By Isobel Leybold-Johnson
Scientists at Geneva University have unveiled research that could be used to help combat cocaine addiction.
They have developed a method that erases a trace left by the drug in the brains of mice and reverses addict behaviour to normal.
Cocaine is highly addictive; it gives users a buzz but the comedown leaves people wanting more. It is known to leave a trace on the brain, meaning that a relapse could take place months or even years after people stop taking the drug.
In research published in this week’s Nature, the team from the neuroscience department at Geneva University used mice to provide a proof of principle that the trace could be erased. And that was not all.
“It’s the first time that we have been able to manipulate specifically a connection between two nerve cells [in the brain] in order to change addiction-related behaviour,” team leader Christian Lüscher told swissinfo.ch.
The areas in the brain concerned were the prefrontal cortex and the nucleus accumbens, which plays an important role in the brain’s reward system – the regulation and control of behaviour through pleasurable effects – and thus in addiction.
To effect the change, researchers used a relatively new process called optogenetics, which Lüscher describes as “a really revolutionary technique that has changed the game”.
“Basically we take a protein, an ion channel that is sensitive to light, and you artificially put this into the neurons that you want to control. Once you have done that, you can then come with fibre optics and control the neurons through light.”
The team observed that, after the procedure, the cocaine-exposed mice reacted to a new dose of the drug as if they had never encountered it before.
This could give hope to human addicts, as the research suggests that changes in behaviour brought on by cocaine could be reversible, which in turn would reduce the chances of a relapse.
But Lüscher said much more research would be needed before any application to humans.
“What we do in a mouse is a very controlled experiment on the very early effects of cocaine, so we do one to five injections. In contrast, a human becomes an addict after years of chronic use so it’s a very different situation,” he said.
“But from the proof of principle standpoint, it’s an interesting concept that certainly could be translated into a clinical application in future.”
Addiction Info Switzerland said it found the results of the research very interesting.
“They are certainly basic principles that are pioneering for the understanding of the physiology of addiction,” spokesman Simon Frey told swissinfo.ch.
Like Lüscher, he said more research would be needed before its application to humans and in drug therapy.
As for how big a problem cocaine addiction is in Switzerland, Frey said there were no absolute figures.
“What we can say is that in a survey of the 15-39 age group in 2007, 4.4 per cent said they had taken cocaine during their lifetime and in 2002 it was only 2.9 per cent, so one can see a rise,” he said.
But such figures are not totally reliable: strong consumers are often not reached by phone surveys and people don’t share all their drug experiences in such polls, he added.
Frey explained that cocaine was, however, a highly addictive drug. People can recover, he added, but the risk of relapse was high – “if they are confronted with a [risky] situation, they are more prone to consuming the drug than a person who hasn’t taken cocaine before”.
As for the future, Lüscher says that any efforts to translate his work from mice to humans would depend on how much society is willing to support further addiction research.
“Although addiction is a frequent disease, it’s sometimes called an orphan disease because, for many reasons, private industry hesitates to develop new therapies because it’s a difficult market; it’s people who are not very reliable in clinical studies precisely because they are addicts,” he said.
“We hope that by providing new ideas from basic science we can help initiate new ideas and initiatives in that direction.”