Scientists in the US have identified an area of the brain which makes heroin-addicted rats relapse.
The study, published in Nature Neuroscience, showed that part of the medial prefrontal cortex was activated.
When the researchers blocked nerve cells in the region, there were fewer relapses.
Experts in the UK said the study was a technical 'tour de force'; however, it did not promise new treatments in humans.
The study worked on the idea that when addicts stopped taking drugs, but then returned to the place they were taking drugs, they were likely to relapse.
Rats were trained to take drugs in one environment, where they were delivered a dose of heroin.
The rodents then "went to rehab" in another environment where the feel of the floor, lights and sounds were different and there was no access to heroin.
Once the rats were "clean" they were returned to the drug-taking environment, where they demonstrated heroin-seeking behaviour.
By examining the rats' brains, the researchers showed increased activity in some neurons in the medial prefrontal cortex.
They then used drugs, muscimol and baclofen, to selectively inhibit this region. Heroin-seeking activity was then decreased.
Dr Jennifer Bossert, from the National Institute on Drugs Abuse in the US, told the BBC: "There are two main implications, at a research level we've demonstrated this cause/effect relationship in a specific set of activated neurons.
"In the clinical setting, heroin relapse is different to cocaine relapse so drug relapse is probably caused by different circuits for different drugs, which would have consequences for medication."
She also warned about transferring the findings into humans, saying: "You have to be very careful, you can't. Human addicts are very different to rat models, they're often multi-drug users, they're complex."
Ian Stolerman, Emeritus Professor of Behavioural Pharmacology at King's College London, said: "It's a considerable achievement, it's a research tour de force, which sheds new insight into the nerve cells in the brain which are important for drug-seeking behaviour in animal models.
"It doesn't, however, suggest a route for new treatments in the near future."