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[Ciguatoxins and brevetoxins: dissection of the neurobiological actions].
J Soc Biol. 1999; 193(3):329-44.JS

Abstract

This review focuses on the neurobiological actions of ciguatoxins and brevetoxins which are phycotoxins produced respectively by the dinoflagellates Gambierdiscus toxicus and Ptychodiscus brevis. These actions are illustrated in particular by the effects of the toxins on myelinated nerve fibres and on skeletal neuromuscular junctions of vertebrates. Ciguatoxins and brevetoxins, through different vectors, are responsible for human intoxications characterized mainly by neurological disturbances. The molecular target of these families of lipid-soluble cyclic polyethers is the voltage-gated sodium channel, a fundamental transmembrane protein involved in cellular excitability. The different toxins share a common binding site (the receptor-site 5) located on the alpha sub-unit of this neuronal transmembrane protein. Electrophysiological studies of the mode of action of ciguatoxins and brevetoxins identify these toxins as specific sodium channel activators. Indeed, during the action of these phycotoxins, sodium channels remain permanently opened, at the resting membrane potential, which produces a continuous entry of sodium ions in most excitable cells. Such a sodium entry has various consequences on sodium-dependent physiological mechanisms, consisting in a membrane depolarization which, in turn, causes spontaneous and/or repetitive action potential discharges and thereby increases membrane excitability. These neuronal discharges may be transient or continuous according to the preparation and the toxin tested. The increase in membrane excitability during the action of ciguatoxins and brevetoxins is responsible for the different effects exerted by these toxins on various chemical synapses and secretory cells. Another consequence of the continuous entry of sodium ions into cells was revealed using confocal laser scanning microscopy and vital staining of plasma membranes with the fluorescent dye FM1-43. These techniques made feasible the dynamic study of morphological alterations produced by ciguatoxins and brevetoxins on various cellular preparations in situ. Thus, it has been possible to bring to the fore that these phycotoxins cause a marked increase in the volume of nodes of Ranvier of myelinated nerve fibres, motor nerve terminals innervating skeletal muscle and perisynaptic non-myelinating Schwann cell somata. This increase could be reversed by hyperosmotic external solutions and completely prevented by the blockade of voltage-gated sodium channels. The mechanisms involved in the increase in cellular volume, during the action of ciguatoxins and brevetoxins, are discussed.

Authors+Show Affiliations

Laboratoire de Neurobiologie Cellulaire et Moléculaire, UPR 9040, CNRS, Gif-sur-Yvette, France.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

English Abstract
Journal Article
Research Support, Non-U.S. Gov't
Review

Language

fre

PubMed ID

10542966

Citation

Mattei, C, et al. "[Ciguatoxins and Brevetoxins: Dissection of the Neurobiological Actions]." Journal De La Societe De Biologie, vol. 193, no. 3, 1999, pp. 329-44.
Mattei C, Molgó J, Legrand AM, et al. [Ciguatoxins and brevetoxins: dissection of the neurobiological actions]. J Soc Biol. 1999;193(3):329-44.
Mattei, C., Molgó, J., Legrand, A. M., & Benoit, E. (1999). [Ciguatoxins and brevetoxins: dissection of the neurobiological actions]. Journal De La Societe De Biologie, 193(3), 329-44.
Mattei C, et al. [Ciguatoxins and Brevetoxins: Dissection of the Neurobiological Actions]. J Soc Biol. 1999;193(3):329-44. PubMed PMID: 10542966.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - [Ciguatoxins and brevetoxins: dissection of the neurobiological actions]. AU - Mattei,C, AU - Molgó,J, AU - Legrand,A M, AU - Benoit,E, PY - 1999/10/30/pubmed PY - 1999/10/30/medline PY - 1999/10/30/entrez SP - 329 EP - 44 JF - Journal de la Societe de biologie JO - J Soc Biol VL - 193 IS - 3 N2 - This review focuses on the neurobiological actions of ciguatoxins and brevetoxins which are phycotoxins produced respectively by the dinoflagellates Gambierdiscus toxicus and Ptychodiscus brevis. These actions are illustrated in particular by the effects of the toxins on myelinated nerve fibres and on skeletal neuromuscular junctions of vertebrates. Ciguatoxins and brevetoxins, through different vectors, are responsible for human intoxications characterized mainly by neurological disturbances. The molecular target of these families of lipid-soluble cyclic polyethers is the voltage-gated sodium channel, a fundamental transmembrane protein involved in cellular excitability. The different toxins share a common binding site (the receptor-site 5) located on the alpha sub-unit of this neuronal transmembrane protein. Electrophysiological studies of the mode of action of ciguatoxins and brevetoxins identify these toxins as specific sodium channel activators. Indeed, during the action of these phycotoxins, sodium channels remain permanently opened, at the resting membrane potential, which produces a continuous entry of sodium ions in most excitable cells. Such a sodium entry has various consequences on sodium-dependent physiological mechanisms, consisting in a membrane depolarization which, in turn, causes spontaneous and/or repetitive action potential discharges and thereby increases membrane excitability. These neuronal discharges may be transient or continuous according to the preparation and the toxin tested. The increase in membrane excitability during the action of ciguatoxins and brevetoxins is responsible for the different effects exerted by these toxins on various chemical synapses and secretory cells. Another consequence of the continuous entry of sodium ions into cells was revealed using confocal laser scanning microscopy and vital staining of plasma membranes with the fluorescent dye FM1-43. These techniques made feasible the dynamic study of morphological alterations produced by ciguatoxins and brevetoxins on various cellular preparations in situ. Thus, it has been possible to bring to the fore that these phycotoxins cause a marked increase in the volume of nodes of Ranvier of myelinated nerve fibres, motor nerve terminals innervating skeletal muscle and perisynaptic non-myelinating Schwann cell somata. This increase could be reversed by hyperosmotic external solutions and completely prevented by the blockade of voltage-gated sodium channels. The mechanisms involved in the increase in cellular volume, during the action of ciguatoxins and brevetoxins, are discussed. SN - 1295-0661 UR - https://www.unboundmedicine.com/medline/citation/10542966/[Ciguatoxins_and_brevetoxins:_dissection_of_the_neurobiological_actions]_ DB - PRIME DP - Unbound Medicine ER -