Cocaine addiction: Scientists discover ‘back door’ into the brain

Individuals addicted to cocaine may have difficulty in controlling their addiction because of a previously-unknown ‘back door’ into the brain, circumventing their self-control, suggests a new study led by the University of Cambridge.

A second study from the team suggests that a drug used to treat paracetamol overdose may be able to help individuals who want to break their addiction and stop their damaging cocaine seeking habits.

Although both studies were carried out in rats, the researchers believe the findings will be relevant to humans.

Cocaine is a stimulant drug that can lead to addiction when taken repeatedly. Quitting can be extremely difficult for some people: around four in ten individuals who relapse report having experienced a craving for the drug – however, this means that six out of ten people have relapsed for reasons other than ‘needing’ the drug.

“Most people who use cocaine do so initially in search of a hedonic ‘high’,” explains Dr David Belin from the Department of Pharmacology at the University of Cambridge. “In some individuals, though, frequent use leads to addiction, where use of the drug is no longer voluntary, but ultimately becomes a compulsion. We wanted to understand why this should be the case.”

Drug-taking causes a release in the brain of the chemical dopamine, which helps provide the ‘high’ experienced by the user. Initially the drug taking is volitional – in other words, it is the individual’s choice to take the drug – but over time, this becomes habitual, beyond their control.

Previous research by Professor Barry Everitt from the Department of Psychology at Cambridge showed that when rats were allowed to self-administer cocaine, dopamine-related activity occurred initially in an area of the brain known as the nucleus accumbens, which plays a significant role driving ‘goal-directed’ behaviour, as the rats sought out the drug. However, if the rats were given cocaine over an extended period, this activity transferred to the dorsolateral striatum, which plays an important role in habitual behaviour, suggesting that the rats were no longer in control, but rather were responding automatically, having developed a drug-taking habit.

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