Nerve growth factor selectively decreases activity-dependent conduction slowing in mechano-insensitive C-nociceptors

Otilia Obreja, Matthias Ringkamp, Brian Turnquist, Michael Hirth, Elmar Forsch, Roman Rukwied, Marlen Petersen, Martin Schmelz

Research output: Contribution to journalArticlepeer-review


Nerve growth factor (NGF) induces acute sensitization of nociceptive sensory endings and long-lasting hyperalgesia. NGF modulation of sodium channel expression might contribute to neurotrophin-induced hyperalgesia. Here, we investigated NGF-evoked changes of the activity-dependent slowing of conduction in porcine C-fibers. Animals received intradermal injections of NGF (2 μg or 8 μg) or saline in both hind limbs. Extracellular recordings from the saphenous nerves were performed 1 week later. Based on sensory thresholds and electrically induced activity-dependent slowing (ADS) of axonal conduction, C-fibers were classified as mechano-sensitive afferents, mechano-insensitive afferents, cold nociceptors, and sympathetic efferents. NGF (2 μg) increased conduction velocity in C-fibers from 1.0 ± 0.05 m/s to 1.2 ± 0.07 m/s. In mechano-insensitive afferents, NGF (8 μg) reduced activity-dependent slowing of conduction, from 5.3 ± 0.2% to 3.2 ± 0.5% (0.125-0.5 Hz stimulation) and from 28.5 ± 1.3% to 20.9 ± 1.9% (2 Hz stimulation), such that ADS no longer differentiated between mechano-sensitive and mechano-insensitive fibers. Accordingly, the number of fibers with pronounced ADS decreased but more units with pronounced ADS were mechano-sensitive. Spontaneously active C-fibers were increased above the control level (1%) by NGF 8 μg (8%). The results demonstrate that NGF changes the functional axonal characteristics of mechano-insensitive C-fibers and enhances spontaneous activity thereby possibly contributing to hyperalgesia.

Original languageEnglish (US)
Pages (from-to)2138-2146
Number of pages9
Issue number9
StatePublished - Sep 2011


  • Activity-dependent slowing
  • Conduction velocity
  • Growth factors
  • Hyperalgesia
  • Mechano-insensitive afferents
  • Pain
  • Pig

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology
  • Anesthesiology and Pain Medicine


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