Abstract
A large amount of [3H]GABA was bound to crude synaptic membrane fractions of rat, by a Na-independent process in a medium containing 100 .mu.M [3H]GABA used for assaying the GABA uptake site. This [3H]-GABA binding was different from receptor binding of GABA. This Na-independent [3H]GABA binding scarcely occurred in the presence of a physiological concentration of NaCl. Na-independent GABA binding had a negligible influence on Na-dependent GABA binding.