IPSCs and EPSCs recorded in layer IV pyramidal cells in response to thalamic stimulation. A, Left, A thalamocortical brain slice preparation (cytochrome c oxidase staining). Scale bar, 1 mm. The black pointer indicates a typical position of stimulation. A barrel is indicated by a dotted circle. Recordings were made from neurons within a barrel. VB, Ventrobasal nucleus of the thalamus; IC, internal capsule. Right, The scheme of the thalamocortical circuit. B1, Synaptic currents evoked by thalamic stimulation were recorded from layer IV pyramidal cells in wt and tg mice (P21–P30). EPSCs were recorded at a holding potential of −60 mV (top traces). When the holding potential was 0 mV, IPSCs became prominent (bottom traces). B2, The outward currents at a holding potential of 0 mV were blocked by picrotoxin (50 μm) (left) and also abolished by CNQX (10 μm) (right). B3, The IPSC and EPSC traces are superimposed in an expanded timescale (the same data used in B1 for wt). The mean delay between the onset EPSC and IPSC was 1.3 ± 0.08 ms (n = 12) for wt and 1.4 ± 0.15 ms (n = 11) for tg mice. C, The relationship between the excitatory and inhibitory conductances. Each point represents data from a single neuron.