NEUROMODULATORY EFFECT OF SULPROSTONE ON THE CIRCADIAN ELEVATION OF INTRAOCULAR-PRESSURE IN RABBITS

Topical application of sulprostone, a preferential prostaglandin EP3 r eceptor agonist, caused a dose - dependent reduction of the circadian elevation of intraocular pressure (IOP) in New Zealand albino rabbits which were entrained to 12-hr/12-hr light-dark environment. Correspond ing to the effect on IOP, 0.2 mug, 2 mug, and 20 mug sulprostone decre ased the norepinephrine (NE) concentration in the aqueous humor in the dark phase. There was no breakdown of the blood-aqueous barrier. Bila teral applications of 2 mug and 20 mug sulprostone to entrained rabbit s that had undergone unilateral, preganglionic transection of the cerv ical sympathetic trunk reduced the circadian IOP elevation in the inta ct eye, but caused little IOP change in the decentralized eye. These r esults indicate that the IOP-lowering effect of topical sulprostone in rabbits is dependent on sympathetic neural activity and that prejunct ional inhibition of NE release may be an important mechanism of action .