Journal of Neuroscience, Vol 2, 633-646, Copyright © 1982 by Society for Neuroscience
Influence of nerve on the formation and survival of acetylcholine receptor and cholinesterase patches on embryonic Xenopus muscle cells in culture
F Moody-Corbett and MW Cohen
Embryonic Xenopus muscle cells grown in culture develop discrete patches of
high acetylcholine receptor (AChR) density. By following identified muscle
cells after staining with fluorescent alpha- bungarotoxin, we have found
that many of these AChR patches survive in a fixed position for several
days. For AChR patches on the lower surface of the cell (the surface
apposed to the culture dish), more than 60% of those which were followed
beginning on day 2 survived for a further 4 days. The survival rate was
greater when patches were followed from day 3 or later and was almost as
high for AChR patches on the upper surface. New AChR patches also formed on
all of the muscle cells. When muscle cells were cultured together with
spinal cord cells, nerve-muscle contacts developed with a characteristic
localization of AChRs along the path of contact. AChR patches did not form
elsewhere on these contacted cells. Nerve-contacted muscle cells examined 2
to 3 days after adding spinal cord cells to established (2- to 5-day-old)
muscle cultures also exhibited a marked reduction of AChR patches away from
the site of contact. This reduction was not due to the nerve having
contacted pre-existing AChR patches. Rather, the findings indicate that
contact by an appropriate nerve inhibits the formation of AChR patches
elsewhere on the contracted muscle cells and reduces the survival of
pre-existing AChR patches. Nerve contact also inhibited the formation of
cholinesterase (ChE) patches remote from the site of contact and appeared
to cause some reduction in the survival of pre- existing ChE patches.
Spontaneous twitching was not observed in these experiments, thereby
indicating that the remote effects of nerve contact were not mediated by
muscle action potentials or contraction. Such remote influences of the
nerve may play a role in determining the pattern of innervation on
individual muscle cells.
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