HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 286/6/R1051    most recent 00708.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (10) Citing Articles via Google Scholar Google Scholar Articles by Watson, A. M. D. Articles by May, C. N. Search for Related Content PubMed PubMed Citation Articles by Watson, A. M. D. Articles by May, C. N.

NEUROHUMORAL CONTROL OF CIRCULATION AND HYPERTENSION

Stimulation of cardiac sympathetic nerve activity by central angiotensinergic mechanisms in conscious sheep

¹Howard Florey Institute of Physiology and Medicine, University of Melbourne, Parkville 3010, Australia; and ²Selcuk University Medical School, Department of Physiology, 42090 Konya, Turkey

Submitted 11 December 2003 ; accepted in final form 27 January 2004

Central actions of angiotensin play an important role in cardiovascular control and have been implicated in the pathogenesis of hypertension and heart failure. One feature of centrally or peripherally administered angiotensin is that the bradycardia in response to an acute pressor effect is blunted. It is unknown whether after central angiotensin this is due partly to increased cardiac sympathetic nerve activity (CSNA). We recorded CSNA and arterial pressure in conscious sheep, at least 3 days after electrode implantation. The effects of intracerebroventricular infusions of ANG II (3 nmol/h for 30 min) and artificial cerebrospinal fluid (CSF) (1 ml/h) were determined. The response to intracerebroventricular hypertonic saline (0.6 M NaCl in CSF at 1 ml/h) was examined as there is evidence that hypertonic saline acts via angiotensinergic pathways. Intracerebroventricular angiotensin increased CSNA by 23 ± 7% (P < 0.001) and mean arterial pressure (MAP) by 7.6 ± 1.2 mmHg (P < 0.001) but did not significantly change heart rate (n = 5). During intracerebroventricular ANG II the reflex relation between CSNA and diastolic blood pressure was significantly shifted to the right (P < 0.01). Intracerebroventricular hypertonic saline increased CSNA (+9.4 ± 6.6%, P < 0.05) and MAP but did not alter heart rate. The responses to angiotensin and hypertonic saline were prevented by intracerebroventricular losartan (1 mg/h). In conclusion, in conscious sheep angiotensin acts within the brain to increase CSNA, despite increased MAP. The increase in CSNA may account partly for the lack of bradycardia in response to the increased arterial pressure. The responses to angiotensin and hypertonic saline were losartan sensitive, indicating they were mediated by angiotensin AT-1 receptors.

angiotensin II; baroreflex; hypertonic saline; intracerebroventricular; losartan

This article has been cited by other articles:

				R. Ramchandra, S. G. Hood, A. M. D. Watson, and C. N. May Responses of cardiac sympathetic nerve activity to changes in circulating volume differ in normal and heart failure sheep Am J Physiol Regulatory Integrative Comp Physiol, September 1, 2008; 295(3): R719 - R726. [Abstract] [Full Text] [PDF]

				R. Frithiof, S. Eriksson, F. Bayard, T. Svensson, and M. Rundgren Intravenous hypertonic NaCl acts via cerebral sodium-sensitive and angiotensinergic mechanisms to improve cardiac function in haemorrhaged conscious sheep J. Physiol., September 15, 2007; 583(3): 1129 - 1143. [Abstract] [Full Text] [PDF]

				A. M. D. Watson, S. G. Hood, R. Ramchandra, R. M. McAllen, and C. N. May Increased cardiac sympathetic nerve activity in heart failure is not due to desensitization of the arterial baroreflex Am J Physiol Heart Circ Physiol, July 1, 2007; 293(1): H798 - H804. [Abstract] [Full Text] [PDF]

				M. Dodic, A. T. McAlinden, A. J. Jefferies, E. M. Wintour, M. L. Cock, C. N. May, R. G. Evans, and K. M. Moritz Differential effects of prenatal exposure to dexamethasone or cortisol on circulatory control mechanisms mediated by angiotensin II in the central nervous system of adult sheep J. Physiol., March 15, 2006; 571(3): 651 - 660. [Abstract] [Full Text] [PDF]

				V. L. Brooks and A. F. Sved Pressure to change? Re-evaluating the role of baroreceptors in the long-term control of arterial pressure Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2005; 288(4): R815 - R818. [Full Text] [PDF]

				C. J. Barrett and S. C. Malpas Problems, possibilities, and pitfalls in studying the arterial baroreflexes' influence over long-term control of blood pressure Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2005; 288(4): R837 - R845. [Abstract] [Full Text] [PDF]