Response properties of SI neurons responding to noxious mechanical stimulation. A: Low-threshold mechanoreceptive (LTM) neurons only responding to non-noxious stimulation (brush). B: Example of wide-dynamic range (WDR) SI neurons responding to both noxious and non-noxious stimulation (blackened area). Arrow heads and broken horizontal line show resting membrane potential. C: Example of nociceptive-specific (NS) neurons - noxious pinch stimuli applied to the orofacial skin (blackened area) produced a barrage of excitatory postsynaptic potentials (EPSPs) accompanied by action potentials in a SI neuron under current-clamp conditions. This neuron did not respond to non-noxious stimulation (brush). Arrow heads and broken horizontal line show resting membrane potential.