Hypertension, Vol 23, 844-847, Copyright © 1994 by American Heart Association
VJ Gorbea-Oppliger and GD Fink
We used the centrally acting sympatholytic drug clonidine to evaluate
neurogenic pressor activity in rats made hypertensive by chronic
intravenous infusion of a low dose (4.0 ng.min-1) of angiotensin II (Ang
II). Male Sprague-Dawley rats were instrumented with arterial and venous
catheters and then housed in metabolic cages for the duration of the
experiment. After 3 days of recovery from surgery, daily measurements were
begun of mean arterial pressure, heart rate, water balance, and urinary
electrolyte excretion. After 3 days of control measurements rats received
either Ang II (4.0 ng.min-1 IV, n = 5) or saline vehicle (n = 4)
continuously over a 15-day period. After the Ang II and vehicle infusions
were ended, measurements were made during 3 days of recovery. On days 2, 7,
and 12 of the experimental infusion period, clonidine hydrochloride was
administered as a bolus (10.0 micrograms.kg-1 IA). The resulting changes in
mean arterial pressure and heart rate were assessed over a 6-hour period.
Fluid measurements were evaluated on a daily basis. In rats receiving only
vehicle, clonidine produced no significant changes in any variable at any
time. In rats given Ang II, mean arterial pressure increased from a control
value (mean +/- SEM) of 106 +/- 1 mm Hg to 135 +/- 6, 139 +/- 6, and 148
+/- 4 mm Hg on days 2, 7, and 12, respectively. The antihypertensive
response to clonidine after 6 hours on days 2, 7, and 12 of the Ang II
infusion in these rats was -18 +/- 8, -16 +/- 5, and - 23 +/- 9 mm Hg,
respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
ARTICLES
Clonidine reverses the slowly developing hypertension produced by low doses of angiotensin II
Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48823.
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