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Drug Addiction and Stress: The Brain Connection

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If you hit a fastball for a home run, chances are the next time you are at the plate and see a fastball coming, you'll be stoked. Why? Part of the reason is long-term potentiation (LTP). LTP is one of the brain's key mechanisms for registering experience and using it to shape future responses, as in learning and remembering. When an experience or some other stimulus induces LTP in a cell, the cell responds more strongly to future exposures to the same stimulus. For example, if you hit a fastball for a home run, LTP is part of the reason you might get excited the next time you are at the plate and see a fastball coming.

Scientists have made important discoveries in the role that LTP may play in drug addiction, as well as in the body's response to stress—which may help to explain a long-observed connection between the two.

Researchers have shown that, in animal studies, a single exposure to some addictive drugs can establish LTP in dopamine-releasing cells in an area of the brain called the ventral tegmental area (VTA). LTP primes these brain cells to react more strongly—and release dopamine more abundantly—in response to future exposure to drugs. Dopamine is a chemical neurotransmitter that triggers feelings of pleasure and also plays a role in alerting people that something important is happening or about to happen.

Researchers have also found that stress alone can induce changes in dopamine-releasing VTA cells similar to those caused by drugs. This raises the possibility of a "priming mechanism" that could make someone who has experienced stress much more vulnerable to addiction, or to relapse during treatment for addiction.

Sources:

National Institute on Drug Abuse, The Brain's Response to Drugs (Teacher's Guide). Accessed at http://teens.drugabuse.gov/mom/teachguide/MOMTeacherGuide.pdf.

Zickler, Patrick, "Addictive Drugs and Stress Trigger Similar Change in Brain Cells, Animal Study Finds," NIDA Notes Research Findings, Vol. 18, No. 5 (December 2003). Accessed at www.drugabuse.gov/NIDA_notes/NNvol18N5/Addictive.html.