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. - --- MAP posted-by: Larry Seguin