The present invention relates to the field of GABA receptor structure and function. In one aspect, the present invention relates to impairment of the gamma-aminobutyric acid (GABA) receptors in parasitic nematodes, for the purpose of crop protection and/or soil treatment. The invention includes mutated nematode GABA receptor subunits, nematode GABA neuromuscular junction receptor complexes, nucleic acids which encode the mutated and functional receptor complexes, antibodies which selectively bind the GABA receptor complexes and/or subunits, and assays for compounds which adversely affect nematode GABA neuromuscular junction receptor function. The present invention therefore relates broadly to recombinant DNA technology, molecular biology tools, and crop protection and/or soil treatment.