DipyridamoleVasodilator AgentsPapaverineNitroprussideVasodilationAcetylcholineVascular ResistanceDilazepAdenosineCoronary CirculationThioinosineThallium RadioisotopesHyperemiaHemodynamicsNitric OxideRegional Blood FlowCoronary DiseaseHeartAspirinEquilibrative-Nucleoside Transporter 2Equilibrative Nucleoside Transporter 1Exercise TestNucleosidesTheophyllineForearmTechnetium Tc 99m SestamibiCoronary VesselsNitroglycerinNitrogen RadioisotopesDogsThalliumTomography, Emission-Computed, Single-PhotonDobutaminePhosphodiesterase InhibitorsTomography, Emission-ComputedBlood PressurePlatelet Aggregation InhibitorsEndothelium, VascularNucleoside Transport ProteinsEpoprostenolDose-Response Relationship, DrugHydralazineSulfinpyrazoneBradykininRubidium RadioisotopesVasoconstrictionNG-Nitroarginine Methyl EsterBlood Flow VelocityEchocardiography, StressEchocardiographyAminophylline2-ChloroadenosineCalcitonin Gene-Related PeptideCoronary AngiographyVasoconstrictor AgentsMesenteric ArteriesLidoflazineEquilibrative Nucleoside Transport ProteinsHeart RateInosineArteriolesPurinesInfusions, Intravenous