Vasoconstrictor AgentsNorbornanesVasoconstrictionPhenylephrineAngiotensin IINorepinephrineVascular ResistanceMuscle, Smooth, VascularBlood PressureEndothelinsEndothelin-1Mesenteric ArteriesRegional Blood FlowSympathetic Nervous SystemVasomotor SystemReceptors, Endothelin15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic AcidVasodilationVasodilator AgentsMethoxamineForearmReceptor, Endothelin ARenal CirculationTyramineNitric OxideThromboxane A2Receptor, Endothelin BArteriolesArteriesEndothelium, VascularHemodynamicsDose-Response Relationship, DrugProstaglandin Endoperoxides, SyntheticUrotensinsNG-Nitroarginine Methyl EsterPotassium ChlorideIndomethacinAdrenergic alpha-AgonistsRats, Sprague-DawleyPerfusionReceptors, ThromboxaneNitroprussideDogsSplanchnic CirculationSerotoninMuscle TonusNordefrinHydroxyeicosatetraenoic AcidsNitric Oxide SynthaseProstaglandinsAcetylcholineViper VenomsPeptides, CyclicRenal ArteryAdrenergic alpha-AntagonistsSumatriptanPulmonary CirculationRats, WistarArginine VasopressinAdrenergic alpha-1 Receptor AgonistsLaser-Doppler FlowmetryHeart RateAdrenergic FibersSkin TemperatureBlood VesselsPhentolamineEnzyme InhibitorsKidneyAstringentsBretylium CompoundsSympathetic Fibers, PostganglionicNitroarginine