If you've ever had the unique experience of trying to get a lab rat off of heroin, then you'll know that it can be very difficult – the narcotic is notoriously addictive. Scientists at The Scripps Research Institute, however, have recently reported success in using deep brain stimulation (DBS) to reduce addicted rats' compulsion to take the drug.

In the study, rats were able to self-administer heroin by pressing a lever, for 12 hours a day over a two-week period. As those two weeks went by, they voluntarily escalated their intake of the drug. Their access to it was then cut off, for another two weeks. Once that period of abstinence was over, the escalating behaviour would typically pick up where it had left off.

The latter didn't apply to all of the rats, however.

Via implanted electrodes, some of them received weak electrical stimulation to the subthalamic nucleus region of the brain. After the two-week break from the heroin, those rats only resumed taking a low dosage of the drug. They also showed less motivation to take it – when the setup was altered so that the lever had to be pressed several times before any heroin was dispensed, the DBS-treated rats gave up sooner than their non-treated counterparts.

When the treatments were suspended for two days, the DBS rats began escalating their heroin intake, just like the control group. Their heroin-intake came back down again, though, once the treatments were resumed.

DBS of the subthalamic nucleus is already used to treat Parkinson's disease and essential tremor, by modulating abnormal muscle activity. It appears to also control compulsive behaviour, as DBS-treated Parkinson's patients have additionally experienced a reduction in compulsive gambling and shopping.

This is likely due to the fact that when DBS reduces the activity level of the subthalamic nucleus, another part of the brain that lies "downstream" from it also settles down. That region, known as the nucleus accumbens shell, is involved in the wanting of pleasurable experiences, and is thought to be responsible for maintaining addiction.

"The results here are very impressive," says associate professor Olivier George, principal investigator of the study. "This is the type of preclinical evidence that one needs, in order to start testing this strategy in humans."

A paper on the research was recently published in the journal Neuropsychopharmacology.