Involvement of histamine H3 receptors in scratching behaviour in mast cell-deficient mice.
BACKGROUND
Although the roles of histamine H3 receptors have been studied in several tissues such as the brain, lung, spleen, colon and peripheral sensory nerve endings, the involvement of H3 receptors in skin responses particularly in relation to scratching behaviour are not well documented.


OBJECTIVE
This work was performed to study the effects of histamine H3 antagonists on scratching behaviour in mast cell-deficient mice.


METHODS
Histamine H3 antagonists iodophenpropit and clobenpropit, histamine and substance P were injected intradermally into the rostral part of the back of mast cell-deficient (WBB6F1 W/Wv) and wild-type (WBB6F1+/+) mice and scratching behaviour was measured for 60 min. The effects of H1 antagonists on scratching behaviour induced by H3 antagonists were also investigated.


RESULTS
Intradermal injection of iodophenpropit and clobenpropit at doses of 10 and 100 nmol per site caused significant increases in scratching behaviour in both mast cell-deficient and wild-type mice. Histamine also caused a dose-related increase in the incidence of scratching behaviour, and a significant effect was observed at a dose of 100 nmol per site in both mast cell-deficient and wild-type mice. Substance P was also effective in causing scratching behaviour in both mast cell-deficient and wild-type mice. However, histamine H1 antagonists diphenhydramine and chlorphenamine failed to inhibit H3 antagonist-induced scratching behaviour in both types of mice.


CONCLUSIONS
Our results indicated that intradermal injection of H3 antagonists induces scratching behaviour and that chemical mediators other than histamine seem to be involved in the response.
Hossen
M A
MA
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Okayama University, Tsushima-naka 1-1-1, Okayama 700-8530, Japan.
Sugimoto
Y
Y
Kayasuga
R
R
Kamei
C
C
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006632:Histamine / Q000009:adverse effects / Q000032:analysis; D006633:Histamine Antagonists / Q000009:adverse effects; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D007271:Injections, Intradermal; D008407:Mast Cells / Q000502:physiology*; D051379:Mice; D008815:Mice, Inbred Strains; D011537:Pruritus / Q000139:chemically induced / Q000503:physiopathology* / Q000523:psychology; D018100:Receptors, Histamine H3 / Q000502:physiology*; D012867:Skin / Q000737:chemistry; D013373:Substance P / Q000009:adverse effects
D006633:Histamine Antagonists; D006634:Histamine H1 Antagonists; D018100:Receptors, Histamine H3; D013373:Substance P; D006632:Histamine