Characterization of hypertension induced by long-term intrarenal norepinephrine infusion in conscious rats

This paper reviews some of the data that we have collected over the last years in an animal model in which, to study the role of renal nerves in hypertension, increased efferent sympathetic activity was simulated by a 5-day intrarenal infusion of norepinephrine (NE; 4-36 ug/kg.hr) in rats. This resulted in an exaggerated hypertensive reaction as compared to intravenous infusions of the same amounts. Hypertension was characterized by increased total peripheral resistance and decreased cardiac output. From plasma volume and renal function studies, no evidence for volume-dependent hypertension could be obtained. The most striking difference between intrarenally and intravenously infused rats was a greater increase in plasma NE levels in the former group. This pointed towards a possible activation of afferent renal nerves by intrarenally applied NE. However, neither total nor selective afferent renal denervation prevented hypertension by intrarenal NE. This suggests either that afferent renal nerves do not play a role or, alternatively, blood pressure is controlled differently in intact and denervated rats.