PMID- 10944181
OWN - NLM
STAT- MEDLINE
DCOM- 20001107
LR  - 20190513
IS  - 0022-3751 (Print)
IS  - 1469-7793 (Electronic)
IS  - 0022-3751 (Linking)
VI  - 527 Pt 1
IP  - Pt 1
DP  - 2000 Aug 15
TI  - Time course of post-excitatory effects separates afferent human C fibre classes.
PG  - 185-91
AB  - 1. To study post-excitatory changes of conduction velocity, action potentials 
      were recorded from 132 unmyelinated nerve fibres (C fibres) in cutaneous 
      fascicles of the peroneal nerve using microneurography in healthy human subjects. 
      The 'marking' technique was used to assess responsiveness to mechanical and heat 
      stimuli or sympathetic reflex provocation. 2. C fibres were classified into three 
      major classes: mechano-responsive afferent (n = 76), mechano-insensitive afferent 
      (n = 48) and sympathetic efferent C fibres (n = 8). 3. During regular stimulation 
      at 0.25 Hz, conditioning pulses were intermittently interposed. Changes of 
      conduction velocity were assessed for different numbers of conditioning impulses 
      and varying interstimulus intervals (ISIs). For all three fibre classes the 
      latency shift following conditioning pulses at an ISI of 1000 ms increased 
      linearly with their number (n = 1, 2 and 4). However, the absolute degree of 
      conduction velocity slowing was much higher in the 32 mechano-insensitive fibres 
      as compared with 56 mechano-responsive or 8 sympathetic fibres. 4. Single 
      additional pulses were interposed at different ISIs from 20 to 2000 ms. For 20 
      mechano-responsive fibres conduction velocity slowing increased with decreasing 
      ISI (subnormal phase). In contrast, for 16 mechano-insensitive C fibres the 
      conduction velocity slowing decreased with shorter ISIs, and at values lower than 
      417 +/- 49 ms (mean +/- s.e.m.) the conduction velocity of the conditioned action 
      potential was faster than before (conduction velocity speeding). This supernormal 
      phase had its maximum at 69 +/- 10 ms. 5. In this study we provide, for the first 
      time, direct evidence of relative supernormal conduction in human 
      mechano-insensitive C fibres. The implications for temporal coding in different 
      afferent C fibre classes are discussed.
FAU - Weidner, C
AU  - Weidner C
AD  - Department of Physiology and Experimental Pathophysiology, University of 
      Erlangen/Nurnberg, Universitatsstrasse 17, 91054 Erlangen, Germany.
FAU - Schmidt, R
AU  - Schmidt R
FAU - Schmelz, M
AU  - Schmelz M
FAU - Hilliges, M
AU  - Hilliges M
FAU - Handwerker, H O
AU  - Handwerker HO
FAU - Torebjork, H E
AU  - Torebjork HE
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - England
TA  - J Physiol
JT  - The Journal of physiology
JID - 0266262
SB  - IM
MH  - Action Potentials
MH  - Adrenergic Fibers/physiology
MH  - Adult
MH  - *Electric Conductivity
MH  - Electric Stimulation
MH  - Electrodes, Implanted
MH  - Female
MH  - Hot Temperature
MH  - Humans
MH  - Male
MH  - Mechanoreceptors/physiology
MH  - Nerve Fibers/*classification/*physiology
MH  - Peroneal Nerve/physiology
MH  - Reflex
MH  - *Refractory Period, Electrophysiological
MH  - Stress, Mechanical
MH  - Time Factors
PMC - PMC2270064
EDAT- 2000/08/16 11:00
MHDA- 2001/02/28 10:01
PMCR- 2001/08/15
CRDT- 2000/08/16 11:00
PHST- 2000/08/16 11:00 [pubmed]
PHST- 2001/02/28 10:01 [medline]
PHST- 2000/08/16 11:00 [entrez]
PHST- 2001/08/15 00:00 [pmc-release]
AID - PHY_1030 [pii]
AID - 10.1111/j.1469-7793.2000.00185.x [doi]
PST - ppublish
SO  - J Physiol. 2000 Aug 15;527 Pt 1(Pt 1):185-91. doi: 
      10.1111/j.1469-7793.2000.00185.x.