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TitleNeuromuscular adaptations to cross-reinnervation in 12- and 29-mo-old Fischer 344 rats.
Publication TypeJournal Article
Year of Publication1991
AuthorsClark, K. I., & White T. P.
JournalThe American journal of physiology
Volume260
Issue1 Pt 1
PaginationC96-103
Date Published1991 Jan
ISSN Number0002-9513
KeywordsAging, Animals, Male, Motor Endplate, Muscle Denervation, Muscle Development, Muscles, Myosins, Nerve Endings, Rats, Rats, Inbred F344, Reference Values, Regeneration
Abstract

The aim was to test hypotheses regarding the adaptive response of the extensor digitorum longus (EDL) muscle of 12- and 29-mo rats following denervation and cross-reinnervation by the soleus nerve. The mass of cross-reinnervated EDL muscle was 87 and 86% of self-reinnervated control values in 12-mo (99 +/- 3 mg) and 29-mo (74 +/- 3 mg) rats, respectively. Cross-reinnervated EDL fiber area was 56 and 67% of self-reinnervated values in 12-mo (1,733 +/- 253 microns 2) and 29-mo (1,264 +/- 71 microns 2) rats, respectively. Cross-reinnervation increased the density of neural contact 26% in 12-mo rats and decreased density by 50% in 29-mo animals. In 12-mo rats 17% of motor end plates (MEP) were void of terminal nerves following cross-reinnervation compared with 48% in 29-mo rats. In cross-reinnervated muscles, slow myosin heavy chain (MHC) was 65 +/- 9 and 25 +/- 3% of total MHC in 12- and 29-mo rats, respectively. The percentage of type I fibers derived histochemically was 65 +/- 8% in 12-mo rats and 18 +/- 1% in 29-mo rats. In conclusion, there is an age-associated decrease in the ability of neurons to reinnervate the MEP area after nerve section. The conversion of fiber type in innervated fibers in response to cross-reinnervation may not differ due to age.

Alternate JournalAm. J. Physiol.

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