The neurons that make us sick when we’re sick

We tend to eat, drink and move less when we are sick. This is not a direct cause of infection, but rather a cause of the body’s immune response. Now, researchers at Rockefeller University in the US, Identified the group of neurons that control these responsesknown as disease behaviours.

The results were published in the scientific journal temper natureInflammation is directly linked to, and information about, the neural pathways that regulate behavior How does the immune system interact with the brain?.

“We’re still in the early days of trying to understand the brain’s role in infection,” says Jeffrey Friedman, a professor at the university. “But with these findings, we now have a unique opportunity to ask: What is your brain like when you’re sick?”

Illness behaviors have been shown to play an important role in an animal’s recovery from infection. Previous studies reinforce this theory, concluding that Animals forced to eat when sick showed a significant increase in mortality. “These behavioral changes during infection are really important for survival,” says lead author Anoj Ilanges and a former student in Friedman’s lab.

But it was never clear how the brain coordinates this near-universal urge to refuse meals and roll under covers with the onset of injury. So Friedman and Elang set out to map the brain regions behind disease behaviors in mice.

The team set out to elicit immune responses from the rodents. Soon after, there was a spike in activity in a region of the brainstem known as the dorsal vagal complex, where a particular group of cells in the brainstem likely causes three pathological behaviors. To make sure they found the correct brain cells, the researchers activated these neurons in healthy mice and found that the animals ate, drank and moved less. In contrast, when the neurons were turned off, these behaviors were significantly reduced.

“We didn’t know if the same or different neurons were regulating each of these behaviors,” says Friedman. “We find it surprising that a single neuronal group appears to regulate each of these components of disease response.”

However, the authors were not entirely surprised that this brainstem region is implicated in mediating disease behaviors. The dorsal vagus complex is one of the precious few physiological crossroads of the central nervous system, where the absence of a barrier protecting the nervous system allows circulatory agents to pass information directly to the brain. “This area has emerged as a kind of alert center for the brain, relaying information about unpleasant or harmful substances that, in most cases, reduce food intake,” says Friedman.

In the coming months, Friedman’s team intends to incorporate these findings into their overall goal of understanding the physiological signals and neural circuits that regulate eating behavior. In the meantime, Ilanges plans to investigate the role of other brain regions in responding to infection, Expand our knowledge of the brain’s role during this critical process.