Effects of age and nerve-repair grafts on reinnervation and fiber type distribution of rat medial gastrocnemius muscles.
Aging is associated with a decline in skeletal muscle function. Previous research suggests that this decline in skeletal muscle function may, in part, be explained by an age-associated decline in the ability of skeletal muscle to reinnervate and/or age-associated changes in fiber types and distribution during reinnervation. This study used a nerve-repair graft model to investigate age-associated changes in the ability to reinnervate via expression of neural cell adhesion molecule (NCAM), a marker of denervated and recently reinnervated muscle fibers and changes in fiber type and Type I fiber grouping in medial gastrocnemius (MG) muscles of 6-, 12- and 24-month-old male Fischer 344 rats. Age had no effect on total MG muscle fiber number. Aging and nerve-repair grafting led to an increase in percent Type I and a decrease in percent Type IIB fibers. Aging and nerve-repair grafting led to an increase in NCAM positive fibers and an increase in the percentage of enclosed Type I muscle fibers, which was greatest in the 24 month nerve-repair grafted group. Thus, we conclude that diminished contractile function of aged and/or nerve-repair grafted MG muscle may be explained, in part, by an increase in the percentage of denervated fibers.
Department of Internal Medicine, Division of Geriatric Medicine, University of Michigan, Ann Arbor 48109-2007, USA. llarkin@umich.edu
Lisa M
LM
Larkin
William M
WM
Kuzon
Jeffrey B
JB
Halter
D000375:Aging / Q000502:physiology*; D000818:Animals; D008297:Male; D009121:Muscle Denervation; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology; D009412:Nerve Fibers / Q000502:physiology; D009416:Nerve Regeneration / Q000502:physiology*; D019006:Neural Cell Adhesion Molecules / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344
D019006:Neural Cell Adhesion Molecules