A modified cannula inserting method for measuring vascular responsiveness of the common carotid artery of the dog

A modified cannula inserting method was developed to investigate effects of either intra- or extraluminal application of vasoactive drugs on the isolated vessel which was cannulated and suspended in an organ bath and perfused under a constant flow rate with modified Krebs solution. By inserting a newly developed stainless steel cannula into the vessel, the space between the internal surface of the vessel and the cannula was filled with perfusate and perfused by a pump. Drugs were administered intraluminally through a cannula or extraluminally in the bath. The perfusate after passing through the inside of the vessel was introduced to the tubing and then drained to the outside. Although a lot of methods have been used to observe contractile responses of isolated vessels, this method may be superior to them as follows: (1) drugs act selectively on the inner or outer surface of the vessel; (2) vascular responses to drugs, not only constriction, but also dilatation, are readily observed in a relatively larger artery (1-3 mm I.D.); 3) the vascular reactivity is kept in a stable condition over 7-8 hr at 37 degrees C because reproducible responses were consistently observed. We used this preparation to examine the constrictive and dilatory responses of the canine common carotid artery to extraluminally administered oxyhemoglobin, and intraluminally injected 5-hydroxytryptamine, norepinephrine and ACh.