Glial contributions to excitatory neurotransmission in cultured hippocampal cells.

Although many glial cells possess neurotransmitter receptors and transporters, little is known about glial participation in neurotransmission. To explore this issue, we recorded neuronal autaptic and glial responses from cultured hippocampal single-neuron micro-islands. Excitatory synaptic events activate rapid electrogenic glial glutamate transporter currents similar to those elicited by exogenous glutamate in other preparations. We show here that glial transporter responses may be used to sense changes in presynaptic efficacy and that glial uptake helps to remove synaptically released glutamate, thereby contributing to the termination of excitatory synaptic currents under certain conditions. These observations provide a framework for understanding the role of glia in both normal and pathological processes.