CIRCULATORY EFFECTS CAUSED BY INTRAARTERIAL INFUSION OF AMP, ADP AND ATP IN THE CANINE FACIAL AND NASAL VASCULAR BEDS

The effects of the intra-arterial infusion of ATP, ADP and AMP into th e internal maxillary artery (IMA), which provides the blood supply to the nasal and forehead regions of the dog, were analyzed. Total blood flow and perfusion pressure measurements in the IMA after administrati on of each adenyl compound indicated dose-dependent and active vasodil atory responses that were restricted to the ipsilateral vessels. The r ank order of potency was ADP greater-than-or-equal-to ATP > AMP. In or der to determine the microcirculatory effects caused by ADP, the trace r microsphere technique combined with absolute blood flow measurement was used. Intra-arterial infusion of ADP in the range 1200 nmol/min pr oduced elevations in the IMA flow on the stimulated side that ranged b etween 11 and 74%. The responses to low doses of ADP were mainly confi ned to the capillaries (CAP), whereas the arteriovenous anastomoses to o were sensitive to high doses. The relative contributions of the anat omically and functionally different compartments of the forehead and n ose to ADP-produced relaxations of the CAP were dependent upon their l ocation. The CAP flows in the tissues which play a crucial role in con ditioning the inspired air increased significantly, while the compartm ents of the furred surfaces were less sensitive to ADP. The results su ggest that, since ATP, ADP and AMP are effective vasodilatory agents i n all the regions examined, purines could have a regulatory or modulat ory role in the complex vascular regulation of the nasal and forehead regions.