IISc researchers find out how the brain suppresses itch during stress

Researchers at the Indian Institute of Science (IISc) have mapped a neural circuit in the brain involved in the complex relationship between itch and stress. Their findings, published in Cell Reports, reveal how specific neurons activated during stress can directly regulate itch.

IISc said that itch and pain are both unpleasant sensations triggered by harmful or irritating stimuli, but they lead to different behavioural responses.

While pain typically causes us to withdraw (such as pulling our hand away from a fire), itch drives scratching.

“Scientists have long known that emotional states such as stress and anxiety can influence the intensity of these sensations. While the neural mechanisms linking stress and pain have been studied extensively, the effect of stress on itch has remained poorly understood,” IISc said.

In the new study, the IISc team focused on the lateral hypothalamic area (LHA), a region in the brain known to regulate stress, motivation, and emotional states. Using genetically engineered mouse models, the researchers identified a specific population of neurons in the LHA that become active during acute stress.

The researchers then tested whether these stress-activated neurons directly influence itch. “We ran some pilot experiments, and we saw that, surprisingly, acute stress was able to suppress acute itching,” said Jagat Narayan Prajapati, PhD student at the Centre for Neuroscience (CNS), IISc, and first author of the study.

When the team artificially activated the stress neurons, scratching behaviour decreased in both short-term chemically induced itch and a psoriasis-like chronic itch model. Conversely, when these neurons were silenced, stress no longer reduced scratching. These results showed that these neurons are both necessary and sufficient for stress-induced suppression of itch.

“We show that a specific circuit in the lateral hypothalamus can suppress itch during acute stress, revealing how the brain directly links emotional states to sensory perception. By identifying the specific neural circuit that links stress to itch, we are opening the possibility of targeting these brain mechanisms to better manage chronic stress-induced worsening of itch,” said Arnab Barik, Assistant Professor at CNS and corresponding author

The study, carried out in collaboration with PhD student Aynal Haque and Giriraj Sahu, Assistant Professor at the Molecular Biophysics Unit, IISc, also uncovered differences between acute and chronic itch.

Chronic itch affects millions of people worldwide. Current treatments largely focus on the skin and immune system, but the new findings highlight the importance of the brain in shaping itch perception.

“Most current treatments for chronic itch are peripheral — they treat the symptoms, not the cause. But the interaction between stress, anxiety, and sensations like itch happens in the brain. Understanding these circuits gives us a framework for eventually developing therapies that address the central mechanisms underlying stress-related itch,” Mr. Barik said.