Worley's research group on a long search for an explanation. Using different types of experiments, they pieced together a complex story of how dopamine released in response to cocaine helps switch cells into synapse-strengthening mode. Knowing the details of the mechanism may help researchers identify targets for potential drugs to treat addiction, Worley says.