Neurotoxins targetting receptor site 5 of voltage-dependent sodium channels increase the nodal volume of myelinated axons - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Neuroscience Research Année : 1999

Neurotoxins targetting receptor site 5 of voltage-dependent sodium channels increase the nodal volume of myelinated axons

Résumé

The effects of a C57 type ciguatoxin (CTX-3C) and two types of brevetoxins (PbTx-1 and PbTx-3), known to bind to receptor site 5 of the neuronal voltage-dependent Na+ channel-protein, were studied on the morphology of living frog myelinated axons using confocal laser scanning microscopy. During the action of CTX-3C, PbTx-1, and PbTx-3 (10-50 nM), a marked swelling of nodes of Ranvier was observed without apparent modification of internodal parts of axons. In all cases, toxin-induced nodal swelling attained a steady-state within 75-100 min that was well maintained during an additional 90-115 min. The nodal swelling was reversed by an external hyperosmotic solution containing 100 mM D-mannitol and could be completely prevented by blocking voltage-dependent Na+ channels with 1 microM tetrodotoxin. It is suggested that CTX-3C, PbTx-1, and PbTx-3 by activating Na+ channels cause a continuous Na+ entry into axons, increasing internal Na+ concentration. Such an increase directly or indirectly disturbs the osmotic equilibrium between intra- and extra-axonal media, resulting in an influx of water, which is responsible for the long-lasting nodal swelling. Similar results were previously reported with two C60 type ciguatoxins (CTX-1B and CTX-4B). Thus, it is concluded that the four types of toxins targetting receptor site 5 of neuronal voltage-dependent Na+ channels, not only enhance nerve membrane excitability but also, on a long-term basis, cause a marked increase in the axonal volume.

Dates et versions

hal-02127473 , version 1 (13-05-2019)

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César Mattei, Marie-Yasmine Dechraoui, Jordi Molgó, Frédéric Meunier, Anne-Marie Legrand, et al.. Neurotoxins targetting receptor site 5 of voltage-dependent sodium channels increase the nodal volume of myelinated axons. Journal of Neuroscience Research, 1999, 55 (6), pp.666-673. ⟨10.1002/(SICI)1097-4547(19990315)55:6<666::AID-JNR2>3.0.CO;2-H⟩. ⟨hal-02127473⟩

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