The effects of pharmacologically relevant concentrations of ethanol on the release of endogenous adenosine from rat cerebellar synaptosomes were investigated. Release was conducted for 5, 10, 30, or 60 s after which time the incubation medium (containing the released adenosine) was rapidly separated from the synaptosomal membranes by vacuum filtration. The adenosine content of the filtrate was measured by HPLC-fluorescence detection. Both basal and KCl-stimulated adenosine release consisted of an initial rapid phase, for the first 10 s, that was followed by a relatively slower phase. Basal endogenous adenosine release was estimated as 199 +/- 14 pmol/mg protein/5 s. Potassium (chloride) increased adenosine release from the basal level to 433 +/- 83 pmol/mg protein/5 s. Ethanol caused a dose-dependent increase of adenosine release. The interaction between dilazep and ethanol indicates that ethanol-stimulated release does not involve the dilazep-sensitive transport system. The results support previous findings that indicate that cerebellar adenosine is involved in the mediation of ethanol-induced motor disturbances in the rat.