GABA transporter mRNA: in vitro expression and quantitation in neonatal rat and postmortem human brain

A previously isolated rat cDNA clone encoding the membrane transporter for the neurotransmitter gamma-aminobutyric acid was expressed in transfected COS cells. The resultant transporter protein was characterized kinetically and pharmacologically. The apparent Kt (6.1 microM) and the pharmacological profile of a neuronal-type transporter observed in these mammalian cells were consistent with previous data obtained in Xenopus laevis oocytes. Post-natal levels of gamma-aminobutyric acid transporter mRNA in rat cerebellum, cerebral cortex and striatum (as measured by nuclease protection assay) transiently exceeded levels present in the adult brain. Human gamma-aminobutyric acid transporter mRNA also was measured by nuclease protection assay using as probe a human transporter cDNA homolog obtained by polymerase chain reaction. These studies suggest that quantitation of rat and human gamma-aminobutyric acid transporter mRNAs may provide a useful index of transporter gene expression.