Role of histamine H4 receptor in allergic conjunctivitis in mice

We investigated the character of histamine H-1 receptor and H-4 receptor in allergic conjunctivitis. Histamine is the most important mediator in allergic conjunctivitis. We measured eye scratching behavior and allergic-like symptoms score, that is, hyperemia and edema in ICR mice, and examined which receptors intimately involved in allergic conjunctivitis. Histamine caused a dose-dependent eye scratching behavior and allergic-like symptoms. Histamine H-1 receptor antagonist (levocabastine) and H-4 receptor antagonist (JNJ7777120) inhibited eye scratching behavior and histamine H-1 receptor antagonist inhibited allergic-like symptoms induced by histamine. Additionally, combination of levocabastine and JNJ7777120 caused more potent inhibition in allergic conjunctivitis. On the other hand, both selective histamine H-1 receptor agonist (HTMT) and selective H-4 receptor agonist (4-methylhistamine) induced a dose-dependent eye scratching behavior and allergic-like symptoms. JNJ7777120 inhibited the effect of HTMT. However, levocabastine caused no inhibition on the response of 4-methylhistamine. H-4 receptor was closely related with allergic conjunctivitis. H-4 receptor antagonists may be effective in allergic conjunctivitis which showed no inhibition by histamine H-1 receptor antagonists. (c) 2009 Elsevier B.V. All rights reserved.