INFLUENCE OF FORMAMIDINES ON BATRACHOTOXIN IN A 20-ALPHA-BENZOATE BINDING TO NEURAL MEMBRANES FROM PYRETHROID SUSCEPTIBLE AND RESISTANT TOBACCO BUDWORM MOTHS HELIOTHIS-VIRESCENS

1. Amitraz stimulated [H-3]batrachotoxin in A 20-alpha-benzoate ([H-3] BTX-B) binding to neural membranes from pyrethroid susceptible (S) and resistant (R) tobacco budworm moths, but N'-(2,4-xylyl)-N-methylforma midine (SN 49844) stimulated binding only with S moths. 2. Chlordimefo rm stimulated [H-3]BTX-B binding only with R moths, and N'-(4-chloro-o -tolyl)-N-methylformamidine (demethylchlordimeform) yielded no signifi cant stimulation with either strain. 3. A mixture of amitraz and delta methrin, a pyrethroid that previously had been shown to enhance [H-3]B TX-B binding with tobacco budworm moths, also gave significant stimula tion of radioligand binding with S moths. 4. When membranes were prepa red from S moths at various intervals following topical application of amitraz, deltamethrin, or a mixture of amitraz and deltamethrin, biph asic stimulation of [H-3]BTX-B binding was observed, with maximum enha ncement occurring at 2 and 6 hr. 5. These results provided a basis for suggesting that a formamidine binding site is located on or closely a ssociated with the sodium channel protein. 6. Whether this site is the same as the pyrethroid/DDT binding domain remains to be demonstrated; however, similarities in responses elicited by amitraz and deltamethr in alone and in combination indicate that some relationship may exist.