The Journal of Neuroscience, July 15, 2002, 22(14):5808-5812
BRIEF COMMUNICATION
Altered Electromyographic Activity Pattern of Rat Soleus Muscle
Transposed into the Bed of Antagonist Muscle
Urszula
Slawinska and
Stefan
Kasicki
Neurophysiology Department, Nencki Institute of Experimental
Biology, 02-093 Warsaw, Poland
Human patients suffering from motor paralysis of the leg can learn,
to some extent, how to use the transposed antagonistic muscle in place
of the damaged or ineffective muscle. Experiments on animals showed
opposite results, although in a few experiments the functional
reorganization of the activity of the transposed muscle was not
excluded. In our experiments, we performed transposition of the soleus
(Sol) with a preserved innervation into the bed of the removed extensor
digitorum longus (EDL) in 6-d-old pups and 3-month-old rats. The
locomotor and reflex EMG activity of the transposed Sol (trSol) was
recorded in chronic experiments 3-4 months later. Our results showed
that the EMG activity of the Sol might be modified when the muscle is
transposed into the bed of the antagonistic muscle EDL. The
modification consisted of an additional burst of activity during the
swing phase and of reflex response of the muscle to the plantar
flexion. This modification was present in all animals operated on at
6 d of age and in two of six adults. After chronic experiments, we
excluded the possibility that the flexor-like activity was induced by
additional innervation of the trSol by the cut end of the EDL nerve.
We suggest that the observed modifications of activity of trSol might
be caused by readjustment of the spinal network organization to the new
functional demands. Two factors might be responsible for this readjustment: the immaturity of the nervous system at the
moment of surgery and preserved afferent innervation
of the transposed muscle.
Key words:
muscle transposition; change of EMG activity; development; chronic EMG; locomotor EMG pattern; rat
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