ADDICTS MAY GET REWARDS FROM ANTICIPATION OF DRUGS

Scientists have long wondered what compels junkies to ditch normal lives
simply to get high day after day after day. Now UNC-Chapel Hill scientists
have a partial answer. Addicts don't only get a chemical charge from their
drugs. They probably get a lift simply by thinking about them.

That finding bolsters the belief that addiction is a disorder lodged in the
brain, not in people's weak wills. And it might give new guidance on how to
prevent relapses among people desperate to kick their habits.

"One of the things we're looking for is a medicine to help addicts get
through the first couple of weeks of detox, when the real temptation to
give in peaks," said Roy Wise, chief of behavioral neurosciences at the
National Institute on Drug Abuse.

The findings, published today in the journal Nature, come from behavioral
psychologist Regina Carelli and analytic chemist Mark Wightman. They and
their laboratories recorded previously undetected surges of an important
brain chemical called dopamine in laboratory rats expecting doses of cocaine.

Carelli has long studied circuitry that rewards healthy human behaviors.
The circuitry boosts dopamine levels in brain regions called reward centers
so people will repeat the behaviors. Addictive drugs hijack the circuitry,
boosting dopamine levels in reward centers when people inject heroin or
smoke cocaine.

Wightman, over two decades, developed the first device that can detect and
measure the release of tiny quantities of dopamine as it is released in
animal brains. He and Carelli suspected the device might give insight into
when dopamine levels surged in rats that compulsively dose themselves with
cocaine.

So they attached carbon filament sensors, one-twentieth the thickness of a
human hair, to reward centers in the rats' brains. Then they switched on
lights and a tone, signals used to let animals know they were about to get
cocaine. Dopamine levels surged immediately, signaling that stimulation
occurs when animals anticipate receiving a drug.

"We're getting insight into what the brain is doing on a really fast time
scale. No one else has been able to look at things on this time scale,"
Carelli said.

Wise, the federal drug research official, said such surges are likely to
occur in the human brain, too, because people and rats respond to drugs
such as cocaine and heroin in very similar ways.

Now that scientists know dopamine levels rise in anticipation of taking a
drug, they can experiment with medicines that block the brain chemical.

Maybe one day that would help curb addicts' cravings, which intensify when
they get reminded about drugs.

"Everything we learn about the circuitry helps us," Wise said.