The effect of kainic acid on the hippocampal content of putative transmitter amino acids

The time courses of the changes in the contents of GABA (gamma-aminobutyric acid), glutamate, aspartate, taurine, glycine and alanine were measured in both hippocampi of rats which were rejected in one hippocampus with kainic acid (KA). The contents of these amino acids were measured with high performance liquid chromatography. The hippocampal contents of GABA, glutamate, aspartate and taurine were reduced homolaterally to the KA injection; in contrast, the contents of glycine and alanine failed to change. The extent of the reductions of GABA, glutamate, aspartate and taurine was dependent on the size of the lesion caused by KA. The greatest decrease occurred after two simultaneous injections of KA, in dorsal and ventral hippocampus. An analysis of the amino acids at different levels of the hippocampus after dorsal injections of KA showed that in the hippocampus the amino acidergic axons do not travel longitudinally. This study suggests that GABA, glutamate, aspartate and taurine are preferentially located in intrinsic hippocampal neurons with short axons.