STUDIES IN THE MODE OF ACTION OF INSECTICIDES

Abstract

Acetylcholine, choline chloride, acetyl‐β‐methylcholine, benzoylcholine, carbamyl choline, adrenaline and d ‐tubocurarine are non‐toxic when injected into the locust. Prostigmine is also non‐toxic, and eserine considerably less toxic to the locust than to man. The toxic effect of tetraethyl pyrophosphate (TEPP) cannot be antagonized by injection of atropine or enhanced by d ‐tubocurarine. The injection of acetylcholine chloride following injection of TEPP does not affect subsequent mortality. These findings are discussed, and it is suggested that the physiology of the nervous system of the insect is unlike that of the mammal, neither cholinesters nor adrenaline being concerned in it. Phosphorus insecticides are thought to inhibit a general esterase not specifically connected with cholinesters.