The invention relates to novel polynucleotides which encode novel polypeptides that are acetylcholine-gated chloride channel subunits and immunogenic or acetylcholine-binding fragments thereof. The novel polypeptides may be used for identifying compounds that modulate the acetylcholine-gated chloride channels, e.g. for use as pesticides and antiparasitic agents. Methods for identifying compounds that modulate the acetylcholine-gated chloride channels are provided.