n. a CNS stimulant derived from the berries of a southeast Asian shrub, Anamirta cocculus. Originally used as a fish poison, picrotoxin was introduced in the 1930s as a therapy for barbiturate overdose. It is a convulsant agent and acts as a GABA antagonist by binding to a specific site on the GABAA receptor complex, blocking the effects of GABA agonists (e.g., the benzodiazepines). Picrotoxin has no modern clinical applications but may be used to induce seizures in nonhuman animals for research purposes.