Chloride Channels as Tools for Developing Selective Insecticides

摘要

ligand-gated chloride channels underlie inhibition in excitable membranes and are proven target sites for insecticides.The gamma-aminobutyric acid (GABA~1) receptor/chloride ionophore complex is the primary sitge of action for a number of currently used insecticides,such as lindane,endosulfan,and fipronil.These compounds act as antaqonists by stabilizing nonconducting conformations of the chloride channel.Blockate of the GABA-gated chloride channel reduces neuronal inhibition,which leads to hyperexcitation of the central nervous system,convulsions,and death.We recently investigated the mode of action of the siliphinenes,plant-derived natural compounds that structurally resemble picrotoxinin.These materials antagonize the action of GABA on insect neurons and block GABA-mediated chloride uptake into mouse brain synatponeurosomes in a noncompetitive manner.In mammals,avermectins have a blocking action on the GABA-gated chloride channel consistent with a coarse tremor,whereas at longer times and higher concentrations,activation of the channel suppresses neuronal activity.Inverte-brates display ataxia,paralysis,and death as the predominant signs of poisoning,with a glutamate-gated chloride channel playing a major role.Additional target site4s for the avermectins or other chloride channel-directed compounds might include recaptors gated by histamine,serotonin,or acetylcholine.The voltage-senisitive chloride channels form another large gene family of chloride channels.Voltage-dependent chloride channels are involved in anumber of physiological processes including:maintenance of electrical excitability,chloride ion secretion and resorption,intravesicular acidification,and cell volume regulation.A subset of these channels is affected by convulsants andinsecticides in mammals,although th role they play in acute lethality in insects is unclear.Given the wide range of functions that they mediate,these channels are also potential targets for insecticide development.