WHITEFLY (HEMIPTERA, ALEYRODIDAE) BINDING-SITE FOR IMIDACLOPRID AND RELATED INSECTICIDES - A PUTATIVE NICOTINIC ACETYLCHOLINE-RECEPTOR

Imidacloprid is used extensively to control sweetpotato whiteflies, Be misia argentifolii Bellows & Perring [also known as B. tabaci (Gennadi us) biotype B]. As a radlioligand, [H-3]imidacloprid binds rapidly to a single class of high-affinity sites in membrane preparations from wh ole adult whiteflies with an apparent dissociation constant of 2 nM an d maximal binding capacity of 101 fmol/mg protein. Three related compo unds (the nitromethylene analog of imidacloprid, acetamiprid, and nite npyram) inhibit [H-3]imidacloprid binding by 50% at 0.40, 2.9, and 57 nM, respectively. The pharmacological profile of the binding site (exa mined with imidacloprid and the analogs listed above, and nicotine, al pha-bungarotoxin, carbachol, acetylcholine [with. paraoxon], and atrop ine) is consistent with that anticipated for a nicotinic acetylcholine receptor and correlates well with binding results for house fly. Musc a domestica L., head membranes under the same conditions. Thus, [H-3]i midacloprid is a suitable radioligand to investigate the putative nico tinic acetylcholine receptor of Bemisia and the possible modifications of this target site associated with selection of resistant strains.