Vascular permeability in allergic conjunctivitis in mice lacking histamine H₁ receptors

To clarify the role of histamine H₁ receptors in allergic conjunctivitis, changes in vascular permeability of the conjunctiva were measured in histamine H₁ receptor deficient mice. Wild-type mice showed a significant increase in vascular permeability of the conjunctiva induced by histamine. However, no such increase was found in histamine H₁ receptor deficient mice. On the other hand, no differences were observed between wild-type and histamine H₁ receptor deficient mice in response to serotonin. A significant increase in vascular permeability was observed in actively sensitized wild-type mice, whereas no increase was observed in histamine H₁ receptor deficient mice. Similar findings were noted in passively sensitized animals. Histamine contents of the conjunctiva were significantly decreased by topical application of antigen in both wild-type and histamine H₁ receptor deficient mice after active sensitization with antigen. These findings suggested that vascular permeability in the conjunctiva in allergic conjunctivitis is entirely regulated through histamine H₁ receptor. (C) 2000 Elsevier Science B.V.