February 23, 2009
Cocaine Users Have Fewer Reward Cells
Cocaine use can have toxic effects on brain cells (neurons) that produce dopamine, say experts at Baylor College of Medicine in Houston in a report that appears today in the journal Psychiatry Research.
Using brain tissue acquired after the subjects died, researchers microscopically compared the number of dopamine cells in the brains of 10 cocaine users to those in the brains of nine people matched for age who did not use the drug.
They found significantly fewer dopamine cells, 16 percent, in the brains of cocaine users.
"Although we have always known that cocaine is a dangerous drug, for the first time we can now physically see that dopamine cells are lost in the brains of cocaine users," said Dr. Karley Little, associate professor in the Menninger Department of Psychiatry and Behavioral Sciences at BCM. Associated measures indicated that the loss of cells was recent and the subjects were not born with this loss.
"Dopamine plays a big role in the awareness of pleasurable things in the environment, including food and sex," said Little, also a staff psychiatrist at the Michael E. DeBakey Veterans Affairs Medical Center in Houston. "The lack of dopamine cells may make a person less responsive to natural rewards, whether it's in the workplace or in a relationship."
The lack of dopamine cells could also lead to withdrawal or depression symptoms, said Little. Although effects of cocaine use vary among users, the study shows the potential dangers of this drug. Cocaine use may theoretically increase the risk of Parkinson's Disease, but the mechanisms involved may be different and not occur in the same individuals.
"This is just the beginning of the story. We can now create a model to understand the biochemistry involved, such as how cocaine is toxic and why it is more toxic in some than others," said Little. Previous work by Little indicated that dopamine uptake is increased by cocaine exposure in the same individuals, which might have contributed to the toxic effects.
Others who participated in the study include Eric Ramssen, Ryan Welchko, Vitaly Volberg , Courtney J. Roland, and Bader Cassin of the University of Michigan.
Funding for this work came from the National Institute of Drug Abuse.
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