Picrotoxin, also known as cocculin, is a poisonous crystalline plant compound, first isolated by Pierre Boullay in 1812. The name "picrotoxin" is a combination of the Greek words "picros" (bitter) and "toxicon" (poison).
Found primarily in the fruit of the climbing plant Anamirta cocculus, it has a strong physiological action. It acts as a noncompetitive antagonist for the GABAA receptor chloride channels. It is therefore a channel blocker rather than a receptor antagonist. As GABA itself is an inhibitory neurotransmitter, infusion of picrotoxin has stimulant and convulsant effects. As such, picrotoxin can be used to counter barbiturate poisoning, that can occur during general anesthesia or during a large intake outside of the hospital.
Picrotoxin is classified as an illegal performance-enhancing "Class 1 substance" by the American Quarterhorse Association. The recommended penalty for a first offense is a one-year suspension and a $10,000 fine.
Dupont, L.; Dideberg, O.; Lamotte-Brasseur, J.; Angenot, L. (1976). "Structure cristalline et moléculaire de la picrotoxine, C15H16O6·C15H18O7". Acta Crystallographica B (in French) 32 (11): 2987–2993. doi:10.1107/S0567740876009424.
Siegel G. J.; Agranoff, B. W.; Albers, R. W. et al., ed. (1999). "GABA Receptor Physiology and Pharmacology". Basic Neurochemistry: Molecular, Cellular and Medical Aspects (6th ed.). Philadelphia, PA, USA: Lippincott-Raven.