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Differential susceptibility of muscles to myotonia and force impairment in a mouse model of myotonic dystrophy
Author(s) -
Moyer Michelle,
Berger Dara S.,
Ladd Andrea N.,
Van Lunteren Erik
Publication year - 2011
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.21988
Subject(s) - myotonia , myotonic dystrophy , weakness , stimulation , medicine , muscle stiffness , endocrinology , muscle weakness , contraction (grammar) , muscle fatigue , muscle relaxation , muscle contraction , diaphragm (acoustics) , anatomy , skeletal muscle , chemistry , electromyography , physical medicine and rehabilitation , stiffness , materials science , physics , acoustics , loudspeaker , composite material
Myotonic dystrophy, or dystrophia myotonica (DM), is characterized by prominent muscle wasting and weakness as well as delayed muscle relaxation resulting from persistent electrical discharges. Methods: We hypothesized heterogeneity among muscles in degree of weakness and myotonia in an expanded [(CUG) 250 ] repeats transgenic ( HSA LR ) mouse DM model. Muscle contraction was compared among diaphragm, extensor digitorum longus (EDL), and soleus muscles. Results: Myotonia was found only in EDL, as manifested by longer late‐relaxation time and elevated myotonic index. EDL, but not the other two muscles, had impaired force over a wide range of stimulation frequencies. During fatigue‐inducing stimulation, DM EDL muscle force per cross‐sectional area was significantly impaired during 25‐Hz stimulation, whereas there were no differences in fatigue response for DM diaphragm or soleus. Conclusion: In an expanded repeats model of DM the EDL is more susceptible to myotonia and force impairment than muscles with lower proportions of fast‐twitch fibers. Muscle Nerve, 2011