Effects of cromakalim and nicorandil on intraocular pressure after topical administration in rabbit eyes.

In the study two potassium channel activators, cromakalim and nicorandil, were investigated in rabbits using three different levels of intraocular pressures (IOPs), including alpha-chymotrypsin-induced ocular hypertension, hypotension (IOP recovery method) and normal tension. Cromakalim significantly increased IOP during the initial period in normotensive and hypotensive rabbits, but in the later time, reduced IOP in the alpha-chymotrypsin-induced model. Nicorandil had a similar but less potent effect. In addition, cromakalim also affected ocular blood flows, which had a trend to reduce blood flow about 2-3 hr later, after topical administration of the eyedrop. Two possible mechanisms for increasing IOP effect of potassium channel activators were: (a) enhancing the formation of aqueous humor; (b) relaxing the trabecular meshwork to reduce the outflow of aqueous humor.