Basal and touch-evoked fos-like immunoreactivity during experimental inflammation in the rat

Qing Ping Ma, Clifford J. Woolf

Research output: Journal PublicationArticlepeer-review

105 Citations (Scopus)


Fos-immunoreactivity can readily be induced in spinal cord neurones by noxious, but to a much more limited extent, by innocuous peripheral stimuli. The present study has investigated whether low intensity stimuli and electrical stimulation of Aβ afferents elicit greater c-fos expression during the behavioural sensory hypersensitivity generated by experimental peripheral inflammation. We have examined the time-course of c-fos expression after inflammation produced by either an intra-plantar injection of the irritant turpentine oil or of complete Freund's adjuvant (CFA). In the former case, a significant initial expression in all dorsal horn laminae was followed by a gradual decrease, whereas after CFA injection, an initial expression limited to the superficial laminae subsequently extended into the deep laminae, with a decrease at 24 h and an increase in labelling at later times. Low intensity touch stimuli repeated for 10 min, when applied at 24 h and 48 h after CFA injection, elicited a significant increase in the number of Fos-immunoreactive neurons in both the superficial and deep laminae of the dorsal horn compared to non-inflamed animals. Electrical stimulation of the sciatic nerve 24 h post-CFA injection, at a strength sufficient only to activate Aβ-afferents fibres (100 μA, 50 μs, 10 min), also elicited a significant increase in labelling relative to the same stimuli applied in control animals, especially in laminae V-VI. The present results demonstrate that low intensity cutaneous stimuli elicit a significantly greater increase in c-fos expression in dorsal horn neurons during peripheral inflammation and that Aβ-afferent input contributes to this, a finding that may relate to the allodynia experienced during inflammation.

Original languageEnglish
Pages (from-to)307-316
Number of pages10
Issue number2-3
Publication statusPublished - Oct 1996
Externally publishedYes


  • Aβ-afferent
  • allodynia
  • hyperalgesia
  • pain
  • spinal cord

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology
  • Anesthesiology and Pain Medicine


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