Extravascular pressure modulates responses of isolated rat coronary arteries to vasodilator, but not vasoconstrictor, stimuli

The aims of the study were to investigate whether elevated extravascular pressure modulates responses of isolated rat coronary arteries to constrictor and dilator stimuli. Isolated segments of rat coronary artery were mounted in a modified pressure myograph system that allowed independent modulation of both intra- and extravascular pressures. The influence of elevated extravascular pressure on stable levels of myogenic tone and on responses to vasoconstrictor and vasodilator stimuli was investigated at constant overall transmural pressures. Stable levels of myogenic tone were independent of the relative levels of intra- and extravascular pressure, as were responses to depolarization and to addition of the thromboxane agonist U-46619. Elevating extravascular pressure, however, significantly reduced dilatory responses to introduction of intraluminal flow and to addition of endothelium-dependent and endothelium-independent vasodilatory agonists. These results support the notion that elevated extravascular pressure may attenuate responses of coronary arteries to a variety of dilatory stimuli. This finding may be of relevance to cardiac disorders associated with elevated ventricular pressures.