Journal of Neuroscience, Vol 8, 3451-3458, Copyright © 1988 by Society for Neuroscience
The location of cues promoting selective reinnervation of axolotl muscles
DJ Wigston and SP Donahue
Department of Physiology, Emory University School of Medicine, Atlanta, Georgia 30322.
The selective reinnervation of muscles suggests that muscles have intrinsic
recognition cues that promote selective synaptogenesis. For example, the
anterior and posterior heads of the axolotl iliotibialis (ILT) muscle are
preferentially reinnervated by their original motoneurons even after
surgically exchanging them. The nature and location of cues that promote
such selectivity are unknown, although previous work suggests that the
muscle fibers themselves might harbor the relevant molecules. To address
this question, we removed anterior and posterior ILT muscles, destroyed
their myofibers by surgically damaging them and treating them with
bupivacaine, and reimplanted them in either a normal or a reversed
anterior/posterior orientation. After the regenerated myofibers became
innervated, we stimulated different spinal nerves and recorded the synaptic
potentials evoked in muscle fibers. Our results showed that if the muscles
were removed, damaged, and reimplanted in their original positions, the
segmental origin of inputs to the regenerated myofibers was similar to that
seen in normal muscles and in muscles reimplanted with their myofibers
intact. However, muscles that were removed and damaged but regenerated in
new positions were innervated differently from normal muscles and from
muscles whose myofibers survived transplantation. Thus, the site at which a
muscle regenerates has an influence on the source of the muscle's
reinnervation. Nevertheless, the innervation of muscles that regenerated
after transplantation to a foreign site was not strictly appropriate for
the new position, but was biased towards the muscle's original innervation
pattern. Therefore, some, but not all, of the cues that reflect the
original identity of the transplanted muscles survive the replacement of
its myofibers.