Picrotin is a natural picrotoxane that antagonizes glycine receptors (GlyRs; IC50s = 57 and 117 μM for α1 and α2 homodimeric GlyRs, respectively). It also inhibits α3 homodimeric GlyRs. Picrotin is inactive in inhibiting γ-aminobutyric acid (GABA) type A and type C receptors. Picrotin occurs in the natural plant-derived poison picrotoxin , equimolar with picrotoxinin.