SCIENTISTS SEE NEW LINK TO COCAINE ADDICTION

LOS ANGELES -- A chemical messenger called serotonin is turning out to be a
bigger player in cocaine addiction than previously thought, according to
two studies that could help researchers find new approaches to treating and
preventing drug abuse.

The studies released Wednesday looked at the roles of dopamine and
serotonin in laboratory mice that pressed levers to get doses of cocaine.

Researchers long have held that increases in the brain of dopamine - a
chemical associated with movement, thought, motivation and pleasure -
produce some of the euphoria and addictive effects of cocaine.

Serotonin - involved in emotions, mood, and probably sleep and aggression -
was thought to play some role in achieving a high. But the new studies show
it provides an important component to how vulnerable an animal - or human
may be.

'We used to have a religion called the dopamine religion that said that you
could explain anything solely on the basis of dopamine," said Alan I.
Leshner, director of the National In-stitute on Drug Abuse, which funded
one of the studies.

The new results suggest "we must pay more attention to serotonin than we
have," Leshner said. "That opens a new line of thinking because we know
serotonin is important in many other mood states, like depression."

Work led by Rene Hen at Columbla University and Beatriz Rocha at the
University of North Texas found that specially bred mice lacking a gene
involved in the brain's response to serotonin were more motivated to take
cocaine than normal mice. They were also more sensitive to the drug's
effects.

"It's a really major dIscovery," said Francis White, who chairs the
department of cellular and molecular pharmacology at the Finch University
of Health Sciences/Chicago Medicat School.

White said he was struck by how mice missing one of their serotonin
receptors - even II they were never given cocaine - showed "changes in the
brain that we see in a normal animal (repeatedly) given ... cocaine." Those
chemical changes made the mutant mouse even more vulnerable to cocaine
addiction and therefore underscore the importance of serotonin to the
addiction process, he said.

The mutant mice also showed an increased attraction to alcohol and more
impulsiveness, a trait often associated with drug abuse.

That study, underscoring the role of genetics in addiction, appears in
today's issue of the journal Nature.