From Scientific American:
Scientists for the first time have identified long-term changes in mice brains that may shed light on why addicts get hooked on drugs—in this case methamphetamines—and have such a tough time kicking the habit. The findings, reported in the journal Neuron, could set the stage for new ways to block cravings—and help addicts dry out.
Researchers, using fluorescent tracer dye, discovered that mice given methamphetamines for 10 days (roughly equivalent to a human using it for two years) had suppressed activity in a certain area of their brains. Much to their surprise, normal function did not return even when the drug was stopped, but did when they administered a single dose of it again after the mice had been in withdrawal.
Study co-author Nigel Bamford, a pediatric neurologist at the University of Washington School of Medicine, says that if similar changes occur in humans, it will indicate that an effective way to fight addiction may be to design therapies that target the affected area—the striatum, a forebrain region that controls movement but also has been linked to habit-forming behavior.