COCAINE CHANGES THE WAY GENES WORK IN BRAIN: STUDY

Findings Help Explain Addictive Properties Of Drug

Prolonged exposure to cocaine can cause permanent changes in the way
genes are switched on and off in the brain, a finding that may lead to
more effective treatments for many kinds of addiction, U.S.
researchers said.

A study in mice by Ian Maze of Mount Sinai School of Medicine in New
York and colleagues found that chronic cocaine addiction kept a
specific enzyme from doing its job of shutting off other genes in the
pleasure circuits of the brain, making the mice crave the drug even
more.

The study helps explain how cocaine use changes the brain, said Dr.
Nora Volkow, director of the U.S. National Institute on Drug Abuse,
part of the National Institutes of Health, which funded the study
published in the journal Science.

"This finding is opening up our understanding about how repeated drug
use modifies in long-lasting ways the function of neurons," Volkow
said in a telephone interview.

For the study, the team gave one group of young mice repeated doses of
cocaine and another group repeated doses of saline, then a single dose
of cocaine.

They found that one way cocaine alters the reward circuits in the
brain is by repressing gene 9A, which makes an enzyme that plays a
critical role in switching genes on and off.

Other studies have found that animals exposed to cocaine for a long
period of time undergo dramatic changes in the way certain genes are
turned on and off, and they develop a strong preference for cocaine.

This study helps explain how that occurs, Volkow said, and may even
lead to new ways of overcoming addiction.

In the study, Maze and colleagues showed these effects could be
reversed by increasing the activity of gene 9A.