Fig. 4.

Characterization of a nociceptive-only neuron responding to noxious mechanical and thermal stimulation, but not to any tested pruritogens or partial pruritogens. A: receptive field. B: lesion (arrow) made at the recording point in the superficial layers of the spinal trigeminal nucleus. C: lesion (arrow) made at the point in the thalamus with the lowest threshold for antidromic activation. D: responses to mechanical stimulation of the receptive field. E: response to thermal stimulation of the receptive field. F–L: the cell did not respond to intradermal injection of vehicle, serotonin, BAM8–22, chloroquine, histamine, or capsaicin or insertion of cowhage spicules into the receptive field [L, inset: response to heat-inactivated (IA) cowhage spicules]. For this cell, pruritogens and partial pruritogens were applied in the following order: serotonin, BAM8–22, chloroquine, histamine, cowhage, and capsaicin. obx, obex.