Limitation of sensitization to injured parts of receptive fields in human skin C-nociceptors

M. Schmelz, R. Schmidt, Matthias Ringkamp, C. Forster, H. O. Handwerker, H. E. Torebjörk

Research output: Contribution to journalArticle

Abstract

Unmyelinated cutaneous mechano-heat fibers (CMH) in the peroneal nerve of healthy human volunteers were studied by means of a 'marking' technique which allows stable recordings from identified single units over extended periods. Mechanoreceptive field sizes were 105 ± 13 mm2 in 25 units. These large receptive fields indicate extensive terminal branching of C fibers in the skin of foot and lower leg. Sensitization of CMHs was tested by assessment of thresholds for mechanical (von Frey hair) and heat stimuli before and after topical application of mustard oil (allyl isothiocyanate) and capsaicin (8-methyl-N-vanillyl-6-noneamide). While in a group of 14 CMHs the entire receptive field was treated with these irritant substances, in another group of 11 CMH units only parts of the receptive field were treated to check for signs of spreading sensitization through axon collaterals. Mustard oil application did not change mechanical thresholds, regardless of whether parts of or complete receptive fields were treated. However, mean heat thresholds dropped by 5.6°C to 36.5 ± 1.5°C in completely treated receptive fields and by 5.7°C to 37.3 ± 3.4°C in treated parts of receptive fields ('primary sensitization'). In contrast, heat thresholds in the non-treated parts did not change significantly (42.1 ± 3.4°C VS 41.2 ± 3.9°C), i.e. 'secondary sensitization' to heat was lacking. The absence of primary sensitization to probing with von Frey hairs indicates that sensitization of insensitive C fibers and recruitment of insensitive axon collaterals may be more important for mechanical hyperalgesia than sensitization of conventional CMH units - apart from the contribution of central mechanisms. The lack of spread of sensitization to untreated parts of the receptive fields o CMHs ('secondary sensitization') indicates that this fiber group is probably not involved in any form of secondary hyperalgesia to heating.

Original languageEnglish (US)
Pages (from-to)141-147
Number of pages7
JournalExperimental Brain Research
Volume109
Issue number1
StatePublished - 1996
Externally publishedYes

Fingerprint

Nociceptors
Hot Temperature
Skin
Unmyelinated Nerve Fibers
Hyperalgesia
Hair
Axons
Peroneal Nerve
Irritants
Capsaicin
Heating
Foot
Leg
Healthy Volunteers

Keywords

  • C-fiber
  • Microneurography
  • Receptive field
  • Sensitization

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Schmelz, M., Schmidt, R., Ringkamp, M., Forster, C., Handwerker, H. O., & Torebjörk, H. E. (1996). Limitation of sensitization to injured parts of receptive fields in human skin C-nociceptors. Experimental Brain Research, 109(1), 141-147.

Limitation of sensitization to injured parts of receptive fields in human skin C-nociceptors. / Schmelz, M.; Schmidt, R.; Ringkamp, Matthias; Forster, C.; Handwerker, H. O.; Torebjörk, H. E.

In: Experimental Brain Research, Vol. 109, No. 1, 1996, p. 141-147.

Research output: Contribution to journalArticle

Schmelz, M, Schmidt, R, Ringkamp, M, Forster, C, Handwerker, HO & Torebjörk, HE 1996, 'Limitation of sensitization to injured parts of receptive fields in human skin C-nociceptors', Experimental Brain Research, vol. 109, no. 1, pp. 141-147.
Schmelz, M. ; Schmidt, R. ; Ringkamp, Matthias ; Forster, C. ; Handwerker, H. O. ; Torebjörk, H. E. / Limitation of sensitization to injured parts of receptive fields in human skin C-nociceptors. In: Experimental Brain Research. 1996 ; Vol. 109, No. 1. pp. 141-147.
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AB - Unmyelinated cutaneous mechano-heat fibers (CMH) in the peroneal nerve of healthy human volunteers were studied by means of a 'marking' technique which allows stable recordings from identified single units over extended periods. Mechanoreceptive field sizes were 105 ± 13 mm2 in 25 units. These large receptive fields indicate extensive terminal branching of C fibers in the skin of foot and lower leg. Sensitization of CMHs was tested by assessment of thresholds for mechanical (von Frey hair) and heat stimuli before and after topical application of mustard oil (allyl isothiocyanate) and capsaicin (8-methyl-N-vanillyl-6-noneamide). While in a group of 14 CMHs the entire receptive field was treated with these irritant substances, in another group of 11 CMH units only parts of the receptive field were treated to check for signs of spreading sensitization through axon collaterals. Mustard oil application did not change mechanical thresholds, regardless of whether parts of or complete receptive fields were treated. However, mean heat thresholds dropped by 5.6°C to 36.5 ± 1.5°C in completely treated receptive fields and by 5.7°C to 37.3 ± 3.4°C in treated parts of receptive fields ('primary sensitization'). In contrast, heat thresholds in the non-treated parts did not change significantly (42.1 ± 3.4°C VS 41.2 ± 3.9°C), i.e. 'secondary sensitization' to heat was lacking. The absence of primary sensitization to probing with von Frey hairs indicates that sensitization of insensitive C fibers and recruitment of insensitive axon collaterals may be more important for mechanical hyperalgesia than sensitization of conventional CMH units - apart from the contribution of central mechanisms. The lack of spread of sensitization to untreated parts of the receptive fields o CMHs ('secondary sensitization') indicates that this fiber group is probably not involved in any form of secondary hyperalgesia to heating.

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