Neuroscientists have long wondered if our perception of an itch involves the same neural circuits that perceive pain or is derived from different neural pathways. The question is whether or not itch is a distinct sensation or a sub-quality of pain, or does an itch really hurt?

A group of collaborating scientists from the Washington University School of Medicine Pain Center in St. Louis and Peking University in Beijing, China have concluded that itch and pain are two separate and distinct sensations. Gastrin-releasing peptide receptors (GRPRs) are known to mediate itch, but not pain sensations. The scientists provided pruritogenic (itch) stimuli to mice and then monitored their scratching response. The group ablated lamina I neurons expressing the GRPRs in an experimental group of mice. These mice exhibited "profound scratching deficits" in response to pruritogenic stimuli. However, the ability of the mice to respond to painful stimuli was unaffected.1 The researchers also proposed that there are a variety of signaling pathways that respond to different types of "itch" stimuli, based on the responses of the mice to both histamine-dependent and histamine-independent pruritogens.

This group plans to continue their research to further identify and classify the itch pathways. Once this information is established and determined in humans, the development of medication to "stop the itch" will not be far behind. Perhaps with enough research and evidence that itch will cease to be a pain.

Reference

1. Sun YZ, Zhao ZQ, Meng ZL, Yin J, Liu XY, Chen ZF. Cellular basis of itch sensation. Science. 2009;325(5947):1531-1534. [Context Link]

Source: Science Cite Track: This Week in Science: A separate system for itch processing. Available athttp://mail.google.com/mail/#inbox/123caed6fd31c59d. Accessed on September 19, 2009.

Submitted by: Robin Pattillo, PhD, RN, News Editor at [email protected].