Pubdate: Sun, 26 Jun 2005
Source: Dallas Morning News (TX)
Copyright: 2005 The Dallas Morning News
Contact:  http://www.dallasnews.com/
Details: http://www.mapinc.org/media/117
Author: Sue Goetinck Ambrose, Dallas Morning News
Note: Strict 200 word count limit on letters
Note: Strict 600 word count limit on guest column BODY'S CLOCK TIED TO ADDICTION

UT Southwestern Links Daily Rhythm To Addiction Chemical

A key component of the body's daily biological clock may influence the
brain's response to drugs of abuse, Dallas scientists and their
colleagues have found.

The new findings are part of a growing body of evidence suggesting
that the body's clock does more than tell you when to sleep and when
to wake up. It may, scientists are realizing, cause ups and downs in a
variety of brain functions over the course of the day.

In the new study, researchers from the University of Texas
Southwestern Medical Center at Dallas linked the daily clock to a
brain chemical known for its role in addiction. The findings could put
scientists in a better position to develop treatments for addiction.

"There are so few medications that are effective," said Jay Hirsh, a
neuroscientist at the University of Virginia in Charlottesville. "This
isn't going to lead to rapid therapies, but long-term, that's the
hope." In recent years, scientists have uncovered a network of genes
and proteins that keep a variety of body functions in tune with the
rising and setting of the sun. This network is the reason people feel
sleepy at night and alert in the day; it also causes daily
fluctuations in body temperature, blood pressure and kidney function.

"The classical idea is that the [network] ... is just involved in
generating the rhythm," said Rainer Spanagel, a neuropharmacologist at
the Central Institute of Mental Health in Mannheim, Germany. "Now we
find out that these clocks are ticking everywhere, in the brain and
also in other organs and tissues. They profoundly influence other
behaviors. This is really astonishing information."

In the new study, researchers from the University of Texas
Southwestern Medical Center at Dallas studied laboratory mice that
were missing a key gene in the body's clock. These mice lose their
natural daily rhythms, and the Dallas scientists also observed that
the mice find cocaine more rewarding than normal mice do. The study
appears online in The Proceedings of the National Academy of Sciences.

The researchers, led by UT Southwestern neuroscientists Colleen
McClung and Eric Nestler, also found that certain cells in the mice's
brains released more dopamine, a nerve cell chemical triggered by
natural pleasurable experiences, like food and sex. Certain drugs of
abuse, including cocaine, also cause release of dopamine in the brain.

Scientists have previously noted that lab animals' interest in drugs
of abuse varies over the course of a day. But the new study is the
first to connect the body's innate daily clock with dopamine.

More research is needed to figure out why disrupting the clock would
make cocaine seem more - and not less, for instance - rewarding, Dr.
Nestler said.

Nevertheless, he said, the results show that the gene, known as Clock,
influences why some experiences are more rewarding at certain times of
day.

"It's a more efficient way to use the brain," he said. "It makes sense
to coordinate the brain's functions. When you're trying to get ready
for sleep, you don't want to feel like going out and looking for food."

Also participating in the study were scientists from Illinois and
Greece.
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MAP posted-by: Larry Seguin