Contractile properties and myosin heavy chain composition of rat tongue retrusor musculature show changes in early adulthood after 19 days of artificial rearing

Departments of 1 Anatomy and Neurobiology and 2 Physical Therapy, Virginia Commonwealth University, Richmond, Virginia Submitted 10 January 2006 ; accepted in final form 20 June 2006 Previously, we showed that artificial rearing using the "pup in a cup" model results in decreased tongue ac...

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Bibliographic Details
Published in:Journal of applied physiology (1985) 2006-10, Vol.101 (4), p.1053-1059
Main Authors: Smith, J. Chadwick, Moore, W. Allen, Goldberg, Stephen J, Shall, Mary S
Format: Article
Language:English
Subjects:
Animal Husbandry - methods
Animals
Animals, Newborn
Animals, Suckling - physiology
Biological and medical sciences
Changes
Electromyography
Enteral Nutrition - methods
Fundamental and applied biological sciences. Psychology
Muscle Contraction - physiology
Muscle, Skeletal - chemistry
Muscle, Skeletal - physiology
Muscular system
Myosin Heavy Chains - analysis
Protein Isoforms - analysis
Rats
Rats, Sprague-Dawley
Rodents
Sucking Behavior - physiology
Tongue
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Summary:Departments of 1 Anatomy and Neurobiology and 2 Physical Therapy, Virginia Commonwealth University, Richmond, Virginia Submitted 10 January 2006 ; accepted in final form 20 June 2006 Previously, we showed that artificial rearing using the "pup in a cup" model results in decreased tongue activity and caused some minor alterations in the tongue retrusor musculature. However, the artificial rearing time frame previously chosen was brief (11 days). The purpose of the present investigation was to extend the artificial rearing period from postnatal days 3 to 21 (P21) to determine whether significant alterations occur as a result of this reduced tongue use. Several changes in contractile properties due to the artificial rearing process were observed, which fully recovered by postnatal days 41 to 42 (P41–2). These changes included a shorter twitch contraction time, shorter twitch half-relaxation time, and decreased fatigue resistance. Styloglossus muscle exhibited more neonatal myosin heavy chain (MHC) isoform at P21 for the artificially reared (AR) group. Changes that were persistent at P41–2 were also observed. Maximum tetanic tension was lower for the AR group at P21 and P41–2 compared with their dam-reared counterparts. Twitch tension was also lower by P41–2 in the AR group. At P41–2, the AR group exhibited an increase in MHC IIa and a decrease in MHC IIb for the styloglossus muscle. In addition, the AR group exhibited a decreased MHC IIb for the long head of the biceps brachii at P41–2. Our results are similar to other models of hindlimb immobilization and suspension. By extending our artificial rearing period, this reduced tongue activity induced acute changes and alterations in the tongue retrusor musculature that persisted into early adulthood. brain stem; hypoglossal nerve; percutaneous endoscopic gastrostomy tube Address for reprint requests and other correspondence: C. Smith, Dept. of Anatomy and Neurobiology, Virginia Commonwealth Univ., P.O. Box 980709, Richmond, VA 23298-0709 (e-mail: jcsmith{at}vcu.edu )
ISSN:8750-7587
1522-1601
DOI:10.1152/japplphysiol.00029.2006