Expression and localization of histamine H1, H2, and H3 receptors in rat olfactory epithelium.

OBJECTIVE: Histamine is an important chemical mediator in the development of allergic rhinitis and plays a key role in eliciting the nasal symptoms of the disorder. Histamine may also affect smell as a neurotransmitter. However, whether histamine receptors are present in the mammalian olfactory epithelium has not yet been examined. The aim of this study was to investigate the expression and distribution of histamine H1, H2, and H3 receptors in rat olfactory epithelium.

METHODS: Real-time quantitative PCR and immunohistochemical staining were performed to examine the mRNA level and protein expression and localization of histamine receptors (H1, H2, and H3) in rat olfactory epithelium.

RESULTS: We demonstrated that mRNAs encoding histamine H1, H2, and H3 receptors were detected in rat olfactory epithelium. Immunohistochemistry also showed strong positive staining for these receptors. Co-localization of histamine H1, H2, and H3 receptors with olfactory mature protein revealed that these three histamine receptors were mainly localized in olfactory receptor neurons.

CONCLUSIONS: These findings indicate that histamine H1, H2, and H3 receptors are present in rat olfactory epithelium and may play a physiological role in olfactory transmission.