OBJECTIVES: The effect of beta-bungarotoxin, botulinum toxin and black widow spider venom will be examined on release of H3-acetylcholine from isolated vesicles, initially using electric skate electroplax. The isozyme pattern of seven insect acetylcholinesterases will be explored. Several comparisons will be made of three vertebrate and three arthropod acetyl-cholinesterases, with respect to the rate-limiting step (acylation or de-acylation?); the sensitivity to selective inhibitors (mostly insecticides); and the isozyme composition and molecular weights. New mutant acetyl-cholinesterases from house flies will be sought, and studies of their inhibitor and substrate preferences used to map the topography of the enzyme's active site. Condylactis toxin will be used to attempt isolation of the arthropod sodium gate; its interactions with DDT and pyrethroids will be explored. The "receptor" for radioactive pyrethroids will be sought. And the effects of DDT and other chlorinated hydrocarbons upon fluorescent probes within synthetic bilayers will be explored.