University of Washington researchers say that animal studies show that methamphetamine use causes lasting changes in the brain's dopamine system, making it especially difficult for users to stop using the drug.

HealthDay News reported April 9 that researcher Nigel Bamford and colleagues found that long-term methamphetamine use depressed the synaptic dopamine-release system in the corticostriatal area of the brain -- a condition that gets temporarily reversed when a dose of methamphetamine is administered.

Researchers said that methamphetamine appears to cause long-term changes in certain dopamine receptors and with the neurotransmitter acetylcholine. The findings "might provide a synaptic basis that underlies addiction and habit learning and their long-term maintenance," Bamford and colleagues wrote.

The findings were published in the April 10, 2008 issue of the journal Neuron.