The present invention relates to the cloning of novel cDNA sequences encoding the α4 and δ receptor subunits of the human GABA A receptor; to stably co-transfected eukaryotic cell lines capable of expressing a human GABAA receptor, which receptor comprises at least one of the novel α4 and δ receptor subunits; and to the use of such cell lines in screening for and designing medicaments which act upon the human GAGAA receptor.