Histamine content and histamine H1 receptor in experimentally-induced nasal hypersensitivity

Quantitative evaluations of histamine and histamine H1 receptor were carried out in nasal mucosa of toluene diisocyanate (TDI) sensitized guinea-pigs at specific points in time during a pre-determined sensitization period. Histamine content is significantly increased at 1 week and definitely elevated after 2 weeks of sensitization. This increase was maintained throughout the sensitization period. It decreased to normal by four weeks post-sensitization. Also the relatively low histamine content immediately after TDI challenge indicated that a certain amount of histamine was released by TDI challenge. On the other hand, the density and affinity of the histamine H1 receptor was not found to be altered during TDI sensitization. These results suggest that enhanced histamine has a role in the development of nasal allergy, whereas the relevance of quantitative-alteration of the H1 receptor to histamine hypersensitivity observed in nasal allergy has not been demonstrated.