Effects of experimental muscle pain on electromyographic activity of masticatory muscles in the rat

Authors

  • Jin Y. Ro PhD,

    Corresponding author
    1. Department of Oral and Craniofacial Biological Sciences, University of Maryland Baltimore School of Dentistry, 666 West Baltimore Street, Baltimore, Maryland 21201, USA
    • Department of Oral and Craniofacial Biological Sciences, University of Maryland Baltimore School of Dentistry, 666 West Baltimore Street, Baltimore, Maryland 21201, USA
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  • Peter Svensson PhD,

    1. Center for Sensory-Motor Interaction, Orofacial Pain Laboratory, Aalborg University, Aalborg, Denmark
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  • Norman Capra PhD

    1. Department of Oral and Craniofacial Biological Sciences, University of Maryland Baltimore School of Dentistry, 666 West Baltimore Street, Baltimore, Maryland 21201, USA
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Abstract

The aim of the present study was to investigate the effects of noxious chemical stimulation of a jaw muscle on postural electromyographic (EMG) activity from several masticatory muscles in lightly anesthetized rats. Unilateral injection of a substance known to induce acute muscle pain (5% NaCl) or longer duration of pain with inflammation (mustard oil) was made into the masseter muscle. The changes in EMG activity following the injection were recorded from the injected and contralateral masseter muscles and the ipsilateral digastric muscle. The algesic chemicals produced a significant but transient increase in EMG activity in all three muscles. The data from the present study and similar observations from clinical and experimental human studies suggest that increased activity from muscle nociceptors is not sufficient to produce a prolonged increase in postural EMG activity. Therefore, the development and maintenance of chronic jaw muscle pain does not appear to result from a feedback cycle mechanism. © 2002 Wiley Periodicals, Inc. Muscle Nerve 25: 000–000, 2002

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