The effects of L-buthionine sulfoximine (L-BSO), 2-cyclohexene-1-one and diethylmaleate (DEM) on the concentration of rat brain glutathione (GSH) were investigated. Both DEM and 2-cyclohexene-1-one, administered subcutaneously, produced marked and rapid reduction of brain GSH, but 2-cyclohexene-1-one appeared less toxic than DEM. Six hours after 2-cyclohexene-1-one (100 microliters/kg) the striatal GSH concentration was 35% of control values, whereas the level was 55% of controls at 24 h and 80% of controls at 48 h. Similar results were obtained with DEM (800 microliters/kg). L-BSO (3.2 mg), administered intracerebroventricularly, produced a slower depletion of brain GSH. A 55% reduction of striatal GSH was obtained 24 h after the administration, and the level was approximately 50% of control at 48 h. Thus, the effect of 2-cyclohexene-1-one and DEM is rapid in onset but relatively short lasting, whereas the disappearance of brain GSH after L-BSO is slower but the effect is more long-lasting. By combining L-BSO with either 2-cyclohexene-1-one or DEM both a rapid and long-lasting GSH depletion was obtained that was more profound than after any of the drugs alone. The combination of L-BSO and 2-cyclohexene-1-one was well tolerated, but the combination of L-BSO and DEM led to death in half of the rats the second day after injection. The disappearance rate of GSH after L-BSO alone gives an estimate of the turn-over of GSH. We found the turn-over of GSH to be higher in the substantia nigra pars compacta than in the striatum. The present work suggest that L-BSO and 2-cyclohexene-1-one would be very useful for evaluation of the biological role of GSH in the central nervous system.