Phosphatidylserine Enhancement of [3H]gamma-aminobutyric Acid Uptake by Rat Whole Brain Synaptosomes

[3H]gamma-Aminobutyric acid ([3H]GABA) binding to purified lipids was examined in an organic solvent-aqueous partition system. In addition, the [3H]GABA binding capacity in the partition system was compared with the capacity of lipids to alter sodium-dependent [3H]GABA uptake into synaptosomes isolated from rat whole brains. [3H]GABA was found to bind to all of the lipids studied in the organic solvent-aqueous partition system [phosphatidic acid (PA), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylserine (PS), gangliosides, and sulfatide], although PS exhibited the greatest binding capacity. [3H]GABA uptake into synaptosomes was enhanced by PS (48.0%) but was not altered by any other lipid. PS enhancement of [3H]GABA uptake required the presence of sodium and was blocked by nipecotic acid (10 microM). These results suggest that PS may play a role in the sodium-dependent GABA reuptake process in the presynaptic nerve end.