Cardiac baroreflex is already blunted in eight weeks old spontaneously hypertensive rats

There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

Abstract

Background

The literature did not evidence yet with which age spontaneously hypertensive rats (SHR) start to present baroreflex reduction. We endeavored to evaluate the baroreflex function in eight-week-old SHR.

Methods

Male Wistar Kyoto (WKY) normotensive rats and SHR aged eight weeks were studied. Baroreflex was calculated as the variation of heart rate (HR) divided by the mean arterial pressure (MAP) variation (ΔHR/ΔMAP) tested with a depressor dose of sodium nitroprusside (SNP, 50 μg/kg) and with a pressor dose of phenylephrine (PHE, 8 μg/kg) in the right femoral venous approach through an inserted cannula in the animals. Significant differences for p < 0.05.

Results

Baseline MAP (p < 0.0001) and HR (p = 0.0028) was higher in SHR. Bradycardic peak was attenuated in SHR (p < 0.0001), baroreflex gain tested with PHE was also reduced in the SHR group (p = 0.0012). PHE-induced increase in MAP was increased in WKY compared to SHR (p = 0.039). Bradycardic reflex responses to intravenous PHE was decreased in SHR (p < 0.0001).

Conclusion

Eight weeks old SHR already presents impairment of the parasympathetic component of baroreflex.

Related collections

Most cited references 31

Record: found
Abstract: found
Article: not found

Amplified respiratory-sympathetic coupling in the spontaneously hypertensive rat: does it contribute to hypertension?

Patricia E. Simms, Anthony E. Pickering, Harriet A. Allen … (2009)

Sympathetic nerve activity (SNA) is elevated in established hypertension. We tested the hypothesis that SNA is elevated in neonate and juvenile spontaneously hypertensive (SH) rats prior to the development of hypertension, and that this may be due to augmented respiratory-sympathetic coupling. Using the working heart-brainstem preparation, perfusion pressure, phrenic nerve activity and thoracic (T8) SNA were recorded in male SH rats and normotensive Wistar-Kyoto (WKY) rats at three ages: neonates (postnatal day 9-16), 3 weeks old and 5 weeks old. Perfusion pressure was higher in SH rats at all ages reflecting higher vascular resistance. The amplitude of respiratory-related bursts of SNA was greater in SH rats at all ages (P < 0.05). This was reflected in larger Traube-Hering pressure waves in SH rats (1.4 +/- 0.8 versus 9.8 +/- 1.5 mmHg WKY versus SH rat, 5 weeks old, n = 5 per group, P < 0.01). Recovery from hypocapnic-induced apnoea and reinstatement of Traube-Hering waves produced a significantly greater increase in perfusion pressure in SH rats (P < 0.05). Differences in respiratory-sympathetic coupling in the SH rat were not secondary to changes in central or peripheral chemoreflex sensitivity, nor were they related to altered arterial baroreflex function. We have shown that increased SNA is already present in SH rats in early postnatal life as revealed by augmented respiratory modulation of SNA. This is reflected in an increased magnitude of Traube-Hering waves resulting in elevated perfusion pressure in the SH rat. We suggest that the amplified respiratory-related bursts of SNA seen in the neonate and juvenile SH rat may be causal in the development of their hypertension.

0 comments Cited 55 times – based on 0 reviews      Review now

Bookmark

Record: found
Abstract: found
Article: not found

Brain renin-angiotensin system dysfunction in hypertension: recent advances and perspectives.

Shereeni Veerasingham, Mohan K. Raizada (2003)

This review focuses on the dysfunction of the intrinsic brain renin-angiotensin system (RAS) in the pathogenesis of hypertension. Hyperactivity of the brain RAS plays a critical role in mediating hypertension in both humans and animal models of hypertension, including the spontaneously hypertensive rat (SHR). The specific mechanisms by which increased brain RAS activity results in hypertension are not well understood but include increases in sympathetic vasomotor tone and impaired arterial baroreflex function. We discuss the contribution of endogenous angiotensin (Ang) II actions on presympathetic vasomotor rostral ventrolateral medulla neurons to enhance sympathetic activity and maintain hypertension. In addition, we discuss Ang II-induced attenuation of afferent baroreceptor feedback within the nucleus tractus solitarius and its relevance to the development of hypertension. We also outline the cellular and molecular mechanisms of Ang II signal transduction that may be critical for the initiation and establishment of hypertension. In particular, we present evidence for a phosphoinositide-3-kinase-dependent signaling pathway that appears to contribute to hypertension in the SHR, possibly via augmented Ang II-induced increases in neuronal firing rate and enhanced transcriptional noradrenaline neuromodulation. Finally, we outline future directions in utilizing our understanding of the brain RAS dysfunction in hypertension for the development of improved therapeutic intervention in hypertension.

