The effect of vasopressin on choroidal blood flow, intraocular pressure, and orbital venous pressure in rabbits.

PURPOSE. To investigate the effects of arginine-vasopressin (AVP) on intraocular pressure (IOP), orbital venous pressure (OVP), and choroidal blood flow (ChorBF) regulation in anesthetized rabbits. METHODS. Mean arterial pressure (MAP), IOP, and OVP were measured by direct cannulation of the central ear artery, the vitreous, and the orbital venous sinus, respectively. Laser Doppler flowmetry was used to record ChorBF. To change the perfusion pressure (PP), MAP was manipulated mechanically with occluders around the aorta and vena cava. In the first group of animals (n 11) the dose-response relationship was measured. In the second group of animals (n 8) pressureflow relationships were determined at baseline and in response to intravenous application of a low (0.08 ng/kg/min) and a high (1.33 ng/kg/min) infusion rate of AVP. RESULTS. AVP caused a dose-dependent increase of MAP and choroidal vascular resistance (ChorR), whereas IOP, OVP, ChorBF, and heart rate (HR) were decreased. In contrast to the high infusion rate, the low infusion rate of AVP had no effect on baseline ChorBF. However, the pressure-flow relationship was shifted downward significantly by both infusion rates at PP below baseline. CONCLUSIONS. AVP reduces IOP and OVP significantly and is a