Wide concentration range (10(-14)-10(-4) M) of bis-(n-tributyltin)-oxide effect on Na(+)-dependent uptake, spontaneous and K(+)-stimulated release, specific receptor binding and GABA metabolism were studied in vitro experiments using brain slices, synaptic membrane fraction and brain tissue homogenates. It is shown that the dependence "concentration-effect" is of non-linear character in all cases. Prevailing suppression of Na(+)-dependent uptake and specific receptor binding during K(+)-stimulated release and metabolism (production and utilization) of GABA activation were marked as a general tendency. Mechanisms of TBTO effect on the studied processes and the involvement of GABA-ergic system in realization of TBTO neurotoxic effects are discussed.