Effects of laser-induced hyperthermia treatment on ionic permeability of myelinated nerve

Shien-Fong Lin*, Chau H. Wu, William Z. Rymer

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

The effect of laser-induced hyperthermia on the ionic permeability of nerve membranes was studied using the nodes of Ranvier in amphibian myelinated nerve as a model. To effect a photothermal modification of nerve membrane functions, con trolled laser irradiation consisting of a 5-sec thermal pulse was applied to the nodal membrane, increasing the temperature to a maximum of 48-58°C at the node. Major electrophysiological changes observed in the nodal membrane following laser-induced hyperthermia were a differential reduction of the sodium and potassium permeability, an increase in the leakage current, and a negative shift on the potential axis of the steady-state Na inactivation. There was no significant change in the kinetics of ion channel activation and inactivation for treatments below 56°C. The results suggest that a primary photothermal damage mecha nism at temperatures below 56°C could be a reduction in the number of active Na channels in the node, rather than a change in individual channel kinetics, or in the properties of the lipid bilayer of intervening nerve membrane. A differential heat sensi tivity between the noninactivated and the inactivated Na channels is also suggested. For the treatments of 56°C and above, a signifi cant increase of membrane leakage current suggests an irrevers ible thermal damage to the lipid bilayer.

Original languageEnglish
Pages (from-to)105-114
Number of pages10
JournalJournal of Membrane Biology
Volume131
Issue number2
DOIs
StatePublished - 1 Jan 1993

Keywords

  • laser-induced hyperthermia ion channel
  • myelinated nerve
  • Na inactivation
  • node of Ranvier
  • thermal damage

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