Level of independence of motor unit properties from neuromuscular activity

David J. Pierotti, Roland R. Roy, John A. Hodgson, V. Reggie Edgerton

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


Neuromuscular activity was eliminated in the tibialis anterior muscle of adult cats for 6 months by spinal isolation (Sl), i.e., complete spinal cord transections at T‐12–13 and at L‐7–S‐1, plus bilateral dorsal rhizotomy between the two transection sites. One motor unit from each muscle was isolated using ventral root teasing procedures and physiologically tested. The fibers belonging to each motor unit were visualized in PAS‐staired sections by the loss of glycogen following prolonged repetitive stimulation. Qualitatively, the normal enzymatic interrelationships among fibers identified by myosin heavy chain composition were unchanged by SI. Generally, each motor unit from SI cats were of a single myosin immunohistochemical type. The same physiological motor unit types that typify control muscles were found in SI cats. In Sl compared to control cats, there was approximately a 10% increase in the number of muscle fibers expressing fast myosin. Mean fiber activity levels of ATPase and SDH for a given fiber type (based on MHC antibody reactions) decreased by approximately 10% and 25%, whereas GPD activity increased approximately 35%. It is concluded that differential levels or patterns of activity are not essential to maintain the range of histochemical and physiological motor unit types found in the tibialis anterior of normal adult cats. © 1994 John Wiley & Sons, Inc.

Original languageEnglish (US)
Pages (from-to)1324-1335
Number of pages12
JournalMuscle & Nerve
Issue number11
StatePublished - Nov 1994


  • inactivity
  • myofibrillar ATPase activity
  • myosin heavy chain isoforms
  • spinal isolation
  • succinate dehydrogenase activity
  • α‐glycerophosphate dehydrogenase activity

ASJC Scopus subject areas

  • Physiology
  • Clinical Neurology
  • Cellular and Molecular Neuroscience
  • Physiology (medical)


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