Abstract
The trivalent rare earth lanthanum was substituted for calcium in the sea water bathing the exterior of an "artificial node" of a lobster axon in a sucrose gap. It caused a progressive rise in threshold, and a decrease in the height of the action potential as well as in its rates of rise and fall. Prolonged application produced an excitation block. Voltage-clamp studies of the ionic currents showed that the time courses of the ionic conductance changes for both sodium and potassium were increased. Concurrently, the potentials at which the conductance increases occurred were shifted to more positive inside values for the La+++ sea water. These effects resemble changes resulting from a high external calcium concentration. Over and above this, La+++ also causes a marked reduction in the maximum amount of conductance increase following a depolarizing potential step. Membrane action potentials similar to those observed experimentally in the La+++ solution have been computed with appropriate parameter changes in the Hodgkin-Huxley equations.
Full Text
The Full Text of this article is available as a PDF (582.3 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Blaustein M. P., Goldman D. E. Competitive action of calcium and procaine on lobster axon. A study of the mechanism of action of certain local anesthetics. J Gen Physiol. 1966 May;49(5):1043–1063. doi: 10.1085/jgp.49.5.1043. [DOI] [PMC free article] [PubMed] [Google Scholar]
- FRANKENHAEUSER B. The effect of calcium on the myelinated nerve fibre. J Physiol. 1957 Jul 11;137(2):245–260. doi: 10.1113/jphysiol.1957.sp005809. [DOI] [PMC free article] [PubMed] [Google Scholar]
- JULIAN F. J., MOORE J. W., GOLDMAN D. E. Current-voltage relations in the lobster giant axon membrane under voltage clamp conditions. J Gen Physiol. 1962 Jul;45:1217–1238. doi: 10.1085/jgp.45.6.1217. [DOI] [PMC free article] [PubMed] [Google Scholar]
- JULIAN F. J., MOORE J. W., GOLDMAN D. E. Membrane potentials of the lobster giant axon obtained by use of the sucrose-gap technique. J Gen Physiol. 1962 Jul;45:1195–1216. doi: 10.1085/jgp.45.6.1195. [DOI] [PMC free article] [PubMed] [Google Scholar]
- LETTVIN J. Y., PICKARD W. F., MCCULLOCH W. S., PITTS W. A THEORY OF PASSIVE ION FLUX THROUGH AXON MEMBRANES. Nature. 1964 Jun 27;202:1338–1339. doi: 10.1038/2021338a0. [DOI] [PubMed] [Google Scholar]
- WEIDMANN S. Effects of calcium ions and local anesthetics on electrical properties of Purkinje fibres. J Physiol. 1955 Sep 28;129(3):568–582. doi: 10.1113/jphysiol.1955.sp005379. [DOI] [PMC free article] [PubMed] [Google Scholar]