Denervation elicits profound alterations in the morphometry of skeletal muscle. These
alterations include changes in fiber type composition as well as reductions in fiber
size. There is evidence that the increased mechanical load placed upon muscle via
rhythmic stretching attenuates denervation induced alterations in muscle morphology.
The purpose of the present study was to determine whether the mechanical stimuli associated
with exercise training, i.e. rhythmic stretching and mechanical loading, would effectively
moderate the changes in muscle morphometry observed following denervation. Unilateral
denervation of the soleus muscle of eight male Sprague-Dawley rats was performed under
aseptic conditions. The animals were then randomly assigned to two groups: sedentary
controls and exercise trained. The exercise training protocol featured treadmill running
five days per week for six weeks. At the conclusion of the experimental period, animals,
from both groups were sacrificed and soleus muscles were histochemically analyzed
for muscle morphometry. Results demonstrated that denervation caused marked alterations
in fiber type profile and in fiber cross-sectional areas. Interestingly, the degree
of denervation induced atrophy appeared to be fiber type specific. However, the data
presented here indicate that in denervated soleus muscles there were no significant
differences in fiber type composition or fiber size between the sedentary and exercise
trained groups. Hence, it appears that the mechanical stimuli provided by treadmill
running of moderate intensity and duration are not sufficiently potent to ameliorate
muscle morphometric responses to denervation.
Key words
Soleus - atrophy - ATPase - histology
