What’s the News: Scientists—and smokers—have long known that nicotine is an appetite suppressant, but just how it kept hunger at bay remained unclear. Now, researchers have uncovered the neural pathway by which nicotine reduces appetite, in a study published today in Science. This discovery could lead to new drugs that help people quit smoking or lose weight.

How the Heck:

The researchers first observed that mice given nicotine or the drug cytisine, which binds to some nicotinic receptors in the brain, ate less and had less body fat than mice not given either drug. When the researchers gave mice a chemical compound that blocked nicotine receptors, the appetite-suppressing effects of these drugs went away.
Since cytisine binds particularly well to a type of nicotinic receptor called ?3?4, the researchers figured that receptor might be the major player in decreasing appetite. Sure enough, when the researchers genetically knocked out that receptor in some mice, those mice were immune to the drugs’ appetite-reducing effects.
The researchers then looked at what parts of the brain had ?3?4 receptors, since different nicotinic receptors are present in different groups of neurons. These particular receptors show up in ...