Basilar ArteryStrokeArteriesVertebrobasilar InsufficiencyCerebral ArteriesVertebral ArteryCarotid ArteriesPulmonary ArterySubarachnoid HemorrhageBrain Stem InfarctionsCerebral AngiographyBrain IschemiaCerebrovascular DisordersVasospasm, IntracranialMesenteric ArteriesRenal ArteryFemoral ArteryVasodilationCarotid Artery, InternalIschemic Attack, TransientVasoconstrictionCerebral InfarctionIntracranial AneurysmMagnetic Resonance AngiographyMuscle, Smooth, VascularCerebrovascular CirculationCoronary Artery BypassTomography, X-Ray ComputedCarotid Artery DiseasesIliac ArteryArterial Occlusive DiseasesTreatment OutcomeMiddle Cerebral ArteryRadial ArteryVasodilator AgentsMammary ArteriesDogsSubclavian ArterySerotoninRisk FactorsFibrinolytic AgentsThrombolytic TherapyTime FactorsIntracranial ArteriosclerosisIntracranial Embolism and ThrombosisCerebral HemorrhageUltrasonography, Doppler, TranscranialProspective StudiesFollow-Up StudiesBrachial ArteryCarotid Artery, CommonCircle of WillisInfarction, Middle Cerebral ArterySplenic ArteryPotassium ChlorideMuscle ContractionCoronary VesselsTissue Plasminogen ActivatorPapaverineVasoconstrictor AgentsHepatic ArteryAngiography, Digital SubtractionPicolinesIntracranial ThrombosisRabbitsCarotid StenosisEndothelium, VascularAcute DiseaseSumatriptanBrain InfarctionAcetylcholineAngiographyMagnetic Resonance ImagingCeliac ArteryAneurysm, RupturedEmbolization, TherapeuticOphthalmic ArteryPonsMesenteric Artery, SuperiorStentsRetrospective StudiesUmbilical ArteriesIntracranial EmbolismRenal Artery ObstructionVasomotor SystemPosterior Cerebral ArteryBlood PressureTemporal ArteriesThoracic ArteriesDose-Response Relationship, DrugInjections, Intra-ArterialBrainInfusions, Intra-ArterialConstriction, PathologicBronchial ArteriesNitroprussideDisease Models, AnimalPredictive Value of TestsMuscle RelaxationNitroglycerin