Differential effects of neonatal denervation on intrafusal muscle fibers in the rat

Kučera, Jan; Walro, Jon M.; Reichler, Judith

doi:10.1007/bf00185898

Cited by 21 publications

(18 citation statements)

References 26 publications

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“…However, efferent innervation, as judged by the presence of axons innervating intrafusal fibers towards the poles of spindles, is found in only a fraction of the spindles. Although it is possible that efferent innervation might return at a later time, these results are very similar to those of Kucera et al [1993] in neonatal rat gastrocnemius muscle spindles. They found that afferents reinnervate spindles more readily than gamma motoneurons because either (1) gamma motoneurons were more susceptible to axotomy or (2) gamma motoneurons follow afferents to intrafusal fibers and transient denervation may disrupt this pathway.…”

Section: Discussionsupporting

confidence: 63%

“…One week after nerve section, intrafusal fibers in the neonatal rat medial gastrocnemius muscle appear to lose their immunoreactivity to antibody ALD 19 and spindle capsules are degenerated to the point that they cannot be identified by light microscopy [Kucera et al, 1993]. We suggest that a similar effect is found, following phenol block, in muscles from older rats.…”

Section: Discussionsupporting

confidence: 55%

“…In mammalian muscle, this isoform is found exclusively in nuclear bag fibers, so that staining with ALD 19 was used to locate muscle spindles [Kucera et al, 1993]. To stain axons innervating muscle spindles, we also used an antibody to the 200-kD neurofilament protein (NF-H) (Sigma N-5389) [Donahue et al, 1988].…”

Section: Neurofilament and Ald 19 Stainingmentioning

confidence: 99%

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Muscle Spindle Reinnervation following Phenol Block

Wolf

English²

2000

Cells Tissues Organs

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Infusion of phenol into peripheral nerves is used clinically to manage spasticity. It produces relief of symptoms by chemical denervation. We simulated the clinical procedure by bathing the lateral plantar nerve of rats in 7% phenol solution for 20 min. We studied the innervation of muscle spindles in the plantar lumbrical muscles of untreated rats and in rats 4 and 6 weeks after a single phenol block. Spindles were identified by the immunoreactivity of nuclear bag₁ fibers to slow tonic myosin (antibody ALD 19). The integrity of the sensory and motor reinnervation of spindles was evaluated using a monoclonal antibody specific for a high molecular weight neurofilament protein. Four weeks after phenol block, muscle spindles were difficult to find, as their immunoreactivity to antibody ALD 19 was reduced. In those spindles studied, most (>80%) were completely denervated. The remainder of which were innervated by afferents only. None received efferent (gamma) innervation. After 6 weeks, spindles were readily identified and nearly all (>90%) received recognizable afferent innervation. A much smaller number (38%) received gamma innervation. Phenol block thus results in a complete denervation of muscle spindles, followed by a fairly rapid sensory reinnervation. Reinnervation by gamma motor neurons is either incomplete or significantly delayed.

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Section: Discussionsupporting

confidence: 63%

Section: Discussionsupporting

confidence: 55%

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Muscle Spindle Reinnervation following Phenol Block

Wolf

English²

2000

Cells Tissues Organs

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“…The identification of putative gamma motor neurons by molecular markers permitted us to begin to explore the mechanisms that control their specification. Muscle spindle differentiation and maturation is initiated by an inductive signal supplied anterogradely by group Ia proprioceptive afferents to nascent muscle fibers (21,33). In turn, gamma motor neurons depend on trophic support from intrafusal fibers in muscle spindles (34,35).…”

Section: Loss Of Muscle Spindles Leads To Absence Of Putative Gamma Mmentioning

confidence: 99%

Gamma and alpha motor neurons distinguished by expression of transcription factor Err3

