In vitro toxicological investigations of isoxazolinone amino acids of Lathyrus sativus

Two non‐protein amino acids of Lathyrus sativus, β‐(isoxazoline‐5‐on‐2‐yl)‐alanine (BIA) and its higher homologue α‐amino‐γ‐Cisoxazoline‐5‐on‐2‐yl)‐alanine (ACI) were tested for excitotoxic potential. BIA (0.5‐2.0 mM) but not ACI (2.0 mM) produced a concentration‐dependent neurodegeneration in mouse cortical explants. The neuronal damage was prevented by the prior and simultaneous application of 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX), indicating that it was mediated by non‐N‐methyl‐D‐aspartate type receptors. BIA (0,5‐2.0 mM) activated CNQX‐sensitive currents which were significantly smaller than those activated by 3‐N‐oxalyl‐L‐2,3‐diaminopropanoic acid (β‐ODAP) or α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole‐propionic acid (AMPA) in the majority of neurons. In a small number of cells, BIA (2 mM) produced currents which were similar in amplitude to those activated by β‐ODAP (50 μM). These results suggest that Lathyrus sativus plants engineered to block the synthesis of β‐ODAP may accumulate a neurotoxic precursor and therefore must be tested for the presence of both BIA and β‐ODAP. © 1995 Wiley‐Liss, Inc.