Drugs affect the functioning of the brain's chemistry. As a result of these effects, a person who uses drugs can become a slave to them. But the brain has its own processes that set the stage for addiction. Research attempts to identify what those processes are and how they work. Addiction is a uniquely human problem, yet the qualities of addiction can be modeled in animals. Research shows that even rats can be turned into drug addicts.

When it comes to choosing an addicting drug, rats are not all that different from people. Scientists can set up experiments in which rats will give themselves repeated doses of drugs that humans find appealing and addicting. Research into human drug addiction that relies on animals may reveal new ways to treat, and even prevent, human problems with addictive drugs.

Reward Center

Experiments have shown that rats with a tiny wire...