NIDA funded the research with the NIH National Center for Research Resources, the US Department of Energy, and the White House Office of National Drug Control Policy. The researchers administered a battery of tests to assess attention, memory, mood, general intelligence and motor function. Results showed that, on average, DAT levels in the striatum of the brain were 24 percent lower in methamphetamine abusers than in control subjects. Like other addictive drugs, methamphetamine is known to trigger short-term release of high levels of dopamine, which stimulates brain cells in the dopamine circuit, thereby enhancing mood and body movement. The current finding of reduced DAT levels in chronic methamphetamine abusers indicates that in humans, too, the drug causes dysfunction in dopamine circuits, Dr. Volkow says.
Tests assess attention, memory, mood, general intelligence and motor function.
That is telling us chronic methamphetamine use is affecting many functions of the brain in a negative way. In a second study, Dr. Volkow and her colleagues used PET scanning to measure glucose metabolism in the brains of the same group of methamphetamine abusers and in control subjects. Glucose metabolism is a measure of brain cell activity, and reduced glucose metabolism can be a very sensitive indicator of brain damage and an early indicator of neurodegenerative disease. To their surprise, the researchers saw a marked overall increase in glucose metabolism in the brains of methamphetamine abusers, suggesting an inflammatory reaction. This effect was most marked in the parietal cortex region, which is involved in sensation and in spatial perception.