Enhancement of Endogenous Release of Glutamate and γ‐Aminobutyric Acid from Hippocampus CA1 Slices After In Vivo Long‐Term Potentiation

: The effect of long‐term potentiation (LTP) on endogenous amino acid release from rat hippocampus slices was studied. LTP was induced in vivo by application of a tetanus (200 Hz, 200 ms) to the Schaffer collateral fibers in unanesthetized rats. Endogenous release of glutamate and γ‐aminobutyric acid (GABA) was investigated 60 min after tetanization in CA1 subslices of potentiated and control rats. No significant effects of LTP were observed in basal and K+‐induced Ca2+‐independent release components of these amino acids. In contrast, K+‐induced Ca2+‐dependent release of both glutamate and GABA increased ∼ 100% in slices from potentiated rats. No differences were observed in total content of glutamate and GABA between the subslices from control and LTP animals. These results suggest a persistent increase in the recruitment of the presynaptic vesicular pool of glutamate and GABA during LTP.