Effects of ciguatoxin and maitotoxin on isolated rat atria and rabbit duodenum.

Ciguatoxin and maitotoxin, extracted from a species of moray-eel, Gymnothorax javanicus, and from a wild dinoflagellate, Gambierdiscus toxicus, were tested on rat atria and rabbit duodenum. Biphasic inotropic and chronotropic responses with excitatory and inhibitory components were observed. The effects of agents such as reserpine, propranolol, phentolamine, atropine and manganese ions were investigated. We conclude that, at the dosage levels used, ciguatoxin acts mainly at the nerve endings, while maitotoxin exerts prominent toxic effects on muscles.