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Risk takers, drug abusers driven by decreased ability to process dopamine
December 30, 2008NASHVILLE, Tenn.--For risk-takers and impulsive people, New Year's resolutions often include being more careful, spending more frugally and cutting back on dangerous behavior, such as drug use. But new research from Vanderbilt finds that these individuals--labeled as novelty seekers by psychologists--face an uphill battle in keeping their New Year's resolutions due to the way their brains process dopamine. The research reveals that novelty seekers have less of a particular type of dopamine receptor, which may lead them to seek out novel and exciting experiences--such as spending lavishly, taking risks and partying like there's no tomorrow.
The research was published Dec. 31, 2008, in the Journal of Neuroscience.
The neurotransmitter dopamine is produced by a select group of cells in the brain. These dopamine-producing cells have receptors called autoreceptors that help limit dopamine release when these cells are stimulated.
"We've found that the density of these dopamine autoreceptors is inversely related to an individual's interest in and desire for novel experiences," David Zald, associate professor of psychology and lead author of the study, said. "The fewer available dopamine autoreceptors an individual has, the less they are able to regulate how much dopamine is released when these cells are engaged. Because of this, novelty and other potentially rewarding experiences that normally induce dopamine release will produce greater dopamine release in these individuals."
Dopamine has long been known to play an important role in how we experience rewards from a variety of natural sources, including food and sex, as well as from drugs such as cocaine and amphetamine. Previous research has shown that individuals differ in both their number of dopamine receptors and the amount of dopamine they produce, and that these differences may play a critical role in addiction. Zald and his colleagues set out to explore the connection between dopamine receptors and the novelty-seeking personality trait.
"Novelty-seeking personality traits are a major risk factor for the development of drug abuse and other unsafe behaviors," Zald and his colleagues wrote.
"Our research suggests that in high novelty-seeking individuals, the brain is less able to regulate dopamine, and this may lead these individuals to be particularly responsive to novel and rewarding situations that normally induce dopamine release," Zald said.
Previous research in rodents showed that some respond differently to novel environments. Those who explore novel environments more are also more likely to self-administer cocaine when given the chance. Dopamine neurons fire at a higher rate in these novelty-responsive rodents, and the animals also have weak autoreceptor control of their dopamine neurons. Zald and colleagues speculated that the same relationships would be seen in humans.
The researchers used positron emission topography to view the levels of dopamine receptors in 34 healthy humans who had taken a questionnaire that measured the novelty-seeking personality trait. The questionnaire measured things such as an individual's preference for and response to novelty, decision-making speed, a person's readiness to freely spend money, and the extent to which a person is spontaneous and unconstrained by rules and regulations. The higher the score, the more likely the person was to be a novelty seeker.
The researchers found that those that scored higher on the novelty-seeking scale had decreased dopamine autoreceptor availability compared to the subjects that scored lower.
Vanderbilt University
"We've found that the density of these dopamine autoreceptors is inversely related to an individual's interest in and desire for novel experiences," David Zald, associate professor of psychology and lead author of the study, said. "The fewer available dopamine autoreceptors an individual has, the less they are able to regulate how much dopamine is released when these cells are engaged. Because of this, novelty and other potentially rewarding experiences that normally induce dopamine release will produce greater dopamine release in these individuals."
Dopamine has long been known to play an important role in how we experience rewards from a variety of natural sources, including food and sex, as well as from drugs such as cocaine and amphetamine. Previous research has shown that individuals differ in both their number of dopamine receptors and the amount of dopamine they produce, and that these differences may play a critical role in addiction. Zald and his colleagues set out to explore the connection between dopamine receptors and the novelty-seeking personality trait.
"Novelty-seeking personality traits are a major risk factor for the development of drug abuse and other unsafe behaviors," Zald and his colleagues wrote.
"Our research suggests that in high novelty-seeking individuals, the brain is less able to regulate dopamine, and this may lead these individuals to be particularly responsive to novel and rewarding situations that normally induce dopamine release," Zald said.
Previous research in rodents showed that some respond differently to novel environments. Those who explore novel environments more are also more likely to self-administer cocaine when given the chance. Dopamine neurons fire at a higher rate in these novelty-responsive rodents, and the animals also have weak autoreceptor control of their dopamine neurons. Zald and colleagues speculated that the same relationships would be seen in humans.
The researchers used positron emission topography to view the levels of dopamine receptors in 34 healthy humans who had taken a questionnaire that measured the novelty-seeking personality trait. The questionnaire measured things such as an individual's preference for and response to novelty, decision-making speed, a person's readiness to freely spend money, and the extent to which a person is spontaneous and unconstrained by rules and regulations. The higher the score, the more likely the person was to be a novelty seeker.
The researchers found that those that scored higher on the novelty-seeking scale had decreased dopamine autoreceptor availability compared to the subjects that scored lower.
Vanderbilt University
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Stress-induced changes in brain circuitry linked to cocaine relapse
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Researchers find brain cell transplants help repair neural damage
A Swiss research team has found that using an animal's own brain cells (autologous transplant) to replace degenerated neurons in select brain areas of donor primates with simulated but asymptomatic Parkinson's disease and previously in a motor cortex lesion model, provides a degree of brain protection and may be useful in repairing brain lesions and restoring function.
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Why antidepressants don't work for so many
More than half the people who take antidepressants for depression never get relief.
Cocaine exposure during pregnancy leads to impulsivity in male, not female, monkeys
Adult male monkeys exposed to cocaine while in the womb have poor impulse control and may be more vulnerable to drug abuse than female monkeys, even a decade or more after the exposure, according to a new study by researchers at Wake Forest University School of Medicine. The findings could lead to a better understanding of human drug abuse.
Scientists demonstrate link between genetic defect and brain changes in schizophrenia
Researchers at the University of North Carolina at Chapel Hill School of Medicine have found that the 22q11 gene deletion - a mutation that confers the highest known genetic risk for schizophrenia - is associated with changes in the development of the brain that ultimately affect how its circuit elements are assembled.
Fine-tuning treatments for depression
New research clarifies how neurotransmitters like norepinephrine, serotonin, and dopamine, are regulated - a finding that may help fine-tune therapies for depression.
Study supports possible role of urate in slowing Parkinson's disease progression
By examining data from a 20-year-old clinical trial, a research team based at the MassGeneral Institute for Neurodegenerative Diseases (MGH-MIND) and Harvard School of Public Health (HSPH), has found evidence supporting the findings of their 2008 study - that elevated levels of the antioxidant urate may slow the progression of Parkinson's disease.
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