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Discharge patterns of afferent cutaneous nerve fibers from the rat's tail during prolonged noxious mechanical stimulation


Feedback controlled constant force stimuli of 4, 6 and 8 N intensities and of 120 s duration were applied to the receptive fields of cutaneous afferent fibers in the rat's tail. Two types of nociceptive units showed sustained discharges during these stimuli: “polymodal” unmyelinated C-units (MH-C units, N = 18, c.v. 0.5–0.9 m/s) and high-threshold mechanoreceptive A-delta-units(HTM-units, N=10, c.v. 1.9–11.2 m/s). In addition two classes of sensitive low threshold mechanoreceptors, SA I (N=6) and SA II (N=5) units, responded to the prolonged mechanical stimuli. At the onset of a noxious pressure, 11 of the 18 polymodal nociceptors exhibited dynamic responses (lasting about 10 s) which were followed by slowly adapting tonic discharges that lasted for the duration of the stimuli. The remaining polymodal C-fiber units (8/18) did not show dynamic discharges at 4 and 6 N. Phasic and tonic discharges were positively correlated with stimulus strength. The HTM-units encoded stimulation intensity mainly by their dynamic discharges. The tonic discharges of these units displayed faster adaptation rates with stronger mechanical stimuli, i.e. encoding of stimulation intensity became progressively weaker during the tonic phase. The discharges of sensitive SA I and SA II units with A beta axons were not positively correlated with the strength of noxious pressure stimuli. Tonic discharge rates of SA I units were negatively correlated to stimulus strength, whereas SA II units usually stopped firing in the course of a stimulus and became reversibly irresponsive to mechanical stimulation. Possible afferent mechanisms underlying the induction of pain by sustained noxious mechanical stimulation are discussed.

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  1. Adriaensen H, Gybels J, Handwerker HO, Van Hees J (1983) Response properties of thin myelinated (A-δ) fibres in human skin nerves. J Neurophysiol 49: 111–121

  2. Adriaensen H, Gybels J, Handwerker HO, Van Hees J (1984) Nociceptor discharges and sensations due to prolonged noxious mechanical stimulation — a paradox. Hum Neurobiol 3: 53–58

  3. Anton F, Kreh A, Reeh PW, Handwerker HO (1984) Algesimetry using natural stimuli of long duration. In: Bromm B (ed) Pain measurement in man. Neurophysiological correlates of pain. Elsevier Science Publishers, Amsterdam, pp 455–461

  4. Beitel RE, Dubner R (1976) Responses of unmyelinated (C) polymodal nociceptors to thermal stimuli applied to monkey's face. J Neurophysiol 39 (6): 1160–1175

  5. Bessou P, Perl ER (1969) Response of cutaneous sensory units with unmyelinated fibers to noxious stimuli. J Neurophysiol 32: 1025–1043

  6. Brown AG, Iggo A (1967) A quantitative study of cutaneous receptors and afferent fibers in the cat and rabbit. J Physiol 193: 707–733

  7. Burgess PR, Perl ER (1973) Cutaneous mechanoreceptors and nociceptors. In: Iggo A (ed) Handbook of sensory physiology, Vol II. Somatosensory system. Springer, Berlin Heidelberg New York, pp 29–78

  8. Chambers MR, Andres KH, During M von, Iggo A (1972) The structure and function of slowly adapting type II mechanoreceptors in hairy skin. Q J Exp Physiol 57: 417–445

  9. Fitzgerald M, Lynn B (1977) The sensitization of high threshold mechanoreceptors with myelinated axons by repeated heating. J Physiol 365: 549–563

  10. Fleischer E, Handwerker HO, Joukhadar S (1983) Unmyelinated nociceptive units in two skin areas of the rat. Brain Res 267: 81–92

  11. Frey M v. (1922) Versuche über schmerzerzeugende Reize. Z Biol 76: 1

  12. Georgopoulos AP (1976) Functional properties of primary afferent units probably related to pain mechanisms in primate globous skin. J Neurophysiol 39: 71–83

  13. Hardy JD, Wolff HG, Goodell H (1952) Studies on pain. Measurement of aching pain threshold and discrimination of differences in intensity of aching pain. J Appl Physiol 5: 247–255

  14. Iggo A, Muir AR (1969) The structure and function of a slowly adapting touch corpuscle in hairy skin. J Physiol 200: 763–796

  15. Knibestöl M, Vallbo AB (1970) Single unit analysis of mechanoreceptor activity from the human glabrous skin. Acta Physiol Scand 80: 178–195

  16. Knibestöl M, Vallbo AB (1980) Intensity of sensation related to activity of slowly adapting mechanoreceptive units in the human hand. J Physiol 300: 251–267

  17. Lynn B (1977) The heat sensitization of polymodal nociceptors and its independence on the local blood flow. J Physiol 287: 493–507

  18. Lynn B, Carpenter SE (1982) Primary afferent units from the hairy skin of the rat hind limb. Brain Res 238: 29–43

  19. Merzenich MM, Harrington T (1969) The sense of fluttervibration evoked by stimulation of the hairy skin of primates: comparison of human sensory capacity with the responses of mechanoreceptive afferents innervating the hairy skin of monkeys. Exp Brain Res 9: 236–260

  20. Perl ER (1968) Myelinated afferent fibres innervating the primate skin and their response to noxious stimuli. J Physiol 197: 593–615

  21. Sachs L (1983) Angewandte Statistik. Springer, Berlin Heidelberg New York Tokyo

  22. Torebjörk HE (1974) Afferent C units responding to mechanical, thermal and chemical stimuli in human non-glabrous skin. Acta Physiol Scand 92: 374–390

  23. Vallbo AB, Johansson RS (1984) Properties of cutaneous mechanoreceptors in the human hand related to touch sensation. Hum Neurobiol 3: 3–14

  24. Van Hees J, Gybels J (1981) C-Nociceptor activity in human nerve during painful and non painful skin stimulation. J Neurol Neurosurg Psychiat 44: 600–607

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Correspondence to H. O. Handwerker.

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Handwerker, H.O., Anton, F. & Reeh, P.W. Discharge patterns of afferent cutaneous nerve fibers from the rat's tail during prolonged noxious mechanical stimulation. Exp Brain Res 65, 493–504 (1987).

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Key words

  • Nociceptor
  • C-fiber
  • A-delta fiber
  • SA receptor