Basilar ArteryVertebrobasilar InsufficiencyCerebrovascular CirculationCerebral ArteriesVertebral ArteryPosterior Cerebral ArteryInfarction, Posterior Cerebral ArteryCerebral AngiographyCerebral InfarctionIntracranial AneurysmSubarachnoid HemorrhageArteriesMagnetic Resonance AngiographyBrain Stem InfarctionsBrain IschemiaBrain InfarctionUltrasonography, Doppler, TranscranialMiddle Cerebral ArteryAneurysm, RupturedBrainStrokeIntracranial ArteriosclerosisCarotid Artery, InternalEmbolization, TherapeuticPia MaterTomography, X-Ray ComputedMoyamoya DiseaseAnterior Cerebral ArteryIschemic Attack, TransientBlood Circulation TimeIntracranial EmbolismMagnetic Resonance ImagingBlood CirculationBlood Flow VelocityCerebrovascular DisordersVertebral Artery DissectionVasodilationCarotid ArteriesAngiography, Digital SubtractionVasoconstrictionBlood PressureTreatment OutcomePulmonary ArteryArterial Occlusive DiseasesVasodilator AgentsCarbon DioxideRegional Blood FlowCerebral RevascularizationIntracranial Embolism and ThrombosisVasospasm, IntracranialAngiographyVasomotor SystemExtracorporeal CirculationPapioCerebral VeinsDogsHypercapniaRetrospective StudiesVascular ResistancePulmonary CirculationAneurysm, DissectingConstriction, PathologicHemodynamicsArteriolesCerebral PalsyFollow-Up StudiesPartial PressureFemoral ArteryMesenteric ArteriesMuscle, Smooth, VascularAcute DiseaseHypocapniaRenal ArteryHypotensionXenon RadioisotopesCarotid Artery DiseasesInfarction, Middle Cerebral ArteryCollateral CirculationTime FactorsEndothelium, VascularIntracranial PressureVasoconstrictor AgentsOxygenCerebellumBlood Gas AnalysisBemegrideProspective StudiesCranial Fossa, PosteriorAcetylcholineStentsRabbitsNitroprussideNitric OxideDisease Models, AnimalRisk FactorsRats, Sprague-DawleyCarotid StenosisHomeostasisHyperventilationSwine