Brain and Body

Research Unearths the Long-Term Effects of Teen Amphetamine Abuse on the Brain

March 31, 2016 | Kelly Tatera

Photo credit: Tony Webster/flickr (CC by SA 2.0)

It’s not pretty.

Amphetamine, commonly known as Adderall or Dexedrine, could have lasting effects on teens, according to recent research. In a recent study on rats, researchers gave the animals regular, high doses of amphetamines at an age corresponding to human adolescence in order to investigate the long-term changes in the brain that persist into adulthood.

Reporting the findings in the journal Neuroscience, the scientists found that amphetamine leads to changes in dopamine signaling, which plays an important role in memory, attention, learning, and feelings of pleasure.

"The dopamine system, which continues to develop throughout adolescence and young adulthood, is a primary target of psychostimulant drugs like amphetamine," said Joshua Gulley, a University of Illinois psychology professor who led the new research, in a press release.

"Changes in dopamine function in response to repeated drug exposure are likely to contribute to the behavioral consequences — addiction and relapse, for example — that abusers experience."

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Gulley says that using rats in the study constitutes a worthy model for the study of human drug addiction since there are many parallels between rat and human development.

"Rats exhibit many of the characteristics that human adolescents do. They tend to be more impulsive than adult rats; they tend to make more risky decisions," he said. They also can engage in "addiction-like behaviors.”

Gulley said that rats also show increased drug use in response to stress, and that just like humans, there’s evidence that animals who use drugs in adolescence are more likely to relapse than animals who start using drugs in adulthood.

However, Gulley notes that a limitation to the new study was that “the rats had no say in whether they got amphetamine,” while humans can generally choose whether or not to partake in drug use.

The researchers focused on a brain region that is among the last to fully develop during adolescence, called the prefrontal cortex. The prefrontal cortex is implicated in a number of complex behaviors, namely personality development.

The findings showed that repeated exposure to amphetamines during adolescence reduced the ability of key cells in the prefrontal cortex to respond to dopamine — at least in the rats. Gulley says that in this brain region, dopamine influences “inhibitory tone,” which tells cells to stop responding to a stimulus.

"Inhibition in the nervous system is just as important as activation," he said. "You need cells that are firing and communicating with one another, but you also need cells to stop communicating with one another at certain times and become quiet."

Specifically, Gulley says that the research hints that a subtype of dopamine receptor, called the D1 receptor, is altered following amphetamine exposure.

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Further, this disruption in dopamine signaling lasted in the rats for 14 weeks after exposure to amphetamine.

"That's akin to a change in humans that persists from adolescence until sometime in their 30s, long after drug use stopped," Gulley said.

There’s plenty of research that shows how critical of a time adolescence is on brain development, so adding drugs into the mix is definitely a gamble.

Gulley says this study adds to the evidences that using drugs during adolescence “has extremely long-lasting consequences that go far beyond the last drug exposure.”

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