Fusimotor-free Spindles In Reinnervated Muscles Of Neonatal Rats Treated With Nerve Growth-factor

Title

Fusimotor-free Spindles In Reinnervated Muscles Of Neonatal Rats Treated With Nerve Growth-factor

Creator

Kucera J; Walro J M; Gao Y

Publisher

Neuroscience

Date

1993
1993-01

Description

Crushing the nerve to the medial gastrocnemius muscle in newborn rats and administering nerve growth factor afterwards results in a reinnervated muscle containing supernumerary muscle spindles. The structure and innervation of 88 spindles in the reinnervated muscles were reconstructed from serial thick and thin transverse sections at 30 35 days after the nerve crush, and compared to those of five control spindles. The spindles consisted of one to four small-diameter encapsulated fibers with features of nuclear chain intrafusal fibers, or infrequently a nuclear bag intrafusal fiber. Some of the spindles were located within a capsule that also contained an extrafusal fiber. Each spindle was innervated by an afferent with features of the primary afferent. The density of secondary afferents was lower in reinnervated muscles than in controls. Endplates were observed on extrafusal fibers in the experimental muscles. attesting to restoration of skeletomotor (alpha) innervation after the nerve crush. However, 78% of the experimental spindles were entirely devoid of efferent innervation. The remainder received either one or two fusimotor (gamma) axons or a skeletofusimotor (beta) axon, compared to the six to eight motor axons that innervated control spindles. The presence of supernumerary spindles composed of fibers that resemble normal intrafusal fibers in the absence of motor innervation suggests that afferents alone can induce the formation and subsequent differentiation of intrafusal fibers in nerve-crushed muscles of neonatal rats. In addition, the paucity of gamma innervation in nerve-crushed muscles suggests that immature gamma neurons are more susceptible than spindle afferents or alpha efferents to cell death after axotomy at birth.

Subject

crush; fibers; hindlimb muscles; injury; innervation; Neurosciences & Neurology; sensory neurons; survival

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

219-228

Issue

1

Volume

52

Citation

Kucera J; Walro J M; Gao Y, “Fusimotor-free Spindles In Reinnervated Muscles Of Neonatal Rats Treated With Nerve Growth-factor,” NEOMED Bibliography Database, accessed January 20, 2021, https://neomed.omeka.net/items/show/10586.

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