Glutamate and aspartate are excitatory neurotransmitters that have been implicated in a number of pathologic states of the nervous system. Accumulation of extracellular excitatory amino acids can be cytotoxic and may also lower the seizure threshold in epilepsy. EAAT1 (SLC1A3) is a member of a family of high-affinity sodium-dependent transporter molecules that regulate neurotransmitter concentrations at the excitatory glutamatergic synapses of the mammalian central nervous system. The cDNA encoded a deduced protein that was 95% homologous to a previously reported rabbit glutamate/aspartate transporter. The highest expression was found in the substantia nigra, red nucleus, and hippocampus, and in cerebral cortical layers