Influence of Sodium-Independent γ-Aminobutyric Acid Binding on the Assay of Sodium-Dependent γ-Aminobutyric Acid Binding in a Membrane Preparation of Rat Brain

A large amount of ³H]GABA was bound to crude synaptic membrane fractions of rat. by sodium-independent process in a medium that contained 100 μM ³H]GABA used for assaying GABA uptake site. This ³H]-GABA binding was different from receptor binding of GABA. It was confirmed that this sodium-independent ²H]GABA binding scarcely occurred in the presence of a physiological concentration of sodium chloride, and that sodium-independent GABA binding had a negligible influence on sodium-dependent GABA binding.