Fig. 4. Schaffer-collateral stimulation reveals two types of glial ePSCs with different inactivation kinetics. (A,B) Sub-threshold field potentials (top traces) were elicited applying a paired pulse protocol (150 microseconds, 150 µA, 50 milliseconds interval, every 20 seconds) while recording a GluR cell in the voltage-clamp mode (–80 mV, bottom traces). Typical examples of rapidly (A, =2.4 milliseconds, arrow) and slowly (B, =33 milliseconds, arrowhead) inactivating glial ePSCs are shown. (C) Fast and slowly decaying ePSCs occurred in the same individual GluR cell. 120 single sub-threshold pulses (100 microseconds, 150 µA) were applied every 3 seconds while currents were recorded at –80 mV. The top left trace represents the total average of all responses. Subsequently, current traces were sorted according to inactivation time constants. The left panel shows averages of pooled responses, while the right panel gives typical original traces. The upper pair of traces shows fast inactivating currents (_fast=3.4 milliseconds, n=16), the next summarizes traces with slowly inactivating currents (t_slow=34.7 milliseconds, n=48), followed by responses with biphasic inactivation (_fast=4.6 milliseconds, _slow=30.3 milliseconds, n=16). The bottom pair shows failure traces (n=35). Arrows denote fast responses, arrowheads denote slowly decaying responses. [Cl^–]_i was always 135 mM.