Ocular hypotensive action of l-stepholidine

Ocular hypotension was made by iv 20% NaCl 2.5 ml/kg in rabbits. On this model, l-stepholidine (l-SPD) lowered intraocular pressure when administered topically to the eyes. The ocular hypotensive action of 0.5% l-SPD was weaker than that of 0.5% timolol, but stronger than that of 0.5% pilocarpine. The maximal actions of the 3 drugs were similar. There were no significant changes of pupil diameter and carbonic anhydrase activity after l-SPD administered, but which suppressed aqueous humor formation. As the ciliary process of the eye behaves much like the renal glomerulus, dopamine increases the glomerular blood flow and dopaminergic antagonist decreases it, the mechanism of l-SPD in lowering intraocular pressure may be related to the dopaminergic receptor blocking effect of it.