Model for Studying Anti- Allergic Drugs for Allergic Conjunctivitis in Animals

Allergic conjunctivitis (AC), which is characterized by ocular itching, hyperemia, and edema, deteriorates quality of life. In this study, effects of anti-allergic drugs were evaluated by assessing eye-scratching behavior, the number of eosinophils in conjunctiva epithelial tissues, and concentrations of chemical mediators in the tears of the guinea pig model of ovalbumin (OA)-induced AC. METHODOLOGY On day 0, 3-week-old guinea pigs were sensitized by OA subconjunctival injections. On days 15, 17, and 19, OA solution was administered. Anti-allergic eye drops were administered 5 and 15 min before the final OA challenge on day 19. Scratching behavior within 1 h after OA exposure was studied. Eosinophils in the conjunctiva were stained with Giemsa reagent. Histamine and substance P (SP) concentrations in tears were measured using ELISA. RESULTS Subconjunctivally injected guinea pigs were observed for clinical symptoms. Scratching responses significantly reduced with ketotifen or olopatadine treatment. Eosinophil numbers reduced in animals treated with ketotifen, levocabastine, or tranilast. Histamine and/or SP concentrations in tears were inhibited by some of these anti-allergic drugs. CONCLUSIONS It is important to assess the anti-allergic AC drugs objectively because there are several of these drugs currently available. This model allows for an objective evaluation of anti-allergic drugs for AC.