Brains of children may undergo changes
where the reward system is not satisfied until it receives a fix.
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.
“Together, these results suggest that
adolescents who abuse prescription pain killers may be tuning their brain to a
lifelong battle with opiate addiction if they re-exposed themselves to the drug
as adults,” says Kreek. ”The neurobiological changes seem to sensitize the
brain to the drug’s powerfully rewarding properties.”
During adolescence, the brain undergoes
marked changes. For example, the brain's reward pathway increases production of
dopamine receptors until mid-adolescence and then either production declines or
numbers of receptors decline. By abusing Oxycontin during this developmental
period, adolescents may inadvertently trick the brain to keep more of those
receptors than it really needs. If these receptors stick around and the
adolescent is re-exposed to the drug as an adult, the rush of euphoria may be
more addictive than the feeling experienced by adults who had never before
tried the drug.