Neuron Path Discovery May Change Our Conception of Itching

Hugh Pickens writes "Historically, many scientists have regarded itching as just a less intense version of pain, though decades spent searching for itch-specific nerve cells have been unfruitful. Now, Nature reports that neuroscientist Zhou-Feng Chen and his colleagues at Washington University in St. Louis, Missouri have found the first behavioral evidence that there are separate circuits of nerve cells to convey itchiness and pain, and their studies suggest that itch and pain signals are transmitted along different pathways in the spinal cord. 'Most people accept that there are specific, highly specialized neurons for sensations like taste,' says Chen. 'But for pain and itch this is much more controversial.'" (Continues below.) "Two years ago, Chen's group discovered that a cell-surface protein called the gastrin-releasing peptide receptor (GRPR) is important for sensing itchiness but not pain in mice. When Chen and his colleagues destroyed GRPR-bearing neurons by means of a cell toxin, the mice reacted to painful stimuli just like normal mice, licking themselves and flinching or jumping in response to heat, highly irritant chemicals and mechanical pressure. But when the researchers injected the animals with chemicals that normally cause scratching, such as histamine, they barely responded, and the greater the number of GRPR-expressing neurons destroyed, the more subdued was the scratching response."

Comments

Does this actually change our conception?

[Trepidity]

This may certainly be interesting from a neuroscience point of view, but I would be troubled if anyone's conception of itching really changed because of a discovery about which neural pathways carry the signal. People who believe in a purely physical world governed by physical laws presumably already accept that everything that happens mentally is in some way or another implemented on our wetware. Is this really drawing some veil back: previously we thought itching was a magical sensation that came directly from fairies, but now we know it's "just neurons"? I would also be cautious about any particularly simplistic reductionist view: most of what goes on in the brain is much more complex than pop-science neuroscience discussions like to make out.