Figure 1.

Example of activation of a pruriceptive VTT neuron by intrathecal (i.t.) application of morphine. A, Lesion at the recording point (arrow) in sDH of C1 segment. B, Receptive field. C, Ten overlaid spike traces exhibit ability to follow high-frequency stimulus train with a fixed latency (11.4 ms) between antidromic stimulation (25 μA) and recorded spike (top), and collision of orthodromic spike (arrow) with antidromic spike (asterisk at expected latency) (bottom). D, Lesion at the stimulation point (arrow) in the thalamus. 3V, third ventricle; Po, posterior nucleus; ml, medial lemniscus; ic, internal capsule. E, Responses to brush, pressure, and pinch. F, Response to intradermal (i.d.) injection of serotonin (5-HT) into the receptive field, i.t. application of vehicle and morphine, and intravenous injection of naloxone. Onset of i.d. and i.v. injections denoted by arrows; onset of i.t. application denoted by dotted line, with duration denoted by shading. Insets, Ten overlaid consecutive spike traces, beginning at arrow.