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Risk-Takers May Lack Ability to Limit Brain Chemical

By Alan Mozes
HealthDay Reporter
Tuesday, December 30, 2008 12:00 AM

TUESDAY, Dec. 30 (HealthDay News) -- Just in time for New Year's Eve comes research suggesting that "thrill-seeking" behaviors may be hard-wired into the brain.

Specifically, the study suggests that risk-takers -- those people who often engage in impulsive, rule-breaking entanglements with food, drink, drugs, sex, money and the like -- have fewer so-called dopamine "auto-receptors." These auto-receptors are designed to limit the release of the brain chemical dopamine. As a result, exciting activities typically associated with "feel good" dopamine stimulation trigger higher levels of dopamine release than normal -- essentially rewarding and encouraging thrill-seeking behavior, the researchers said.

"It starts to suggest that these auto-receptors might be an appropriate target for drug abuse," said lead author David H. Zald, an associate professor of psychology at Vanderbilt University in Nashville, Tenn. "Of course, we do not yet have good drugs to target these auto-receptors alone, and until there's a proven way to intervene pharmacologically, I would say this is all still hypothetical. But if you can understand the basic risk factors, you may ultimately be able to both reduce the risk for drug abuse or, more probably, readily treat people during the withdrawal stage of drug abuse."

Zald went on to say that "if you took away the novelty-seekers, we would be a very boring society. So, I would be very hesitant to describe this type of spontaneous personality as an entirely negative thing. But it is a style that does put people at greater risk for developing troubling drug-abuse problems. And now, we've been able to link this specific personality type with a specific aspect of the dopamine neurotransmitter system."

Zald and his colleagues reported on their work, funded by the U.S. National Institute on Drug Abuse, in the Dec. 31 issue of The Journal of Neuroscience.

Building on prior studies with rodents, the researchers examined differences in the neural structure of human risk-takers by analyzing personality-trait questionnaires completed by 34 healthy adults -- 18 men and 16 women, with an average age of about 24.

The participants answered questions about their novelty-seeking tendencies, spontaneity, decision-making speed, and rule-breaking inclinations. The researchers then compared the responses to brain scans of the same participants.

The results: Those who displayed risk-taking traits possessed a smaller number of dopamine auto-receptors in their brains, giving them a relatively weakened ability to control and inhibit dopamine release.

Dr. Adam Bisaga, an addiction psychiatrist at the New York State Psychiatric Institute, agreed that the findings could help lead to improved addiction treatment.

"The importance of this research is that, hopefully, in the future, we'll be able to treat patients better, because we can do some genotyping and target treatment better depending on a patient's genetic make-up," Bisaga said. "Probably, dopamine receptor variability is not going to explain all the differences in behavior. It's a little more complicated than that. But this work now gives us at least some biological basis for understanding temperament and other personality characteristics."

More information

For more on drug abuse and addiction, visit the U.S. National Institute on Drug Abuse.

SOURCES: David H. Zald, Ph.D., associate professor, department of psychology, Vanderbilt University, Nashville, Tenn.; Adam Bisaga, M.D., associate professor of clinical psychiatry, the College of Physicians and Surgeons of Columbia University, and research scientist, New York State Psychiatric Institute, New York City; Dec. 31, 2008, The Journal of Neuroscience

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