5-Hydroxytryptamine (5-HT)2 receptor involvement in acute 5-HT-evoked scratching but not in allergic pruritus induced by dinitrofluorobenzene in rats.
We investigated the role of serotonin (5-hydroxytryptamine; 5-HT)2 and 5-HT3 receptor subtypes in acute itch-associated scratching behavior as well as in an allergic pruritus model in rats. Intradermal 5-HT evoked hind limb scratching directed toward the injection site in naïve rats. Scratching behavior was significantly reduced by pretreatment with the 5-HT2 receptor antagonist ketanserin. Intradermal injection of alpha-methylserotonin, a 5-HT2 receptor agonist, also elicited scratching behavior in a dose-dependent manner, indicating that acute 5-HT-induced scratching is mediated via peripheral 5-HT2 receptors. To produce a model of allergic pruritus, skin was sensitized by topical application of 5% dinitrofluorobenzene (DNFB). One month later, repeated challenge of the skin with 0.2% DNFB at weekly intervals elicited scratching as part of the immediate allergic response. Scratching was not affected by ketanserin or by the 5-HT3 receptor antagonist ondansetron, indicating that neither 5-HT2 nor 5-HT3 receptors is involved in itch-associated scratching behavior caused by allergic skin dermatitis in rats.
Nojima
Hiroshi
H
Section of Neurobiology, Physiology and Behavior, University of California-Davis, 1 Shields Ave., Davis, CA 95616, USA.
Carstens
E
E
D000818:Animals; D004139:Dinitrofluorobenzene; D006967:Hypersensitivity / Q000188:drug therapy / Q000209:etiology / Q000378:metabolism*; D007271:Injections, Intradermal; D008297:Male; D011537:Pruritus / Q000139:chemically induced / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011985:Receptors, Serotonin / Q000502:physiology*; D044406:Receptors, Serotonin, 5-HT3; D012701:Serotonin / Q000009:adverse effects / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000627:therapeutic use
D011985:Receptors, Serotonin; D044406:Receptors, Serotonin, 5-HT3; D012702:Serotonin Antagonists; D012701:Serotonin; D004139:Dinitrofluorobenzene