Some Brains May Be Predisposed to Substance Abuse

We've known for some time that dopamine D2 receptors play an inportant role in addiction, but this is news:

Do the brain changes noted in drug addicts help cause their addiction, or are they the result of drug abuse?

A new study might solve that chicken-and-egg puzzle - pointing to new ways of preventing and treating addiction, researchers say.

The rat study suggests that "some individuals may be predisposed to the effects of cocaine on the brain," making them more likely to try the drug and become addicts, said lead researcher Dr. Jeffrey Dalley, of Cambridge University's Behavioural and Clinical Neuroscience Institute in the United Kingdom.

Specifically, rats that went on to compulsively self-administer cocaine intravenously were more likely to have fewer brain cell-surface receptors for the neurotransmitter dopamine in an area of the brain called the nucleus accumbens, compared to rodents that were less prone to addiction.

"The study is the first to conclusively demonstrate that changes in dopamine receptors in the nucleus accumbens pre-date cocaine use," Dalley said. That means that these brain changes are not caused by cocaine exposure but may encourage use of the drug.