Discovery may lead to treatments for cocaine addiction


Scientists have discovered a molecular process in the brain triggered by cocaine use that could provide a target for treatments to prevent or reverse addiction to the drug.

Michigan State University neuro scientist A J Robison and colleagues explained that cocaine alters the nucleus accumbens, the brain's pleasure center that responds to stimuli such as food, sex and drugs.

"Understanding what happens molecularly to this brain region during long-term exposure to drugs might give us insight into how addiction occurs," said Robison.

The researchers found that cocaine causes cells in the nucleus accumbens to boost production of two proteins, one associated with addiction and the other related to learning.

The proteins have a reciprocal relationship the yincrease each other's production and stability in the cells so the result is a snowball effect that Robison calls a feed-forward loop.

Robison and colleagues demonstrated that loop's essentialrole in cocaine responses by manipulating the process in rodents. They found that raising production of the protein linked to addiction made animals behave as if they were exposed to cocaine even when they weren't.

They also were able to break the loop, disrupting rodents' response to cocaine by preventing the function of the learning protein.

"At every level that we study, interrupting this loop disrupts the process that seems to occur with long-term exposure to drugs," said Robison, who conducted the study as a post doctoral fellow at Mount Sinai School of Medicine in NewYork City before joining the faculty at MSU.

Robison said the study was particularly compelling because it found signs of the same feed-forward loop in the brains of people who died while addicted to cocaine.

"The increased production of these proteins that we foundin the animals exposed to drugs was exactly parallelled in a population of human cocaine addicts," he said."That makes us believe that the further experiments and manipulations we did in the animals are directly relevant to humans," he said in the study published in the Journal of Neuroscience.

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