Drug addiction might someday be cured with a simple treatment to "wake up" a dysfunctional region of the addict's brain. Researchers report they were able to eliminate drug-seeking behavior in cocaine-addicted rats by stimulating a part of their brain known as the prefrontal cortex with laser light. Investigators also discovered they could reverse the effect, turning rodents that were not addicted to cocaine into drug-seekers.
For several weeks, scientists exposed a group of rats to cocaine, an alkaloid derived from the coca plant that's used widely - and illegally - as a drug. The rodents quickly became hooked on the highly addictive substance. Then, for four days, whenever the rats pushed a lever to get more cocaine, they received a mild and unpleasant electric shock to their foot.
Antonello Bonci, scientific director at the U.S. National Institute on Drug Abuse and a researcher involved in the study, says that after the shocks, 70 percent of the rodents stopped their drug-seeking. But the remaining 30 percent continued to display addictive cravings for the cocaine, in spite of the foot shocks.
Scientists compared nerve cell firing patterns in both groups of rats by examining cells from a brain region known as the prefrontal cortex. It’s involved in higher functions, including decision-making, impulse control and behavioral inflexibility.
Researchers discovered that the addicted rats had reduced activity in a part of this brain cortex called the prelimbic region, indicating weakness in the self-control mechanisms necessary to resist the drug. So investigators devised a plan to bolster the rat's self-control. The first step was to inject the brain area with a harmless virus carrying a light-sensitive protein.
After several weeks, researchers inserted a tiny fiber optic device into the prefrontal cortex, and transmitted pulses of light to stimulate the sluggish region.
The result, accorded to Bonci, was striking.
“When we turned on some activity in this prefrontal cortex, we could see that the compulsive cocaine seeking was gone," said Bonci.
Bonci says researchers then reversed the process, turning rats that had responded to the foot shocks back into compulsive cocaine-seekers by using the fiber optic technique to lower neuronal firing in their prefrontal cortex.
Bonci says investigators are now designing human clinical trials using external, non-invasive electromagnetic brain stimulation to boost the hypoactive, or inactive, prefrontal cortex of volunteer drug users.
“Our idea now is to set up clinical trials in the near future to basically stimulate this portion of the brain that is hypoactive with the idea that we should be able, ideally, [in] patients to remove craving and seeking an interest in taking cocaine," he said.
The work by Antonello Bonci and scientists at the University of California San Francisco, activating brain regions to curb cocaine addiction, is published in the journal Nature.