Itch evoked by electrical stimulation of the skin.

Psychophysical experiments were done to test the possibility that a single receptor population signals both itch and pain by generating different patterns of activity for each type of stimulus. Electrical stimulation of hairy skin evoked pruritus in 92% of the subjects tested, and for the majority the pruritus elicited by electrical stimulation felt the same as that provoked by cowhage. The intensity of pruritus increased with the frequency of stimulation with no change in the quality of the sensation from itch to pain. Electrical stimulation of human skin with response patterns obtained from individual cat polymodal nociceptive neurons to pain- and itch-producing stimuli caused no differences in the quality of the evoked pruritic sensations. These results do not support the idea that the same population of primary sensory neurons can produce both itch and pain by changing their pattern of discharge.