Participation of Histamine H3 Receptors in Experimental Allergic Rhinitis of Mice

Abstract

The present study was performed to study the participation of histamine H3 receptors in nasal symptoms using Sch 50971, a potent and selective agonist of the H3 receptor. Repeated topical application of antigen caused an increase in sneezing and nasal rubbing in sensitized mice. Oral administration of Sch 50971 and imetit, specific H3-receptor agonists, resulted in an inhibition of nasal symptoms induced by an antigen similar to an H1-receptor antagonist, cetirizine. Furthermore, simultaneous use of H3-receptor agonists, Sch 50971 or imetit, and an H1-receptor antagonist, cetirizine, caused a significant inhibitory effect on nasal symptoms at doses that showed no effect when used separately. The number of eosinophils in the nasal mucosa of mice sensitized with antigen was significantly decreased by cetirizine; however, Sch 50971 and imetit had no effect on eosinophil infiltration. These results clearly indicate that H3 receptors are involved in the etiology of nasal allergy, and the stimulation of H3 receptors may be useful as a novel therapeutic approach in nasal allergy.