When the insula was switched off, rats lost the craving, scientists say
THURSDAY, Oct. 25 (HealthDay News) -- A specific brain region may be crucial to drug addiction, according to a new study conducted with amphetamine-addicted rats.
"This work in rats lines up nicely with new findings in humans involved with drug-seeking behavior," said one outside expert, Dr. Robert Vorel, a fellow at Columbia University Medical Center's division of drug abuse in New York City.
The brain segment, called the insular cortex, "may be a key structure in decision-making by informing the executive prefrontal cortex of our needs -- as in the case of drug abuse," study lead author Dr. Fernando Torrealba, a neuroscientist at the Pontifical Catholic University of Chile, in Santiago, said in a statement.
The insular cortex, also known as the insula, is part of the sensory system that monitors the body's perception of physical states and needs. The new study shows that the insula "may guide behavior in humans," Torrealba said.
Prior studies done in humans looked at the role of the insula in nicotine craving. They revealed insula activity in smokers exposed to tobacco fumes, Vorel said.
And he added that other work has studied people who suffered brain injuries. They showed that smokers who had strokes that damaged the insula were most likely to give up smoking. "That raised a lot of attention," Vorel said.
The new Chilean work on amphetamines and the insula, "probably confirms what is already known in humans," Vorel said.
The Chilean researchers worked with amphetamine-addicted rats. In one series of studies, insular cortex activity was silenced by injections of a drug that inactivated brain cells in the area. When that happened, the rats stopped seeking amphetamines and returned to their normal behaviors -- for example, going to a dark compartment rather than the brighter region they favored while taking amphetamines. However, their craving for amphetamines returned when the insula went back into action.
In a second experiment, the rats received injections of lithium, a drug used to treat mood disorders that can cause gastrointestinal discomfort. The malaise promptly appeared under normal conditions but not when the rats' insulas were inactivated just before the lithium shots.
The Chilean researchers said they plan human trials to confirm what has been seen in the animal studies. They also plan more animal work to see if they can prevent amphetamine craving for longer periods and perhaps alleviate other distressing symptoms of amphetamine addiction.
There's more on drug addiction at the U.S. National Institute on Drug Abuse.
SOURCES: Robert Vorel, M.D., Ph.D, fellow, division of drug abuse, Columbia University Medical Center, New York; Oct. 26, 2007, Science
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