Scientists at the University of Cambridge have discovered why some individuals may be predisposed to drug addiction and believe it may lead to better treatments for this brain disorder.
The new findings, published in today's edition of Science, may lead to more targeted treatments for addiction and other compulsive behaviour disorders with fewer side effects than current alternatives.
Certain changes in brain chemistry have been linked with drug addiction in humans. However, previous studies were unable to conclude whether individuals were predisposed to drug addiction because of these chemical changes or if chronic drug use itself caused the chemical changes in the brain.
Dr Jeff Dalley and colleagues, at the Behavioural and Clinical Neuroscience Institute, may have resolved this debate by demonstrating that changes in a neurotransmitter receptor in a particular part of the brain actually pre-dates drug use. Using positron emission tomography (a PET scan), they discovered that rats that were behaviourally impulsive, but which had not been exposed to drugs, had significantly less brain dopamine receptors than their more restrained counterparts. Additionally, these same impulsive rats were found to be considerably more likely to self-administer cocaine intravenously, thus linking impulsive behaviour with drug addiction vulnerability.
Dr Dalley's research, funded by the Medical Research Council and the Wellcome Trust, demonstrates that the changes in dopamine receptors and impulsivity pre-date drug use and do not emerge as a result of prolonged addiction. His findings may have important ramifications for a range of addictive substances, including nicotine and opiates, where high consumption rates have also been linked to a similar reduction in this particular brain receptor.
Dr Dalley said, "The next step is identifying the gene or genes that cause this diminished supply of brain receptors. This may provide important 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."
Government reports estimate there are between 281,000 and 506,000 individuals addicted to Class A drugs (to include ecstasy, LSD, heroin, cocaine, crack, mushrooms and injectable amphetamines) in England and Wales.