The mental boost smokers get from nicotine is linked to the same area of the brain in mice as its addictiveness and the two are probably inseparable, French scientists said on Wednesday.
In a study that may hold insights into ways to help people quit smoking, researchers at the CNRS-Pasteur Institute in Paris showed that receptors on cells in the ventral tegmental area (VTA) of the brain are involved in nicotine’s addictive and cognitive qualities in mice.
“This is a very critical area for self-administration for nicotine in the brain,” said Jean-Pierre Changeux, who headed the research team.
The VTA is involved in responses to natural rewards such as food, sex and the effect of drugs. Addictive drugs activate the release of dopamine, a chemical linked to pleasurable sensations, which is made in cells of the VTA.
Scientists have known that a family of receptors, or doorways into cells, called nicotinic acetylcholine receptors are involved in addiction to smoking.
Changeux and his team genetically engineered mice so they lacked a gene for a portion of a nicotine receptor, to discover the impact it would have on how the mice functioned.
The mutant mice had a mild learning impairment and unlike normal mice, which had learned to press a lever to self-administer nicotine, they showed no interest in getting nicotine.
“When there is a loss of the nicotine receptor then there is a loss of cognitive function in the mouse,” Changeux, who reported the finding in the science journal Nature, told Reuters.
But when the scientists re-injected the gene, the mice’s cognitive function was restored. The rodents were also more likely to seek out nicotine.
“Given the intricacies of the brain, it is striking that reintroduction of a single molecule to just one small area of the brain should so dramatically affect behavior,” said Julie Kauer of Brown University in Providence, Rhode Island, in a commentary in the journal.
Changeux and his team do not know whether humans would react in the same way but they believe their work could advance the search for drugs to cure addiction. If researchers could find a way to stop nicotine attaching to brain cells, it may be possible to prevent addiction.
Drug companies are already trying to harness the positive effect of nicotine to treat brain disorders such as memory impairment in Alzheimer’s disease.