Mind & Brain / Drugs & Addiction

Over the past few years, several studies have found that people who smoke have about half the risk that nonsmokers have of developing Parkinson’s disease. Last February researchers reported a possible reason for this strange link: an enzyme called monoamine oxidase B (mao B). mao B is one of the enzymes involved in breaking down the neurotransmitter dopamine, which the brain uses when it creates and controls movement. Because people with Parkinson’s have unusually low levels of dopamine, they suffer from uncontrollable tremors, rigid muscles, and difficulty walking and talking.

Chemist Joanna Fowler and her colleagues at Brookhaven National Laboratory in Upton, New York, pet-scanned the brains of eight smokers, eight nonsmokers, and four former smokers. They found that mao B levels in the smokers’ brains were 40 percent lower than in the other two groups. If you have less mao B, the researchers speculate, then you’ll have more available dopamine and be less prone to Parkinson’s--indeed, some of the best drugs used against the disease work by inhibiting mao B. What’s the ingredient in cigarette smoke that does the job? The researchers only know that it’s not nicotine.