“…When aryl pyrazoles synthesized as herbicides were found to be insecticidal, their convulsive activity was not immediately recognized to result from GABA-antagonism (Klis et al, 1991). Cole et al (1993) reported subsequently that several compounds, including fipronil (27, Figure 96.11) (Colliot et al, 1992;Hatton et al, 1988), which has become a commercially successful insecticide, blocked the GABA-gated chloride ionophore with higher potency for a site in housefly than in mouse brain, offering the possibility of selective toxicity.…”