"The VTA is a brain region involved in the development of drug addiction, write the researchers, who included Julie Kauer, PhD, a professor of medical science at Brown University."

"Kauer and colleagues focused on certain nerve cell connections in the VTA that usually limit levels of a brain chemical called dopamine."

"One dose of morphine blocked those nerve cell connections�in the rats' brains. That created a surge in dopamine levels, throwing off the brain's chemical balance."

"The activity
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