A dual resistance model of adenosine vasodilation

In 6 anesthetized, open chest dogs, the time course of coronary blood flow during intra-coronary adenosine infusion and after its cessation were assessed. Continuous adenosine infusion (1.8 mg/min) produced in 9-15 s rapid vasodilation of similar degree to post-ischemic peak; continuing the infusion, there was a further coronary vasodilation, 1.5 time larger than the maximal hyperemic one. In this phase transient ischemia did not induce further vasodilation. Discontinuation of adenosine determined a rapid reduction of coronary flow; at this time it was possible to obtain post-ischemic reactive peak flows larger than before adenosine infusion. On the basis of these experimental results, we discuss analogies and differences with respect to an electric model of 2 variable resistances (functional vascular resistances) and a constant one (anatomical vascular resistance).