The Mode of Action of Pyrethroids

Abstract

The comparative mode-of-action as well as quantitative structure-activity studies of pyrethroids were performed at whole insect body and excised nerve preparation levels. Knockdown activity of a set of variously substituted benzyl chrysanthemates and pyrethrates and their related compounds against the house fly was separated into the intrinsic activity and a penetration factor into the target sites. The intrinsic knockdown activity of the compounds was determined under synergistic conditions using inhibitors of oxidative and hydrolytic metabolic activities. The penetration rate constant of the compounds was evaluated from the progress of the knockdown symptom using a first order kinetic model. Symptomatic activities of pyrethroids against the American cockroach and the house fly determined under synergistic conditions were analyzable with such neurophysiological indices as repetitive and neuroblocking activities, which were determined by an extracellular recording technique using the excised central nerve cord of the American cockroach. The repetitive activity of pyrethroids, in turn, was analyzed with the activity to affect the after-potential determined by an intracellular recording method using the giant axon of the crayfish. Activities at whole body and excised nerve levels were shown to be quantitatively analyzable using physicochemical properties of the substituents or molecules by regression analyses. © 1984, Pesticide Science Society of Japan. All rights reserved.