Inhibitions of the GABA-induced currents of rat neurons by the alkaloid isocoryne from the plant Corydalis pseudoadunca.

A novel substance, isocoryne, affecting the GABA receptor complex, was isolated from the Corydalis pseudoadunca plant. The inhibitory effect of isocoryne on GABA-activated transmembrane current of single neurons isolated from trigeminal ganglia of rats was tested using concentration-clamp, voltage-clamp and intracellular perfusion techniques. Isocoryne, like other phthalide isoquinoline alkaloids with a 1S,9R isomeric form, produced an inhibitory effect on GABA-activated currents with a Ki = 10(-6) M.