GLUTAMATE RELEASE MONITORED WITH ASTROCYTE TRANSPORTER CURRENTS DURING LTP

Long-term potentiation (LTP) of synaptic transmission in the CA1 regio n of the hippocampus is thought to result from either increased transm itter release, heightened postsynaptic sensitivity, or a combination o f the two. We have measured evoked glutamate release from Schaffer col lateral/commissural fiber terminals in CA1 by recording synaptically a ctivated glutamate transporter currents in hippocampal astrocytes loca ted in stratum radiatum. Although several manipulations of release pro bability caused parallel changes in extracellular field potentials and synaptically activated transporter current amplitudes, induction of L TP failed to alter transporter-mediated responses, suggesting that LTP does not alter the amount of glutamate released upon synaptic stimula tion.