Chilean researchers found that when rats get addicted to the drug called amphetamine, they were longing for the drug. These drug cravings occur due to the presence of insular cortex in brain, which is a part of the interceptive sensory system that monitors the body's perception of its physiological states and needs.
It is believed that the new finding, published by the American Association for the Advancement of Science (AAAS) in the journal Science, may eventually lead to the development of new treatments for therapies for drug addiction as well as certain behavioural side effects of medications.
"Our finding that blocking the insula prevents the craving for amphetamine in amphetamine-dependent rats, indicates to us that this region of the brain processes information about the physiological states of the body and may guide behavior," said researcher Fernando Torrealba of the Pontifical Catholic University of Chile.
During the study, the researchers inactivated the insular cortices of amphetamine-addicted rats by injecting them with a drug that temporarily silenced all neuronal activity in this area.
Upon being injected, the addicted rats did not seek amphetamines and returned to their normal behavior—specifically, preferring a darkened compartment rather than a bright white region of an experimental apparatus.
When the researcher reversed the blocking of insula, the mice once again showed signs of craving amphetamines, preferring the white compartment.
In another experiment, the researchers injected rats with lithium—a drug used to treat mood disorders that also can cause gastrointestinal discomfort and malaise—whereupon rats "quickly laid on their bellies," showing signs of malaise.
However, rats in which the insula had been inactivated before administering them lithium did not show 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 the signs of gastrointestinal discomfort, and that this information about bodily states may guide behaviour," Torrealba said.
"Since this region serves the perception of bodily needs and emotions, it may be a key structure in decision making by informing the executive prefrontal cortex of our needs as in the case of drug abuse," he added.
The researchers are now planning to continue their research to see whether drug craving can be prevented for longer time periods. They also wish to investigate whether other distressful systems can be alleviated.
"This study is significant, not only for its practical and therapeutic implications for the development of future treatments for drug addiction, but also from a basic science point of view because it gives new insights into the function of the insular cortex," said Peter Stern, a senior editor for Science.