How brain controls hunger decoded

Scientists are developing a wiring diagram of the complex brain circuits that regulate the intense urge to munch in office or rush for refrigerator in night, a finding that may unlock mystery behind hunger pangs.
Beth Israel Deaconess Medical Center (BIDMC), US, neuroendocrinologist Bradford Lowell has discovered that Agouti-peptide (AgRP) expressing neurons - a group of nerve cells in the brain's hypothalamus - are activated by caloric deficiency.
When these neurons are either naturally or artificially stimulated in animal models, they cause mice to eat voraciously after conducting a relentless search for food.
Now, Lowell's lab has made the surprising discovery that the hunger-inducing neurons that activate these AgRP neurons are located in the paraventricular nucleus - a brain region long thought to cause satiety, or feelings of fullness.

This unexpected finding not only provides a critical addition to the overall wiring diagram, but adds an important extension to our understanding of what drives appetite.
This unexpected finding not only provides a critical addition to the overall wiring diagram, but adds an important extension to our understanding of what drives appetite.

"Our goal is to understand how the brain controls hunger," said Lowell.
"Abnormal hunger can lead to obesity and eating disorders, but in order to understand what might be wrong - and how to treat it - you first need to know how it works. Otherwise, it's like trying to fix a car without knowing how the engine operates," Lowell said.

"It's clear that fasting increases the gain on how rewarding we find food to be, while a full stomach decreases this reward. But while this model has been extremely important in understanding the general features of the 'hunger system,' it's told us nothing about what's inside the 'black box' - the brain's neural circuits that actually control hunger," said Lowell.
To deal with this particularly complex brain region - a dense and daunting tangle of circuits resembling a wildly colourful Jackson Pollack painting - the team is taking a step-by-step approach to find out how the messages indicating whether the body is in a state of feeding or fasting enter this system.

"By making use of these new technologies, we are able to follow the synapses, follow the axons, and see how it all works," said Lowell.
The study was published in the journal Nature.