Development of spontaneous activity and mechanosensitivity in axotomized afferent nerve fibers during the first hours after nerve transection in rats

J Neurophysiol. 1995 Sep;74(3):1020-7. doi: 10.1152/jn.1995.74.3.1020.


1. Spontaneous activity and ectopic mechanical excitability of axotomized unmyelinated and myelinated fibers in the sural nerve were examined in anesthetized rats. The analysis was performed within 30 h after the nerve lesion using single-fiber recordings that were performed proximal to the severed nerve end. 2. Among all unmyelinated fibers tested (n = 865), 4-8% exhibited persistent spontaneous activity of low and irregular frequency. The percentage of spontaneously active C fibers did not change significantly during the first 30 h. Only 6 of 796 A fibers had spontaneous activity. 3. Mechanical stimulation of the cut nerve end excited 5-8% of all C fibers under investigation. No development with time could be detected in the frequency of mechanically excitable C fibers. In contrast, beginning 6 h after nerve transection, the number of mechanically excitable A fibers rose with time, reaching 27% after 22-30 h. 4. Among the A fibers (C fibers) that exhibited mechanical excitability or spontaneous activity, only 4% (25%) had both properties, whereas 96% (75%) were either mechanosensitive or spontaneously active. 5. With time after the nerve lesion, the mean discharge rate of all spontaneously discharging C fibers decreased significantly from 49 imp/min (0.5-9 h after nerve lesion) to 11 imp/min after 22-30 h. The mean discharge rate of C fibers exhibiting solely spontaneous activity and those C fibers that were additionally mechanosensitive did not differ significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology
  • Afferent Pathways / physiology*
  • Animals
  • Axons / physiology*
  • Male
  • Nerve Fibers / physiology*
  • Rats
  • Rats, Wistar
  • Sural Nerve / physiology*
  • Time Factors