title: Force deficits in skeletal muscle after delayed reinnervation.
abstract: Using a rat hindlimb model, the authors tested the hypothesis that, in muscles reinnervated after long-term denervation, atrophy-dependent and atrophy-independent mechanisms operate independently to produce force deficits. In adult rats, gastrocnemius muscles were subjected to denervation via tibial nerve transection. Reconstruction of the nerve lesion was delayed for periods ranging from 2 weeks to 1 year. After a minimum recovery period of 6 months after nerve repair, muscle mass and maximum isometric tetanic force were measured and specific force was calculated for each muscle (n = 40 muscles from 23 animals). After recovery, observed deficits in muscle mass and maximum tetanic force were directly proportional to the denervation interval. On the other hand, the deficit in specific force was not proportional to the denervation interval; all groups in which the nerve reconstruction was delayed for a month or longer demonstrated a deficit of 30 percent to 50 percent. These data support our hypothesis that, after prolonged denervation followed by reinnervation, the magnitude of the deficit in whole muscle force does not parallel the deficit in specific force. These data support the idea that mechanisms governing muscle atrophy are independent of those resulting in specific force deficits.
authors.affiliation: Section of Plastic Surgery, Department of Surgery, University of Michigan, 2130 Taubman Health Care Center, Ann Arbor, MI 48190-0340, USA.
authors.forename: Mustafa Asim
authors.initials: MA
authors.lastname: Aydin
authors.forename: Susan E
authors.initials: SE
authors.lastname: Mackinnon
authors.forename: Xiaoa Ming
authors.initials: XM
authors.lastname: Gu
authors.forename: Jun
authors.initials: J
authors.lastname: Kobayashi
authors.forename: William M
authors.initials: WM
authors.lastname: Kuzon
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D006614:Hindlimb; D008297:Male; D009119:Muscle Contraction; D009121:Muscle Denervation; D018482:Muscle, Skeletal / Q000294:innervation* / Q000503:physiopathology*; D009133:Muscular Atrophy / Q000209:etiology / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D013979:Tibial Nerve / Q000601:surgery; D013997:Time Factors