Targeting a specific group of neurons in the brain could help people quit smoking, say scientists.
Studies in mice show that nicotine addiction can be traced to a single brain region called the interpeduncular nucleus.
Neurons here "fire up" when someone is gasping for a cigarette, research suggests.
Treatments aimed at reducing activity in the interpeduncular nucleus could one day help people overcome tobacco addiction, the scientists believe.
"We were surprised to find that one population of neurons within a single brain region could actually control physical nicotine withdrawal behaviours," said lead researcher Dr Andrew Tapper, from the University of Massachusetts Medical School in Boston, in the United States.
Dr Tapper's team first delivered nicotine to mice in their water for six weeks, then took the drug away. The mice started scratching and shaking, displaying withdrawal symptoms due to being deprived of nicotine.
Close examination of the animals' brains revealed abnormally increased activity in neurons within the interpeduncular nucleus.
When the neurons were artificially activated with light, the mice again showed signs of nicotine withdrawal, whether or not they had been exposed to the drug. Lowering activity of the neurons had the opposite effect.
The findings are reported in the journal Current Biology.
The role of the interpeduncular nucleus in nicotine addiction makes sense, say the researchers. The region receives signals from other areas of the brain involved in nicotine use and response, and is linked to feelings of anxiety.
It is also densely packed with molecular receptors that are sensitive to nicotine.
The scientists do not know whether the findings are relevant to other types of addiction, but have not ruled this out.
"Smoking is highly prevalent in people with other substance-use disorders, suggesting a potential interaction between nicotine and other drugs of abuse," said Dr Tapper.
"In addition, naturally occurring mutations in genes encoding the nicotinic receptor subunits that are found in the interpeduncular nucleus have been associated with drug and alcohol dependence."
