For any smoker trying to quit, tobacco's addictive nature is abundantly clear. However, the mechanism behind the leaf's habit-forming properties has been hazy. Now, a study of mouse brains suggests that nicotine, the chemical considered the foundation of tobacco cravings, works via the same pathways that give morphine and other opiates their addictively rewarding qualities.
In previous studies, Julie Blendy of the University of Pennsylvania in Philadelphia and her colleagues used genetically modified mice that were unable to produce a brain protein called cyclic AMP-response element binding protein (CREB). Unlike normal mice, the CREB-deficient rodents seemed to receive no reward from morphine or nicotine and formed no attachment to these highly addictive drugs.
Although the researchers weren't sure how CREB works in the brain, "we thought that maybe this protein is a common link" between the mechanisms of tobacco and morphine addiction, says Blendy.