endogenous plasma norepinephrine concentrations doubled during the infusion of phentolamine without propranolol but rose to nearly fourfold higher values during the infusion of phentolamine with propranolol indicating that beta-adrenergic blockade reduces the clearance of norepinephrine as well as that of epinephrine .
C0028351
norepinephrine
C0014563
epinephrine