“Anorexia is an eating disorder. People affected are highly concerned about gaining weight and usually severely restrict the amount of food they eat and exercise excessively, which leads to severe weight loss. Anorexia has the highest mortality rate among all psychiatric diseases,” said lead author Dr. Yong Xu, professor of pediatrics – nutrition and molecular and cellular biology at Baylor. “The condition has no approved treatment and the underlying cause is unclear. In this study we worked with an animal model of the condition that mimics many of the characteristics we observe in people to investigate brain circuit alterations that could be involved in the condition.”

Previous work in the Xu lab and by other groups has shown that dysfunction of dopamine and serotonin neurons, which regulate feeding, is associated with individuals with anorexia. However, how these two populations of neurons in the brain contribute to the condition was not clear.

“First, we found that under normal conditions dopamine neurons do communicate with serotonin neurons, and we studied this interaction to determine how it regulates feeding,” Xu said.

The researchers found that the strength of the signal transmitted along the dopamine-serotonin brain circuit determined how much the animals would eat.“When dopamine neurons fired a lower-frequency signal, for example, between 2 and 10 Hertz, the result was inhibition of the serotonin neurons and overeating behavior,” Xu explained. “On the other hand, when dopamine neurons fired at a higher frequency between 10 and 30 Hertz, the serotonin neurons were activated and this led to lack of feeding.”