The temporal fidelity of postsynaptic responses requires active glutamate uptake. (A) Example EPSCs evoked by 100 Hz stimulation in ACSF (top) and following the addition of the 200 μM dl-TBOA (bottom), which resulted in the accumulation of a tonic current in addition to phasic EPSC responses. (B) In dl- TBOA, phasic EPSC responses remained rate-invariant in response to train stimulation at 10, 50, and 100 Hz, however the tonic current progressively increased with rate (n=4). EPSCs normalized to EPSC1 peak amplitude. (C) Example evoked postsynaptic firing responses to a 1-s, 50-Hz train (left) and following dl-TBOA application (right). The instantaneous firing rate (below) demonstrates a step-like response under control conditions and an enhanced, long-lasting response in dl- TBOA. (D) The population effects of blocking glutamate transporters on the firing rate (left) and duration (right) of postsynaptic responses to 1-s stimuli.