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Isometric and Eccentric Force Generation Assessment of Skeletal Muscles Isolated from Murine Models of Muscular Dystrophies
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Sarcolemmal excitability in the myotonic dystrophies

Robert Boland-Freitas1,2, James Lee1, James Howells3

  • 1Department of Neurology and Neurophysiology, Royal North Shore Hospital, Reserve Road, St Leonards, New South Wales, Australia.

Muscle & Nerve
|September 8, 2017
PubMed
Abstract

Insights

Muscle excitability is altered in myotonic dystrophy type 1 (DM1) and type 2 (DM2). Advanced DM1 shows prolonged muscle relative refractory periods, suggesting resting membrane potential depolarization, which may inform future therapies.

Area of Science:

  • Neurology
  • Muscle Physiology

Background:

  • Chloride channel dysfunction contributes to sarcolemmal issues in myotonic dystrophy types 1 (DM1) and 2 (DM2).
  • Previous research suggests impaired Na+/K+-ATPase activity in advanced DM1.

Purpose of the Study:

  • To investigate muscle excitability in DM1 and DM2 using muscle velocity recovery cycles (MVRCs).
  • To identify electrophysiological differences between mild, advanced DM1, DM2, and healthy controls.

Main Methods:

  • Muscle velocity recovery cycles (MVRCs) were employed to assess muscle excitability.
  • Measurements were taken from patients with mild DM1 (n=8), advanced DM1 (n=11), DM2 (n=4), and 30 healthy controls.

Main Results:

  • Increased residual supernormality was observed in DM2 and advanced DM1 patients.
  • Advanced DM1 exhibited prolonged muscle relative refractory periods (MRRP), reduced early supernormality, and peak amplitude decrements during repetitive stimulation.

Conclusions:

  • Prolongation of the MRRP in advanced DM1 suggests depolarization of the resting muscle membrane potential.
  • These findings may offer insights for developing future therapeutic strategies for myotonic dystrophy.
Keywords:
chloride channeldepolarizationexcitabilitymembrane potentialmyotonic dystrophyrelative refractory periodsodium-potassium pumpvelocity recovery cycle

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