Craving a snack in the afternoon? Take a drag on a cigarette, and your hunger will probably disappear. Smoking is the leading cause of preventable death in the United States and other developed countries, which causes lung cancer, heart disease, and chronic bronchitis. But smokers are, on average, thinner than nonsmokers. A new study reveals how nicotine, the active ingredient in cigarettes, works in the brain to suppress appetite smokers. The discovery also highlights a new therapeutic target for nicotine withdrawal and loss of weight.
The nicotine receptor in the brain has 15 subunits; they can be combined in a multitude of ways to form different receivers with different jobs. Nicotine can bind to each combination and stimulate a cascade of individual events; some lead to the addictive properties of cigarettes, others an increase in blood pressure or a feeling of relaxation. It has long been known that nicotine causes a drop in appetite, and scientists suspect that it worked through receptors associated with reward and reinforcement of behavior. After all, the brain considers both cigarettes and food for rewards. But the new finding suggests that appetite has its own way.
Behavioral neuroscientist Marina Picciotto of Yale University began to study whether the activation of a particular nicotine receptor, α3β4 nicknamed, had antidepressant effects in mice. But as Yale colleague Picciotto, Neurogeneticist behavioral Yann Mineur cured the mice given drugs designed to stimulate only α3β4 receptors, he noticed a side effect: mice ate less.
"Before this study, we really do not think this type of receptor would have such an important role in brain food intake," said Picciotto. She Minor and then showed that nicotine is actually binding to α3β4 receptors, which then send a signal through the rest of the brain, signaling satiety. It is impossible to distinguish the signal from the brain spreads after eating a large meal. The mice that received the drug binding to the α3β4 receptor ate half the amount of food than untreated mice within 2 hours following administration of the drug. Their body fat dropped from 15% to 20% over 30 days, the team reports online today in Science .
Because the weight gain that comes with smoking cessation is often a deterrent to smokers to quit, Picciotto suggests that the new route could be targeted by drugs to suppress appetite during the early stages of smoking cessation. In addition, such a drug could have wider application as an appetite suppressant to help in losing weight without risk to cigarette smoke-related health.
Neil Grunberg, a behavioral neuroscientist at the Uniformed University of Health Sciences Services in Bethesda, Maryland, was the first to prove by rat studies in 1982 that nicotine causes a decrease appetite. He says the new study is a step forward in understanding the phenomenon it was first observed.
"Most people have accepted that decreased appetite was caused by a dopamine reward pathway and left at that," says Grunberg. "So I think that the most important contribution of this article is to prove that there is another way that the entire nicotine works through. "
Grunberg notes, however, that the study relates only to male mice. in his previous work, he found differences in the effects of nicotine on weight between males and females. women, he said, the biggest weight loss experience when they start smoking and increased weight gain if they quit. that means the nicotine works by an additional lane, the hormone regulated in the female brain is yet to be determined.
Picciotto said his group repeated the experiments with female mice. "We are also always try back to that original question we had, "she said," is it also has antidepressant actions "
* this article has been corrected to reflect the accurate title of Yann Mineur.
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