Quantitative Structure-Activity Relationships of DDT-Type Compounds in a Sodium Tail-Current in Crayfish Giant Axons

Effects of DDT‐type compounds including 1,1‐bis(para‐substituted phenyl)‐2,2‐dichlorocyclopropanes (DCC‐series compounds) on sodium currents in crayfish giant axons were measured under voltage‐clamp conditions. Variations in the activity to prolong the tail‐current that was observed upon step repolarization of the membrane were quantitatively analysed by use of physicochemical parameters of aromatic substituents and regression analysis. Introduction of lengthy and narrow substituents was favourable to the activity. Variations in the activity were parabolically related to the hydrophobicity, optimum value being around that of H. DDT‐ and prolan‐series compounds were 2–3 times more active than DCC‐series compounds when other structural factors were the same. Insecticidal activity of the compounds was linearly correlated with the tail‐current activity when the hydrophobic factor was separately considered. The insecticidal activity of DDT‐series compounds was 2·5 times higher than that of others when the other factors were the same. © 1997 SCI.