Journal of Neuroscience, Vol 15, 6137-6144, Copyright © 1995 by Society for Neuroscience
Long-term maintenance of presynaptic function in the absence of target muscle fibers
A Dunaevsky and EA Connor
Department of Biology, University of Massachusetts, Amherst 01003, USA.
Here we have investigated the role of the muscle fiber in the maintenance
of presynaptic function at frog motor nerve terminals. Muscle fibers were
selectively damaged and prevented from regenerating while leaving the motor
innervation intact. Presynaptic activity of the resulting target-deprived
nerve terminals was assayed using the fluorescent dye, FM1-43. FM1-43
stains nerve terminals in an activity- dependent fashion in that it
incorporates into synaptic vesicles and can be released upon stimulation.
We demonstrate that nerve terminals permanently deprived of target for 1 to
5 months maintain the ability to release and recycle synaptic vesicles in
response to stimulation. The level of presynaptic function of
target-deprived nerve terminals was not detectably different from that of
nerve terminals in contact with muscle fibers. The remarkable maintenance
of presynaptic function in these target-deprived nerve terminals indicates
that the molecular machinery required for vesicular release is maintained
in a functional state for long periods without target muscle fibers.
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