From the article: The link between chronic pain and a loss of appetite may finally be understood – in mice at least.

Zhi Zhang at the University of Science and Technology of China in Hefei and his colleagues injected mice with bacteria that provoke chronic pain. Ten days later, these mice were eating less frequently and for shorter periods of time compared with control mice that had been injected with saline. When the first group of mice were later given pain medication, they ate normally, the researchers wrote in a paper published in Nature Metabolism.

To better understand the neuronal activity responsible for this change in behaviour, the researchers analysed the brains of the first group of mice while the animals were in chronic pain. They found substantial neuron signalling in the mice’s anterior cingulate cortex, a pain-processing region of the brain in the prefrontal cortex.

To determine whether that signalling was related to appetite loss, the researchers provoked chronic pain in another group of mice, with these animals going on to eat less. The team then administered a chemical that prevents neuronal signalling in the anterior cingulate cortex and the mice’s appetites improved.

The prefrontal cortex isn’t generally associated with appetite control. To better understand how neurons in the anterior cingulate cortex may influence appetite, the team injected various traceable substances into these neurons in a third group of mice that were similarly made to feel pain.

They found that these neurons’ signals led to the lateral hypothalamic area, the brain’s “feeding centre”.