Metabolic substrates other than glucose support axon function in central white matter.
We tested the hypothesis that non-glucose energy sources can support axon function in the rat optic nerve. Axon function was assessed by monitoring the stimulus-evoked compound action potential (CAP). CAP was maintained at full amplitude for 2 hr in 10 mM glucose. 20 mM lactate, 20 mM pyruvate, 10 mM fructose, or 10 mM mannose supported axon function as effectively as did glucose, and 10 mM glutamine provided partial support, but beta-hydroxybutyrate, octanoate, sorbitol, alanine, aspartate, and glutamate failed to support axon function. Our results indicated that a variety of compounds can sustain function in CNS myelinated axons. Axons probably use lactate, pyruvate, and glutamine directly as energy substrates, whereas mannose and fructose could be shuttled through astrocytes to lactate, which is then exported to axons.
Brown
A M
AM
Department of Neurology, Box 356465, University of Washington School of Medicine, Seattle, WA 98195, USA. ambrown@u.washington.edu
Wender
R
R
Ransom
B R
BR
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000596:Amino Acids / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000378:metabolism*; D002264:Carboxylic Acids / Q000378:metabolism* / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002490:Central Nervous System / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology*; D005947:Glucose / Q000378:metabolism; D009005:Monosaccharides / Q000378:metabolism* / Q000494:pharmacology; D009413:Nerve Fibers, Myelinated / Q000187:drug effects / Q000378:metabolism*; D009900:Optic Nerve; D051381:Rats; D020318:Rats, Long-Evans
D000596:Amino Acids; D002264:Carboxylic Acids; D009005:Monosaccharides; D005947:Glucose