Two lipid esters of U-14C-labeled and unlabeled gamma-aminobutyric acid (GABA) were synthesized to test the possibility that natural lipid analogues, which resemble normal components of lipid bilayer membranes, can penetrate the blood-brain barrier and transport exogenous GABA to the brain. The uptake of 1-linolenoyl-2,3-bis(4-aminobutyryl)propane-1,2,3-triol and 1,2-dilinolenoyl-3-(4-aminobutyryl)propane-1,2,3-triol into mouse brain relative to liver was found to be, respectively, 75- and 127-fold greater than that of free GABA. The results indicate that there is little or no blood-brain barrier for the GABA ester molecules at doses up to 0.36 mmol/kg. Both ester compounds, but neither free GABA nor the lipid components delivered systemically, demonstrated central nervous system depressant properties by inhibiting the general motor activity of mice. Brain tissue has esterase activity which can release GABA from these compounds. This suggests that these compounds function as "prodrugs" to release GABA in the CNS.