The involvement of dopamine in maintaining intraocular pressure (IOP) was investigated with the rabbit IOP recovery model after intravenous infusion of hypertonic saline. Dopamine facilitated the IOP recovery while reserpine did the opposite. When dopamine was administered after reserpinization, the IOP recovery was facilitated again. These results indicate that dopamine is involved in the maintenance of IOP because depletion of dopamine with reserpine resulted in an opposite effect produced by dopamine whereas administration of dopamine in reserpinized animals induced dopaminergic responses. Timolol produced similar effects as reserpine, which supports the idea that timolol reduces aqueous humor formation through elimination of dopaminergic function and reduction of blood flow in the ciliary body.