MyographyMesenteric ArteriesElectric ImpedanceVasodilationVasoconstrictionVasoconstrictor AgentsVasodilator AgentsArteriesEndothelium, VascularBiological FactorsVascular ResistanceBasilar ArteryMuscle, Smooth, VascularRats, Inbred SHRRats, Inbred WKYRats, WistarAcetylcholineNitroprussideDose-Response Relationship, DrugPhenylephrineMuscle, SkeletalNitric OxideEndothelin-1Blood PressureAortaRats, Sprague-Dawley