Batrachotoxin (BTX) is an extremely potent cardiotoxic and neurotoxic steroidal alkaloid found in certain species of beetles, birds, and frogs.

Batrachotoxin binds to and irreversibly opens the sodium channels of nerve cells and prevents them from closing, resulting in paralysis and death.

Batrachotoxin was discovered by Fritz Märki and Bernhard Witkop, at the National Institute of Arthritis and Metabolic Diseases, National Institutes of Health, Bethesda, Maryland, U.S.A. Märki and Witkop separated the potent toxic alkaloids fraction from Phyllobates bicolor and determined its chemical properties in 1963.

However, Takashi Tokuyama, who joined the investigation later, converted one of the congener compounds, batrachotoxinin A, to a crystalline derivative and its unique steroidal structure was solved with x-ray diffraction techniques (1968).

In fact, batrachotoxin was able to be partially hydrolyzed using sodium hydroxide into a material with identical TLC and color reactions as batrachotoxinin A.

[5] The toxin is released through colourless or milky secretions from glands located on the back and behind the ears of frogs from the genus Phyllobates.

Neurological function depends on depolarization of nerve and muscle fibres due to increased sodium ion permeability of the excitable cell membrane.

Batrachotoxin in the PNS produces increased permeability (selective and irreversible) of the resting cell membrane to sodium ions, without changing potassium or calcium concentration.

Furthermore, the massive influx of sodium ions produces osmotic alterations in nerves and muscles, which causes structural changes.

Heart conduction is impaired resulting in arrhythmias, extrasystoles, ventricular fibrillation and other changes which lead to asystole and cardiac arrest.

[11] Veratridine, aconitine and grayanotoxin—like batrachotoxin—are lipid-soluble poisons which similarly alter the ion selectivity of the sodium channels, suggesting a common site of action.

While it is not an antidote, the membrane depolarization can be prevented or reversed by either tetrodotoxin[11] (from puffer fish), which is a noncompetitive inhibitor, or saxitoxin ("red tide").

Batrachotoxin has been found in four Papuan beetle species, all in the genus Choresine in the family Melyridae; C. pulchra, C. semiopaca, C. rugiceps and C. sp.

Just as in the birds, it is believed that these frogs gain the toxin from batrachotoxin-containing insects that they eat, and then secrete it through the skin.

Other accounts say that a stick siurukida ("bamboo tooth") is put through the mouth of the frog and passed out through one of its hind legs.