0 comments Cited 43 times – based on 0 reviews      Review now

Bookmark

Record: found
Abstract: found
Article: not found

Sympathetic nerve activity: role in regulation of blood pressure in the spontaenously hypertensive rat.

Jack W Judy, Mari A Watanabe, Michael Henry … (1976)

Sympathetic nerve activity (SNA) and high pressure baroreceptor regulation of SNA were studied in the Okamoto strain of spontaneously hypertensive rat (SHR). Mean arterial pressure (MAP) and SNA were not significantly affected by anesthesia with low doses of pentobarbital (20-25 mg/kg). Thus, most of these studies were performed in anesthetized rats. SNA in visceral sympathetic nerves increased rapidly with age up to 24 weeks and slowly thereafter. MAP increased with SNA, following the same time course. Both SNA and MAP in SHR were significantly greater than that found in normotensive Wistar control rats of comparable ages. Abolition of ganglionic transmission with hexamethonium in both SHR and normotensive controls reduced postganglionic SNA and MAP to comparable levels. In SHR less than 16 weeks old, increased baroreceptor stimulation effectively inhibited SNA with the same sensitivity as found in Wistar control rats. However, older SHR appeared to lose their ability to completely inhibit SNA during induced hypertension, whereas in Wistar control rats as old as 52 weeks, elevation of blood pressure to 165.3 +/- 2.3 mm Hg completely suppressed SNA. These results suggest that SNA may play an important role in the development and maintenance of hypertension in SHR, and that central sympathetic centers, uninhibited by baroreceptor afferents, become active during the development of hypertension in the SHR.

0 comments Cited 39 times – based on 0 reviews      Review now

Bookmark

All references

Author and article information

Journal

Journal ID (nlm-ta): Int Arch Med

Title: International Archives of Medicine

Publisher: BioMed Central

ISSN (Electronic): 1755-7682

Publication date Collection: 2010

Publication date (Electronic): 27 January 2010

Volume: 3

Page: 2

Affiliations

[1 ]Department of Morphology and Physiology, School of Medicine of ABC, Av. Príncipe de Gales, 821, Santo André 09060-650, Brazil

[2 ]Department of Clinical Medicine, Cardiology Division, School of Medicine of ABC, Av. Príncipe de Gales, 821, Santo André 09060-650, Brazil

[3 ]Department of Medicine, Cardiology Division Federal University of São Paulo (UNIFESP), Rua Napoleão de Barros, 715 Térreo, São Paulo 04039-032, Brazil

[4 ]Department of Physiology, Federal University of São Paulo (UNIFESP), Rua Napoleão de Barros, 715 Térreo, São Paulo 04039-032, Brazil

[5 ]Cardiovascular Surgery Division, School of Medicine of ABC, Av. Príncipe de Gales, 821, Santo André 09060-650, Brazil

[6 ]Speech Pathology and Audiology Department, Faculty of Philosophy and Sciences, Paulista State University (UNESP), Av. Hygino Muzzi Filho, 737, Campus Universitário, Marília 17525-900, Brazil

Article

Publisher ID: 1755-7682-3-2

DOI: 10.1186/1755-7682-3-2

PMC ID: 2830929

PubMed ID: 20181028

SO-VID: 7501e7a3-d6ab-4338-bb41-e243202f6dc8

License:

This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Cardiac baroreflex is already blunted in eight weeks old spontaneously hypertensive rats

Read this article at

Abstract

Background

Methods

Results

Conclusion

Related collections

ScienceOpen Clinical Case Reports Collection

Most cited references 31

Amplified respiratory-sympathetic coupling in the spontaneously hypertensive rat: does it contribute to hypertension?

Brain renin-angiotensin system dysfunction in hypertension: recent advances and perspectives.

Sympathetic nerve activity: role in regulation of blood pressure in the spontaenously hypertensive rat.

Author and article information

Journal

Affiliations

Article

History

Categories

Comments

Comment on this article

Similar content 747

Cited by 8

Most referenced authors 212