Experimental demonstration of postinhibitory facilitation. A: patch-clamp recordings (in vitro gerbil medial superior olive [MSO], P22) of membrane potential for a pair of inhibitory and subthreshold excitatory inputs, Gex = 20 nS, are applied with the dynamic-clamp method with varying preceding times of inhibition, Ginh = 100 nS, (see text for experimental details). B: elimination of PIF after application of the IKLT blocker dendrotoxin I (DTXI). Over the same range of δ as in A the inhibitory conductance transient (IPSG) does not facilitate the subthreshold excitatory conductance (EPSG) to generate a spike. C: Gex was increased by 5% relative to B for just-suprathreshold EPSG, which was preceded by an IPSG in the presence of DTXI. In all cases of the δ-range expected to show facilitation the IPSG suppressed spiking–no facilitation. To compensate for membrane conductance changes in B and C, the amplitudes of Gex and Ginh were reduced approximately 2-fold from the control conditions.