Grayanotoxin (GTX), one of the lipid-soluble Na+ channel openers, contains four rings (A, B, C and D) and the chemical groups essential for the pharmacological action are located on the A- and B-rings. To study the biological significance of functional groups on the D-ring, 51 new derivatives were prepared from α-dihydro GTX- 11 . These new compounds and the previously prepared GTXS ere directly applied to the intracellular phase of internally perfused squid giant axons
