Scientists believe they are close to identifying genes in these flies which prevent them from becoming addicted to alcohol.

Researchers at the University of California at San Francisco are confident that the same genes also play an important but opposite role in humans.

We can dissociate the activating and sedative effects of alcohol

Dr Ulrike Heberlein, UCSF

They believe that triggering changes in these genes could stop alcoholics from drinking.

They are also hopeful that the genes could be manipulated to stop humans from becoming tolerant to alcohol.

While fruit flies live off fermented fruits, they do not get addicted to alcohol.

Drunk as a fly

But previous studies have shown that alcohol affects these insects in the same way it does humans.

They, too, become hyperactive and move erratically. At high doses they also tend to pass out. In addition, they become tolerant to alcohol.

Dr Ulrike Heberlein and colleagues at UCSF have already identified mutations of changes in a gene that makes fruit flies less hyperactive when they first detect a type of alcohol called ethanol.

According to a report on the science website BioMedNet, they have also identified a gene that makes them more resistant to ethanol, which means they need more each time before they become 'drunk'.

These genes regulate a protein in their bodies called the kinase enzyme.

The scientists have now developed a breed of fruit flies which does not become tolerant to alcohol.

"We can dissociate the activating and sedative effects of alcohol," Dr Heberlein said.

They are currently trying to breed another set of fruit flies which do not like alcohol.

They believe this could help them to pinpoint genes that lead some people to drink too much and to become addicted to alcohol.

Dr Leslie Griffith of Brandeis University in Massachusetts said there was a good chance that the genes in fruit flies also play a role in people.

"Once you start to understand the molecular processes underlying something like addiction or tolerance, you might begin to understand something about the human condition," Dr Griffith told BioMedNet.

The research findings were presented at the US Society of Neurosurgery annual meeting in Florida.