Does metabosensitive afferent fibers activity differ from slow- and fast-twitch muscles?

Exp Brain Res. 2015 Sep;233(9):2549-54. doi: 10.1007/s00221-015-4326-5. Epub 2015 May 21.


This study was designed to investigate the metabosensitive afferent response evoked by electrically induced fatigue (EIF), lactic acid (LA) and potassium chloride (KCl) in three muscle types. We recorded the activity of groups III-IV afferents originating from soleus, gastrocnemius and tibialis anterior muscles. Our data showed a same pattern of response in the three muscles after chemical injections, i.e., a bell curve with maximal discharge rate at 1 mM for LA injections and a linear relationship between KCl concentrations and the afferent discharge rate. Furthermore, a stronger response was recorded after EIF in the gastrocnemius muscle compared to the two other muscles. The change in afferent discharge after 1 mM LA injection was higher for the gastrocnemius muscle compared to the response obtained with the corresponding concentration applied in the two other muscles, whereas changes to KCl injections did not dramatically differ between the three muscles. We conclude that anatomical (mass, phenotype, vascularization, receptor and afferent density…) and functional (flexor vs. extensor) differences between muscles could explain the amplitude of these responses.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / drug effects
  • Action Potentials / physiology*
  • Afferent Pathways / drug effects
  • Afferent Pathways / physiology*
  • Animals
  • Dose-Response Relationship, Drug
  • Electric Stimulation / adverse effects
  • Lactic Acid / adverse effects
  • Male
  • Muscle Contraction / drug effects
  • Muscle Contraction / physiology*
  • Muscle Fatigue / drug effects
  • Muscle Fatigue / physiology*
  • Muscle, Skeletal / physiology*
  • Potassium Chloride / adverse effects
  • Rats
  • Rats, Sprague-Dawley


  • Lactic Acid
  • Potassium Chloride