Bidirectional movement of gamma-aminobutyric acid in rat spinal cord slices

The bidirectional movement of GABA (gamma-aminobutyric acid) was studied in slices of rat spinal cord which were incubated in small volumes of medium. The appearance in the medium of endogenous GABA and the disappearance from the medium of [14C]GABA were used to calculate the rates of unidirectional uptake and unidirectional release of GABA. Under these conditions, no net uptake of GABA was observed when slices were incubated in media containing concentrations of gABA as high as 25 microM. Elevated potassium (60 mM) stimulated the unidirectional release of endogenous GABA from spinal cord slices by a calcium-dependent process. Ouabain (0.1 mM) more than doubled the unidirectional release of endogenous GABA in a calcium-independent manner, while unidirectional uptake was inhibited by 44%. Nipecotic acid (1.0 mM) stimulated unidirectional release and inhibited unidirectional uptake of GABA.