Response of cutaneous A- and C-fiber nociceptors in the monkey to controlled-force stimuli

J Neurophysiol. 2000 Apr;83(4):2179-91. doi: 10.1152/jn.2000.83.4.2179.


The goal of this study was to determine the capacity of primary afferent nociceptive fibers (nociceptors) to encode information about noxious mechanical stimuli in primates. Teased-fiber techniques were used to record from 14 A-fiber nociceptors and 18 C-fiber nociceptors that innervated the hairy skin. Stimulus-response functions were examined with an ascending series of force-controlled stimuli. Stimulus-interaction effects were examined with use of a series of paired stimuli in which the interval between the stimulus pairs was varied systematically. Both A-fiber and C-fiber nociceptors exhibited a slowly adapting response to the stepped force stimuli. The response of the A fibers increased monotonically with increasing force, whereas the response of the C fibers reached a plateau at low force levels. The slope of the stimulus-response function for the A fibers was significantly steeper than that for the C fibers, and the total response was greater. The A fibers also provided more discriminative information regarding stimulus intensity. The C fibers demonstrated a significant fatigue in response when the interstimulus interval between the paired stimuli was </=150 s, whereas the A fibers did not demonstrate a significant fatigue until the interstimulus interval was </=30 s. This fatigue in response was not due to changes in tissue compliance. These results suggest that A- and C-fiber nociceptors have different mechanical transduction mechanisms. A-fiber nociceptors exhibit steeper stimulus-response functions and less fatigue than C-fiber nociceptors.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adaptation, Physiological / physiology
  • Animals
  • Compliance
  • Evoked Potentials, Somatosensory / physiology
  • Forelimb
  • Haplorhini
  • Hot Temperature
  • Nerve Fibers / classification
  • Nerve Fibers / physiology*
  • Neurons, Afferent / physiology*
  • Neurons, Afferent / ultrastructure
  • Nociceptors / physiology*
  • Pain / physiopathology*
  • Physical Stimulation
  • Skin / innervation
  • Stress, Mechanical