Regional distribution of slow-twitch muscle fibers after reinnervation in adult rat hindlimb muscles.
In adult rats, the sciatic nerve was unilaterally sectioned and reunited above the knee. Following a survival time of 21 weeks, five muscles were removed from both lower hindlimbs after determining their intra-limb positions. In each muscle, cryostat sections from seven equidistant proximo-distal levels were stained for myofibrillar ATPase. Intramuscular positions were determined for all slow-twitch type I fibers. Within each muscle, type I fibers were heterogeneously distributed, and the direction of type I fiber accumulation was, on average, almost identical in reinnervated muscles and contralateral controls. Furthermore, as in controls, a proximo-distal decline of type I fiber density was found in reinnervated muscles. Compared to contralateral controls, reinnervated muscles consistently showed a very high number of type I fibers at close interfiber distances, indicating respecification of muscle fiber types by the ingrowing nerve fibers. The results suggest that slow-twitch motor axons preferentially grew back toward the original slow-twitch muscle regions.
Department of Medical Physiology, University of Groningen, Groningen, The Netherlands. lcwang@sci.kun.nl
Liangchun
L
Wang
Sjef
S
Copray
Nieske
N
Brouwer
Marcel F
MF
Meek
Daniel
D
Kernell
D019412:Anatomy, Cross-Sectional; D000818:Animals; D006614:Hindlimb; D008297:Male; D018657:Muscle Fibers, Slow-Twitch / Q000145:classification / Q000502:physiology; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000294:innervation* / Q000502:physiology; D009416:Nerve Regeneration / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012584:Sciatic Nerve / Q000502:physiology