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Hypertension Unit, University of Ottawa Heart Institute, Ottawa, Ontario, K1Y 4W7 Canada
Sympathetic hyperactivity and hypertension caused by chronic
treatment with ouabain or sodium-rich artificial cerebrospinal fluid
(aCSF) can be prevented by central administration of an angiotensin
type 1 (AT1) receptor blocker. In the present study, we
assessed whether, in Wistar rats, chronic peripheral treatment with the
AT1 receptor blockers losartan and embusartan can exert sufficient central effects to prevent these central effects of ouabain
and sodium. Losartan or embusartan (both at 100 mg · kg
1 · day
1) were given
subcutaneously once daily. Ouabain (50 µg/day) was infused
subcutaneously, and sodium-rich aCSF (1.2 M Na+, 5 µl/h)
was infused intracerebroventricularly, both by osmotic minipump for
13-14 days. The mean arterial pressure (MAP) at rest and in
response to air stress and intracerebroventricularly injection of
guanabenz (75 µg/7.5 µl), ANG II (30 ng/3 µl), and ouabain (0.5 µg/2 µl) were then measured. In control rats, chronic treatment with ouabain subcutaneously and hypertonic saline
intracerebroventricularly both increased baseline MAP by 20-25
mmHg and enhanced twofold the pressor responses to air stress and
depressor responses to the
2-adrenoceptor agonist
guanabenz. Simultaneous treatment with losartan or embusartan fully
prevented hypertension, maintained normal responses to air stress and
guanabenz, and attenuated pressor responses to acute
intracerebroventricular injection of ANG II and ouabain. We concluded
that peripheral administration of losartan as well as embusartan can
cause sufficient central effects to prevent the sympathetic
hyperactivity and hypertension induced by chronic peripheral ouabain
and central sodium.
brain renin-angiotensin system; losartan; embusartan; angiotensin II
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