Spontaneous and evoked ectopic discharges recorded from single human axons

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Abstract

A quantitative assessment was made of the firing characteristics of repetitive axonal discharges encountered during microneurographic recordings from human peripheral nerves. Spontaneous activity was recorded from 16 single axons using tungsten microelectrodes inserted percutaneously into fascicles of the median or peroneal nerves in normal subjects. These discharges typically consisted of brief bursts of 2-5 spikes occurring at a frequency of 7-10 Hz. Peak instantaneous frequencies usually exceeded 300 Hz. Based on their similarity with spontaneous high-frequency discharges recorded from single axons following nerve damage, ischemia, prolonged electrical stimulation, or hyperventilation, it is concluded that they are generated ectopically at the site of a previous impalement of a nerve fiber. It is suggested that short-term damage to the nerve fiber caused by the microelectrode may allow accumulation of K+ underneath the myelin, triggering an inward flow of K+ and regenerative depolarizations. Alternatively, internodal channels may be exposed following damage to the myelin, resulting in the generation of spontaneous pacemaker potentials and repetitive discharges.

Original languageEnglish
Pages (from-to)461-468
Number of pages8
JournalMuscle & Nerve
Volume21
Issue number4
DOIs
Publication statusPublished - 1998
Externally publishedYes

Keywords

  • Axonal excitability
  • Ectopic discharges
  • Human
  • Microneurography
  • Nerve damage
  • Sensory axons

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