Fig. 1.
GABAergic network neurons generated inward and outward IPSCs in a single target neuron through GABAAreceptors. A1, Spontaneous IPSCs were inward and outward current transients in a cell recorded at VH−63 mV. Inward and outward sIPSCs occurred in isolation (1), or inward currents were curtailed by outward sIPSCs (2). Note the difference in calibration between 1 and 2. A3, In another cell inward sIPSCs occurred in clusters interrupted by “silent” periods, whereas outward sIPSCs occurred rather continuously (VH −71 mV). B, The GABAA antagonist bicuculline (bic) reversibly blocked all inward and outward sIPSCs. a, b, Expanded segments of the top trace where indicated. C, D, Inward and outward sIPSCs differed in their time courses. Inward (D1) and outward (C1) sIPSCs that occurred in separation could be fitted by a single exponential function (solid line; VH −63 mV). For the sIPSCs shown, the time constant of decay was 26.2 msec (amplitude coefficient 39.4) and 6.0 msec (amplitude coefficient −33.1). For analysis, only sIPSCs that had no inflections in the rise or decay phase were accepted. Rise time (10–90%) histogram of all inward (D2) and outward (C2) sIPSCs showed that rise time was slower for outward sIPSCs. Similarly, histograms of decay time constant (C3, D3) revealed a much slower decay for outward sIPSCs (C3). For the histograms, 31 outward and 45 inward IPSCs (sampled in 1 min) were analyzed. All recordings in this Figure were obtained in the presence of ionotropic glutamate receptor antagonists and of 2 mm[K+]o([A−]pip 15 mm).