Affiliations: Institute of Gerontology, University of Michigan, Ann
Arbor, Michigan, 48109-2007, USA | Department of Biomedical Engineering, University of
Michigan, Ann Arbor, Michigan, 48109-2007, USA | Department of Mechanical Engineering, University of
Michigan, Ann Arbor, Michigan, 48109-2007, USA
Note: [] Corresponding author: John A. Faulkner, Institute of
Gerontology, 300 North Ingalls Building, University of Michigan, Ann Arbor, MI
48109-2007, USA. Tel.: +1 734 764 4378; Fax: +1 734 936 2116; E-mail:
jafaulk@umich.edu
Abstract: Purpose: Denervated skeletal muscles lack contractile activity and
subsequently lose mass and force generation. Prolonged periods of denervation
prior to nerve-implant grafting limit the recovery of mass and force. We
hypothesized that electrical stimulation during a period of denervation that
maintains mass and force above the levels of denervated muscles enhances the
recovery of mass and force following nerve-implant grafting. Methods: The extensor digitorum longus (EDL) muscles of
anesthetized rats were denervated, and a stimulator was implanted. Following 4
or 7 months of denervation, with or without electrical stimulation, the EDL
muscles were removed, evaluated in vitro for mass and contractile
properties, and then nerve-implant grafted into syngeneic rats. Unoperated,
contralateral muscles were also evaluated and grafted. Results: The hypothesis was not supported by the experimental
data. Compared with values for 4- or 7-month denervated muscles, the
stimulated-denervated muscles maintained higher mass and force, less prolonged
time-to-peak tensions and half-relaxation times, and higher excitability.
Nevertheless, the recovery of mass and force following grafting was not
improved. Conclusion: The factors within long-term denervated muscles
that hinder recovery following grafting appear to be related primarily to
factors associated with the duration of denervation and not to the level of
atrophy and weakness prior to grafting.
