Journal of neurophysiology
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Clinical Trial
Chemical response pattern of different classes of C-nociceptors to pruritogens and algogens.
Vasoneuroactive substances were applied through intradermal microdialysis membranes and characterized as itch- or pain-inducing in psychophysical experiments. Histamine always provoked itching and rarely pain, capsaicin always pain but never itching. Prostaglandin E(2) (PGE(2)) led preferentially to moderate itching. ⋯ CMH units (polymodal nociceptors) and CMi(His-) units showed significantly weaker responses to histamine, PGE(2), and acetylcholine. Capsaicin and bradykinin responses were not significantly different in the two classes of mechano-insensitive units. We conclude that CMi(His+) units are "selective," but not "specific" for pruritogenic substances and that the pruritic potency of a mediator increases with its ability to activate CMi(His+) units but decreases with activation of CMH and CMi(His-) units.