Myocardial ContractionMuscle ContractionVentricular FunctionMyocardiumSystoleHeart VentriclesHeartVentricular Function, LeftVentricular Dysfunction, LeftEchocardiographyCoronary CirculationCalciumDogsMyocytes, CardiacIsometric ContractionUterine ContractionMuscle, SmoothElectric StimulationMuscle, SkeletalIsotonic ContractionVasoconstrictionGuinea PigsMuscle, Smooth, VascularMuscle RelaxationMuscle FatigueElectromyographyPotassium ChlorideGastrointestinal MotilityTracheaVasoconstrictor AgentsPeristalsisUrinary BladderMusclesNorepinephrineDose-Response Relationship, DrugAcetylcholineRabbitsAtropinePhenylephrineVas DeferensIleumNifedipineAorta, ThoracicMuscle Tonus