Behavioral Profiling in Zebrafish Identifies Insecticide-Related Compounds.

Pesticides, including insecticides, are indispensable for large-scale agriculture. Modulating chloride ion channels has proven highly successful as a mode of action (MoA) for insect management. Identifying new ligands for these channels affords opportunities for the potential development of new insecticide products. We discovered an unexpected behavioral response in larval zebrafish exposed to endosulfan, a γ-aminobutyric acid (GABA)-gated chloride channel modulator. At low concentrations, endosulfan increased zebrafish motor activity under strobing blue or green light stimuli. Using this distinct behavioral phenotype as a proxy for similar modes of action, we screened over 9,000 compounds and identified several structurally diverse hits that phenocopied endosulfan's effects in vivo. Nine selected hits were tested in an in vitro GABA receptor (GABAR) oocyte assay, confirming that certain compounds block Drosophila GABAR activation. Subsequent in vivo insect assays revealed that one of these GABAR antagonists showed insecticidal activity against the Western corn rootworm (Diabrotica virgifera virgifera), which is a commercially important pest of corn. Our findings demonstrate a new approach for identifying GABAR-targeting insecticides through behavior-based screening in zebrafish.