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Abstract
Axonal transport of neurotransmitter receptors is a well established phenomenon. In
this study, we sought to determine whether the cellular components necessary for mechanical-to-electrical
transduction in primary afferents are also conveyed to the peripheral terminals via
fast axonal transport. In previous studies, severed cutaneous nerves have been shown
to develop mechanical sensitivity at their ligated ends within hours of injury. Since
the rate of development of this mechanical sensitivity was temperature dependent,
we postulated that axonal transport was involved. In this study, we performed two
experiments in which the rate of axonal transport was modified. In the first experiment,
the nerve was cut at a proximal site to block the supply of additional transported
components to the distal end of the nerve. At a point 80 to 120 mm distal to this
proximal cut, a nerve crush and ligation were performed either 3 or 12 h after the
proximal nerve ligation. The centripetally conducted action potentials generated by
applying mechanical stimuli to the nerve subjacent to the distal ligature were recorded
10 h after the distal ligature was placed. Given a fast axonal transport rate of 400
mm/day, transported molecules should traverse a 100-mm segment within 6 h. Consistent
with this calculation, 29% of the myelinated fibers responded to mechanical stimuli
when the time lapse between lesions was 3 h, whereas only 3% responded when the time
between lesions was 12 h. In the second experiment, axonal transport was enhanced
by a prior nerve injury (conditioning lesion).(ABSTRACT TRUNCATED AT 250 WORDS)