Figure 1. Drawing of a hippocampal slice (A) showing the relative positions of a bipolar tungsten stimulating electrode (STIMULATE), and extracellular glass recording electrodes (RECORD). The recording electrode position was different for population spikes (PS) than for fiber volleys (FV) and excitatory postsynaptic potentials (EPSP). The three major excitatory pathways in hippocampal slices are shown: the perforant path (pp) originates in entorhinal cortex and projects to granule cells of the dentate gurus (DG), the mossy fiber pathway (mf) comprises granule cell axons and projects to pyramidal cells of CA 3, and Schaffer collateral (sc) fibers from CA 3 neurons form excitatory synapses with dendrites of CA 1 neurons. Synaptically evoked discharge (PS) was used to measure riluzole effects on the output of the CA 1 circuit (B). Circled numbers correspond to the four measures used to determine the major sites of action for riluzole in this circuit (see beginning of article).