In vivo effects of nipecotic acid on levels of extracellular GABA and taurine, and hippocampal excitability.

The effect of nipecotic acid on the extracellular levels of the putative hippocampal inhibitory transmitters, gamma-aminobutyric acid (GABA) and taurine, and also excitability in the dentate gyrus, were studied in anaesthetised rats using the dialytrode technique. The dentate gyrus was perfused by means of a dialytrode , using Krebs-Ringer bicarbonate or nipecotic acid solutions. Dentate field potentials, evoked by electrical stimulation of the perforant pathway, were recorded. Nipecotic acid drastically elevated the levels of extracellular GABA and taurine and the amplitude of population spikes in the dentate was concomitantly decreased. These results indicate that changes in extracellular levels of endogenous GABA and/or taurine influence the excitability of the hippocampus.