A major pathway for inactivation of biogenic amine and amino acid neurotransmitters is by uptake into neurons or glia cells through Na+-dependent, high-affinity uptake systems. Here, we show that Xenopus oocytes, microinjected with poly(A)+ RNA from developing rat brain, express a Na+-dependent GABA uptake system, which is similar in its properties to the high-affinity GABA uptake system, present in rat brain. These results suggest that the oocyte expression system may be useful in the isolation of mRNAs and subsequent cloning of the genes encoding the polypeptides involved in GABA transport in the nervous system.