Early misuse of painkillers leads to addiction?

More research suggesting that opiate addiction can be aquired by early exposure:

No child aspires to a lifetime of addiction. But their brains might. In new research to appear online in the journal Neuropsychopharmacology this week, Rockefeller University researchers reveal that adolescent brains exposed to the painkiller Oxycontin can sustain lifelong and permanent changes in their reward system – changes that increase the drug’s euphoric properties and make such adolescents more vulnerable to the drug’s effects later in adulthood.

The research, led by Mary Jeanne Kreek, head of the Laboratory of the Biology of Addictive Diseases, is the first to directly compare levels of the chemical dopamine in adolescent and adult mice in response to increasing doses of the painkiller. Kreek, first author Yong Zhang, a research associate in the lab, and their colleagues found that adolescent mice self-administered Oxycontin less frequently than adults, suggesting that adolescents were more sensitive to its rewarding effects. These adolescent mice, when re-exposed to a low dose of the drug as adults, also had significantly higher dopamine levels in the brain’s reward center compared to adult mice newly exposed to the drug.