The discovery was made when scientists found the first of 11 sub-units, or molecules, of the nicotine receptor in the brain of mice. Because the habit-forming properties of nicotine are similar to those of other drugs, such as cocaine and heroin, the finding could also 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.
Nicotine addiction occurs because of a rapid dopamine release in the brain.
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 sub-unit. In a series of experiments they discovered that the mutant mice did not react to nicotine. The study also 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. The 11 receptor sub-units are similar in structure but have different functions. Scientists have some ideas of what the sub-units do but are only at the very beginning of identifying which molecule does what.