Abstract
Abstract: :
Purpose: In a previous study, we found that intravenous infusion of dopamine causes dose-dependent, parallel changes in ciliary blood flow and aqueous flow, with vasodilation and increased aqueous flow occurring at a low dose and vasoconstriction and decreased aqueous flow occurring at a higher dose. In the present study, we sought to determine the extent of endogenous dopaminergic D1 receptor activation. Methods: Two groups of anesthetized rabbits were instrumented with an ear artery cannula to measure mean arterial pressure (MAP), a vitreous cannula to measure IOP, and a catheter in the orbital venous sinus to measure orbital venous pressure (OVP). In one group (n=12), aqueous flow was measured by fluorophotometry. In the other group (n=7), ciliary blood flow was measured by laser Doppler flowmetry. Measurements were performed before and after giving the D1 antagonist SCH-23390 (250 µ g/kg, iv). Results: SCH-23390 did not alter baseline ciliary blood flow or the ciliary pressure-flow relationship. Conclusion: The anesthetized rabbit eye receives tonic dopaminergic input. Loss of D1 activation causes increased aqueous production, and slight decreases in orbital venous pressure and IOP.
Keywords: 389 dopamine • 348 ciliary body • 444 intraocular pressure