Fig. 2.

Characterization of a pruriceptive VTT neuron responding to serotonin, histamine, and capsaicin. 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: the cell did not respond to intradermal injection of vehicle into the receptive field. G–I: the cell responded to the pruritogen serotonin and to the partial pruritogens histamine and capsaicin, each injected intradermally into the receptive field. For this cell, pruritogens and partial pruritogens were applied in the following order: serotonin, cowhage, histamine, chloroquine, BAM8–22, and capsaicin. hb, habenular n.; ic, internal capsule.