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

Published

Journal Article

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.

Full Text

Cited Authors

  • Thomas, CK; Sesodia, S; Erb, DE; Grumbles, RM

Published Date

  • March 2003

Published In

Volume / Issue

  • 180 / 1

Start / End Page

  • 25 - 31

PubMed ID

  • 12668146

Pubmed Central ID

  • 12668146

Electronic International Standard Serial Number (EISSN)

  • 1090-2430

International Standard Serial Number (ISSN)

  • 0014-4886

Digital Object Identifier (DOI)

  • 10.1016/s0014-4886(02)00024-9

Language

  • eng