Regional Blood FlowBlood Flow VelocityCerebrovascular CirculationLaser-Doppler FlowmetryFlow CytometryBlood PressureVascular ResistancePulsatile FlowXenon RadioisotopesMicrospheresHemodynamicsDogsMicrocirculationRenal CirculationOxygenVasodilationLiver CirculationOxygen ConsumptionPulmonary CirculationTomography, Emission-ComputedRheologySplanchnic CirculationCarbon DioxideHyperemiaOxygen RadioisotopesBrainUltrasonography, DopplerHeart RateXenonGene FlowBlood Circulation TimeUltrasonography, Doppler, ColorBlood VolumePlethysmographyVasodilator AgentsCollateral CirculationCerebral ArteriesTime FactorsArteriesVasoconstrictionModels, CardiovascularUltrasonography, Doppler, TranscranialCapillariesNitric OxideHindlimbPartial PressureIschemiaBlood Gas AnalysisLegMiddle Cerebral ArteryRetinal VesselsAntipyrinePerfusionMuscle, SkeletalChoroidSkin TemperatureVasomotor SystemFemoral ArteryBrain IschemiaSkinAdenosineRats, Sprague-DawleyNitrogen RadioisotopesTomography, Emission-Computed, Single-PhotonSheepTechnetium Tc 99m ExametazimeReference ValuesOximesArteriolesOphthalmic ArteryKryptonNitroprussideAcetazolamideSwineEndothelium, VascularHomeostasisRetinal ArteryBlood ViscosityNG-Nitroarginine Methyl EsterHypercapniaUltrasonography, Doppler, PulsedPhysical ExertionMagnetic Resonance ImagingKidneyAnoxiaAnesthesiaHeartBlood VesselsUterusIntracranial PressureCoronary CirculationCatsHematocritNitric Oxide SynthaseDisease Models, AnimalInfusions, Intra-ArterialInjections, Intra-ArterialRestOrganotechnetium CompoundsHypotension