Basilar ArteryVertebrobasilar InsufficiencyVertebral ArteryCerebral AngiographyBrain Stem InfarctionsArterial Occlusive DiseasesPosterior Cerebral ArteryArteriesCerebral ArteriesInfarction, Posterior Cerebral ArteryMagnetic Resonance AngiographyCerebral InfarctionCerebrovascular CirculationIntracranial AneurysmRetinal Artery OcclusionTomography, X-Ray ComputedSubarachnoid HemorrhageComaMechanical ThrombolysisThrombolytic TherapyStrokeSkull Fracture, BasilarInjections, Intra-ArterialBrain IschemiaFibrinolytic AgentsCarotid Artery, InternalBrain InfarctionSkull Fracture, DepressedTreatment OutcomeUltrasonography, Doppler, TranscranialAneurysm, RupturedEmbolization, TherapeuticTissue Plasminogen ActivatorIntracranial ArteriosclerosisPulmonary ArteryPonsInfarction, Middle Cerebral ArteryIschemic Attack, TransientCarotid ArteriesBrain StemFemoral ArteryInfusions, Intra-ArterialAcute DiseaseVertebral Artery DissectionRenal ArteryMoyamoya DiseaseMesenteric ArteriesMonoacylglycerol LipasesAnterior Cerebral ArteryAngiography, Digital SubtractionMagnetic Resonance ImagingAngiographyVasodilationDogsHeadacheVasoconstrictionCarotid Artery DiseasesMiddle Cerebral ArteryIliac ArteryIntracranial EmbolismCerebral RevascularizationProspective StudiesCerebrovascular DisordersConstriction, PathologicBrainMuscle, Smooth, VascularCollateral CirculationStentsRetrospective StudiesCerebral Arterial DiseasesCoronary Artery BypassFollow-Up StudiesInjections, IntravenousAneurysm, DissectingCoronary VesselsVasodilator AgentsRadial ArteryCircle of WillisTime FactorsSubclavian ArteryCoronary OcclusionMammary ArteriesDisease Models, AnimalSerotoninRegional Blood FlowRabbitsRats, Sprague-DawleyOphthalmic ArteryCarotid Artery, CommonSplenic ArteryIntracranial Embolism and ThrombosisBrachial ArteryCeliac ArteryCranial Fossa, PosteriorEndothelium, VascularBalloon OcclusionCoronary CirculationCarotid StenosisMuscle ContractionPapaverine