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Wednesday, 30 May, 2001, 17:59 GMT 18:59 UK
'One dose danger' of cocaine
Cocaine makes the brain more responsive to addiction
The first exposure to cocaine could leave users vulnerable to addiction.

Using mice for testing, scientists found that just one single use of cocaine could trigger a long-lasting surge of activity in the part of the brain linked to the development of addiction.

And they said this could also be the reason why former drug users fall back into addiction after just one relapse.

Drug groups are now hoping to dispel the widely held misconception that cocaine is a safer, less addictive, drug than others.

What's so amazing is that nearly all dopamine neurons are affected by this single cocaine exposure

Dr Mark Ungless


A spokeswoman for Addaction said that many drug users mistakenly thought they were safe taking cocaine as a recreational drug, but that this new study proved this was not the case.

"It is a general belief that cocaine is less addictive and that this is assumed by users. So it is important to look at this study."

But Harry Shapiro, director of communications at the drug addiction group DrugScope, said he would want to see more research before accepting the findings of the research.

"Its impossible to make sense of a condition as complicated as addiction from one study, particularly one conducted on mice. There is little correlation between the brain patterns of mice and humans and I would therefore be cautious about placing too much emphasis on a single piece of research."

The research, published in Nature, showed that just one single use of cocaine doubled the responsiveness of cells in the brain to the chemical dopamine, which produces feelings of satisfaction and pleasure.

Scientists that for up to a week or ten days after taking the drug, the brain was more sensitised to the pleasure of taking cocaine.

The research led by a team at University of California, San Francisco's Ernest Gallo Clinic and Research Centre, provides the first direct evidence that a single cocaine exposure - a recreational use - causes dramatic changes in the brain to areas that cover learning and memory.

Dr Antonello Bonci, senior author of the paper and assistant professor of neurology at the university said: "The study shows that the capacity for strengthening connections between nerve cells - the basis for learning and memory - can be usurped by drugs of abuse.

Cocaine has a significant effect on the functions of the brain

"The single exposure appears to hijack the brain's normal molecular mechanisms of memory formation for around a week."

Other scientific research has shown that learning and memory are crucially important in the development of addiction and also involve the activation of the same brain cells - the dopamine neurons.


Dr Mark Ungless, lead author of the paper, said the changes they had found in brain activity were "stunning."

"What's so amazing is that nearly all dopamine neurons are affected by this single cocaine exposure.

"This kind of response is rare, and would have a profound effect throughout the brain particularly other areas involved in addiction."

The researchers said the drug patterns they had found could also apply to other drugs as well as cocaine.

They now want to look into how the research can help develop treatments for addiction.


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