Eventually, amphetamines destroy your teeth. Paradoxically, in such cases, dentists hold the secret of our salvation: and that's lidocaine, a drug usually employed to numb your gums. Lidocaine shuts off insula, a brain nucleus controlling drug addiction, and targeting the insula's activity could one day free people of their drug addiction.

Other brain areas like the prefrontal cortex and nucleus accumbens have been connected to drug craving . Still, the team led by Fernando Torrealba at the Pontifical Catholic University of Chile in Santiago focused on the insula. The insula is an important brain nucleus controlling the body's heart rate, blood sugar, hunger, cravings and other functions. An impaired insula has been proven to rid smokers from smoking overnight.

Lab rats were placed in cages with dark and lit patches. Rats love the dark, but whenever they enter a well-lit area, they got a dose of amphetamines. In the experiment, the rodents soon got addicted and returned continuously to the same point for a new dose. The addicted animals spent from under 5% of their time in the well-lit area to about 25%.

After that, part of the addicted rats got lidocaine shots into the insula, while others into another brain area. Some addicted rats got saline solution shots into the insula. Lidocaine impairs signal transmitting between the brain cells.

The lidocaine shots in the insula made individuals stay less than 10% of their time in the well-lit areas, while the other addicted rats had the same schedule as before. "We may be able to switch off memories related to the drug-taking experience, and possibly prevent future relapse in addicted individuals," said Steve Laviolette of the University of Western Ontario in London, Ontario, Canada.

Still, "giving injections of lidocaine into the brain does not make sense for humans because of the risk of infection and potential changes in heart rate. If I were an addict I would think thrice before I would let anyone inject something into my brain," said Torrealba, who bets rather on an oral drug targeting insula.

In fact, the lidocaine shots had a short-lasting effect, erasing the drug addiction in the lab animals for just 20 minutes. But the new study "should herald development of new, potentially more effective treatments for addictions", said Paul Matthews, from Imperial College, London, UK. And "it is important to keep in mind that the drug addiction process is highly complex, involving multiple interactions between a variety of brain regions and neurochemical pathways", warned Laviolette.