Selectivity to insects over mammals is one of the important characteristics for a chemical to become a useful insecticide. Fipronil was found to block cockroach GABA receptors more potently than rat GABA A receptors. Furthermore, glutamate-activated chloride channels (GluCls), which are present in cockroaches but not in mammals, were very sensitive to the blocking action of fipronil. The IC 50s of fipronil block were 30nM in cockroach GABA receptors and 1600nM in rat GABA A receptors. Moreover, GluCls of cockroach neurons had low IC 50s for fipronil. Two types of glutamate-induced chloride current were observed: desensitizing and non-desensitizing, with fipronil IC 50s of 800 and 10nM, respectively. We have developed methods to separately record these two types of GluCls. The non-desensitizing and desensitizing currents were selectively inhibited by trypsin and polyvinylpyrrolidone, respectively. In conclusion, in addition to GABA receptors, GluCls play a crucial role in selectivity of fipronil to insects over mammals. GluCls form the basis for development of selective and safe insecticides.
- Cockroach neuron
- GABA receptor
- Glutamate-activated chloride channel
- Rat neuron
ASJC Scopus subject areas
- Agronomy and Crop Science
- Health, Toxicology and Mutagenesis