Action of bioresmethrin on the corpus cardiacum of Locusta migratoria

The action of the pyrethroid insecticide bioresmethrin on the corpus cardiacum (CC) has been studied in Locusta migratoria. Bioresmethrin increased the spontaneous electrical activity recorded from both the glandular and storage lobes, and induced repetitive discharge in these lobes in response to single electrical stimulation of the nervus corpus cardiacum II (NCC II) and NCC I, respectively. Incubation of the isolated CC in low concentrations of bioresmethrin (0.1‐1.0 μmol) induced the release of bioassayable hyperlipaemic hormone. Injection of bioresmethrin into locusts was found to induce an elevation in the haemolymph lipid at a stage when there was no overt symptom of poisoning. It is concluded that bioresmethrin may act directly on the CC of locusts to modulate electrical activity and induce the release of hormones. The effects may precede overt symptoms of poisoning.