Blood Flow VelocityArteriovenous AnastomosisCarotid ArteriesRegional Blood FlowCarotid Artery, ExternalCerebrovascular CirculationMetergolineCarotid Artery, InternalUltrasonography, Doppler, TranscranialCarotid Artery, CommonCarotid Artery ThrombosisReceptor, Serotonin, 5-HT1DCarotid StenosisMethiothepinBlood PressureHemodynamicsErgotamineCarotid Artery DiseasesMiddle Cerebral ArterySumatriptanUltrasonography, DopplerHeart RateEndarterectomy, CarotidCerebral ArteriesOphthalmic ArteryPulsatile FlowReceptors, SerotoninVascular ResistanceUltrasonography, Doppler, ColorUltrasonographyDogsAnesthesiaUltrasonography, Doppler, PulsedCoronary CirculationCarotid BodyLaser-Doppler FlowmetryHypocapniaSwineCiliary ArteriesRetinal ArteryCarotid SinusEchoencephalographyEchocardiography, DopplerRheologyUmbilical ArteriesHyperventilationCarbon DioxideRabbitsMicrocirculationDiastoleAnterior Cerebral ArteryUltrasonography, PrenatalHyperemiaGuanethidineModels, CardiovascularArteriesReference ValuesSystoleTime FactorsAcetazolamideProspective StudiesCoronary VesselsVasodilationIntracranial PressureHeart Rate, FetalCeliac ArteryCircle of WillisDoppler EffectHomeostasisUltrasonography, Doppler, DuplexVasodilator AgentsCarotid Artery InjuriesGestational AgeOxygenBrainCollateral CirculationReproducibility of ResultsHemorheologyPregnancyCerebrovascular DisordersMesenteric Artery, SuperiorArterial Occlusive DiseasesVasomotor SystemMagnetic Resonance AngiographyFetal Growth RetardationTilt-Table TestEchocardiography, Doppler, ColorHypercapniaCarotid Intima-Media ThicknessPlacental CirculationSheepEchocardiographyPosterior Cerebral ArteryFetal HeartHypotension, OrthostaticTunica IntimaSplanchnic CirculationBlood ViscosityFlow CytometryCerebral Angiography