Blood Volume DeterminationBlood VolumeConstrictionCerebrovascular CirculationVasoconstrictionConstriction, PathologicEcho-Planar ImagingImage Interpretation, Computer-AssistedArteriolesMagnetic Resonance ImagingHistory, 21st CenturyBrain MappingDuctus ArteriosusImage EnhancementVasoconstrictor AgentsReflex, PupillaryBrainBronchoconstrictionAmniotic Band SyndromePupilReproducibility of ResultsVasodilationMuscle TonusSensitivity and SpecificityMuscle, Smooth, VascularPericarditis, ConstrictiveCardiomegalyPia MaterDogsRats, Sprague-DawleyCerebral ArteriesMesenteric ArteriesVascular ResistanceHyperesthesiaPressureVasomotor System15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic AcidPhenylephrineSciatic NeuropathyBlood PressureActomyosinArteriesMicrocirculationCoronary VesselsNorepinephrineNeuralgiaCytokinesisEndothelin-1Dose-Response Relationship, DrugPotassium ChlorideRegional Blood FlowEndothelium, VascularIndomethacinAcetylcholineDisease Models, AnimalMyographyBronchial SpasmNitric OxideVasodilator AgentsRats, WistarAirway ResistanceHemodynamicsPerfusionReceptors, Adrenergic, alpha-2Pulmonary ArteryMuscle ContractionAdrenergic alpha-AgonistsSciatic NerveTracheaEnzyme InhibitorsEndothelinsHyperalgesiaMyosin Type IIPericardiectomyAortaHydrazinesAngiotensin IISerotoninThromboxane A2Mesenteric VeinsMethacholine ChlorideGastrulationVenulesMyocardiumTime FactorsAnalgesicsBasilar ArteryRetinal ArteryReceptors, EndothelinReceptor, Endothelin ACell ShapeCalciumBlood Flow VelocityPericardiumCoronary CirculationRenal Arteryrho-Associated KinasesNitroarginineNG-Nitroarginine Methyl EsterVena Cava, Inferior