Increased pressor responsiveness of femoral arteries to exogenous norepinephrine in renal hypertensive dogs mediated through alpha 2 adrenoceptors.

Changes of perfusion pressure induced by femoral arterial perfusion of norepinephrine (NE) were studied in renal hypertensive dogs made with the method of wrapping both kidneys. The NE threshold dose which induced perfusion pressure increase was lower in hypertensive dogs than that in normotensive dogs. The NE pressor response in low concentration (1, 2, 10 ng.kg-1) was increased in hypertensive dogs, after alpha 2 adrenoceptors antagonized by idazoxan this increased response had been eliminated. These suggested that increased vasoconstriction by exogenous NE in hypertensive dogs was mediated through the increased reactivity of postsynaptic alpha 2 adrenoceptors to NE.