GABAA receptors with different subunit composition, were expressed in kidney cells and studied by whole cell recording. Expressed GABAA receptors were differentially sensitive to inhibition by zinc; receptors which lacked the gamma subunit were inhibited by zinc. Embryonic neurons also exhibited zinc-sensitive GABA responses, in contrast to adult neurones. This developmentally-sensitive aspect of GABAA receptor pharmacology may be partly dependent on expression of the gamma subunit.