Unlike myofibers, neuromuscular junctions remain stable during prolonged muscle unloading.
This study assessed the effect of muscle unloading on the neuromuscular system. Sixteen male Fischer 344 rats were randomly assigned to either a hindlimb suspension (unloaded) or control group (N=8/group) for 16 days. Following this intervention period, pre- and postsynaptic features of the neuromuscular junctions (NMJs) of soleus muscles were stained with cytofluorescent techniques, and myofibers were histochemically stained for ATPase activity. The data indicate that 16 days of muscle unloading resulted in significant (P<0.05) atrophy among myofibers (>50%) that was evident among all three major fiber types (I, IIA and IIX), but failed to significantly alter any aspect of NMJ morphology quantified. These results demonstrate an impressive degree of NMJ resilience despite dramatic remodeling of associated myofibers. This may be of benefit during post-unloading rehabilitative measures where effective neuromuscular communication is essential.
Department of Kinesiology, The College of William and Mary, Williamsburg, VA 23187-8795, USA. mrdesc@wm.edu
Michael R
MR
Deschenes
Kristin M
KM
Will
Frank W
FW
Booth
Scott E
SE
Gordon
D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D015992:Body Mass Index; D002038:Bungarotoxins / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D019417:Hindlimb Suspension / Q000502:physiology*; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000145:classification / Q000166:cytology / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009469:Neuromuscular Junction / Q000378:metabolism / Q000502:physiology*; D011897:Random Allocation; D051381:Rats; D011916:Rats, Inbred F344; D012235:Rhodamines / Q000378:metabolism; D013569:Synapses / Q000378:metabolism
D002038:Bungarotoxins; D005456:Fluorescent Dyes; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D012235:Rhodamines; C489618:Sv2a protein, rat