(A–D) Analysis of excitatory and inhibitory input onto lamina I neurons upon brushing of the skin (grey bars). At a holding potential of −70 mV, only EPSCs are observed, whereas at a holding potential of −40, IPSCs are clearly visible as outward current. Example of a lamina I cell that receives EPSCs and IPSCs (A), EPSCS only (B) and IPSCs only (C). Summary (D) of input type from 26 lamina I neurons. (E–F) Spatial analysis of the receptive fields of lamina I neurons. Example of a neuron that shows center-surround organization (E). Stimulation (von Frey filament 2 g) in the center of the receptive field (dark green) elicited EPSCs in voltage clamp at VH of −70 mV (top trace). In current clamp, mechanical stimulation causes IPSPs as well as action potentials (middle trace). Mechanical stimulation on the outer side of the receptive field (light green area) caused IPSPs but no EPSPs (bottom trace). Summary (F) of receptive fields from seven lamina I neurons. 6 of 7 showed inhibitory receptive fields that were significantly larger than their excitatory receptive fields. (G–I) Temporal analysis of responses of lamina I neurons. Example of a neuron that showed time-locked responses (G) and afterdischarge (boxed dashed line; H) to mechanical stimulation (von Frey filament, 2 g, black bar) of the receptive field. Summary (I) of temporal responses of 61 lamina I neurons.