Best Information for Health Educators

10 Apr 2008

Researchers have identified, for the first time, long-term changes in the brain circuitry of methamphetamine-addicted mice that can explain why the craving of addiction is so stubborn and long-lived. The research could lead to more effective treatments for addiction to methamphetamine and related drugs.

In their experiments, the researchers treated mice with methamphetamine and studied how long exposure to the drug affected levels of the brain chemical dopamine. Researchers have long known that methamphetamine and amphetamine enhance release of dopamine at the connections between neurons, called synapses. Dopamine is one of the brain’s major neurotransmitters, the chemical messengers by which one neuron triggers its neighbor to fire a nerve impulse.

The researchers concentrated on the dopamine machinery in the brain’s corticostriatal region, believed to harbor the “habit” circuitry central to the compulsive drug-seeking of addiction to methamphetamine and amphetamine.

To reveal the flow of dopamine, they used a fluorescent tracer dye that is taken up by the same microscopic sacs, called vesicles, that store and release dopamine in the process of signaling between neurons. Using microscopy to follow the movement of the dye, they could study how methamphetamine affected the dopamine transport machinery in the brain.

Their studies revealed that giving the animals the drug long enough to cause chronic effects caused a depression of the synaptic dopamine machinery in the corticostriatal region that lasted for months after the drug was withdrawn. However, giving the animals a dose of methamphetamine reversed the depressive effects on the synaptic machinery.

Filed under: Drug Use and