What Triggers Overeating: Scientists Discover Brain Circuitry Behind Behavior

First Posted: Oct 01, 2013 01:10 PM EDT

It turns out that overeating is a disorder that's connected to the brain. Now, scientists have discovered the precise cellular connections responsible for triggering the behavior. The findings could lend further insight into the cause of obesity and could even lead to treatments for anorexia, bulimia nervosa and binge eating disorder.

In the past, researchers have been able to electrically stimulate a region of a mouse's brain to cause the rodent to eat--whether it was hungry or not. This region of the brain was called the lateral hypothalamus. Yet in order to hone in on exactly what cells might be associated with overeating, the scientists needed to take a much more precise look at the brain.

One cell type in the brain is known as gaba neurons in the bed nucleus of the stria terminalis, or BNST. The BNST is an outcropping of the amygdala, the part of the brain associated with emotion. The BNST also forms a bridge between the amygdala and the lateral hypothalamus, the brain region that drives primal functions such as eating.

During this particular study, the researchers wanted to stimulate BNST cells. In order to do so, the scientists used genetically engineered proteins from algae that are sensitive to light. They then used genetically engineered viruses to deliver them to the brains of mice. The proteins were then expressed only in the BNST cells, including the synapses that connect to the hypothalamus.

Next, the researchers implanted fiber optic cables in the brains of the mice, which allowed them to shine light onto the BNST synapses. As soon as the light hit BNST synapses the mice began to eat voraciously even though they'd already been well fed. In addition, the mice showed a preference for high-fat foods.

"They would essentially eat up to half their daily caloric intake in about 20 minutes," said Garret Stuber, one of the researchers, in a news release. "This suggests that this BNST pathway could play a role in food consumption and pathological conditions such as binge eating."

The findings reveal a little bit more about how the brain processes and causes eating disorders. More specifically, the scientists were able to home in on the precise neural circuit connection that was causing this phenomenon. The new study could help develop therapies to treat these eating disorders in the future.

The findings are published in the journal Science.

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