Lausanne researchers find trigger for cocaine addiction

Cocaine molecules bind to a glutamate receptor in the brain to produce pleasurable effects.

Scientists from the University of Lausanne may have found the genetic key to cocaine addiction. Their work, which is financed by a major pharmaceutical company, could lead to practical applications in a few years time.

This content was published on September 24, 2001 minutes

The findings are the result of more than five years work. The scientists had originally planned to study genetic links to psychiatric disorders before they came across their "addiction" gene.

"In a sense, it was a stroke of luck," said François Conquet, head of the team. "We did not follow standard procedures to get our result."

They tested their theory using genetically modified (GM) and normal mice. The mice were taught to self-administer food intravenously before it was replaced with a cocaine solution.

While the normal mice developed addictive behaviour patterns, the modified rodents failed to take an interest in the drug. Force-fed GM mice also showed no signs of changed behaviour, although cocaine was present in their bodies.

Key to addiction

By binding with a receptor for glutamate, a chemical compound that helps carry messages between brain cells, cocaine indirectly induces the flow of another chemical called dopamine, which produces feelings of satisfaction and pleasure. The gene responsible for expressing the glutamate receptor was removed from the GM mice.

Since removing the receptor from the circuit seems to be the key to cocaine addiction, the researchers are now searching for a substance that can block the glutamate receptor without producing dangerous side effects.

Current treatments for addiction only have a cushioning effect, while this latest discovery would be like turning a switch off. "In the future, it might be possible to use antagonists, chemical compounds, to deactivate this receptor and treat drug addiction," Conquet told swissinfo.

The research could therefore lead to appropriate medication for fighting a number of types of addiction. Other experiments have also shown that the receptor also binds to drugs such as heroin or methadone.

Huge market potential

A pharmaceutical application is still some distance away for the researchers. "The next step is to continue studying the functions of the receptor, which we don't understand entirely yet," said Conquet.

The market potential is huge, running into billions of dollars alone for smokers who suffer from nicotine addiction.

Pharmaceutical giant GlaxoSmithKline has so far financed the research at Lausanne University although the Lausanne team is considering creating a spin-off to market its discovery.

The research team's finding are published in September's issue of Nature Neuroscience.

by Scott Capper

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