Differences in Age-Related Alterations in Muscle Contraction Properties in Rat Tongue and Hindlimb Purpose Because of differences in muscle architecture and biomechanics, the purpose of this study was to determine whether muscle contractile properties of rat hindlimb and tongue were differentially affected by aging. Method Deep peroneal and hypoglossal nerves were stimulated in 6 young and 7 old Fischer 344-Brown Norway ... Research Article
Research Article  |   August 01, 2008
Differences in Age-Related Alterations in Muscle Contraction Properties in Rat Tongue and Hindlimb
 
Author Affiliations & Notes
  • Nadine P. Connor
    University of Wisconsin–Madison
  • Fumikazu Ota
    Jikei University, Tokyo, Japan
  • Hiromi Nagai
    Kitasato University, Kanagawa, Japan
  • John A. Russell
    University of Wisconsin–Madison
  • Glen Leverson
    University of Wisconsin–Madison
  • Contact author: Nadine P. Connor, University of Wisconsin Clinical Science Center, Room K4/711, 600 Highland Avenue, Madison, WI 53792-7375. E-mail: connor@surgery.wisc.edu.
Article Information
Swallowing, Dysphagia & Feeding Disorders / Special Populations / Older Adults & Aging / Research Issues, Methods & Evidence-Based Practice / Speech / Research Articles
Research Article   |   August 01, 2008
Differences in Age-Related Alterations in Muscle Contraction Properties in Rat Tongue and Hindlimb
Journal of Speech, Language, and Hearing Research, August 2008, Vol. 51, 818-827. doi:10.1044/1092-4388(2008/059)
History: Received November 10, 2006 , Revised June 28, 2007 , Accepted September 28, 2007
 
Journal of Speech, Language, and Hearing Research, August 2008, Vol. 51, 818-827. doi:10.1044/1092-4388(2008/059)
History: Received November 10, 2006; Revised June 28, 2007; Accepted September 28, 2007
Web of Science® Times Cited: 12

Purpose Because of differences in muscle architecture and biomechanics, the purpose of this study was to determine whether muscle contractile properties of rat hindlimb and tongue were differentially affected by aging.

Method Deep peroneal and hypoglossal nerves were stimulated in 6 young and 7 old Fischer 344-Brown Norway rats to allow recording of muscle contractile properties of tongue and extensor digitorum longus (EDL) muscle in the hindlimb. In the same animals, the following measurements were made: (a) twitch contraction time (CT; in milliseconds), (b) half decay time (HDT; in milliseconds), (c) maximum twitch force (in grams), (d) tetanic force, and (e) fatigue index determined from repetitive stimulation of the muscles.

Results No significant differences were observed in young versus old groups in retrusive tongue forces, whereas a significant (p < .05) decrement in EDL tetanic forces was found in old rats. Slower CT in old rats was observed only in the tongue. Old and young groups were not significantly different in fatigue index or HDT for tongue or EDL.

Conclusions Old animals generated equivalent maximum tongue forces with stimulation, but they were slower in achieving these forces than young animals. Limb and cranial muscles were not affected equally by aging. As such, information derived from limb muscle studies may not easily generalize to the cranial motor system.

Acknowledgment
This study was partially supported by Grants R01DC005935 and R01DC008149 from the National Institute on Deafness and Other Communication Disorders. We gratefully acknowledge the assistance of Jack Jiang, who provided us with a computer program for making our force measurements.
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