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. 1989 Feb;86(4):1406–1410. doi: 10.1073/pnas.86.4.1406

Low density of sodium channels supports action potential conduction in axons of neonatal rat optic nerve.

S G Waxman 1, J A Black 1, J D Kocsis 1, J M Ritchie 1
PMCID: PMC286700  PMID: 2537496

Abstract

The density of sodium channels in premyelinated axons was estimated from measurements of the binding of [3H]saxitoxin to neonatal rat optic nerve. The maximum saturable binding capacity of the nerve was 16.2 +/- 1.2 fmol/mg of wet weight, with an equilibrium dissociation constant of 0.88 +/- 0.18 nM (mean +/- SEM). These values correspond to a high-affinity saxitoxin-binding site density of approximately 2/microns 2 within premyelinated axon membrane. Action potential propagation in neonatal rat optic nerve is completely blocked by 5 nM saxitoxin, indicating that action potential electrogenesis is mediated by channels that correspond to high-affinity saxitoxin-binding sites. These results demonstrate that action potential conduction is supported by a low density of sodium channels in this system. Since the internodal axon membrane of myelinated fibers may contain a low density of sodium channels, it is possible that restoration of conduction in some demyelinated fibers may not require additional sodium channel incorporation into the demyelinated axon membrane.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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