Detection of γ-aminobutyric acid-induced glutamate release in acute mouse hippocampal slices with a patch sensor

γ-Aminobutyric acid (GABA)-stimulated release of l-glutamate from various neuronal regions of acute mouse hippocampal slices was detected with a patch sensor that responds to l-glutamate at the sub-micromolar level. The response of the patch sensor to l-glutamate was evaluated in terms of an integrated current. The integrated current increased with the concentration of l-glutamate ranging from 0.50 to 5.0 μM. By using the patch sensor, GABA-induced l-glutamate release from acute mouse hippocampal slices was detected. The effect of antagonists for GABAA and GABAB receptors on the l-glutamate release was also investigated. The GABA (25 μM) stimulation induced the release of l-glutamate via GABAA receptor in the CA1 region, but GABA did not induce l-glutamate release in the CA3 region. However, in the presence of the GABAB receptor antagonist (3-aminopropyl)(diethoxymethyl)phosphinic acid (CGP-35348), release of l-glutamate in the CA3 region was evoked by GABA stimulation. The glutamate release was completely suppressed when both GABAA and GABAB receptor were inhibited. The current results show that the glutamate release in the CA3 region occurs via a GABAA pathway when GABAB receptors are inhibited.