Purpose:
To investigate the effect of intravenous vasopressin on choroidal and ciliary blood flow regulation in rabbits.
Methods:
Mean arterial pressure (MAP), intraocular pressure (IOP) and orbital venous pressure (OVP) were measured by direct cannulation of the central ear artery, the vitreous, and the orbital venous sinus, respectively. In two groups Laser Doppler flowmetry was used to measure choroidal blood flow (ChorBF, n=10) and ciliary blood flow (CilBF, n=7) while MAP was manipulated mechanically with occluders on the aorta and vena cava, thus changing ocular perfusion pressure (PP) over a wide range. Pressure–flow (PF) relationships were performed at control and in response to 0.5 µg/kg/h i.v. vasopressin. CarBF was measured with a bidirectional ultrasonic probe on the ipsilateral carotid artery.
Results:
Vasopressin significantly increased MAP, choroidal and ciliary vascular resistance (ChorR, CilR) whereas IOP, CilBF, OVP, CarBF and HR were decreased. The effect on ChorBF was not significant, however, the resistance of the choroidal vessels was doubled. The choroidal as well as the ciliary pressure flow relationship was shifted downwards significantly. The baseline results are summarized in the table. Baseline effects of Vasopressin
Conclusions:
Vasopressin is a strong vasoconstrictor in the choroidal and ciliary vascular bed and substantially lowers intraocular pressure.
Keywords: choroid • ciliary body • blood supply