Y-33075 (Y-39983) is a potent ROCK inhibitor, with an IC 50 of 3.6 nM. It also inhibits PKC and CaMKII more potently than Y-27632, and the IC 50 s of Y-27632 and Y-33075 for PKC are 9.0 μM and 0.42 μM, respectively, whereas the IC 50 s of Y-27632 and Y- 33075 for CaMKII are 26 μM and 0.81 μM, respectively. The IC 50 s of Y-27632 and Y-33075 for PKC are 82 and 117 times those for ROCK, respectively, whereas the IC 50 s of Y-27632 and Y-33075 for CaMKII is 236 and 225 times those for ROCK, respectively. Y-33075 (Y-39983, 10 μM) extends neurites in the retinal ganglion cells (RGCs) compared with those in RGCs treated without Y-39983. It (Y-39983, 1 μM) inhibits the contraction of rabbit ciliary artery segments evoked by histamine in Ca 2+ -free solutions. Y-33075 ( 10 μM) shows no effect on the [Ca 2+ ]i increase with the high-potassium (high-K) solution.
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