Basilar ArteryArteriesVertebrobasilar InsufficiencyVertebral ArteryCerebral ArteriesPulmonary ArterySubarachnoid HemorrhageCarotid ArteriesBrain Stem InfarctionsCerebral AngiographyVasospasm, IntracranialMesenteric ArteriesRenal ArteryFemoral ArteryVasodilationCranial Fossa, PosteriorIntracranial AneurysmCarotid Artery, InternalVasoconstrictionPosterior Cerebral ArteryMuscle, Smooth, VascularIliac ArteryCoronary Artery BypassArterial Occlusive DiseasesMagnetic Resonance AngiographyTomography, X-Ray ComputedRadial ArteryMammary ArteriesCerebrovascular CirculationDogsVasodilator AgentsCarotid Artery DiseasesSerotoninSubclavian ArteryCircle of WillisMiddle Cerebral ArteryTreatment OutcomeMagnetic Resonance ImagingBrachial ArterySplenic ArteryPotassium ChlorideCoronary VesselsMuscle ContractionPapaverineRabbitsHepatic ArteryVasoconstrictor AgentsCarotid Artery, CommonPicolinesAngiography, Digital SubtractionAneurysm, RupturedSumatriptanUltrasonography, Doppler, TranscranialAcetylcholineEndothelium, VascularOphthalmic ArteryEmbolization, TherapeuticIntracranial ArteriosclerosisIschemic Attack, TransientCeliac ArteryAngiographyIntracranial Embolism and ThrombosisMesenteric Artery, SuperiorPonsCerebral InfarctionUmbilical ArteriesThoracic ArteriesTime FactorsRenal Artery ObstructionVasomotor SystemTemporal ArteriesPopliteal ArteryPosterior Cruciate LigamentBronchial ArteriesBrain StemFollow-Up StudiesDose-Response Relationship, DrugMuscle RelaxationNitroprussideInfarction, Posterior Cerebral ArteryUlnar ArteryStentsNitroglycerinSubclavian Steal SyndromeRegional Blood FlowRetrospective StudiesSpasmConstriction, PathologicInfusions, Intra-ArterialThrombolytic TherapyUterine ArteryIntracranial ThrombosisInjections, Intra-ArterialDilatation, PathologicRats, Sprague-DawleyCoronary AngiographyComaCarotid Artery, ExternalCisterna MagnaBrain