Adding menthol to nicotine increased the "communication" between a brain area in the reward pathway and one involved in memory.
Source: Used with permission of Guillaume L. Poirier.
Mentholated cigarettes account for about a quarter of the U.S. market, and appeal particularly to adolescents. Menthol give cigarettes a minty taste and masks the burning sensation of smoking by stimulating cool receptors in the nose and mouth. A study supported by the National Institute on Drug Abuse bolsters evidence that it may also make cigarettes more addictive.
In the study, researchers injected rats with menthol and nicotine in concentrations approximating those absorbed by smokers of mentholated cigarettes. Adolescent animals that received both chemicals exhibited greater locomotor stimulation—that is, moved about their cages more extensively—following the injections than rats that received only nicotine or only menthol. This finding suggests that menthol amplifies nicotine-induced changes in the young brain’s reward system that contribute to addictive behaviors.
Using brain imaging, the researchers further discovered that exposure to both chemicals together enhanced functional connectivity between two brain regions, compared to nicotine alone. One of the regions, the ventral tegmental area, mediates reward responses; the other, the retrosplenial cortex, participates in memory and other responses.
The study’s results may contribute to understanding previous research findings. Other studies have suggested that smokers of mentholated cigarettes display more severe nicotine dependence and have greater difficulty quitting smoking, compared to smokers of non-mentholated cigarettes.