Fig. 6. Properties of postsynaptic GABA_A receptor currents in hippocampal GluR cells. Data were taken in the presence of NBQX (10 µM) and D-APV (25 µM). (A) Membrane currents were evoked as described in Fig. 2A. (B) Paired-pulse stimulation (150 µs, 29 V, 50 milliseconds delay, 10 seconds interstimulus interval; 37 double pulses) evoked slowly decaying PSCs (17 milliseconds). Currents were sorted according to stimulation success, and averaged. In 8 cases, both pulses evoked glial PSCs (upper left trace; amplitudes 3.0 and 2.4 pA) while 14 paired pulses produced double failures (right, top). Seven stimulation pairs induced responses upon the first (left, bottom), another 8 upon the second pulse (right, bottom). The total failure rate was 58%. (C) Short (150 µs) stimulation pulses evoked glial PSCs, which had opposite directions at –80 mV and 0 mV (averaged responses of 120 and 30 single traces, respectively). (D) Spontaneous GABA-mediated PSCs occurred rarely (about 1 event per minute; arrow). (E) Kinetics of the GABA-mediated glial sPSC labelled by an arrow in (D) at higher time resolution. (F) Increasing [K⁺]_o to 10 mM significantly increased the frequency glial GABA sPSCs (50 events per minute). (G) Analysis of averaged sPSCs (187 events) revealed an amplitude of 3.2 pA, a desensitization time constant of 19.5 milliseconds, a rise time of 1.9 milliseconds (10-90% time to peak), and a half width of 14.6 milliseconds. With the exception of (B), all recordings in this figure were obtained from the same individual cell; [Cl^–]_i was always 27 mM.