In-vitro release of [14C]glutamate from dentate gyrus is modulated by GABA

The effect of GABA (10(-3) and 10(-4) M) on the release of preloaded [14C]glutamate from slices of rat dentate gyrus, in response to K+ stimulation, was studied in Ca2+-free and normal Krebs solutions. Release in Ca2+-free solution was significantly enhanced, but there was no change in release in normal Krebs solution. These results imply that Ca2+-dependent (presumably neuronal) release of glutamate from the dentate gyrus is depressed by GABA, while non-neuronal Ca2+-independent release is enhanced.