Lipid-soluble polyether marine toxin produced by the red tide dinoflagellate, Ptychodiscus brevis, found along the Gulf Coast of Florida. Voltage-dependent Na+ channel activator that causes contractile paralysis in animal models by binding to a unique site on these channels. The excitatory action of brevetoxins on nerve and muscle membranes is responsible for a wide spectrum of the toxic effects, including massive transmitter release from nerve endings, muscle fasciculations, and ventricular fibrillation. The toxin does not bind to either tetrodotoxin or aconitine/veratridine sites.