Figure 5. SDH neurones exhibit four response profiles during innocuous brush and noxious pinch.

A–D, voltage responses from four different neurones during application of brush (upper trace) and pinch (lower trace). A, nociceptive neurones responded maximally (fired APs) to pinch stimulation and in most recordings responded only with subthreshold depolarizations during brush. B, light touch neurones responded maximally to brush (upper trace). Typically, these neurones also responded to pinch stimulation, but APs were restricted to pinch onset and resembled brush-evoked responses (lower trace). C, subthreshold neurones responded to brush and pinch with small depolarizations that failed to reach AP threshold. D, hyperpolarizing neurones responded to both brush and pinch with membrane hyperpolarization, most evident during pinch stimulation. E, the proportion of neurones, grouped according to discharge patterns (as in Fig. 2), exhibiting each of the peripherally evoked response profiles. Each firing pattern group (TF, IB, DF and SS) included neurones with light touch and nociceptive profiles. Subthreshold responses were only observed in DF and SS neurones, whereas hyperpolarizing responses were restricted to IB and SS neurones. Together, these data suggest that SDH neurones expressing the four discharge patterns play a role in processing both noxious and innocuous peripheral stimuli.