Analysis of Caribbean ciguatoxin-1 effects on frog myelinated axons and the neuromuscular junction.

Caribbean ciguatoxin-1 (C-CTX-1) induced, after about 1h exposure, muscle membrane depolarisation and repetitive post-synaptic action potentials (APs) in frog neuromuscular preparations. This depolarising effect was also observed in a Ca(2+)-free medium with a strong enhancement of spontaneous quantal transmitter release, compared with control conditions. The ciguatoxin-induced increase in release could be accelerated when Ca(2+) was present in the extracellular medium.

Muscarinic effects of the Caribbean ciguatoxin C-CTX-1 on frog atrial heart muscle.

The effects of Caribbean ciguatoxin (C-CTX-1) isolated from horse-eye jack (Caranx latus) on the electrical and mechanical activities of frog auricle were studied. C-CTX-1 (1 pM-50 nM) dose-dependently shortened the duration of the plateau and the repolarizing phase of the action potential (AP). The AP shortening induced by C-CTX-1 (50 nM) was suppressed or prevented either by tetrodotoxin (TTX; 0.

Ionic mechanisms involved in the nodal swelling of myelinated axons caused by marine toxins.

This review describes the ionic mechanisms involved in the nodal swelling of frog myelinated axons caused by specific marine neurotoxins (ciguatoxins, brevetoxins, Conus consors toxin and equinatoxin-II), analysed using confocal laser scanning microscopy. We have focussed on toxins that either target neuronal voltage-dependent Na+ channels, or that form cation-selective pores and indirectly affect the functioning of the Na(+)-Ca(++)exchanger.

[Effect of ciguatoxins on the cardiocirculatory system].

The aim of the present review was to collect the main observations reported until now concerning the cardio-circulatory effects of polyether toxins, called ciguatoxins, which are involved in an endemic intoxication named ciguatera found in tropical and subtropical countries. Ciguatera is caused by the ingestion of fishes contaminated with the dinoflagellate Gamberdiscus toxicus. Due to both tropical fish exportation destined for food and tourism, the disease has now spread out to temperate areas.

Hyperosmolar D-mannitol reverses the increased membrane excitability and the nodal swelling caused by Caribbean ciguatoxin-1 in single frog myelinated axons.

The effects of hyperosmolar D-mannitol were studied on single frog myelinated nerve fibres previously poisoned with Caribbean ciguatoxin-1 (C-CTX-1), a new toxin isolated from the pelagic fish Caranx latus inhabiting the Caribbean region. In current-clamped myelinated axons, C-CTX-1 (50-120 nM) caused spontaneous and repetitive action potential discharges after a short delay. In addition, the toxin produced a marked swelling of nodes of Ranvier of myelinated axons that reached a steady state within about 90 min, as revealed by using confocal laser scanning microscopy.