Localization and activation of substance P receptors in unmyelinated axons of rat glabrous skin

Susan M. Carlton, Shengtai Zhou, Richard E. Coggeshall

Research output: Contribution to journalArticlepeer-review

81 Scopus citations


Immunohistochemical staining for the substance P (neurokinin 1, NK1) receptor labels 32% of the unmyelinated axons in the glabrous skin of the rat hindpaw. This is the first demonstration of substance P (SP) receptors associated with the membranes of primary afferent fibers. Injection of SP into the subcutaneous tissue of the third hind toe results in behavioral changes interpreted as mechanical hyperalgesia and mechanical allodynia. These nocifensive behaviors can be blocked by the NK1 antagonist CP99,994-1. The presence of peripheral axons immunolabelled for NK1 receptors and the demonstration that exogenous peripheral SP causes nocifensive behaviors would seem to indicate that SP can have a direct effect on sensory afferents with activation of these receptors resulting in fine afferent firing and thus the pain-related behaviors. Additionally, the presence of round, clear vesicles in some of the SP receptor-labelled axons suggests the presence of autoreceptors since it is known that many primary sensory afferents contain SP.

Original languageEnglish (US)
Pages (from-to)103-108
Number of pages6
JournalBrain Research
Issue number1-2
StatePublished - Sep 23 1996
Externally publishedYes


  • CP-99,994-1
  • Mechanical allodynia
  • Mechanical hyperalgesia
  • NK1 antagonist
  • Tachykinin

ASJC Scopus subject areas

  • General Neuroscience
  • Molecular Biology
  • Clinical Neurology
  • Developmental Biology


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