Addiction Research

Study Explores Why People Respond Differently to Environmental Drug Cues

A new study has found that differences in people’s responses to environmental cues can change chemical responses in the brain. This finding could help researchers develop new treatments for substance abuse, compulsive gambling, sexual addiction, and other compulsive behaviors. 

Co-lead author Shelly B. Flagel, Ph.D., a research investigator at the U-M Medical School’s Molecular and Behavioral Neuroscience Institute, said they were able to answer the question of what role the neurotransmitter dopamine plays in the reward center of the brain.

To get some perspective, think about a rat learning to associate a lever with the appearance of food. Until now, scientists hadn’t figured out whether dopamine was released in the rats’ brains at the sight of the lever itself or when the rats accurately predicted the appearance of food. With this study, the researchers found that the answer depends on the rat’s genes. 

Flagel said to think about a sign for an ice cream store. Some people will see the sign and think of it as an indicator that ice cream is available. Other people, however, will have a stronger reaction to the sign, and they’ll hurry over to the store, unable to resist the opportunity. 

The researchers studied rats that were bred for certain personality traits, including increased risk for drug addiction. Rats that were more prone to substance abuse tended to focus their attention on the lever, whereas the other rats focused on the area where the food appeared.

The researchers used a method called fast-scan cyclic voltammetry to measure the dopamine responses in the rats’ brains, and found that the rats that were more susceptible to drug abuse experienced a reward just from seeing the lever, whereas the other rats did not. Even when the food was removed, the drug-prone rats’ desire for the lever continued.

The study also measured the rats’ ability to learn when the reward feelings (dopamine) were blocked, and repeated the experiments with rats that had not been selectively bred.

The researchers, including co-lead author Jeremy J. Clark, Ph.D., of the University of Washington, hope their study will help scientists discover my some people are much more influenced by environmental cues and are at a higher risk for compulsive behavior such as addiction.

Source: Science Daily, Unlocking the Secrets of Our Compulsions, December 8, 2010