Net uptake of gamma-aminobutyric acid by a high-affinity system of rat brain synaptosomes.

Rat brain synaptosomes isolated on discontinuous Ficoll gradient carry out rapid net uptake of gamma-aminobutyric acid through a high-affinity system (Km = 6.25 microM; Vmax = 1.2 nmol/min per mg of protein). The uptake of the labeled neurotransmitter is dependent on sodium concentration and is abolished by addition of 40 microM veratridine or 0.5 mM 2,4-diaminobutyric acid. Homoexchange in this preparation accounts for less than 10% of the measured uptake of gamma-amino[14C]butyric acid. It is concluded that the high-affinity transport exhibits properties characteristic of a system that is responsible for the rapid removal of gamma-aminobutyric acid from the synaptic cleft after neuronal transmission.