title: Mouse model of touch-evoked itch (alloknesis).
abstract: Lightly touching normal skin near a site of itch can elicit itch sensation, a phenomenon known as alloknesis. To investigate the neural mechanisms of alloknesis, we have developed an animal model. Low-threshold mechanical stimulation of the skin normally does not elicit any response in naive C57/BL6 mice. Following acute intradermal (i.d.) injection of histamine in the rostral back, mechanical stimulation 7 mm from the injection site elicited discrete hindlimb scratch bouts directed toward the stimulus. This began at 10 minutes and peaked 20-40 minutes post histamine injection, declining over the next hour. Histamine itself elicited bouts of scratching not associated with the mechanical stimulus, which ceased after 30 minutes. Histamine- and touch-evoked scratching was inhibited by the μ-opiate antagonist naltrexone. Touch-evoked scratching was observed following i.d. 5-HT (5-hydroxytryptamine), a protease-activated receptor (PAR)-4 agonist, and an MrgprC11 agonist BAM8-22, but not chloroquine or a PAR-2 agonist. The histamine H1 receptor antagonist terfenadine prevented scratching and alloknesis evoked by histamine, but not 5-HT, a PAR-4 agonist or an MrgprC11 agonist. In mice with experimental dry skin, there was a time-dependent increase in spontaneous and touch-evoked scratching. This animal model appears to be useful to investigate neural mechanisms of itch and alloknesis.
authors.affiliation: Department of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, California, USA.
authors.forename: Tasuku
authors.initials: T
authors.lastname: Akiyama
authors.forename: Mirela Iodi
authors.initials: MI
authors.lastname: Carstens
authors.forename: Akihiko
authors.initials: A
authors.lastname: Ikoma
authors.forename: Ferda
authors.initials: F
authors.lastname: Cevikbas
authors.forename: Martin
authors.initials: M
authors.lastname: Steinhoff
authors.forename: Earl
authors.initials: E
authors.lastname: Carstens
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D006632:Histamine / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D009271:Naltrexone / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D010446:Peptide Fragments / Q000494:pharmacology; D011537:Pruritus / Q000209:etiology*; D018179:Receptors, Thrombin / Q000502:physiology; D014110:Touch
chemical_list: D009842:Oligopeptides; D010446:Peptide Fragments; D018179:Receptors, Thrombin; C571042:bovine adrenal medulla 8-22; C112356:seryl-leucyl-isoleucyl-glycyl--arginyl-leucinamide; D009271:Naltrexone; D006632:Histamine; C112908:protease-activated receptor 4