gamma-Aminobutyric acid type A receptors (GABA_A) are responsible for the fast synaptic inhibitory neurotransmission in the mammalian brain. Their structural diversity forms the basis for the functional and pharmacological heterogeneity of the GABAergic neurotransmission. Most of the known pharmacological heterogeneity concerns the sensitivity of the benzodiazepine site. It depends, firstly, on the a variant, with alpha4 and alpha6 subunit-containing receptors being practically insensitive to benzodiazepine site agonists and, secondly, on the presence of a gamma subunit in alphaXbetaXgammaX receptors for the formation and function of the binding site. The advanced compounds will be characterized for their activity at the GABA_A receptor using the whole cell variation of the patch-clamp-technique. Therefore, HEK293 cells will be transiently transfected and the recombinant receptors will be tested at their individual EC₂₀ of GABA together with increasing concentrations of the new compounds. By the use of the compounds alone at increasing concentration a potential intrinsic activity will be analyzed.