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Published Online
on February 11, 2008

Hypertension. 2008
Published online before print February 11, 2008, doi: 10.1161/HYPERTENSIONAHA.107.100800
A more recent version of this article appeared on April 1, 2008
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Submitted on September 3, 2007
Revised on September 28, 2007

Levels of Renal and Extrarenal Sympathetic Drive in Angiotensin II–Induced Hypertension

Sandra L. Burke; Roger G. Evans; John-Luis Moretti; and Geoffrey A. Head*

From the Neuropharmacology Laboratory (S.L.B., J.-L.M., G.A.H.), Baker Heart Research Institute, Melbourne, Australia; and the Department of Physiology (R.G.E.), Monash University, Victoria, Australia.

* To whom correspondence should be addressed. E-mail: geoff.head{at}baker.edu.au.

Abstract—We examined the contribution of the renal nerves to mean arterial pressure (MAP) during 5-week chronic infusion of angiotensin II (Ang II; 50 ng/kg per minute SC) in conscious rabbits. Basal MAP was 68±1 mm Hg, and the maximum depressor response to ganglion blockade was -20±2 mm Hg. MAP increased by 25±2 mm Hg after 1 week and remained stable over the next 4 weeks. Depressor responses to pentolinium (6 mg/kg IV) were similar to control during the first week of hypertension but thereafter became increasingly greater in Ang II–treated rabbits but not vehicle-treated rabbits. After 5 weeks, the fall in MAP was 54% greater in Ang II- than in vehicle-treated rabbits (-34±2 versus -22±2 mm Hg), but renal sympathetic nerve activity was similar in both groups. Renal denervation produced a small fall in MAP in all of the vehicle-treated rabbits after 4 days (-6±2 mm Hg; P=0.01), but there was no consistent effect in hypertensive rabbits. The depressor response to ganglion blockade was enhanced in vehicle-treated but not Ang II–treated rabbits. The finding that renal sympathetic nerve activity is not altered by Ang II hypertension nor is the hypertension altered by renal denervation suggests that renal sympathetic nerves do not contribute to the hypertension. The greater depressor effect of acute ganglion blockade in hypertensive rabbits suggests that the sympathetic nervous system exerts increased vasoconstriction in the peripheral vasculature in Ang II–induced hypertension.


Key words: Ang hypertension • sympathetic nervous system • ganglion blockade • renal denervation • rabbits • blood pressure • heart rate