Itch is relieved by scratching, but the neural mechanisms that are responsible for this are unknown. Spinothalamic tract (STT) neurons respond to itch-producing agents and transmit pruritic information to the brain. We observed that scratching the cutaneous receptive field of primate STT neurons produced inhibition during histamine-evoked activity but not during spontaneous activity or activity evoked by a painful stimulus, suggesting that scratching inhibits the transmission of itch in the spinal cord in a state-dependent manner.
Bibliographical noteFunding Information:
We thank H. Truong for his valuable technical assistance. This work was supported by US National Institutes of Health/National Institute of Neurological Disorders and Stroke grants NS-047399 and NS-059199 and by the Graduate School of the University of Minnesota.