Region of Brain Linked to Addiction in Rats
> 10/26/2007 1:20:42 PM

Last year when scientists observed stroke patients who were able to stop smoking without any difficulties, they began to study the area of the brain where these patients had sustained damage. The insular cortex, or insula, provides emotional context for sensory experiences and is associated with decision-making. Now Chilean researchers have released the results of a study  demonstrating that the insula may play an important role in drug addiction.

Researchers from the Pontifical Catholic University of Chile in Santiago injected amphetamine-addicted rats with a drug designed to stop neural activity in the insula. Prior to being given the injections, the rats could choose to stay in one of two chambers in their enclosures: a lighted chamber where amphetamines were available and a darkened chamber where amphetamines were not available. Although rats naturally prefer dark places, these rats chose the lighted chamber—and the amphetamines. After being injected, with the neural activity in the insula stopped, the rats preferred the dark chamber. Once the injections wore off and neural activity in the insula resumed, the rats again sought out the lighted chamber. In another experiment, the researchers explored the insula's role in withdrawal symptoms. They injected rats with lithium, which causes rats to experience malaise and gastrointestinal discomfort. However, when the researchers deactivated the insula before injecting the lithium, the rats did not experience these symptoms and behaved normally. The researchers speculate that by developing treatments to reduce or stop the activity of the insula, they can more effectively help drug addicts to overcome addiction and relieve the unpleasantness of withdrawal.

Scientists first began to study the insula after observing the ease with which some stroke patients were able to quit smoking, and previous studies have discovered an association between the insula and tobacco addiction. In one study, researchers used a database of stroke patients to identify 69 patients who had smoked at least five cigarettes a day for the two years prior to their stroke. 19 of these patients had suffered damage to the insula, and of these 19, 13 had given up smoking. Of the remaining 50 stroke patients, only 19 had given up smoking. When the scientists compared how easily the patients had given up their addiction, they found that those with damage to the insula had stopped smoking more easily. 12 of the 13 reported giving up their addiction quickly and without difficulty, compared to only 4 of the 19 who had not suffered damage to the insula.

By utilizing what we now know about the insula, researchers could help addicts to endure withdrawal symptoms successfully and even prevent addicts from experiencing cravings. Researchers will continue to study the function of the insula in addicted animals before testing their theories on humans, but hopefully the information they discover will soon lead to more effective ways of treating addiction.

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