PET Scans Shows Brain’s Response to Drugs in Real Time
At the annual meeting of the American Society for Biochemistry and Molecular Biology, researchers at the U.S. Department of Energy’s Brookhaven National Laboratory presented a PET imaging protocol that visualizes the activity of the brain’s reward circuitry, showing how drugs affect the release of the neurotransmitter dopamine, which controls pleasure in the brain.
Joanna Fowler, PhD, senior scientist at the U.S. Department of Energy's Brookhaven National Laboratory in Upton, New York, and Gene-Jack Wang, MD, senior scientist at Brookhaven, used positron emission tomography (PET) with radioactive tracers that bind to dopamine receptors in the brain. This combination can create real-time three-dimensional images of dopamine working in the brain. Nora D. Volkow, MD, director of the National Institute on Drug Abuse, also contributed to the research.
Performing PET scans on several volunteers (some who were addicted to different types of drugs and some control subjects who were matched in age but did not suffer from addiction), the researchers found that people with addiction generally have 15 to 20 fewer dopamine receptors than healthy people. This means that when dopamine is released in the brain (upon drug use or natural actions like eating food), the dopamine receptors don’t bind to the dopamine.
Dr. Fowler explained that the addicted individuals have a blunted response to dopamine, which suggests that their feelings of pleasure are diminished. This could help explain why people are driven to continually use drugs in an attempt to replicate the euphoric feelings they once experienced.
She also noted that while different drugs elicit different responses in the brain, the brains of all the addicted participants showed a compromised dopamine response.
Interestingly, Dr. Wang used the PET scans on obese individuals, finding very similar lowered dopamine responses, reinforcing the link between obesity and addiction.
Source: HealthImaging.com, PET imaging shows fewer dopamine receptors in drug addicts, April 28, 2010.