Y-33075 is potent and selective ROCK (Rho-associated coiled-coil-forming protein kinase) inhibitor, developed by Yoshitomi Pharmaceutical Industries for encephalomyelitis treatment. In rabbits and in monkeys, Y-33075 lowers IOP in a dose-dependent fashion. An increase in regenerating axons of RGCs in 100 mM Y-33075-treated eyes is observed compared with saline-treated eyes. Y-33075 dose-dependently increases the number of RGCs with regenerating axons. Both Y-33075 induces a concentration-dependent relaxation in rabbit ciliary arteries precontracted with a high-potassium (high-K) solution. The amplitude of relaxation induced by Y-33075 is not affected by either 100 μM N (G)-nitro-L: -arginine methyl ester (L: -NAME) or 10 μM indomethacin. In Ca2 -free solution, Y-27632 and Y-39983 significantly inhibit the transient contraction of ciliary arteries induced by 10 μM histamine. However, neither Y-27632 nor Y-39983 affects the elevation of [Ca2 ](i) induced by high-K solution and histamine.