Basilar ArteryTomography, X-Ray ComputedInfarction, Posterior Cerebral ArteryEpidermal CystPosterior Cerebral ArteryArteriesVertebrobasilar InsufficiencyInfarction, Middle Cerebral ArteryMagnetic Resonance ImagingVertebral ArteryCerebral ArteriesAcute DiseaseBrain IschemiaPulmonary ArteryBrain Stem InfarctionsCarotid ArteriesSubarachnoid HemorrhageCerebral AngiographyBrainVasospasm, IntracranialMesenteric ArteriesRenal ArteryFemoral ArteryVasodilationSensitivity and SpecificityVasoconstrictionCarotid Artery, InternalIntracranial AneurysmMuscle, Smooth, VascularIliac ArteryDogsTreatment OutcomeCoronary Artery BypassMagnetic Resonance AngiographyRetrospective StudiesFatal OutcomeArterial Occlusive DiseasesRadial ArteryMammary ArteriesVasodilator AgentsCerebrovascular CirculationCarotid Artery DiseasesSerotoninTime FactorsSubclavian ArteryMiddle Cerebral ArteryDelayed DiagnosisSplenic ArteryPotassium ChlorideBrachial ArteryCoronary VesselsRabbitsMuscle ContractionFollow-Up StudiesPapaverineCircle of WillisPredictive Value of TestsEarly DiagnosisHepatic ArteryPrenatal DiagnosisVasoconstrictor AgentsAngiographyCarotid Artery, CommonBiopsyProspective StudiesPicolinesAngiography, Digital SubtractionEndothelium, VascularAcetylcholineSumatriptanUltrasonography, Doppler, TranscranialIschemic Attack, TransientCeliac ArteryImmunohistochemistryAneurysm, RupturedPonsMesenteric Artery, SuperiorIntracranial ArteriosclerosisReproducibility of ResultsOphthalmic ArteryEmbolization, TherapeuticDiagnostic ErrorsIntracranial Embolism and ThrombosisCerebral InfarctionDose-Response Relationship, DrugUmbilical ArteriesRenal Artery ObstructionRisk FactorsTemporal ArteriesConstriction, PathologicThoracic ArteriesVasomotor SystemDilatation, PathologicRats, Sprague-DawleyComaCalorimetry, Differential ScanningBronchial ArteriesNitroprussideMuscle RelaxationPopliteal Artery