Effects of topical adrenergic agents on prostaglandin E2-induced aqueous flare and intraocular pressure elevation in pigmented rabbits.

PURPOSE: To evaluate the effects of signals through adrenergic receptors on the changes in the aqueous flare and intraocular pressure (IOP) induced by topical prostaglandin E2 (PGE2) in pigmented rabbits. METHODS: Adrenergic agents were applied topically to pigmented Dutch rabbits, and PGE2 was then applied to induce an increase in the aqueous flare and IOP. The degree of aqueous flare was measured with a laser flare meter, and the IOP was measured with a rebound tonometer. Measurements were made every 30 min after the PGE2 had been applied for 2 h and at 4.0 and 4.5 h. Repeated measure analysis of variance and Dunnett's post hoc tests were used for the statistical analyses. RESULTS: The topical application of PGE-2 increased the aqueous flare for more than 4.5 h. The topical instillation of 1.0 % apraclonidine significantly inhibited the increase in the PGE2-induced aqueous flare by 75.1 %, of 0.1 % brimonidine by 57.2 %, of 0.04 % dipivefrin by 57.4 %, and a combination of 0.1 % brimonidine and 5 % phenylephrine by 78.9 %. Topical 5.0 % phenylephrine and 0.05 % isoproterenol had little effect on the aqueous flare elevation induced by PGE2. The IOP increased 0.5 h after the topical application of PGE-2. Topical 1.0 % apraclonidine, 0.1 % brimonidine, 0.1 % dipivefrin, and the combination of 0.1 % brimonidine and 5.0 % phenylephrine significantly inhibited the PGE2-induced IOP elevation. However, topical 5.0 % phenylephrine and 0.05 % isoproterenol did not significantly inhibit the IOP elevation caused by PGE2. CONCLUSIONS: Signaling by the α2 receptor inhibits both the PGE2-induced flare and IOP elevation caused by topical PGE2 application.