Brain chemistry linked to drug addiction
1 March 2007
MRC scientists have discovered why some people are more likely to develop a drug addiction than others. Their research suggests that changes in brain chemistry influence an individual’s chances of becoming addicted even before they have used drugs.
This discovery may lead to better treatments for compulsive behaviour disorders like addiction with fewer side effects than current therapies.
Dr Jeff Dalley and colleagues at Cambridge University’s Behavioural and Clinical Neuroscience Institute looked at rats’ brains. They were interested in changes in a receptor for a signalling molecule called dopamine that has effects on emotion, perception and movement.
They discovered the rats which were behaviourally impulsive, but had not been exposed to drugs, had significantly fewer dopamine receptors in their brains than rats that exhibited more restrained behaviour.
The highlighted region shows activity in the part of the human brain where dopamine receptors are found.
Given the opportunity, the same impulsive rats were also more likely to self-administer cocaine. This choice illustrates a link between impulsive behaviour and vulnerability to drug addiction. It also demonstrates that changes in dopamine receptors pre-date drug use rather than being caused by drug abuse.
The discovery could be helpful in developing therapies for other addictive substances, for example nicotine and opiate drugs, that are also linked to a reduction in dopamine receptors.
“The next step is to identify the gene or genes that cause this diminished supply of brain receptors. This may provide new leads in the search for improved therapies for attention deficit/hyperactivity disorder (ADHD) and compulsive brain disorders such as drug addiction and pathological gambling,” said Dr Dalley.
This research was funded by the Medical Research Council and The Wellcome Trust.
Original research paper: Nucleus Accumbens D2/3 Receptors Predict Trait Impulsivity and Cocaine Reinforcement is published in the 02 March 2007 edition of Science.
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