FUNCTIONAL EXPRESSION AND CNS DISTRIBUTION OF A BETA-ALANINE-SENSITIVE NEURONAL GABA TRANSPORTER

The synaptic action of gamma-aminobutyric acid (GABA) is terminated by high affinity, Na+-dependent transport processes in both neurons and glia. We have isolated a novel GABA transporter cDNA, GAT-B, which encodes a high affinity (K(m) = 2.3-mu-M), Na+- and Cl--dependent GABA transport protein that is potently blocked by beta-alanine, a compound generally considered a selective inhibitor of glial transport. However, in situ hybridization studies indicate that GAT-B mRNA is expressed predominantly within neurons. These data indicate that the neuronal-glial distinction of GABA transporters based on inhibitor sensitivities must be reconsidered and suggest a greater diversity of GABA transporters than has been predicted by previous pharmacologic studies.