Dl. Bishop et Rl. Milton, THE EFFECTS OF DENERVATION LOCATION ON FIBER-TYPE MIX IN SELF-REINNERVATED MOUSE SOLEUS MUSCLES, Experimental neurology, 147(1), 1997, pp. 151-158
Mouse soleus muscles were denervated by crushing the soleus nerve wher
e it enters the muscle to determine if denervation followed by self-re
innervation can permanently alter the mix of fiber types in a muscle.
Reinnervated and contralateral control muscles were sectioned at 2 and
7 months postdenervation and histochemically stained for myosin ATPas
e to determine the percentages of fast and slow twitch fibers in the m
uscles. It was found that, at both 2 and 7 months postdenervation, rei
nnervated muscles had a significantly higher percentage of slow twitch
fibers than did contralateral control muscles (86.7 versus 67.8% at 2
months and 90.0 versus 69.3% at 7 months). Soleus muscles were also d
enervated by crushing the soleus nerve where it exits the gastrocnemiu
s muscle (approximately 4 mm proximal to where the nerve enters the so
leus muscle) to ascertain if the location of the nerve lesion plays a
role in the ultimate outcome of the process of self-reinnervation. Rei
nnervated muscles and their contralateral muscles were sectioned at 2
months postdenervation and histochemically stained for myosin ATPase a
s before. It was found that, in contrast to muscles denervated at the
point of nerve entry, muscles denervated 4 mm more proximal exhibited
only a small increase in their percentage of slow twitch fibers which
was not statistically significant (71.4 versus 68.4%). These results s
uggest that denervation followed by self-reinnervation can cause a per
manent change in a muscle's fiber type mix and that the location of th
e nerve lesion strongly influences the final outcome of the reinnervat
ion process. (C) 1997 Academic Press.