Friese

Kaltschmidt

Ladle

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

193

256

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Spinal motor neurons are specified to innervate different muscle targets through combinatorial programs of transcription factor expression. Whether transcriptional programs also establish finer aspects of motor neuron subtype identity, notably the prominent functional distinction between alpha and gamma motor neurons, remains unclear. In this study, we identify DNA binding proteins with complementary expression profiles in alpha and gamma motor neurons, providing evidence for molecular distinctions in these two motor neuron subtypes. The transcription factor Err3 is expressed at high levels in gamma but not alpha motor neurons, whereas the neuronal DNA binding protein NeuN marks alpha but not gamma motor neurons. Signals from muscle spindles are needed to support the differentiation of Err3 on /NeuN off presumptive gamma motor neurons, whereas direct proprioceptive sensory input to a motor neuron pool is apparently dispensable. Together, these findings provide evidence that transcriptional programs define functionally distinct motor neuron subpopulations, even within anatomically defined motor pools.motor neuron ͉ spinal cord ͉ transcription factors N euronal diversity underlies many features of central nervous system (CNS) organization and function. Neurons located within different regions of the CNS typically exhibit distinct morphologies and patterns of connectivity that help to determine their physiological functions. Within a single region, neurons that serve closely related functions can be further subdivided, both anatomically and physiologically. The retina, for example, contains multiple subclasses of ganglion and amacrine neurons that are distinguishable by position, patterns of dendritic arborization, and their role in visual processing (1, 2). Similarly, the cerebral cortex contains many local circuit interneurons, each with specialized anatomy, circuitry, and physiology (3). Little is known, however, about how such fine distinctions in CNS neuronal subtype identity and connectivity are assigned.The spinal cord represents a region of the CNS where the diversity of neuronal subtypes has been shown to emerge as a consequence of the expression of intrinsic molecular determinants, acting in a hierarchical manner to assign subtype identities to a generic set of motor neurons (4, 5). The motor neurons that project to skeletal muscle targets can be subdivided into distinct columnar subgroups, each projecting to a different target domain-axial, body wall, and limb targets. The lateral motor column (LMC) neurons that project their axons to limb muscles can be further subdivided into divisional and pool subclasses that, together, specify the pattern of target muscle connectivity (4, 5). The sequential steps involved in controlling motor neuron subtype identities and target projections are programmed through the cell-type selectivity of transcription factor expression, notably members of the Hox, LIM, Nkx6, and ETS families (6-10). Thus combinatorial programs of transcription factor expression appear to provide...

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“…ALD 19 or ALD 58, antibodies against slow-tonic MHC, are highly specific markers for tracing the fate of nuclear bag intrafusal fibers during development and after denervation at birth (Pedrosa and Tbornell 1990;Kucera and Walro 1993). However, preliminary observations indicated that some denervated extrafusal fibers in neonatal rats also bind mAbs ALD 19 and ALD 58.…”

Section: Introductionmentioning

confidence: 98%

Transient expression of a slow-tonic MHC isoform by extrafusal fibers in the developing rat

Kučera

Walro

1993

Anat Embryol

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ALD 19, a monoclonal antibody that recognizes the slow-tonic myosin heavy chain (MHC) isoform, has been used extensively as a marker for nuclear bag intrafusal fibers of muscle spindles in developing and adult rats. Extrafusal fibers of adult rat hindlimb muscles do not express slow-tonic MHC. However, while using ALD 19 to trace the fate of intrafusal fibers following neonatal denervation, we noted that some extrafusal fibers of neonates also bound this antibody. The immunolabeled extrafusal fibers were a subset of slow fibers located in the deep axial regions of crural muscles. The same fiber subset transiently displayed a weak affinity for ALD 19 during the first postnatal week in normal muscles. Denervation at birth increased the intensity of ALD 19 immunolabelling by these extrafusal fibers and extended the duration of the slow-tonic immunoreactivity into the 2nd postnatal week, after which expression diminished or ceased. Demonstration that some developing extrafusal fibers have a nerve-independent capacity for transiently expressing slow-tonic MHC, an MHC previously though to be expressed only by intrafusal fibers, raises the possibility that both types of fiber originate from a subset of bipotential slow primary myotubes in rat hindlimbs.

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Differential effects of neonatal denervation on intrafusal muscle fibers in the rat

Cited by 21 publications

References 26 publications

Muscle Spindle Reinnervation following Phenol Block

Muscle Spindle Reinnervation following Phenol Block

Gamma and alpha motor neurons distinguished by expression of transcription factor Err3

Transient expression of a slow-tonic MHC isoform by extrafusal fibers in the developing rat

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