( part of a brain circuit that transmits ...)Drug abuse leads to long standing changes in the brain,Health

part of a brain circuit that transmits signals using the chemical dopamine, which plays a role in movement control and feelings of pleasure. 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. But previous animal studies show that long-term exposure to methamphetamine damages dopamine-producing brain cells and leads to reduced dopamine levels. 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.

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. Animal studies show this area to be particularly sensitive to the damaging effects of methamphetamine.

However, after controlling for this overall increase in metabolism in the methamphetamine abusers, the investigators showed that metabolism was significantly reduced in two brain regions?the thalamus and striatum. These regions are involved in dopa
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