Functional Adaptation to Loading of a Single Bone Is Neuronally Regulated and Involves Multiple Bones

Authors

  • Susannah J Sample,

    1. Comparative Orthopaedic Research Laboratory, University of Wisconsin-Madison, Madison, Wisconsin, USA
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  • Mary Behan,

    1. Comparative Orthopaedic Research Laboratory, University of Wisconsin-Madison, Madison, Wisconsin, USA
    2. Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, Wisconsin, USA
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  • Lesley Smith,

    1. Department of Surgical Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA
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  • William E Oldenhoff,

    1. Comparative Orthopaedic Research Laboratory, University of Wisconsin-Madison, Madison, Wisconsin, USA
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  • Mark D Markel,

    1. Comparative Orthopaedic Research Laboratory, University of Wisconsin-Madison, Madison, Wisconsin, USA
    2. Department of Medical Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA
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  • Vicki L Kalscheur,

    1. Comparative Orthopaedic Research Laboratory, University of Wisconsin-Madison, Madison, Wisconsin, USA
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  • Zhengling Hao,

    1. Comparative Orthopaedic Research Laboratory, University of Wisconsin-Madison, Madison, Wisconsin, USA
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  • Vjekoslav Miletic,

    1. Department of Anesthesiology, School of Medicine & Public Heath, University of Wisconsin-Madison, Madison, Wisconsin, USA
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  • Peter Muir

    Corresponding author
    1. Comparative Orthopaedic Research Laboratory, University of Wisconsin-Madison, Madison, Wisconsin, USA
    2. Department of Surgical Sciences, University of Wisconsin-Madison, Madison, Wisconsin, USA
    • Address reprint requests to: Peter Muir, BVSc, PhD, Diplomate ACVS, University of Wisconsin-Madison, School of Veterinary Medicine, Department of Surgical Sciences, 2015 Linden Drive, Madison, WI 53706, USA
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  • The authors state that they have no conflicts of interest.

  • Published online on April 14, 2008

Abstract

Regulation of load-induced bone formation is considered a local phenomenon controlled by osteocytes, although it has also been hypothesized that functional adaptation may be neuronally regulated. The aim of this study was to examine bone formation in multiple bones, in response to loading of a single bone, and to determine whether adaptation may be neuronally regulated. Load-induced responses in the left and right ulnas and humeri were determined after loading of the right ulna in male Sprague-Dawley rats (69 ± 16 days of age). After a single period of loading at −760-, −2000-, or −3750-μϵ initial peak strain, rats were given calcein to label new bone formation. Bone formation and bone neuropeptide concentrations were determined at 10 days. In one group, temporary neuronal blocking was achieved by perineural anesthesia of the brachial plexus with bupivicaine during loading. We found right ulna loading induces adaptive responses in other bones in both thoracic limbs compared with Sham controls and that neuronal blocking during loading abrogated bone formation in the loaded ulna and other thoracic limb bones. Skeletal adaptation was more evident in distal long bones compared with proximal long bones. We also found that the single period of loading modulated bone neuropeptide concentrations persistently for 10 days. We conclude that functional adaptation to loading of a single bone in young rapidly growing rats is neuronally regulated and involves multiple bones. Persistent changes in bone neuropeptide concentrations after a single loading period suggest that plasticity exists in the innervation of bone.

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