Basilar ArteryPonsArteriesVertebrobasilar InsufficiencyVertebral ArteryCerebral ArteriesBrain Stem InfarctionsPulmonary ArteryCarotid ArteriesSubarachnoid HemorrhageCerebral AngiographyVasospasm, IntracranialMesenteric ArteriesFemoral ArteryRenal ArteryVasodilationVasoconstrictionBrain StemCarotid Artery, InternalIntracranial AneurysmMuscle, Smooth, VascularIliac ArteryCoronary Artery BypassTomography, X-Ray ComputedArterial Occlusive DiseasesCerebrovascular CirculationRadial ArteryMagnetic Resonance ImagingMagnetic Resonance AngiographyMammary ArteriesDogsVasodilator AgentsCarotid Artery DiseasesSubclavian ArterySerotoninMiddle Cerebral ArteryCoronary VesselsBrainTreatment OutcomeSplenic ArteryBrachial ArteryPotassium ChlorideCerebral InfarctionCircle of WillisRabbitsPapaverineCarotid Artery, CommonMuscle ContractionHepatic ArteryVasoconstrictor AgentsPicolinesEndothelium, VascularSumatriptanAngiography, Digital SubtractionAcetylcholineTime FactorsIntracranial ArteriosclerosisIschemic Attack, TransientUltrasonography, Doppler, TranscranialCeliac ArteryAngiographyAneurysm, RupturedOphthalmic ArteryEmbolization, TherapeuticIntracranial Embolism and ThrombosisMesenteric Artery, SuperiorStentsRats, Sprague-DawleyUmbilical ArteriesRenal Artery ObstructionThoracic ArteriesVasomotor SystemTemporal ArteriesCoronary AngiographyDisease Models, AnimalPopliteal ArteryFollow-Up StudiesDose-Response Relationship, DrugBronchial ArteriesCerebellumRetrospective StudiesConstriction, PathologicRegional Blood FlowPosterior Cerebral ArteryNitroprussideBrain IschemiaUlnar ArteryMuscle RelaxationNitroglycerinCerebrovascular DisordersSubclavian Steal SyndromeThrombolytic TherapyInfusions, Intra-ArterialIntracranial ThrombosisUterine ArterySpasmNorepinephrineProspective StudiesComaInjections, Intra-Arterial