Microvascular architecture of the rat choroid: Corrosion cast study

This study presents the details of the microvasculature of the rat choroid visualized by scanning electron microscopy of vascular corrosion casts. Wis tar Kyoto rats were anesthetized with intraperitoneal sodium pentobarbital. The vascular system was perfused with heparinized saline, and Mercox resin was injected into the cannulated carotid arteries. After polymerization of the resin, the vascular casts were macerated with potassium hydroxide, was hed with water, and freeze dried. The casts were examined with a Hitachi S- 2360N scanning electron microscope SEM). Corrosion casts of the entire chor oidal vasculature revealed that the two long posterior ciliary arteries sup plied the entire uveal vasculature. In the posterior choroid, these arterie s formed five to seven branches on each side supplying the adjacent chorioc apillaris. No interarterial or arteriovenous anastomoses were seen. The cho riocapillaris appeared as a nonhomogeneous and nonlobular monolayer capilla ry network, consisting of dense honeycomb and irregular patterns. There are two distinct venous systems in the rat choroid. The venous blood from the central region, peripapillary choroid, and sometimes the optic nerve head d rain into the posterior ciliary vein. The venous blood from the iris, cilia ry body, anterior choroid, and half of the posterior choroid drain into the vortex veins. Corrosion casts and the SEM have shown details of the choroi dal vascular architecture. These three-dimensional observations indicate th at the rat choroidal vasculature has different features from those of human s and other primates. Despite these interspecies differences, the establish ment of a thorough baseline concept of choroidal vasculature should permit additional studies of the choroidal pathology and enable the proper interpr etation of results from rat experimental models for extrapolation to humans . Anat Rec 264:63-71, 2001. (C) 2001 Wiley-Liss, Inc.