Stress switch: Indian Institute of Science study finds how brain scratches the itch

Bengaluru: Anyone who has been caught in a tense moment knows the feeling: a mosquito bite or a skin irritation seems to fade into the background when the mind is gripped by stress. Now, scientists in Bengaluru say they have found how the brain pulls off this trick.Researchers at the Indian Institute of Science (IISc) mapped a small but crucial circuit in the brain that can suppress itching during acute stress. Their findings were published in the journal Cell Reports.
Itch and pain are both warning signals. Touch a hot stove and you instantly withdraw your hand. Feel an itch and you scratch. But unlike pain, itch remains poorly understood, especially when it comes to how emotions such as stress and anxiety change what we feel.The IISc team focused on a region deep inside the brain called the lateral hypothalamus, known to regulate stress, motivation, and emotional states. Using specially bred mice, the researchers identified a group of neurons that became active during short bursts of stress.When these "stress neurons" were switched on artificially, the mice scratched less. When the same neurons were silenced, stress no longer reduced scratching. In simple terms, the circuit was both necessary and sufficient to dampen itch during acute stress."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 the Centre for Neuroscience and corresponding author of the study.The study also found a worrying twist. In mice with long-term, psoriasis-like inflammation, the same stress-sensitive neurons behaved differently. They became more excitable and more active during scratching, suggesting that chronic stress may disrupt the brain's natural ability to suppress the itch. This may help explain why people with long-standing skin conditions often report flare-ups during stressful periods.Chronic itch affects millions worldwide and can severely affect sleep, work, and mental health. Most treatments today focus on the skin or the immune system. The new findings suggest that part of the answer may lie in the brain.However, the researchers caution that they studied only one form of acute stress and that other brain circuits are likely involved. The work was done on mice, and more research is needed before any human treatments emerge.Still, the message is clear: the brain does not just register an itch. It can turn the volume up or down, depending on what else is happening in one's life.