Narrator: This is Science Today. Drug addiction has always been very hard to treat-partly because the science behind it is still poorly understood. Now scientists at the University of California, San Francisco have discovered one reason drugs can take such a strong hold on an addict's brain. Dr. Antonello Bonci found in test subjects that a significant change occurs in the brain after just one exposure to cocaine.
Bonci: What is also incredible for us is that this phenomenon lasts for up to five days. And this very short exposure to cocaine, we have estimated that the rat and the mice will experience cocaine in their blood for a few hours.
Narrator: This change creates a kind of cellular memory, which allows the brain to make decisions based on getting more of the drug.
Bonci: The idea that we want to emphasize is that if we can understand the series of events that change, maybe we'll be able to design drugs that will interfere with the development of the addictive behaviors by blocking the functional changes.
Narrator: For Science Today, I'm Larissa Branin.