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The Journals of Gerontology Series A: Biological Sciences and Medical Sciences Advance Access published online on February 17, 2009
The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, doi:10.1093/gerona/gln074
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© The Author 2009. Published by Oxford University Press on behalf of the Gerontological Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org.

Functional and Morphological Evidence of Age-Related Denervation in Rat Laryngeal Muscles

Colleen A. McMullen and Francisco H. Andrade

Department of Physiology, University of Kentucky, Lexington

Address correspondence to Colleen A. McMullen, MA, Department of Physiology, University of Kentucky, MS508, 800 Rose Street, Lexington, KY 40536-0298. Email: cmcmu2{at}email.uky.edu


  Abstract

Laryngeal muscle dysfunction compromises voice, swallowing, and airway protection in elderly adults. Laryngeal muscles and their motor neurons and their motor neurons communicate via the neuromuscular junction (NMJ). We tested the hypothesis that aging disrupts NMJ organization and function in the laryngeal thyroarytenoid (TA) and posterior cricoarytenoid (PCA) muscles We determined NMJ density and size and acetylcholine receptor (AChR) subunit mRNAs in TA and PCA muscles from 6-, 18-, and 30- month old-rats. NMJ function was determined with tubocurarine (TC) and contractions during nerve and muscle stimulation. NMJ size, abundance, and clustering decreased in 30-month TA and PCA muscles. AChRe mTNA and protein increased with age in both muscles. AChRg mRNA increased with age in both muscles while protein content increased in TA only. Aging PCA and TA were more sensitive to TC, demonstrating functional evidence of denervation. These results demonstrate that NMJs become smaller and less abundant in aging TA and PCA muscles.

Keywords Larynx; Aging; Neuromuscular junction

Received: December 15, 2008; Accepted: December 15, 2008

Decision Editor: Huber R. Warner, PhD


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