Smoking’s Reward: Nicotine triggers opiate-pleasure response

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.