Properties of medial gastrocnemius motor units and muscle fibers reinnervated by embryonic ventral spinal cord cells

Christine K Thomas, Sanjay Sesodia, Daniel E. Erb, Robert M. Grumbles

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Severe muscle atrophy occurs after complete denervation. Here, Embryonic Day 14-15 ventral spinal cord cells were transplanted into the distal tibial nerve stump of adult female Fischer rats to provide a source of neurons for muscle reinnervation. Our aim was to characterize the properties of the reinnervated motor units and muscle fibers. Some reinnervated motor units contracted spontaneously. Electrical stimulation of the transplants at increasing intensity produced an average (± SE) of 7 ± 1 electromyographic and force steps. Each signal increment represented the excitation of another motor unit. These reinnervated units exerted an average force of 12.0 ± 1.5 mN, strength similar to that of control fatigue-resistant units. Repeated transplant stimulation depleted 17% of the muscle fibers of glycogen, an indication of some functional reinnervation. Reinnervated (glycogen-depleted), denervated (no cells transplanted), and control fibers were of histochemical type I, IIA, or IIB. Fibers of the same type were grouped after reinnervation. The proportion of fiber types also changed. Reinnervated fibers were primarily type IIA, whereas most fibers in denervated and control muscles were type IIB. Reinnervated fibers of each type had significantly larger cross-sectional areas than the corresponding fiber types in denervated muscles. These data suggest that neurons with different properties can reside in the unusual environment of the adult rat peripheral nerve, make functional connections with muscle, specify muscle fiber type, and reduce the amount that each type atrophies.

Original languageEnglish
Pages (from-to)25-31
Number of pages7
JournalExperimental Neurology
Volume180
Issue number1
DOIs
StatePublished - Mar 1 2003

Fingerprint

Spinal Cord
Muscles
Glycogen
Transplants
Neurons
Tibial Nerve
Muscular Atrophy
Inbred F344 Rats
Denervation
Peripheral Nerves
Electric Stimulation
Atrophy
Fatigue

Keywords

  • Axon regeneration
  • Embryonic ventral spinal cord
  • Glycogen depletion
  • Muscle denervation
  • Muscle fiber types
  • Muscle reinnervation
  • Transplantation

ASJC Scopus subject areas

  • Neurology
  • Neuroscience(all)

Cite this

Properties of medial gastrocnemius motor units and muscle fibers reinnervated by embryonic ventral spinal cord cells. / Thomas, Christine K; Sesodia, Sanjay; Erb, Daniel E.; Grumbles, Robert M.

In: Experimental Neurology, Vol. 180, No. 1, 01.03.2003, p. 25-31.

Research output: Contribution to journalArticle

Thomas, Christine K ; Sesodia, Sanjay ; Erb, Daniel E. ; Grumbles, Robert M. / Properties of medial gastrocnemius motor units and muscle fibers reinnervated by embryonic ventral spinal cord cells. In: Experimental Neurology. 2003 ; Vol. 180, No. 1. pp. 25-31.
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