Abstract: The ability of tetrandrine (Tet),as a Ca²⁺ antagonist isolated from a traditionalChinese herb,to reduce cortical neuronal injury was quantitatively examined in cell cultures derivedfrom fetal rats by measurement of lactate dehydrogenase(LDH)released to the extracellular bathingmedia.Cell cultures exposed to excitotoxins-glutamate(Glu),N-methyl-D-aspartate(NMDA),β-N-oxalylamino-L-alanine(BOAA, on non-NMDA receptors)and β-N-methylamino-L-alanine(BMAA,on NMDA receptors)-for 24 h showed widespread neuronal injury, which was subetantially attenuatedby addition of Tet 10^-7～100^-6mol·L^-1 except to NMDA,Tet failed to protect neurons againstNMDA. These resuIts suggest that Tet has protective effect on fetal rat corticaI neuronal injuryinduced by some excitotoxins in vitro,The mechanism of action was hypothesized that opening of Ca²⁺ channel in cellular membrane would not happen,beeause of inhibition of Na⁺ influx and membranedepolarization induced by Tet.As a result, cytosolic free Ca²⁺ overload and then neuroal injury wereprevented or lightened.