Document Detail

Role of endogenous angiotensin II on sympathetic reflexes in conscious rabbits.
MedLine Citation:
PMID:  9227595     Owner:  NLM     Status:  MEDLINE    
In the present study we sought to determine the contribution of endogenous brain stem angiotensin to renal sympathetic reflexes in conscious rabbits. Initial studies determined the subtype of receptor involved in the pressor response to angiotensin II (ANG II) administration into the fourth ventricle (4V). The AT1 antagonist losartan (0.001-10 micrograms 4V) had no effect on blood pressure alone but caused a dose-dependent blockade of the pressor effect of ANG II, with complete blockade produced by 10 micrograms, an effect that lasted for at least 3 h. The AT2 antagonist PD-123319 (0.1-1,000 micrograms) and vehicle had no effect on the ANG II pressor response. The effect of losartan (10 micrograms) on the baroreceptor, chemoreceptor, and trigeminal reflexes was examined in eight rabbits that had been implanted with 4V catheters and an electrode for recording renal sympathetic nerve activity (RSNA) 1 wk earlier. Baroreflex assessments were made during normoxia and two conditions of hypoxia (10% O2 and 10% O2 + 3% CO2) before and after 10 micrograms losartan or vehicle, on separate experimental days. During normoxia and hypoxia+CO2 losartan increased resting RSNA, the range, and upper plateau of the RSNA-MAP baroreflex curves. By contrast the marked increase in RSNA due to activation of trigeminal afferents was not affected by losartan. In conclusion the effect of losartan to increase RSNA activity in conscious rabbits, particularly during hypoxia and baroreceptor unloading, suggests that endogenous ANG II via AT1 receptors normally inhibits renal sympathetic baroreceptor and chemoreceptor reflexes.
R D Bendle; S C Malpas; G A Head
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The American journal of physiology     Volume:  272     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1997 Jun 
Date Detail:
Created Date:  1997-08-18     Completed Date:  1997-08-18     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  R1816-25     Citation Subset:  IM    
Baker Medical Research Institute, Prahran, Victoria, Australia.
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MeSH Terms
Angiotensin II / pharmacology,  physiology*
Anoxia / blood,  physiopathology
Antihypertensive Agents / pharmacology
Baroreflex / drug effects,  physiology
Biphenyl Compounds / pharmacology
Blood Pressure / drug effects
Cardiovascular System / drug effects
Dose-Response Relationship, Drug
Hemodynamics / drug effects
Imidazoles / pharmacology
Kidney / innervation*
Nasopharynx / drug effects,  physiology
Pyridines / pharmacology
Reflex / physiology*
Sympathetic Nervous System / drug effects,  physiology*
Tetrazoles / pharmacology
Reg. No./Substance:
0/Antihypertensive Agents; 0/Biphenyl Compounds; 0/Imidazoles; 0/Pyridines; 0/Tetrazoles; 11128-99-7/Angiotensin II; 114798-26-4/Losartan; 130663-39-7/PD 123319

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