A new study of itch adds to growing evidence that the chemical signals that make us want to scratch are the same signals that make us wince in pain.
The interactions between itch and pain are only partly understood, said itch and pain researcher Diana Bautista, an assistant professor of molecular and cell biology at the University of California, Berkeley. The skin contains some nerve cells that respond only to itch and others that respond only to pain. Others, however, respond to both, and some substances cause both itching and pain.
If itch and pain are closely linked, however, the implications are huge, Bautista said. If pain and itch use the same molecules to communicate with the brain, drugs now being developed to alleviate pain may also help quiet intractable itch.
"Some types of itch respond to antihistamines, but most itch, especially itch associated with chronic diseases like kidney and liver failure, diabetes and cancer, does not," she said. "Even allergic itch only partly responds to antihistamines. We've shown that one of the drugs now being looked at by pharmaceutical companies as a pain reliever also blocks some types of histamine-independent itch."
Bautista's new research, published in this week's print edition of the journal Nature Neuroscience, shows that two specific irritants induce itching by way of the wasabi receptor, a pain receptor familiar to sushi lovers.
Other recent studies have shown that some itch inducers called pruritogens lead to activation of the capsaicin receptor, a pain receptor named for the incendiary chemical in chili peppers.
"It's starting to look like many pain receptors are linked to the itch system," she said. "Both itch and pain use some of the same molecules to send signals to the brain."
Bautista has genetically altered mice so that they don't produce the wasabi receptor, and hopes that the mouse strain will help lead to a better understanding
|Contact: Robert Sanders|
University of California - Berkeley