Itched to Death? They May Be One and the Same

It happened to me coming out of anesthesia.  After I had my son by c-section and then another minor surgery, I awoke to the most infernal itching on my face.  I scratched and rubbed until my face swelled and my doctor asked if I had fallen!

Chronic itching, which, of course, is not really what I had (it went away after about one miserable hour), which can occur in many medical conditions, from eczema and psoriasis to kidney failure and liver disease, is different from the fleeting urge to scratch a mosquito bite, according to newswise.com.

"That’s because chronic itching appears to incorporate more than just the nerve cells, or neurons, that normally transmit itch signals," the Web site reports. Researchers found that in chronic itching, neurons that send itch signals "also co-opt pain neurons to intensify the itch sensation.

Apparently, itching isn't so different from chronic pain, even in mice.

“In normal itching, there’s a fixed pathway that transmits the itch signal,” newswise.com quotes senior investigator Zhou-Feng Chen, PhD, who directs Washington University’s Center for the Study of Itch. “But with chronic itching, many neurons can be turned into itch neurons, including those that typically transmit pain signals. That helps explain why chronic itching can be so excruciating.”

A gene that continuously sends signals inside itch neurons and the protein it makes are involved in the body’s pain response, but scientists didn't know whether the gene also played a role in itch, newswise.com explains.

Further studies discovered that the protein could turn on many itch genes, and "they showed similar changes of gene expression in mice with chronic itch induced by dry skin and in mice with allergic contact dermatitis, two of the skin conditions that frequently cause people to scratch incessantly," the scientists note.

“Certain drugs are used to inhibit some of the same targets in patients with chronic pain, and those medications also may quiet down itch,” Chen told newswise.com.

Unlike scratching a mosquito bite, which usually is only a temporary sensation, chronic itch can persist much longer, according to Chen, also a professor of psychiatry and of developmental biology, newswise.com says. "His team found that the mice in this study not only scratched spontaneously but also had more severe responses when exposed to substances that normally would induce acute itching," the Web site attests.

“In people, chronic itching can last for weeks, months or even years,” Chen told newswise.com. “These mice are helping us to understand the pathways that can be involved in transmitting itch signals and the many contributors to chronic itching."









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