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Scandinavian Journal of Pain

Official Journal of the Scandinavian Association for the Study of Pain

Editor-in-Chief: Werner, Mads


CiteScore 2018: 0.85

SCImago Journal Rank (SJR) 2018: 0.494
Source Normalized Impact per Paper (SNIP) 2018: 0.427

Online
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1877-8879
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Volume 16, Issue 1

Issues

Expression of α1 adrenergic receptor subtypes by afferent fibers that innervate rat masseter muscle

B.E. Cairns
  • Center for Neuroplasticity and Pain, SMI, Department of Health Science and Technology Faculty of Medicine, Aalborg University, Frederik Bajers Vej 7D3, 9220, Aalborg East, Denmark
  • Faculty of Pharmaceutical Sciences, University of British Columbia, 2405 Wesbrook Mallm, Vancouver, BC, Canada V6 T 1Z3
  • Email
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ J. Liu
  • Faculty of Pharmaceutical Sciences, University of British Columbia, 2405 Wesbrook Mallm, Vancouver, BC, Canada V6 T 1Z3
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  • De Gruyter OnlineGoogle Scholar
/ H. Wong
  • Faculty of Pharmaceutical Sciences, University of British Columbia, 2405 Wesbrook Mallm, Vancouver, BC, Canada V6 T 1Z3
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
Published Online: 2017-07-01 | DOI: https://doi.org/10.1016/j.sjpain.2017.04.010

Abstract

Aims

In temporomandibular disorders sufferers, muscle pain is more severe in individuals who have undergone a traumatic stress. Why stress exacerbates masticatory muscle pain in these individuals is not known. One possibility is that under conditions of stress there is an interaction between the sympathetic and sensory nervous systems. This study investigated whether trigeminal ganglion neurons that innervate the masseter muscle express α1 adrenergic receptor subtypes to identify whether a direct interaction between the sympathetic and sensory nervous systems is feasible.

Methods

Masseter muscle ganglion neurons were identified by injection of the fluorescent dye fast blue into the masseter muscle of 4 Sprague Dawley rats (2 male, 2 female). Trigeminal ganglion sections were stained for α1a, α1b or α1d adrenergic receptors, as well as the transient receptor potential vanilloid 1 (TrpV1) receptor. Sections were examined with a Leica confocal microscope. The percent of masseter ganglion neurons expressing each receptor was calculated.

Results

Masseter muscle ganglion neurons expressed α1a(29 ± 9%), α1b (34 ± 4%) and α1d (19 ± 13%) adrenergic receptors. Expression of all three α1 receptor subtypes was higher in female rats than in male rats. Expression of α1b receptors was more commonly found on larger diameter masseter ganglion neurons. Overall 11±3% of masseter ganglion neurons expressed the TrpV1 receptor, which suggests they served a nociceptive function. The TrpV1 receptor was co-expressed by about ~10% of α1a and α1b receptor positive masseter ganglion neurons.

Conclusions

Afferent fibers that innervate the masseter muscle express all three α1 adrenergic receptor subtypes. Agonists at the α1 receptor have been previously shown to depolarize trigeminal ganglion neurons, which suggests that activation of these receptors on masseter muscle afferents would be excitatory. The expression of α1 receptors by putative nociceptors that innervate the masseter may permit a direct interaction between the sensory and sympathetic system that contributes to pain in this muscle.

About the article

Published Online: 2017-07-01

Published in Print: 2017-07-01


Citation Information: Scandinavian Journal of Pain, Volume 16, Issue 1, Pages 167–167, ISSN (Online) 1877-8879, ISSN (Print) 1877-8860, DOI: https://doi.org/10.1016/j.sjpain.2017.04.010.

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