title: Ciguatoxin is a novel type of Na+ channel toxin.
abstract: Purified ciguatoxin at 0.1 to 10 ng/ml inhibits the net accumulation of neurotransmitters (gamma-aminobutyric acid and dopamine) by brain synaptosomes. This action is due to a stimulation of neurotransmitter release. The half-maximum effect of the toxin is observed at 0.62 ng/ml. The effect of ciguatoxin is completely inhibited by tetrodotoxin (K0.5 = 4 nM). Electrophysiological studies on neuroblastoma cells indicate that ciguatoxin induces a membrane depolarization which is prevented by tetrodotoxin and which is due to an action that increases Na+ permeability. Under appropriate conditions ciguatoxin creates spontaneous oscillations in the membrane polarization level and repeated action potentials. Ciguatoxin stimulates 22Na+ entry through the voltage-dependent Na+ channels of neuroblastoma cells and rat skeletal myoblasts when it is used in synergy with veratridine, batrachotoxin, pyrethroids, sea anemone, or scorpion toxins. The half-maximum effect of ciguatoxin on 22Na+ flux in the presence of veratridine occurs at a concentration of 0.5 ng/ml. Stimulation of 22Na+ flux by ciguatoxin is abolished by tetrodotoxin. These results taken together indicate that ciguatoxin belongs to a new class of toxins acting on Na+ channels.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D002460:Cell Line; D002922:Ciguatoxins / Q000302:isolation & purification / Q000633:toxicity*; D004298:Dopamine / Q000378:metabolism*; D005399:Fishes; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008387:Marine Toxins / Q000633:toxicity*; D051379:Mice; D009132:Muscles / Q000032:analysis; D009447:Neuroblastoma; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D007473:Ion Channels; D008387:Marine Toxins; D002922:Ciguatoxins; D005680:gamma-Aminobutyric Acid; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D004298:Dopamine