Long-term changes in the brain's dopamine-releasing machinery may explain why methamphetamine addiction is so strong, according to a study published by lead author Nigel S. Bamford, MD, UW Department of Neurology, and colleagues from the UW and other research institutions.
The research team 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.
[U.S. News & World Report, April 9, 2008]