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A bioenergetic basis for peripheral nerve fiber dissociation.
Raymond B Fink1, Andrew M Cairns
1Department of Anesthesiology, University of Washington School of Medicine, Seattle, Wash. 98195 U.S.A.
Pain
|April 1, 1982
Summary
Resting large myelinated (A) fibers in peripheral nerves require more energy than small unmyelinated (C) fibers. This suggests energy deprivation may cause selective large fiber destruction in chronic pain conditions.
Area of Science:
- Neuroscience
- Cellular Physiology
- Peripheral Nerve Biology
Background:
- The selective vulnerability of myelinated axons in peripheral nerve lesions is not fully understood.
- This vulnerability appears to contradict the energy efficiency of saltatory conduction in these fibers.
Purpose of the Study:
- To evaluate the relative energy requirements of resting A and C fibers in rabbit vagus nerve.
- To determine the impact of glucose availability on nerve fiber function and survival.
Main Methods:
- Measurement of compound action potential components in rabbit vagus nerve segments.
- Incubation in varying glucose concentrations (0-20 mM) with and without the perineurial sheath.
- Assessment of fiber recovery after glucose reintroduction.
Main Results:
- Resting A fibers showed a rapid decline in amplitude with glucose concentrations below 5 mM, while C fibers maintained amplitude down to 2 mM (intact sheath) or 0.5 mM (desheathed).
- A fibers were significantly more susceptible to energy deprivation (low glucose) than C fibers in vitro.
- Partial recovery of nerve potentials was more rapid and complete in C fibers compared to A fibers.
Conclusions:
- Resting A fibers have a substantially higher energy demand than resting C fibers.
- Energy deprivation is a likely factor contributing to the preferential destruction of large fibers (fiber dissociation) observed in chronic pain syndromes.