How Your Brain Stops You From Scratching: New Insights into Itch Control

Scientists have identified a molecular and neural mechanism that governs the cessation of itching, revealing why scratching provides temporary relief and offering potential insights into chronic itch conditions. The research, conducted in the laboratory of Roberta Gualdani, a professor at the Université catholique de Louvain in Brussels, was presented at the 70th Annual Meeting of the Biophysical Society in San Francisco.

The study centers on the unexpected role of the ion channel TRPV4 in regulating itch. “Initially, we were studying TRPV4 in the context of pain,” explained Gualdani in a statement. “But, instead of a pain phenotype, what emerged with great clarity was a dysfunction in itch, specifically, in how scratching behavior is regulated.”

TRPV4 belongs to a family of ion channels that function as molecular gates in the membranes of sensory neurons, allowing the flow of ions in response to physical or chemical stimuli. These channels are crucial for the nervous system’s detection of temperature, pressure, and tissue stress, according to the research team.

To investigate this mechanism, Gualdani’s team created a genetic mouse model with TRPV4 selectively deleted in sensory neurons. When the researchers induced a chronic itch condition mimicking atopic dermatitis, the results were notable. Mice lacking neuronal TRPV4 scratched less frequently, but each scratching episode lasted significantly longer than normal.

“At first glance, this seems paradoxical,” Gualdani said. “But, in fact, it reveals something very important about how itch is regulated.”

The data suggest that TRPV4 doesn’t initiate itch, but rather helps trigger a negative feedback signal—a neural message informing the spinal cord and brain that the itch has been sufficiently scratched. Without this signal, the sensation of relief is absent, and scratching continues excessively. TRPV4 is part of the nervous system’s internal circuit that prevents prolonged scratching.

“When we scratch, at some point we stop because there is a negative feedback signal that tells us we are satisfied. Without TRPV4, the mice don’t feel this feedback, so they continue to scratch for much longer than normal,” Gualdani explained.

The findings indicate that TRPV4’s role in itch is more nuanced than previously understood. While the channel in skin cells appears to initiate itch sensations, the same channel in neurons seems to help regulate and control them. This dual function has important implications for drug development. Blocking TRPV4 broadly may not be the optimal approach.

“Future therapies may need to be much more targeted—perhaps acting only in the skin, without interfering with the neuronal mechanisms that tell us when to stop scratching,” Gualdani stated.

Chronic itch affects millions of people with conditions such as eczema, psoriasis, and kidney problems, but effective treatments remain limited. According to her LinkedIn profile, Gualdani is a Principal Investigator and Professor at the Université catholique de Louvain. Understanding the precise mechanisms that regulate itch—including the signal to stop scratching—could pave the way for latest therapies. Roberta Gualdani’s research is conducted at the Institute Of NeuroScience (IoNS) and the Pôle Cellulaire et moléculaire (CEMO) within the university’s Faculty of Pharmacy and Biomedical Sciences, as detailed on the UCLouvain website.