Vascular responsiveness of simian digital artery to various vasoactive substances

The stainless steel cannula inserting method was used to observe vascular effects of 7 vasoactive substances on the isolated and cold-stored digital artery of the monkey. The arterial preparation was suspended in a bath at 37 degrees C and perfused with Ringer's solution under constant flow rate. Drugs were administered in the endothelial side of the artery through a cannulated tubing, and the response was obtained as changes in perfusion pressure. All used agonists increased perfusion pressure in a dose-related manner. The order of potency for inducing vasoconstriction was norepinephrine greater than serotonin = phenylephrine = clonidine greater than xylazine greater than tyramine greater than potassium chloride. Inhibiting effect of prazosin (0.001-0.01 microgram) was greater on phenylephrine (0.03 microgram)-induced contractile responses than on clonidine (0.03 microgram)-induced responses, and the reverse was true in the case of yohimbine (0.01-1.0 microgram). Thus, it was suspected that the simian digital artery would be a good model for in vitro investigation of vascular responsiveness as a conduit artery which mainly supplies blood flow to the skin, and that this artery might be contracted not only via postjunctional alpha 1- but also alpha 2-adrenoceptors.