Itch Neurons

That is the most common type of itch — one caused by the chemical histamine, released by our immune cells.

But there's a second type of itch that is chronic and quite debilitating because, unlike the common itch, it is not treatable with a simple topical ointment.

In a previous episode we talked about chronic itch and said that until recently itching had been considered a mild form of pain. But scientists determined the two sensations are perceived differently by the brain and travel along different nerve pathways.

In 2007 investigators at Washington University identified the first "itch" gene. This gene produces a protein called gastrin-releasing-peptide-receptor or GRPR.

The protein is found in one population of cells in the spinal cord. When these cells are activated, we experience an 'itch'. But when scientists working with mice deleted their GRPR gene encoding this receptor — guess what happened? The mice did not experience the itch and therefore did not scratch!

This is significant because it can lead to new treatments for people whose chronic itch led them to scratch through skin and into tissue. Already studies show a neurotoxic drug called bombesin-saporin specifically blocks the GRPR receptor. Apparently, the drug blocks up to 80% of both chronic and histamine provoked itching responses.

The drug did not block pain sensations or interfere with motor control, which are also controlled by neuronal pathways.

This confirms pain and itch sensations use separate nerve pathways, which will make treatment for chronic itch much easier.

Just talking about this has made me itchy all over!

How about you? Let us know at our website if we have verbally induced an itchy response in you!