Dr. Zhou-Feng Chen, left, director of the Center for the Study of Itch at Washington University School of Medicine in St. Louis, and Dr. Devin M. Barry found that certain pathways in the sensory neurons of mice can work together to transmit itch signals. The discovery may help scientists find more effective ways to make itching stop, they say. Photo by Robert Boston/Washington University School of Medicine in St. Louis
ST. LOUIS, July 20 (UPI) -- Scientists have found how signals for itching travel through neurons from one nerve cell to another, which they think could help lead to better treatments.
It was previously thought two types of calcium channels were responsible for separately transmitting signals about itching, but scientists at Washington University School of Medicine in St. Louis found a third pathway can transmit the same signals -- suggesting blocking the channel could relieve conditions with itch.
Calcium channels in neurons allow for the transport of calcium ions between nerve cells, allowing itch signals to move from the skin to the spinal cord.
Histamine-induced itching, caused by bug bites, and chloroquine-induced itching, caused by the malaria drug chloroquine in some patients, were thought to travel through separate channels. The scientists found, however, that not only do they assist each other but there is a third channel that may represent a chance to treat both kinds of itch, and possibly other types.
"It gives us new therapeutic targets upstream of the neurons in the spinal cord," Dr. Zhou-Feng Chen, director of the Center for the Study of Itch at Washington University, said in a press release. "By targeting a single channel in the periphery, it may be possible to reduce histamine-induced itching, chloroquine-induced itching and even types of chronic itching that don't respond to current therapies."
For the study, published in the journal Science Signaling, the scientists studied how itch signals in mice are processed by the dorsal root ganglion after traveling from the skin to neurons in the spinal cord.
Scientists genetically engineered mice without the channel processing histamine and exposed them to it, finding they still scratched themselves, an effect that was the same with mice lacking the channel involved with chloroquine-related itch.
The experiments gave scientists a better understanding how itch is transmitted, finding a third channel called TRPV4 transmits both types of itch, as well as others like chronic itch.
"By interfering with the activity of sensory neurons, we may be able to inhibit multiple types of itching," said Chen. "It appears there is cross-talk between pathways called calcium channels in sensory nerve cells that process the itch signal."