April 09, 2008

Researchers Define Mechanism of Methamphetamine Addiction

WEDNESDAY, April 9 (HealthDay News) -- Long-term changes in the brain's dopamine-releasing machinery may explain why methamphetamine addiction is so strong, U.S. researchers say.

Dopamine is one of the brain's major neurotransmitters.

The research team, led by Nigel Bamford, of the University of Washington, Seattle, treated mice with methamphetamine and monitored how extended exposure to the drug affected dopamine levels. The researchers focused on the dopamine machinery in the brain's corticostriatal region, which is believed to contain the "habit" circuitry that plays a major role in the compulsive drug seeking seen in people addicted to methamphetamine and amphetamine.

Long-term exposure to methamphetamine caused a depression of the synaptic dopamine machinery in the corticostriatal region that lasted for months after the mice were no longer given the drug. However, a dose of methamphetamine reversed the depressive effects on the synaptic dopamine machinery.

The researchers also found that the drug produced its long-term effect by altering specific types of receptors for dopamine and another neurotransmitter called acetylcholine.

They concluded that the mechanism they identified "might provide a synaptic basis that underlies addiction and habit learning and their long-term maintenance."

The findings, which were published in the April 10 issue of the journal Neuron, could help lead to more effective treatments for addiction to methamphetamine and related drugs.

In a preview of the research article in the same issue of Neuron, Jeremy Day and Regina Carelli suggested that methamphetamine's effects on the brain discovered by Bamford and his colleagues might disrupt the normal machinery for learning in the brain, "leading to aberrant reward processing and action selection. If so, the discovery of methods to reverse this plasticity may be a promising avenue for addiction treatment."

More information

The U.S. National Institute on Drug Abuse has more about methamphetamine.

-- Robert Preidt
SOURCE: Cell Press, news release, April 9, 2008
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