Basilar ArteryVertebrobasilar InsufficiencyPosterior Cerebral ArteryVertebral ArteryInfarction, Posterior Cerebral ArteryCerebral AngiographyIntracranial AneurysmBrain Stem InfarctionsCerebral ArteriesArteriesSubarachnoid HemorrhageMagnetic Resonance AngiographyCerebrovascular CirculationBrain InfarctionAneurysm, RupturedCerebral InfarctionIntracranial ArteriosclerosisEmbolization, TherapeuticMoyamoya DiseaseVertebral Artery DissectionStrokeCarotid Artery, InternalAnterior Cerebral ArteryTomography, X-Ray ComputedBrain IschemiaMagnetic Resonance ImagingUltrasonography, Doppler, TranscranialPulmonary ArteryIschemic Attack, TransientIntracranial EmbolismAngiography, Digital SubtractionArterial Occlusive DiseasesCarotid ArteriesTreatment OutcomeAngiographyCerebrovascular DisordersAneurysm, DissectingCerebral RevascularizationRetrospective StudiesVasospasm, IntracranialConstriction, PathologicMesenteric ArteriesFemoral ArteryRenal ArteryVasodilationFollow-Up StudiesBlood CirculationAcute DiseaseVasoconstrictionCranial Fossa, PosteriorBrainStentsCerebellumProspective StudiesMuscle, Smooth, VascularDogsRisk FactorsCoronary Artery BypassIliac ArteryRegistriesVasodilator AgentsRadial ArteryRecurrenceMammary ArteriesCarotid Artery DiseasesMiddle Cerebral ArterySerotoninPredictive Value of TestsSubclavian ArteryCircle of WillisPulmonary CirculationDiffusion Magnetic Resonance ImagingCoronary VesselsExtracorporeal CirculationRabbitsBrachial ArterySplenic ArteryCollateral CirculationVasoconstrictor AgentsPapaverineMuscle ContractionPotassium ChlorideEndothelium, VascularRegional Blood FlowHepatic ArteryCarotid Artery, CommonTime FactorsOphthalmic ArteryAcetylcholinePicolinesSumatriptanCoronary CirculationCeliac ArteryIntracranial Embolism and ThrombosisMesenteric Artery, SuperiorUmbilical ArteriesBronchial ArteriesVasomotor SystemPonsDose-Response Relationship, Drug