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New insights into the mechanisms of itch: are pain and itch controlled by distinct mechanisms?

Publication ,  Journal Article
Liu, T; Ji, R-R
Published in: Pflugers Arch
December 2013

Itch and pain are closely related but distinct sensations. They share largely overlapping mediators and receptors, and itch-responding neurons are also sensitive to pain stimuli. Itch-mediating primary sensory neurons are equipped with distinct receptors and ion channels for itch transduction, including Mas-related G protein-coupled receptors (Mrgprs), protease-activated receptors, histamine receptors, bile acid receptor, toll-like receptors, and transient receptor potential subfamily V1/A1 (TRPV1/A1). Recent progress has indicated the existence of an itch-specific neuronal circuitry. The MrgprA3-expressing primary sensory neurons exclusively innervate the epidermis of skin, and their central axons connect with gastrin-releasing peptide receptor (GRPR)-expressing neurons in the superficial spinal cord. Notably, ablation of MrgprA3-expressing primary sensory neurons or GRPR-expressing spinal cord neurons results in selective reduction in itch but not pain. Chronic itch results from dysfunction of the immune and nervous system and can manifest as neural plasticity despite the fact that chronic itch is often treated by dermatologists. While differences between acute pain and acute itch are striking, chronic itch and chronic pain share many similar mechanisms, including peripheral sensitization (increased responses of primary sensory neurons to itch and pain mediators), central sensitization (hyperactivity of spinal projection neurons and excitatory interneurons), loss of inhibitory control in the spinal cord, and neuro-immune and neuro-glial interactions. Notably, painful stimuli can elicit itch in some chronic conditions (e.g., atopic dermatitis), and some drugs for treating chronic pain are also effective in chronic itch. Thus, itch and pain have more similarities in pathological and chronic conditions.

Duke Scholars

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Published In

Pflugers Arch

DOI

EISSN

1432-2013

Publication Date

December 2013

Volume

465

Issue

12

Start / End Page

1671 / 1685

Location

Germany

Related Subject Headings

  • Toll-Like Receptors
  • Synaptic Transmission
  • Spinal Cord
  • Serotonin
  • Sensory Receptor Cells
  • Receptors, G-Protein-Coupled
  • Pruritus
  • Physiology
  • Perception
  • Pain
 

Citation

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Liu, T., & Ji, R.-R. (2013). New insights into the mechanisms of itch: are pain and itch controlled by distinct mechanisms? Pflugers Arch, 465(12), 1671–1685. https://doi.org/10.1007/s00424-013-1284-2
Liu, Tong, and Ru-Rong Ji. “New insights into the mechanisms of itch: are pain and itch controlled by distinct mechanisms?Pflugers Arch 465, no. 12 (December 2013): 1671–85. https://doi.org/10.1007/s00424-013-1284-2.
Liu, Tong, and Ru-Rong Ji. “New insights into the mechanisms of itch: are pain and itch controlled by distinct mechanisms?Pflugers Arch, vol. 465, no. 12, Dec. 2013, pp. 1671–85. Pubmed, doi:10.1007/s00424-013-1284-2.
Journal cover image

Published In

Pflugers Arch

DOI

EISSN

1432-2013

Publication Date

December 2013

Volume

465

Issue

12

Start / End Page

1671 / 1685

Location

Germany

Related Subject Headings

  • Toll-Like Receptors
  • Synaptic Transmission
  • Spinal Cord
  • Serotonin
  • Sensory Receptor Cells
  • Receptors, G-Protein-Coupled
  • Pruritus
  • Physiology
  • Perception
  • Pain