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

Abstract

Rat brain synaptosomes isolated on discontinuous Ficoll gradient carry out rapid net uptake of γ-aminobutyric acid through a high-affinity system (k(m)=6.25 μM; V(max) = 1.2 nmol/min per mg of protein). The uptake of the labeled neuro-transmitter is dependent on sodium concentration and is abolished by addition of 40 μM veratridine or 0.5 mM 2,4-diaminobutyric acid. Homoexchange in this preparation accounts for less than 10% of the measured uptake of γ-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 γ-aminobutyric acid from the synaptic cleft after neuronal transmission.