The Science of Itching and Scratching (Part One)

I had always thought that pain and itching were two of a kind — activated by the same neurotransmission pathways and differing only in some small quality.

Scientists had long also made the same assumption, until 2008, when researchers from the Washington University Pain Center found a way to breed mice that responded to pain but not to itch-inducing stimuli.  The result of this study was the finding that pain and itch responses are regulated separately; in fact, there is a gene (at least in mice, but probably also in humans) that codes for itch response, independent of pain receptivity.

But a quote from lead researcher Zhou Feng-Chen, Ph.D., in the above linked Science Daily article is what really caught my eye:

“There are two major types of itching,” says Chen, an associate professor of anesthesiology, psychiatry and developmental biology. “There is histamine-dependent itching caused by bug bites or allergic reactions, the kind of itching that can be treated with antihistamine drugs, such as Benadryl®. But the majority of chronic, severe itching is resistant to antihistamine treatment.”

The majority?  Ah, so I’m right: the obstetricians and dermatologists I’ve seen thus far really HAVE been stabbing around in the dark.

Not that I can blame them, because apparently, science doesn’t have a very good grasp on what causes non-histamine-induced itching.  And if science has half a clue, you can bet medicine has about one tenth of that half-a-clue, all spread out among specialties that don’t trust each other.

But at least as of 2008, humanity’s gotten a pretty good clue: the GRPR (gastrin-releasing peptide receptor) gene, which codes for a receptor in the spinal cord responsible for transmitting the itch signal from the skin.

“Our findings could have important therapeutic implications,” Chen says. “More research needs to be done, but it may be possible to relieve itching in patients by blocking GRPR function without affecting the pain pathway.”

In other words, hopefully, eventually, when some celebrity starts suffering from chronic pruritis (itch) and donates money to start a foundation, a GRPR blocker could be developed which would help those of us for whom anti-histamines are completely useless.

So that’s good news: when the pharmaceuticals have all been tested and the doctors have caught up to science, something like a decade from now, I can get some sleep.

References:
Washington University School of Medicine (2008, November 25). Pain And Itch Responses Regulated Separately. ScienceDaily. Retrieved June 27, 2010, from http://www.sciencedaily.com/releases/2008/11/081117153156.htm

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