title: Recovery and loss of muscle force of rat plantaris after partial denervation.
abstract: The isometric contractile characteristics of rat plantaris muscles were assessed 1, 3, 6, 9, and 12 months after resection of the L4 radicular nerve. After 1 month of partial denervation, twitch and tetanus were significantly lower (26.1 and 22.1%, respectively) than those of sham-operated rats. Plantaris muscle weight was reduced (22.5%), but twitch-to-tetanus ratio (TW/TT), time-to-peak, and one-half relaxation time were not changed significantly. At 3 months, average twitch force was normal but average tetanic force was significantly lower (27.1%) than control value. Muscle weight was reduced (28.9%), but TW/TT was increased by 31%. After 6 months, twitch, tetanus, and all other variables were similar to those of control rats. Normal twitch at 3 months indicates that all muscle fibers have been reinnervated by sprouting from L5 motor axons; however, the new synaptic contacts may not support the tetanic response. At 9 months, muscle force was again reduced and remained at about the same level at the 12-month interval. These results are consistent with the recovery and loss of function seen in poliomyelitis and the postpolio syndrome.
authors.affiliation: Department of Rehabilitation Medicine, New York University Medical Center, New York 10016.
authors.forename: A
authors.initials: A
authors.lastname: Eberstein
authors.forename: B R
authors.initials: BR
authors.lastname: Pachter
mesh_terms: D000818:Animals; D003714:Denervation; D008297:Male; D009119:Muscle Contraction; D009132:Muscles / Q000294:innervation / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains