Synaptic activation of GABAA receptors induces neuronal uptake of Ca2+ in adult rat hippocampal slices

Synaptically evoked transmembrane movements of Ca2+ in the adult CNS have almost exclusively been attributed to activation of glutamate receptor channels and the consequent triggering of voltage-gated calcium channels (VGCCs). Using microelectrodes for measuring free extracellular Ca2+ (Ca2+]o) and extracellular space (ECS) volume, we show here for the first time that synaptic stimulation of gamma-aminobutyric acid-A (GABAA) receptors can result in a decrease in Ca2+]o in adult rat hippocampal slices. High-frequency stimulation (100-200 Hz, 0.4-0.5 s) applied in stratum radiatum close (