She and colleagues at the Pasteur Institute in Paris, the Karolinska Institute in Stockholm and the research arm of Glaxo-Wellcome in Geneva found the first of 11 subunits, or molecules, of the nicotine receptor in the brain of mice. Humans have the same so-called b2 subunit. Because the habit-forming properties of nicotine are similar to those of other drugs such as cocaine and heroin, the finding could have important implications for treating drug abuse. Like many drugs, the addictive elements of nicotine are connected with the release of the neurotransmitter dopamine in the brain.
People get addicted because of the rapid activation that leads to the dopamine release.
The discovery could lead to the development of a drug that would block the receptor responsible for addiction or activate it in a slower way. In a report in the scientific journal Nature, the scientists described how they found that nicotine stimulated the release of dopamine in the brains of normal mice but not the brains of mutant mice lacking the b2 subunit. In a series of experiments, they discovered that the mutant mice did not react to nicotine. The study further showed that nicotine improved the performance of mice on avoidance-learning tests, which could explain why some smokers claim it enhances their concentration and memory. Clinical trials have shown that it enhances memory in Alzheimer's patients.