Changes in motor unit properties in SOD1 (G93A) rats.
BACKGROUND
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.


CONCLUSIONS
Changes in MU properties of SOD1 rats have progressive and multidirectional character and speed depending on the MU type.
Department of Neurobiology, University School of Physical Education, 27/39 Królowej Jadwigi Street, 61-871, Poznań, Poland.
Katarzyna
K
Kryściak
Paweł
P
Grieb
Jan
J
Celichowski
D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics* / Q000473:pathology*; D000818:Animals; D004195:Disease Models, Animal; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000235:genetics*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000235:genetics; D018482:Muscle, Skeletal / Q000503:physiopathology*; D051381:Rats; D055647:Rats, Transgenic; D011930:Reaction Time / Q000235:genetics; D013482:Superoxide Dismutase / Q000235:genetics*
C109415:SOD1 G93A protein; D013482:Superoxide Dismutase
ALS; EMG; contractile properties; motor unit; transgenic model