Aminobutyric Acid Greatly Increases the in Vivo Extracellular Taurine in the Rat Hippocampus

The effects of gamma-aminobutyric acid (GABA) on the extracellular levels of taurine and on excitability in the dentate gyrus were studied in anesthetized rats by the dialytrode technique. The dentate gyrus was perfused by means of a dialytrode with Krebs-Ringer-bicarbonate or GABA solutions. Amino acid contents in perfusates and dentate field potentials evoked by electrical stimulation of the perforant pathway were evaluated. GABA drastically elevated the levels of extracellular taurine in a dose-dependent manner, decreasing the amplitude of the population spike. This result indicates that GABA stimulates taurine release, probably by a counter-transport process. It is suggested that in physiological conditions an increase in extracellular taurine may be produced by synaptically released GABA.