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 language | English (US) |
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Pages (from-to) | 105-114 |
Number of pages | 10 |
Journal | Journal of Membrane Biology |
Volume | 131 |
Issue number | 2 |
DOIs | |
State | Published - Jan 1 1993 |
Keywords
- Na inactivation
- laser-induced hyperthermia ion channel
- myelinated nerve
- node of Ranvier
- thermal damage
ASJC Scopus subject areas
- Biophysics
- Physiology
- Cell Biology