Axon excitability testing shows increased IH activity in populations of slow versus fast motor axons of the rat

• Author / Creator

  Lorenz, Chad D

• Despite extensive knowledge of variations in motoneuron (MN) soma and muscle properties across different healthy muscles or motor units, there is comparatively little knowledge about variations in motor axon electrophysiology across different axon groups. Axon excitability testing (AET) is an in vivo method which indirectly examines motor axon electrophysiology. We used AET in Sprague-Dawley rats to compare axons innervating tibialis anterior (“fast” motor axons) to axons innervating soleus (“slow” motor axons). We found that fast and slow motor axons differ significantly in their accommodation to hyperpolarizing currents, and in their post-spike excitability oscillation. Specifically, we found compelling evidence that slow motor axons have greater activity of the hyperpolarization-activated inwardly rectifying cation conductance (IH) than fast motor axons. Since fast and slow motor axons have different daily activity patterns, this foreshadows the possibility of activity-dependent plasticity in at least one ionic conductance of the motor axon.

• Subjects / Keywords

  • Axon plasticity
  • IH
  • ALS
  • Amyotrophic lateral sclerosis
  • Axon excitability testing
  • Axon physiology
  • Axon ion channels
  • Hyperpolarization-activated inwardly rectifying cation conductance
  • Motor control
  • Axon
  • Ionic conductances
  • Motor axons

• Graduation date

  Fall 2013

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3XW4846Q

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.