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Histamine receptors and the conjunctiva.
Leonard Bielory1, Sadia Ghafoor
1UMDNJ, New Jersey Medical School, Newark, New Jersey 07103, USA. bielory@umdnj.edu
Current Opinion in Allergy and Clinical Immunology
|September 1, 2005
Summary
Histamine H1 receptors in the conjunctiva primarily cause ocular itching, while H2 receptors contribute to vasodilation. Targeting both H1 and H2 receptors offers a promising approach for treating ocular allergy symptoms.
Area of Science:
- Ophthalmology
- Allergy Research
- Pharmacology
Background:
- Histamine plays a significant role in ocular allergic responses.
- Understanding histamine receptor subtypes in the conjunctiva is crucial for effective treatment.
Purpose of the Study:
- To review the effects of histamine on H1, H2, and H3 receptors in the human conjunctiva.
- To evaluate histamine's role in ocular allergy mechanisms.
Main Methods:
- A Medline search was conducted for studies from 1980 onwards.
- Focused on histamine receptor subtypes (H1, H2, H3) in the human conjunctiva.
Main Results:
- Histamine H1 receptor stimulation in the conjunctiva leads to pruritus via the phospholipase C pathway.
- Histamine H2 receptor stimulation is indirectly linked to conjunctival vasodilation.
Conclusions:
- Conjunctival H1 receptors are key targets for treating ocular pruritus in allergies.
- H2 receptors complement H1 in managing vasodilation and injection.
- Antihistamines with broad H1 and H2 receptor activity, like ketotifen, pyrilamine, and epinastine, may improve ocular allergy treatment.