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Updated: May 3, 2026
Measuring Neuromuscular Junction Functionality
Published on: August 6, 2017
Changes in motor unit properties in SOD1 (G93A) rats
Katarzyna Kryściak1, Paweł Grieb, Jan Celichowski
1Department of Neurobiology, University School of Physical Education, 27/39 Królowej Jadwigi Street, 61-871, Poznań, Poland.
Introduction:
In amyotrophic lateral sclerosis (ALS), progressive death of motor neurons results in denervation and reinnervation of muscles. It is not clear how ALS affects the properties of motor units (MUs).
Methods:
Properties of single MUs in the medial gastrocnemius (MG) muscle of rats bearing the human mutated superoxide dismutase gene type 1 (SOD1) were determined at 3 stages: asymptomatic (ALS I); early symptomatic (ALS II); and terminal (ALS III).
Results:
In ALS II, higher proportions of FF (fast fatigable) and S (slow) MUs were observed, whereas in ALS III higher percentages of S and lower percentages of FF MUs were noted compared with controls. S motor neurons reinnervated fast muscle fibers, and those MUs gained some properties of fast MUs, including lower fatigue resistance, greater force generation, and higher action potential amplitudes.
Conclusion:
Changes in MU properties of SOD1 rats have progressive and multidirectional character and speed depending on the MU type.
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