A new method for measuring vascular responsiveness of relatively larger arteries of dogs.

A new model of isolated vascular preparation was developed in the dog. Several canine arteries were isolated and suspended in a bath and perfused under a constant flow rate with Ringer-Locke solution. In each experiment, resting perfusion pressure was set at a constant level at 40-60 mm Hg. Drugs were administered in the endothelial side of the artery through a cannulated tubing, and the response was obtained as changes in the perfusion pressure. By inserting the polyethylene cannula into the artery, the space between the luminar wall of the artery and the cannula was decreased enough to obtain a suitable perfusion pressure, while the cannula was filled with the fluid by pumping. Although some other methods have been used to observe contractile responses of the artery, this method might be superior to them because: 1) drugs act only on the luminar wall; 2) vascular responses to drugs, not only constriction, but also dilatation, in nontreated preparations, are readily observed in a relatively larger artery (2-3 mm I.D.); 3) the vascular reactivity is kept in a stable condition over 7-8 hours at 37 degrees C. We used this preparation to examine the contractile responses of the common, internal, external carotid, and femoral arteries to 5-hydroxytryptamine.