The identification of brain receptors in mice that seem to control nicotine addiction may lead to new drugs to help smokers quit, researchers hope.
Nicotine is highly addictive
It is thought nicotinic acetylcholine receptors found on the surface of brain cells are key.
The team from the California Institute of Technology found that carrying a particular variant of the receptor increases vulnerability to nicotine.
The findings are published in the journal Science.
The receptors can be composed of different combinations of subunits. The California team discovered that mice with a mutation in the "alpha4" subunit were unusually sensitive to the effects of nicotine.
Compared to normal neurons, the mutant neurons responded to lower concentrations of nicotine and, after this exposure, they also responded more robustly to larger doses.
Behavioral tests showed that mutant mice exhibited signs of addiction at lower doses than normal mice.
Professor Robert West, of the Cancer Research UK Health Behaviour Unit at University College London, said: "This study is useful in helping with development of medications that target the receptors involved in nicotine dependence but not others and so minimising unwanted side effects."
Professor West said the pharmaceutical company Pfizer have a drug, varenicline, which is undergoing clinical trials at the moment that they believe targets just this receptor.
He said the study also highlighted the fact that susceptibility to nicotine addiction may be passed down the generations.
"In fact the 'heritability' of nicotine dependence is estimated at around 50% which is similar to that for alcohol dependence."
Professor Andrew Peacock, of the British Thoracic Society, said: "This is an interesting piece of research as it could eventually lead to new technologies that could help the 70% of smokers in the UK who want to kick the habit.
"The research also demonstrates that there is a lot more for us to learn about how the brain works in relation to nicotine addiction - we need to see much more research in this area."