Pubdate: Mon, 23 Aug 1999
Source: Reuters
Copyright: 1999 Reuters Limited.


NEW YORK, Aug 23 (Reuters Health) -- Heavy drinking strips the brain of
substances that stimulate feelings of well being, while boosting chemicals
that cause tension and depression, report California researchers.

The findings, from studies conducted in lab animals, suggest that changes in
levels of chemicals in the brain caused by heavy alcohol intake lead to
"dark feelings" that lead to more drinking, according to the report
presented Monday at the American Chemical Society meeting in New Orleans.

The cycle "ultimately raises the 'set point' for alcohol intake, i.e., the
amount it takes to make an alcoholic feel 'normal,"' researcher Dr. George
F. Koob of The Scripps Research Institute in La Jolla, explained in a statement.

The researchers found that alcohol depletes chemical messengers associated
with the "reward" or "pleasure" pathways of the brain, including opioid
peptides in the brain, and monoamine neurotransmitters such as dopamine,
serotonin, and gamma aminobutyric acid.

Koob commented in an interview with Reuters Health that "the interesting
thing is that the effects are seen in multiple (neurotransmitter) systems.
The changes are as strong as what is seen with methamphetamine, but the
effects are wider spread... all the good guys go down."

As these neurotransmitter systems are compromised with alcohol dependence,
the brain attempts to compensate for the stress by releasing
corticotropin-releasing factor, a stress chemical that leads to depression.

"This increase is more dramatic (than the decrease in neurotransmitters),"
Koob noted. "I'm beginning to think this effect is more important than the
changes seen with the monoamines." He said that the increase in
corticotropin-releasing factor persists for as long as a month after
abstinence from alcohol.

"The combination effect (of the decrease in monoamine neurotransmitters and
increase in corticotropin-releasing factor) leaves the brain in a state of
dependence. It wants to take more alcohol to get things back to normal,"
Koob explained.

Finding the molecular basis of alcoholism may lead to new ways of screening
for the risk of developing alcoholism. In a statement, Koob's team notes
that currently, family history is the only marker of such risk. Among
individuals with an alcoholic parent, men have a 5 to 1 chance and women a 3
to 1 chance of developing alcoholism.

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