Picrotoxin

Picrotoxin is a crystalline mixture of two closely related sesquiterpene lactones, picrotoxinin and picrotin, derived from the seeds of the tropical shrub Anamirta cocculus, commonly known as fish berry. The mixture has a long history of use in traditional contexts and, in modern times, is primarily employed as a pharmacological tool in neuroscience research due to its potent neurotoxic effects.

Mechanism of action and effects: Picrotoxin acts as a noncompetitive antagonist of the GABA_A receptor chloride channel. It binds within the ion channel and inhibits chloride conductance regardless of GABA binding, thereby diminishing inhibitory neurotransmission. The result is increased neuronal excitability, which lowers the seizure threshold and can produce convulsions in animals and humans exposed to sufficient doses.

Applications and usage: In laboratory settings, picrotoxin is used to study GABAergic synaptic transmission and to induce seizures in animal models for research on epilepsy and neuronal excitability. Its strong convulsant properties and toxicity mean that it has no approved therapeutic use and is not employed clinically. Historically, extracts containing picrotoxin or related compounds were used as fish poisons and, less commonly, as insecticides, though such uses are now largely obsolete due to safety concerns.

Safety and handling: Picrotoxin is highly toxic and can cause severe seizures, coma, and death if ingested, inhaled, or absorbed through the skin. It requires careful handling in specialized laboratory settings, with appropriate protective equipment and disposal procedures.