RELATIONSHIP BETWEEN PYRETHROID ENHANCED BATRACHOTOXININ A 20-ALPHA-BENZOATE BINDING AND PYRETHROID TOXICITY TO SUSCEPTIBLE AND RESISTANT TOBACCO BUDWORM MOTHS HELIOTHIS-VIRESCENS

1. Pyrethroid enhanced [H-3]batrachotoxinin A 20-alpha-benzoate ([H-3]BTX-B) binding was observed with preparations from susceptible (S) tobacco budworm, Heliothis virescens (F), moths with deltamethrin, bifenthrin, and cypermethrin, and with preparations from resistant (R) moths with deltamethrin. 2. Deltamethrin enhanced [H-3]BTX-B binding was more pronounced with preparations from S moths than from R moths. 3. Permethrin inhibited [H-3]BTX-B binding with preparations from R moths, and esfenvalerate was without significant effect on radioligand binding with preparations from either strain. 4. A direct relationship existed between pyrethroid enhanced [H-3]BTX-B binding with membranes from S moths and pyrethroid toxicity following topical treatment of S moths. Esfenvalerate, which did not enhance radioligand binding but was highly toxic, was an exception to the generalization. 5. DDT enhanced [H-3]BTX-B binding with preparations from both strains, but it was not toxic when applied topically to pyrethroid S moths, an apparent disparity, possibly related to pharmacokinetic events. 6. It was concluded that pyrethroid induced nerve insensitivity resistance in tobacco budworm moths was due, at least in part, to a decreased affinity of the pyrethroid binding site in the sodium channel protein. 7. Esfenvalerate, however, may be interacting with sodium channels by a mechanism different from that of the other pyrethroids.