'Switch off' drug cravings
2007-10-26 15:05
Chicago - An animal study released on Thursday bolsters the notion that drug cravings can be "switched off" by shutting down a key part of the brain, a finding that could have implications for treating addicts.
The insular cortex, or insula, is a region deep within the brain that filters information about the body's physiological states and needs.
Researchers have previously shown that damage to the insula can dramatically extinguish a smoker's need for nicotine.
A study earlier this year found that 12 of 19 habitual smokers had effortlessly given up the weed after sustaining injuries, such as a stroke, to the small island in the cerebral cortex.
At the time, investigators were not sure whether the finding had wider implications and whether disruptions to the insula could ease the grip of other addictions, such as those to alcohol, over-eating or drugs.
Drug-addicted rats
But in experiments on rats, Chilean researchers have shown that temporarily "silencing" the insula suppresses cravings in drug-addicted rats and insulates them from the unpleasant side effects of medication, according to the study published in Science.
For the first experiment, the investigators gave a group of rats that were addicted to amphetamine a shot of anaesthetic to numb the insula for 20 minutes.
The rats were caged in an experimental set-up composed of a darkened chamber and an adjoining bright white chamber which the rodents had been trained to associate with amphetamines.
The intervention had a pronounced impact on their behaviour, changing their preference from the white chamber to the darkened chamber - which is a more natural setting for rats.
When the blocking was reversed, the rats once again demonstrated their desire for the drug, returning to the white chamber.
In a second experiment, the researchers injected rats with lithium, a medication used to treat mood disorders that often causes an upset tummy by way of a side effect.
Alleviated side effects
The rats quickly laid on their stomachs - showing signs of malaise. When the researchers numbed the insula prior to giving the rats the medication, they did not show any signs of discomfort and appeared to behave normally.
"This showed us that the insular cortex not only informs the rest of the brain about craving, but also gastrointestinal discomfort and that this information about bodily states may guide behaviour," said Fernando Torrealba, a neuroscientist at the Pontifical Catholic University of Chile in Santiago.
Taken together, his study in rats and the earlier one on smoking provide powerful evidence that the insula "underlies the conscious sense of craving," making it a good target for drugs designed to help addicts break the habit, he said.