Superfluousness Of Motor Innervation For The Formation Of Muscle-spindles In Neonatal Rats

Title

Superfluousness Of Motor Innervation For The Formation Of Muscle-spindles In Neonatal Rats

Creator

Kucera J; Walro J M

Publisher

Anatomy and Embryology

Date

1992
1992-09

Description

Muscle spindles form de novo in reinnervated muscles of neonatal rats treated with nerve growth factor. Whether the spindles can also form in muscle reinnervated only by afferents was investigated by removing the lumbosacral segment of the spinal cord immediately after crushing the nerve to the medial gastrocnemius muscle at birth, and administering nerve growth factor for 10 days afterwards. As predicted, the medial gastrocnemius muscles were reinnervated by afferents, but not efferents. No motor endplates were visible on any muscle fibers, and extrafusal fibers were atrophied. The reinnervated muscles contained spindle-like encapsulations of one to four fibers at 5, 7, 9 and 30 days after the nerve crush. The number of spindles as well as encapsulated fibers exceeded that of normal medial gastrocnemius muscles. The encapsulated fibers resembled typical intrafusal fibers. They had normal sensory-muscle contacts, but no motor endings. The fibers displayed equatorial clusters of myonuclei and expressed the spindle-specific slow-tonic myosin heavy chain isoform at postnatal day 30. Thus, efferents are not essential for the formation and differentiation of muscle spindles in reinnervated muscles of neonatal rats.

Subject

afferents; Anatomy & Morphology; Developmental Biology; efferents; expression; fibers; intrafusal muscle fiber; muscle differentiation; neonatal rat; nerve dependence; nerve lesion; spindle development

Identifier

Format

Journal Article or Conference Abstract Publication

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Rights

Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).

Pages

301-309

Issue

4

Volume

186

Citation

Kucera J; Walro J M, “Superfluousness Of Motor Innervation For The Formation Of Muscle-spindles In Neonatal Rats,” NEOMED Bibliography Database, accessed October 21, 2021, https://neomed.omeka.net/items/show/10583.

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