Interactions between the renin-angiotensin system (RAS) and the sympathetic system

Angiotensin II is able to modulate both the presynaptic sympathetic system and the adrenal medulla resulting in an enhanced release of noradrenaline and adrenaline. Consequently, the inhibition of the converting enzyme by ACE inhibitors resulting in a lower concentration of angiotensin II or blockad...

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Bibliographic Details
Published in:Basic research in cardiology 1998-01, Vol.93 Suppl 2, p.24-s029
Main Authors: Dendorfer, A, Raasch, W, Tempel, K, Dominiak, P
Format: Article
Language:English
Subjects:
Angiotensin II - pharmacology
Animals
Antihypertensive Agents - pharmacology
Benzimidazoles - pharmacology
Biphenyl Compounds - pharmacology
Dose-Response Relationship, Drug
Imidazoles - pharmacology
Losartan - pharmacology
Male
Norepinephrine - metabolism
Presynaptic Terminals - drug effects
Rats
Rats, Inbred SHR
Receptors, Angiotensin - physiology
Renin-Angiotensin System - physiology
Sympathetic Nervous System - physiology
Tetrazoles - pharmacology
Vasoconstrictor Agents - pharmacology
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Summary:Angiotensin II is able to modulate both the presynaptic sympathetic system and the adrenal medulla resulting in an enhanced release of noradrenaline and adrenaline. Consequently, the inhibition of the converting enzyme by ACE inhibitors resulting in a lower concentration of angiotensin II or blockade of the specific AT1 receptors by AT1 receptor blocking agents should lead to a decrease in both noradrenaline and adrenaline release. It has been demonstrated that ACE inhibition did not influence the net catecholamine overflow during stimulation of the sympathetic nerves in contrast to AT1 antagonists which can specifically and dose dependently diminish noradrenaline and adrenaline release, an effect that could be explained by a compensating mechanism of bradykinin. Bradykinin may accumulate during ACE inhibition and is able to stimulate catecholamine release via B2 receptors. To verify the class effect of AT1 antagonists on presynaptic AT1 receptors, the AT1 antagonist candesartan was investigated regarding its presynaptic effect in pithed spontaneously hypertensive rats. As could be demonstrated with losartan and HR 720, candesartan lowered AT1 receptor mediated angiotensin II-induced noradrenaline release in a dose-dependent manner. It is concluded that AT1 antagonists inhibit angiotensin II mediated catecholamine release on presynaptic sympathetic nerves and the adrenal medulla at the specific AT1 receptor site. The effect can be described as a class effect of these imidazole derivatives.
ISSN:0300-8428
1435-1803
DOI:10.1007/s003950050202