ISOLATED, PERFUSED RABBIT EAR ARTERY - A MODEL FOR STUDYING SEGMENTALVASOCONSTRICTION AND DILATATION

Severe increases in blood pressure (BP) are associated with a segmenta l pattern of constriction and dilatation in small arteries and arterio les, but the pathogenesis is poorly understood. We showed that the iso lated, perfused rabbit ear artery typically develops segmental constri ction and dilatation when intraluminal pressure is > 160-180 mm Hg dur ing field stimulation of perivascular nerves (> 6 Hz) or extra- or int raluminal infusions of norepinephrine (NE > 10(-7) M) or phenylephrine (PE) (> 5 x 10(-7) M). Light, transmission, and scanning electron mic roscopy showed that the dilated vessel segments initially show endothe lial injury with no smooth muscle lesions. After repeated or prolonged exposure to high intraluminal pressure, dilated segments manifest ext ensive and severe endothelial and smooth muscle damage. Dilated region s also became abnormally permeable to tracer particles (ferritin). Con stricted segments did not show evidence of endothelial or smooth muscl e injury or hyperpermeability. These changes, i.e., segmental vasocons triction/dilatation , hyperpermeability, and vessel wall damage locali zed to dilated segments, are comparable to those that occur in small a rteries and arterioles during severe hypertension. We discuss the pote ntial usefulness of the isolated ear artery as a model for studying th e pathogenesis and morphology of segmental vasoconstriction/dilatation .