An epilepsy drug used in Europe eliminates key signs of cocaine addiction in baboons and rats, according to a study in this week's Synapse. If confirmed in human studies, the finding may lead to a novel way of helping cocaine addicts kick the habit.
The drug, called gamma vinyl-GABA (GVG), seems to erase a chemical hallmark of cocaine and other addictive drugs: a surge of the neurotransmitter dopamine in the brain's reward centers. GVG doesn't act on dopamine directly, but boosts levels of a neurotransmitter called gamma-aminobutyric acid (GABA) that acts as a brake on dopamine release; this GABA boost can dampen the excessive neural activity that leads to epileptic seizures. In the early 1990s neuropharmacologist Stephen Dewey of Brookhaven National Laboratory in Upton, New York, and his colleagues set out to test whether GVG also suppresses a cocaine-induced dopamine rise.
In the current study, Dewey's team gave cocaine to 20 baboons, some of which had earlier received injections of GVG, and monitored the dopamine levels in the baboons' brains using an imaging technique called Positron Emission Tomography. Although cocaine produced a large increase in dopamine in the baboons not given GVG, the researchers saw no such rise in the animals treated with GVG, suggesting that the drug "blocks the neurochemical action of cocaine," says team member Charles Ashby, a neuropharmacologist at St. Johns University in Jamaica, New York.
The researchers then investigated whether GVG could also block an addiction-related behavior in rats: their tendency to return to a place where they had previously received an addictive drug. This behavior reflects the rats' ability to link environmental cues with drug-taking, an association that often triggers drug cravings in people. The researchers found that GVG stopped the behavior, indicating that it might weaken drug cravings.
"We hope that GVG will dramatically attenuate an addict's tendency to go back to cocaine," says Ashby. Of course, whether that hope is realized will depend on the results of clinical trials expected to begin later this year. "This is something that should obviously be followed up," adds neuropharmacologist Frank Vocci of the National Institute on Drug Abuse.